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Légère, Jean-Guy Joseph. "Capsule-based microwave digestion." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39940.
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A large tube microwave digestion system with capsule sample introduction has been developed. This is the first automatic pressurized microwave digestion system to use: (1) capsule sample introduction, (2) reagent addition, and (3) controlled venting, during a digestion. The digestion tube has built-in cooling, an infrared temperature sensor, an in-line pressure sensor, automatic venting, and a new type of valve, called the "Flange Valve". The flange valve was designed for loading capsules into the digestion tube and for easy cleaning of all valve and tube parts wetted by the sample.The digestion tube is made of Teflon PFA$ sp circler,$ which is capable of operating at 200 psi and 200$ sp circ$C. Water, salt solutions, and concentrated nitric acid were used to characterize the system.
A process was developed to make capsules from ultra-clean polyacrylamide gel; it was used to make capsules for the analysis of soils, botanicals, and biological samples. A "Squeegee", a device equipped with a soft, gas-tight Teflon$ sp circler$ end pushed through the digestion tube with a flexible rod, was used to insert capsules into and remove digestate from the digestion tube.
Micro2, an interpretive language, written in-house, uses English-like instruction files to control the digestion. Micro2 uses pressure, temperature and time data to control venting, cooling, and heating during the digestion. Triggers and feedback loops in the instruction file allow Micro2 to adapt to changing conditions in the digestion tube to complete a digestion without loss of analyte.
Analysis of the digested samples revealed that, for the same digestion temperature, dissolution is identical to that performed in a conventional microwave bomb.
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Broomhall, G. A. "The microwave digestion of solids." Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/8348.
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Bibliography: leaves 115-116.Microwave ovens have been available for domestic cooking since 1956. This method of heating is very efficient compared to conventional cooking methods. As a result many applications have arisen particularly in the field of analytical chemistry. Most routine analysis of biological and chemical samples by atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) involves the time consuming operation of digesting the samples in acid on a hot plate. However, much time saving has been demonstrated by the use of microwave digestion, and successful digestions have been achieved in 10% of the time required for traditional methods. The first digestions using microwave heating were performed in open vessels. However many problems were identified.
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Lamble, Kathryn Judith. "The development of on-line microwave digestion techniques for environmental matrices." Thesis, University of Plymouth, 1997. http://hdl.handle.net/10026.1/1908.
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As a consequence of our advancing knowledge of the impact of trace elements in environmental and biological systems there is increasing need for quantitative analytical techniques to accurately, sensitively and rapidly determine a wide range of trace elements in environmental samples. Since their emergence in 1975 microwave digestion techniques have revolutionised conventional approaches to sample digestion and have rapidly gained widespread acceptance as an effective method of sample preparation. This thesis describes how a number of novel on-line microwave digestion techniques have been developed, characterised and applied to the digestion of a range of environmental matrices which have proved time consuming or troublesome to digest by conventional techniques. A variety of batch open focused microwave digestion methods have been developed and utilised for the analysis of a range of environmental samples including tea leaves, seaweed and sediment samples. The techniques were optimised to determine a range of trace metals including Al, As, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Pb, Ni, Ti, V and Zn and in each case were successfully validated by the analysis of suitable certified reference materials. These techniques demonstrated a number of advantages over conventional methods including less reagent usage, less contamination and substantial time savings. Speciation studies have been a focus for this work and have included the evaluation of an acetic acid microwave extraction method for the extraction of tributyltin, dibutyltin, monobutyltin and triphenyltin from sediment samples prior to analysis by high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). In addition the speciation of arsenic in biological samples was addressed by the development and evaluation of an on-Une microwave digestion technique. This enabled the speciation of arsenobetaine (AsBet), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and inorganic arsenic following their separation by HPLC. Decomposition was achieved by microwave digestion and followed by pre-reduction with L-cysteine and detection by hydride generation-atomic absorption spectrometry. Simple modification of the technique also facilitated the determination of total arsenic. In addition the total reducible arsenic species (inorganic arsenic, MMA and DMA) were determined directly by on-line pre-reduction-HG-AAS. The results obtained were in good agreement with the certified values for the reference materials NRCC DORM-1 (dogfish muscle) and TORT-1 (lobster hepatopancreas). The on-line microwave digestion approach was further developed for the determination of the total mercury content of solid environmental samples. This involved the combination of an on-line microwave digestion and a bromide/bromate oxidation reaction to facilitate complete oxidation of the organomercury species in slurried biological samples. Following this approach detection could be performed by cold vapour-atomic fluorescence spectrometry, giving a limit of detection of 13 ng l-1. In addition a batch method in which samples were digested with a mixture of hydrogen peroxide, nitric acid and sulphuric acid was developed and studied using temperature profile measurements. Both methods were successfully validated by analysis of the certified reference materials NRCC DORM-2 and PACS-1 (harbour marine sediment).
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Chan, Ian Ching Yuen. "Anaerobic digestion of dairy manure using the microwave hydrogen peroxide advanced oxidation process." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44854.
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Anaerobic digestion (AD) of dairy manure is an alternative to traditional manure management using land application. There are many benefits of AD but it is currently not an economically viable option in many parts of North America. The focus of this investigation was to determine whether liquid dairy manure treated by microwave hydrogen peroxide advanced oxidation process (MW/H₂O₂-AOP) would increase the anaerobic biodegradability of the substrate, producing higher methane yields. Biochemical methane potential (BMP) tests were conducted to measure biogas generation and the Modified Gompertz equation was used to determine the kinetics of anaerobic biodegradability. The research found that MW/H₂O₂-AOP was effective in solubilizing nutrients and organics in liquid dairy manure, but it does not necessarily translate into enhanced anaerobic biodegradability. The BMP tests revealed that digestion of untreated dairy manure at 35ºC had the highest methane yields.
Severe inhibition was observed for the digestion of acidified dairy manure. This was attributed to sulfide inhibition. In addition, ammonia concentrations were suspected as the main reason for severe inhibition of microwave treated dairy manure with no acid addition, but a number of other factors could also be responsible, including sulfide, light metals and lack of temperature acclimation for inoculum. Pretreatment of sewage sludge and BMP tests were also conducted to compare the effect of MW/H₂O₂-AOP with dairy manure. The results showed that the microwave treatment had a positive impact on anaerobic digestibility of sewage sludge, especially for mesophilic digestion. At 35ᵒC, MW alone generated the highest methane yields followed by MW/H₂O₂ and then the control. In terms of methane yield, microwave treatment improved the methane production rate for mesophilic digestion, but not thermophilic digestion. The positive results for BMP tests of microwave treated sewage sludge suggest that the influence of microwave treatment on anaerobic biodegradability is substrate and solid concentration specific. There was no clear and consistent increase or decrease in soluble metal (Ca, K, Mg, Na) concentrations after MW/H₂O₂-AOP. However, it was found that acidified treatment was effective in releasing calcium and magnesium into solution. After digestion, the soluble calcium, potassium, magnesium and sodium content of dairy manure was reduced.
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Zheng, Jian. "Effect of mild microwave pretreatment on characteristics and mesophilic digestion of primary sludge." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27314.
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Wastewater treatment produces a large amount of contaminant-containing sewage sludge, disposal of which is of great concern and is tightly regulated. Anaerobic digestion of sewage sludge is used in most large-scale wastewater treatment plants prior to sludge end use or ultimate disposal mainly due to its advantages of low energy consumption and potential energy recovery. Thermal pretreatment has been studied and successfully applied to improve the quality of the digestion product. Microwave (MW) irradiation has become of interest with some advantages over conventional thermal pretreatment. The objective of this research is to investigate whether MW pretreatment can enhance the anaerobic digestion of primary sludge (PS).
The influence of MW irradiation on the characteristics of pretreated primary sludge was studied in terms of MW intensity, sludge solid concentration, and temperature achieved. The experimental range of sludge of sludge characteristics was sludge solid concentration of 1-4% (w/v) total solids (TS), temperature 35-90°C, and MW intensity of 40 and 80%. MW irradiation was found to increase the concentration of soluble COD (SCOD) in the sludge. The ratio of SCOD/TCOD increased from 2.5% to around 6-7% for 4% TS sludge and MW pretreatment temperature of 90°C. Both sludge solid concentration and MW irradiation temperature were shown to be the most important MW pretreatment parameters in solubulizing primary sludge. MW intensity in the range of temperatures studied had no impact on primary sludge solubilization.
Mesophilic biochemical methane potential (BMP) assays were applied to primary sludge pretreated at MW scenarios of 1-4% TS, temperatures 35-90°C, and MW intensity of 40 and 80%. Again, the BMP assay indicated no obvious difference in samples with the same TS concentration and pretreated to similar temperatures but at different MW intensities. Both higher MW pretreatment temperatures and higher TS concentrations significantly improved biogas production rate and reduced required digestion time to achieve 85% of ultimate digestion. For 4% TS primary sludge samples pretreated to 90°C, biogas production rate increased 37% or resulted in a 28% reduction in digestion time to achieve 85% of the ultimate biogas production. There was some indication that MW pretreatment may have caused some very mild inhibition of the whole (soluble and suspended) sludge sample based on the existence of a 2-3 day lag phase for pretreated sludge samples. While MW pretreatment increased the rate of digestion of primary sludge it resulted in no significant increase in the ultimate biogas production and biodegradation of organic matter in terms of VS and TCOD removal. Analysis of biogas production results from the BMP assays indicated that they could be described by a first order reaction. The reaction rate constant increased with increase of TS concentration and MW pretreatment temperature, but was not affected by MW intensity.
BMP assay of the soluble fraction of pretreated primary sludge was carried out on 4% TS primary sludge pretreated at MW intensity of 80% and temperatures of 65°C and 90°C. The soluble fraction was shown to exhibit no methanogenic inhibitory effects.
In general MW pretreatment at the conditions tested did not result in any significant microbial inhibition and resulted in increased rate of primary sludge digestion without increase of the ultimate degradability of the sludge.
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Shahriari, Zavareh Haleh. "Enhancement of Anaerobic Digestion of Organic Fraction of Municipal Solid Waste by Microwave Pretreatment." Thesis, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20282.
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This study evaluates the enhancement of anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) by microwave pretreatment (MW) at high temperatures (115, 145 and 175°C). The highest level of solubilization was achieved at 175ºC, with a supplemental water addition of 30% (SWA30). Pretreatments combining two modalities; MW heating in presence or absence of hydrogen peroxide (H2O2) was also investigated. Biochemical methane potential (BMP) tests were conducted on the whole OFMSW, as well as on the liquid fractions.
The whole OFMSW pretreated at 115 and 145 ºC showed little improvement in biogas production over control. When pretreated at 175 ºC, biogas production decreased due to formation of refractory compounds, inhibiting digestion. For the liquid fraction of OFMSW, the effect of pretreatment on the cumulative biogas production (CBP) was more pronounced for supplemental water addition of 20% (SWA20) at 145 ºC. Combining MW and H2O2 modalities did not have a positive impact on OFMSW stabilization and enhanced biogas production.
Based on the BMP assay results, the effects of MW pretreatment (145 ºC) on the AD of OFMSW (SWA20) were further evaluated in single and dual stage semi-continuous digesters at hydraulic retention times (HRTs) of 20, 15, 12 and 9 days. Overall, MW pretreatment did not enhance the AD of the whole waste at the HRTs tested. However, the use of a dual stage reactor digesting non pretreated whole OFMSW had the best performance with the shortest HRT of 9 days. Conversely, for free liquid after pretreatment in two stage reactors at 20 day HRT methane production was tripled. In general, the performance of the dual stage digesters surpassed that of the single stage reactors.
Cyclic BMP assays indicated that using an appropriate fraction of recycled effluent leachate can be implemented without negatively effecting methanogenic activity and biogas production.
Based on the results obtained in this study, digestion of OFMSW by dual stage reactors without pretreatment appears to provide the best potential for waste stabilization in terms of biogas production and yield, process stability and volumetric loading rates.
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Totland, Marina. "Determination of the platinum group metals in geological materials." Thesis, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390298.
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Chatreewongsin, Urai. "Metal Extraction From Soil Samples By Chelation in a Microwave System." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/26982.
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This work involves the combination of chelation and microwave extraction as a technique for extracting adsorbed metals in soil. It has been termed in this work, Chelate Assisted Microwave Extraction (CAME). Unlike other extraction methods, CAME is able to differentiate between anthropological and geological trace metals.
The method has been applied to major sample matrices included three types of soils (Bertie Sandy Loam, Davidson Silty Clay, and Davidson Clayey Loam) as well as sea sand, alumina, and iron oxide. In order to investigate the effects of sorptive coatings on metal concentrations, a sample set was first treated with humic acids, which represented organic coated materials. Afterwards, copper (II) solutions were spiked to both untreated and treated matrices and the efficiencies of recoveries were studied. Metal determinations were performed by Inductively Coupled Plasma-Atomic Emission Spectrophotometry (ICP-AES).
Initial studies of control (untreated soil) and long-term Cu amended (spiked) Bertie Sandy Loam (BSL) indicated that extraction efficiencies were method dependent. Ethylenediaminetetraacetic acid (EDTA) was a primary chelating agent used for method comparisons. Extracting solutions having a pH range from 7.8 to 10.1 did not affect the EDTA-microwave method, but the increase in pH enhanced Cu removal by the EDTA-shaking extraction method which was a conventional chelation using a mechanical shaker. With the EDTA-microwave method, complete extraction was achieved in a short period of time (20 minutes). Compared to the EDTA-shaking method using two sandy soils, the EDTA-microwave method proved to be more efficient in extracting sorbed metals in soils (5.9 vs. 4.6 µg/g for the control BSL and 37.5 vs. 27.8 µg/g for the amended BSL.
FT-IR and C13 NMR were used to characterize extracted and commercially available humic acids. The latter was employed to prepare the humate coated materials. Iron oxide containing materials such as Davidson Silty Clay (DSC), Davidson Clayey Loam (DCL), and iron oxide (Fe2O3), showed extremely high adsorption capabilities for humic acids, while sea sand, Bertie Sandy Loam, and alumina (Al₂O₃) provided lower adsorption capabilities for humic acids. Two sets of uncoated and humate coated materials were used for Cu spiking procedures using 0.001 M Cu (II) at pH 5.3 for 24 hour-equilibration. Three original soils and alumina showed high adsorption capabilities for Cu (II). The presence of coated humate helped increase Cu adsorption capabilities of these soils, but diminished the ability of alumina to react with Cu (II) ions. For HA-uncoated matrices, iron oxide had a higher Cu adsorption capability than sea sand but less than real soils. Humate coating improved Cu adsorption capabilities of not only real soils but iron oxide and sea sand as well.
Lastly, the developed method named Chelate Assisted Microwave Extraction (CAME) was further examined and optimized. Several samples were investigated for extraction efficiencies. A two-step extraction, applying 120 W for 5 min followed by 60 W for 10 min, was efficient in removing sorbed metals from different matrices regardless of sorptive oxide and organic components. Concentrations of chelating agents slightly affected percent metal removal; however, there was no significant difference in results obtained using EDTA or diethylenetriaminepentaacetic acid (DTPA). Recoveries of spiked metals (Cu and Cd) ranged from 96 to 107%. Using the untreated (control) Davidson Silty Clay and Bertie Sandy Loam, the comparison of other chelating solutions were made. Clearly, CAME was promising and proved to be a good alternative to classical shaking method for extracting adsorbed metals from soils.Ph. D.
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Lundholm, Amalia. "Determination of trace and major elements in oil by ICP-AES after microwave digestion." Thesis, Uppsala universitet, Institutionen för kemi - BMC, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256370.
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Ara, Efath. "Anaerobic Co-digestion of Organic Fraction of Municipal Solid Waste with Municipal Sludge with or without Microwave Pre-treatment." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23069.
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Anaerobic co-digestion of organic fraction of municipal solid waste (OFMSW), with thickened waste activated sludge (TWAS) and primary sludge (PS) has the potential to enhance (biodegradation) of solid waste, increase longevity of existing landfills and lead to more sustainable development by improving waste to energy production. This study reports on mesophilic batch anaerobic biological methane potential (BMP) assays carried out with different concentrations and combinations (ratios) of OFMSW, TWAS (microwave (MW) pre-treated and untreated) and PS to assess digester stability and potential improved specific biodegradability and potential increased specific biogas production by digestion of OFMSW with PS and TWAS in various tri-substrate mixtures. Results indicated improvements in specific biogas production with concomitant improvements in COD and volatile solid (VS) removal for co-digestion of OMSW, TWAS and PS vs. controls. In terms of improvements in biogas production and digester stability the OFMSW:TWAS:PS:50:25:25 ratio with or without TWAS MW treatment was deemed best for further continuous digester studies. At a 15d HRT which is the regulatory policy in the province of Ontario for municipal mesophilic anaerobic TWAS:PS treatment, co-digestion of OFMSW:TWAS:PS, and OFMSW:TWASMW:PS resulted in a 1.38 and 1.46 fold relative improvement in biogas production and concomitant waste stabilization when compared to TWAS:PS and TWASMW:PS digestion at the same HRT and volumetric VS loading rate respectively. Treatment of OFMSW with PS and TWAS provides beneficial effects that could be exploited at MWWTP that are being operated at loading rates less than design capacity.
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Elis, [forename not supplied], and elis cen@student rmit edu au. "The optimisation of a method for total selenium analysis and application to cereal grain foods." RMIT University. Applied Sciences, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20081128.143142.
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Cereal based foods, including breakfast cereals and Asian noodles are potentially good sources of selenium. Although these are major foods consumed globally, their contribution to dietary intakes of selenium is unclear. In addition, there has been very limited research into the effect of processing steps on the analysis and apparent retention of selenium. The low levels typically present in foods and the presence of multiple chemical forms of the element provide significant analytical challenges to research in this area. Therefore, the aims of this study were firstly to evaluate and validate procedures for extraction and measurement of selenium in wheat flour. Secondly, the procedure has been applied to analysis of selenium in cereal foods. The methods employed were firstly validated using wheat-based reference materials and then samples of various breakfast cereals as well as different styles of Asian noodles were analysed. Selenium was extracted using closed- v essels by microwave digestion with a mixture of nitric acid and hydrogen peroxide, followed by determination through Inductively Coupled Plasma - Mass Spectrometry (ICP-MS). The optimum conditions for selenium determination in cereal based foods involved the digestion of 0.1 g samples using 1 mL of nitric acid and 1 mL of hydrogen peroxide. The addition of 1% (v/v) methanol was found to enhance the sensitivity of the ICP-MS system. Two particular isotopes of selenium (77 and 82) could be effectively employed in the analysis and there was no significant decrease in total selenium in the digested extracts during storage for up to twelve days under refrigeration and room temperature conditions. Good precision levels were obtained and the total selenium levels in the breakfast cereal samples ranged from 0.059 to 0.378 µg/g. For white salted noodles the values varied between 0.057 and 0.712 µg/g, for yellow alkaline noodles, 0.109 to 0.265 µg/g and 0.077 to 0.284 µg/g for fried instant noodles. There was no appar ent change observed in total selenium during the processing of fried instant noodles, indicating the effectiveness of the extraction method developed here. It is concluded that microwave digestion is an effective approach to sample extraction, the procedures validated in this study are suitable for cereal grain foods and that there is considerable variation in the selenium contents of breakfast cereal and Asian noodle products.
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Hamid, Hanna. "Effect of microwave hydrolysis on transformation of steroidal hormones during anaerobic digestion of municipal sludge cake." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/43963.
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Thibault, Gabriel. "Effects of microwave irradiation on the characteristics and mesophilic anaerobic digestion of sequencing batch reactor sludge." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27186.
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Wastewater treatment generates large quantities of sewage sludge whose disposal is expensive. Mainly because anaerobic digestion produces methane, which can be beneficially used as an energy source, this process has become the most popular means of stabilizing sewage sludge prior to spreading on agricultural land or disposal to landfills. Several pretreatment technologies have recently been developed to render sludge more degradable during anaerobic digestion. The purpose of this study is to investigate whether microwave irradiation can enhance the anaerobic degradability of aerobic sequencing batch reactor sludge.
Relationships relating microwave irradiation duration, microwave intensity, sludge concentration and the temperature reached by the sludge were developed. Sludge concentration in the 1.2-4.3% total solids range was found not to impact the temperature reached by the sludge. Three techniques were used to assess the impact of microwave irradiation on the size of the particles: visual analysis of sludge settling, microscopic analysis and particle size distribution analysis. (Abstract shortened by UMI.)
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Jin, Ying. "Microwave-based Pretreatment, Pathogen Fate and Microbial Population in a Dairy Manure Treatment System." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77287.
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Anaerobic digestion and struvite precipitation are two effective ways of treating dairy manure for recovering biogas and phosphorus. Anaerobic digestion of dairy manure is commonly limited by slow fiber degradation, while one of the limitations to struvite precipitation is the availability of orthophosphate. The aim of this work was to study the use of microwave-based thermochemical pretreatment to simultaneously enhance manure anaerobic digestibility (through fiber degradation) and struvite precipitation (through phosphorus solubilization). Microwave heating combined with different chemicals (NaOH, CaO, H₂SO₄, or HCl) enhanced solubilization of manure and degradation of glucan/xylan in dairy manure. However, sulfuric acid-based pretreatment resulted in a low anaerobic digestibility, probably due to the sulfur inhibition and side reactions. The pretreatments released 20-40% soluble phosphorus and 9-14% ammonium. However, CaO-based pretreatment resulted in lower orthophosphate releases and struvite precipitation efficiency as calcium reacts with phosphate to form calcium phosphate. Collectively, microwave heating combined with NaOH or HCl led to a high anaerobic digestibility and phosphorus recovery. Using these two chemicals, the performance of microwave- and conventional-heating in thermochemical pretreatment was further compared. The microwave heating resulted in a better performance in terms of COD solubilization, glucan/xylan reduction, phosphorus solubilization and anaerobic digestibility. Lastly, temperature and heating time used in microwave treatment were optimized. The optimal values of temperature and heating time were 147°C and 25.3 min for methane production, and 135°C and 26 min for orthophosphate release, respectively.
Applying manure or slurry directly to the land can contribute to pathogen contamination of land, freshwater and groundwater. Thus it is important to study the fate of pathogens in diary manure anaerobic digestion systems. The goal of the project was to establish a molecular based quantitative method for pathogen identification and quantification, compare the molecular based method with culture based method and study pathogen fate in dairy manure and different anaerobic digesters. Result showed that molecular based method detected more E.coli than the culture based method with less variability. Thermophilic anaerobic digestion can achieve more than 95% pathogen removal rate while mesophilic anaerobic digester had increased E.coli number than fresh manure, indicating temperature is a key factor for pathogen removal.
In general, the overall goal of the study is to develop an integrated dairy manure treatment system. The microwave based pretreatment enhanced the subsequent biogas production and struvite precipitation, and the molecular tool based method provided a more precise and faster way to study the pathogen fate in various anaerobic digestions.Ph. D.
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Savic, Dejan. "Optimization of Microwave-Assisted Acid Digestion Method for Determination of Trace Elements in Coal and Coal Fly Ash." TopSCHOLAR®, 2008. http://digitalcommons.wku.edu/theses/4.
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In most of the analytical and environmental laboratories today inductively coupled plasma (ICP) is a method of choice for analysis of trace metal elements present in coal and coal combustion products. This method requires use of liquid samples, so all coal and coal combustion products must be digested prior to analysis by ICP. Traditionally an open-air hot-plate acid digestion method published as ASTM D6357-04 was used to extract all trace metal elements into solution.
Recent development of microwave systems designed for digestions under extreme acidic conditions and high temperatures and pressures shifted focus toward more rapid and precise microwave-assisted digestion of samples. A number of papers have been published involving research efforts toward development of quantitatively satisfying digestion methods. However, there is still no published ASTM or EPA method for microwave-assisted digestion of coal and coal combustion products. The goal of this research is compare the recoveries obtained by using hot plate method with results obtained by microwave-assisted digestion, as well as to attempt to optimize method conditions for latter.
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Mason, Christopher James. "The use of microwave flow-through digestion in the analysis of trace metals and total nitrogen in soils." Thesis, University of Greenwich, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325665.
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Cella, Monica Angela. "Assessment of microbial cell viability in municipal sludge after microwave and ultrasound and subsequent impacts on anaerobic digestion." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54796.
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Anaerobic digestion (AD) is an effective method of waste sludge stabilization with lower costs and energy footprints; recently, researchers have begun to optimize the enhancement of AD by pretreating sludge prior to AD. In this study, two sludge pretreatment methods, ultrasonication (US) and microwave irradiation (MW) were compared to determine the relative amounts of microbial inactivation within pretreated secondary sludge, and how this cellular destruction translates to AD processes. The intensities chosen for MWpretreatment were based on previous studies using sludge from the wastewater treatment plant in Kelowna, BC, Canada. The intensity range chosen for MW possessed specific energy inputs of 2.17, 2.62, 4.89, and 6.48 kJ/g total solids (TS). For comparison purposes, US intensities were calculated to be 2.37, 4.74, 6.73, 23.09, and 27.71 kJ/g TS. Using a novel approach, the extent of cellular destruction caused at these intensities was measured using microbial viability fluorophore assays: 1) a molecular assay to measure live and dead cells and 2) a fluorescein diacetate assay to measure relative metabolic activity of sludge micro-organisms. From the results of the viability assays, it was determined that MW had the greatest effect on cells, having several times greater cell death and inactivation than both US-pretreated and non-pretreated sludge, even at lower specific energy values. Additionally, a MW and US intensity with similar specific energy inputs (2.62 kJ/gTS and 2.37 kJ/gTS, respectively) were applied to feed sludge of bench-scale digesters to compare effects on AD over three consecutive sludge retention times (SRTs), at 20 d, 14 d, and 7 d. The MW-fed digester had the highest overall methane production (248.2 L CH₄/kg volatile solids), greatest pathogen removal (73.4% and 69.8% less fecal coliforms over control during the 14 d and 7 d SRTs, respectively), and greatest solids removal (44.2% TS reduction). Interestingly, fecal coliform concentrations in the digester fed USpretreated sludge increased over the control for both the 14 d (31%) and 7 d (39.6%) SRT. All digesters possessed positive net energy production over the three chosen SRTs.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
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Hosseini, Koupaie Ehssan Ollah. "Radio frequency sludge hydrolysis as an energy efficient alternative to microwave and conductive heating for advanced anaerobic digestion." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62451.
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The slow degradation of complex organics such as waste activated sludge (WAS) is a well-known limitation that impacts the process rate of conventional anaerobic digestion (AD). Thermal pretreatment can accelerate the digestion process by disrupting the structure of WAS before AD. The present research was initiated by comparing the two commonly used thermal pretreatment methods, conductive (conventional) heating (CH) and microwave (MW) hydrolysis, for enhanced sludge disintegration and AD performance. A bench-scale programmable MW oven operated at a frequency of 2.45 GHz was used for MW pretreatment. The CH was performed using a custom-built pressure sealed vessel which could simulate the MW pretreatment under any arbitrary heating profiles. After comparing the CH and MW pretreatments, a novel and highly efficient radio frequency (RF) pretreatment system at a frequency of 13.56 MHz was designed, manufactured, and tested for the first time. The RF system was custom-designed based on the dielectric characteristics of thickened WAS (TWAS) to achieve very efficient as well as uniform heating. The effects of the novel RF pretreatment system on sludge solubilization and AD performance were compared with those of the commercially available MW ovens.
Considering the obtained results and analyses, under identical thermal profiles, the thermal pretreatment methods (CH, MW at 2.45 GHz, and RF at 13.56 MHz) achieved similar sludge disintegration as well as AD performance (p-value>0.05). However, the pretreatment temperature, heating rate, and holding time were significant factors in determining the sludge solubilization ratio and AD performance. Ohmic heating was found as the primary heating mechanism at a frequency of 13.56 MHz. It causes the ionic conduction flow to dominate the heating mechanism in the custom-designed RF pretreatment system by contributing to more than 99% of the total dissipated power. Considering the impedance measurement results, the power transfer efficiency of the RF heating system was above 88% throughout the operation. The overall energy efficiency of the RF pretreatment system was measured between 67.3 to 95.5% for the temperature range of 25 to 120°C which was significantly higher than the MW system efficiency which varied from 37 to 43%.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
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Yu, Huimin. "Li, Hf and Os Isotope Systematics of Azores Basalts and A New Microwave Digestion Method for Os Isotopic Analysis." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1322847998.
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Berg, Isabelle. "Validation of MP-AES at the Quantification of Trace Metals in Heavy Matrices with Comparison of Performance to ICP-MS." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-45800.
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The MP-AES 4200 using microwave plasma and an atomic emission spectroscopy detector provide a new and improved instrument to the analytical field. In this project will the performance of the equipment be evaluated in controlled NaCl-heavy matrices for selected metals (Cu, Zn, Li) and the result from this will be used to optimize a method for specific samples. These samples consist of combustion ashes from the incineration of hazardous waste and are provided by the company SAKAB AB. The sample preparation consisted of several cycles of L/S 10 followed by microwave assisted dissolution with concentrated HNO3, aqua regia or 18.2 MΩ. An extended amount of metals were quantified for these samples (Al, As, Ba, Ca, Cd, Cr, Cu, Fe, K, Li, Mn, Na, Ni, Pb, V, Zn) and most (not Ca, Li, K or Na) were compared with an ICP-MS instrument equipped with a collision cell used for the elements As, Fe and V. A final experiment was made on an L/S 10 of the samples to attempt to separate the metals from the salt with ion exchange, something that would make it possible to recycle this otherwise unused waste. The detection limits were all in the low μg L-1 except for Cd, Mn and Zn, which were between 2-4 μg L-1. The MP-AES was found to be able to handle matrices up to 5 g L-1 NaCl without a significant loss of response and provided near identical results to the ICP-MS for the elements that could be compared, this did not included the elements not quantified with the ICP-MS or V which was the only element under the limit of detection for the MP-AES. The experiment where an attempt was made to separate the metals from the salt was proven successful after treatment of bark compost and another type of waste ash as cation exchangers.
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Perfetta, Cory. "Diatom Analysis of Tikal Reservoir Sediments." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573570531434833.
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Dogan, Ilgin. "Combination Of Alkaline Solubilization With Microwave Digestion As A Sludge Disintegration Method: Effect On Gas Production And Quantity And Dewaterability Of Anaerobically Digested Sludge." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609685/index.pdf.
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The significant increase in the sewage sludge production in treatment plants makes anaerobic digestion more important as a stabilization process. However hydrolysis is the rate-limiting step of anaerobic digestion because of the semirigid structure of the microbial cells. Pretreatment of waste activated sludge
(WAS) leads to disruption of cell walls and release of extracellular and intracellular materials. Therefore biodegradability of sludge will be improved in terms of more biogas production and sludge minimization. Among the pretreatment methods, alkaline, thermal and thermochemical pretreatments are effectual ones. Considering the effect of thermal pretreatment, microwave technology in which the sample reaches to elevated temperatures very rapidly is a very new pretreatment method. However no previous research has been conducted to test the effectiveness of microwave (MW) irradiation combined with alkaline pretreatment. Since both of these techniques seem to be highly effective, their combination can act synergistically and even more efficient method can be obtained. Therefore the main objective of this study was to investigate the effect of combination of a chemical method (alkaline pretreatment) and a physical method (microwave irradiation) in improving anaerobic digestion of WAS.
In the first part of the study, alkaline and MW pretreatment methods were examined separately, then their combinations were investigated for the first time in the literature in terms of COD solubilization, turbidity and CST. Highest SCOD was achieved with the combined method of MW+pH-12. In the second part, based on the results obtained in the first part, alkaline pretreatments of pH-10 and pH-12MW pretreatment alone and combined pretreatments of MW+pH-10 and MW+pH-12 pretreated WAS samples were anaerobically digested in small scale batch anaerobic reactors. In correlation with the highest protein and carbohydrate releases with MW+pH-12, highest total gas and methane productions were achieved with MW+pH-12 pretreatment reactor with 16.3% and 18.9% improvements over control reactor, respectively. Finally the performance of MW+pH-12 pretreatment was examined with 2L anaerobic semi-continuous reactors. 43.5% and 53.2% improvements were obtained in daily total gas and methane productions. TS, VS and TCOD reductions were improved by 24.9%, 35.4% and 30.3%, respectively. Pretreated digested sludge had 22% improved dewaterability than non-pretreated digested sludge. Higher SCOD and NH3-N concentrations were measured in the effluent of pretreated digested sludge
however, PO4-P concentration did not vary so much. Heavy metal concentrations of all digested sludges met Soil Pollution Control Regulation Standards. Finally a simple cost calculation was done for a MW+pH-12 pretreatment of WAS for a fictitious WWTP. Results showed that, WWTP can move into profit in 5.5 years.
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Ozsoy, Gulcin. "An Investigation Of Agricultural Use Potential Of Wastewater Sludges In Turkey With Respect To Heavy Metals And Pathogens." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607739/index.pdf.
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Landfilling is the most common method that is used in the final disposal of sludge all around the world as well as in Turkey. However increasing sludge quantities and limited landfilling areas make this method invalid. Use of sludge in agriculture presents a possible alternative for disposal. However, it also poses some risks to be evaluated.
In this respect, it is important to identify heavy metal and pathogen content of sewage sludges because of their adverse health effects. This study aims to determine the heavy metal contents and pathogen levels of sludges from four different wastewater treatment plants of Turkey. The selection of plants was done according to the different treatment technologies applied to wastewater and sludge in those plants. Heavy metal analysis of sludges was conducted by using microwave assisted digestion procedure and pathogen levels were done by methods from Standard Methods (SM), ISO and USA EPA.
After sampling and analysis, the results show that all the related metal concentrations are below the values that are set in the Soil Pollution Control Regulation of Turkey. However in sludges from Ankara and Kayseri wastewater treatment plants, Zinc and Nickel concentrations should be tracked carefully. The results related with pathogen levels in sludges show that dewatered sewage samples taken from Ankara, Kayseri and Kemer wastewater treatment plants do not meet neither Class A nor Class B fecal coliform limits set by USA EPA however lime stabilized dewatered sludge from izmir wastewater treatment plant meet the requirement. In addition, Salmonella levels in Kayseri dewatered sludges exceed the limit value.
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Countess, Stephanie Jean. "Evaluating Leachability of Residual Solids from Hydraulic Fracturing in the Marcellus Shale." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/56156.
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The process of natural gas extraction through hydraulic fracturing produces large quantities of fluid containing naturally-occurring salt, radionuclides, and heavy metals which form residual solids during storage and treatment. The purpose of this research was to characterize the residual solids from hydraulic fracturing operations in the Marcellus Shale to predict the leaching behavior of select elements in disposal environments.
Samples collected for this research were: (1) drilling mud, (2) treated sludge from the chemical treatment of process waters, (3) solids from the gravity settling of produced water, and (4) sludge solidified prior to disposal in a municipal landfill. These samples were subjected to various digestion techniques to determine the composition and leaching potential for elements of concern. Strong acid digestions were performed to determine the total environmentally available composition, whereas weak acid digestions were used to predict the leaching potential of these solids under various environmental conditions. The extraction fluids for the leaching experiments included weak acetic acid, acid rain, reagent water, and synthetic landfill leachate. Solids were agitated in a standard tumbling apparatus to simulate worst-case conditions based on ASTM and EPA recommendations. Results from EPA's Toxicity Characteristic Leaching Procedure (TCLP) were used to determine if solids were considered hazardous based on the metal leaching potential.
The results from strong and weak acid digestions were compared to better understand the types and quantity of materials that have the potential to leach from the samples. This research may be used to develop best management practices for hydraulic fracturing residual solids.Master of Science
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鄧善均 and Shin-kwan Andrew Tang. "Analysis of di(2-ethylhexyl) phthalate in polyvinyl chloride and monosodium glutamate in foodstuff using high performance liquidchromatography and the investigation of microwave digestion method forpaint analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31209452.
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Swann, Christina Talbot. "Evaluating the Leachability of Elements from Residuals Generated by Hydraulic Fracturing in Marcellus Shale." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/73707.
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The purpose of this research was to characterize the residual solids produced from hydraulic fracturing operations in the Marcellus Shale region. Four field samples were evaluated: drilling mud, treated sludge from the chemical treatment of process water, solids from the gravity settling of produced water, and sludge solidified prior to disposal in a municipal landfill. Cement kiln dust (CKD), used for solidification, was also considered in this study. All samples were subjected to a variety of laboratory techniques to determine their elemental composition and the potential for the elements to leach from the landfill. Strong acid digestion using a 3:1 combination of nitric acid to hydrochloric acid in a microwave with closed vessels was used to determine overall elemental composition. Leaching experiments were performed with de-ionized water and acetic acid (0.57%, pH 2.88) in an attempt to respectively evaluate the effects of weak and strong fluids that might be encountered by the residuals in landfill environments. Elements were analyzed by means of ICP-MS revealing the increased tendency for alkali metals, alkaline earth metals and halogens to leach. Leachablility was further increased for metals when exposed to acidic conditions.Master of Science
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Tang, Shin-kwan Andrew. "Analysis of di(2-ethylhexyl) phthalate in polyvinyl chloride and monosodium glutamate in foodstuff using high performance liquid chromatography and the investigation of microwave digestion method for paint analysis /." [Hong Kong : University of Hong Kong], 1989. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12720434.
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Tukur, Aminu. "Antimony and acetaldehyde migration from Nigerian and British PET bottles into water and soft drinks under typical use conditions : concentration of migrants and some trace elements in polyethylene terephthalate and in bottled contents." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5369.
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Also aged bottles are safer to use than new bottles because their chemical leaching was found to be lower than that of new bottles. This study recommends the reassessment of the absence of international guidelines for acetaldehyde in water and foods. The study also recommends that the amount of acetaldehyde that can be added to soft drinks as flavouring agent should be below the specific migration limit (SML) for migration of acetaldehyde from PET bottle into bottle contents. This is essential since the SML was designed to ensure that exposure to acetaldehyde, as a result of intake of bottled water and soft drinks in PET bottles, is below the tolerable daily intake (TDI) for acetaldehyde. As antimony was reported to go beyond the safe limits in some Nigerian bottled water and soft drinks after 11 months of storage this study discourages the use of bottle contents stored for a very long time.
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Nobre, Eva Michelly Carvalho Santana. "PROCEDIMENTO VOLTAMÉTRICO OTIMIZADO PARA DETERMINAÇÃO DE Ni2+ EM AMOSTRAS PRÉ-TRATADAS DE BIODIESEL, USANDO ELETRODO MODIFICADO COM FILME DE MERCÚRIO." Universidade Federal do Maranhão, 2011. http://tedebc.ufma.br:8080/jspui/handle/tede/920.
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Previous issue date: 2011-07-04The presence of metals in biodiesel can be related to raw material, the process used to obtain biodiesel or its storage and can cause reactions of oxidation, corrosion and clogging engines, besides causing risks to human health and the environment. In this paper, we propose a procedure based on voltammetric experimental conditions suitable for the determination of Ni2+ ion in biodiesel (B100) through Square Wave Adsorptive Stripping Voltammetry, using the mercury film electrode prepared ex situ. First, the mercury film was prepared and then was conducted the analysis of a biodiesel pre-treated (digested) sample. The sample digestion was performed with microwave oven in a closed system in the presence of ultra-pure nitric acid and hydrogen peroxide. After this, ammonia buffer 0.01 mol L-1 pH 9.23 and NaOH 0.46 mol L-1 was added into the cell to adjust the pH of the sample to a final value of approximately 9.2. Finally, the chelator dimethylglyoxime (DMG) 0.01 mol L-1 was added, which acts as a complexing element to capture the Ni2+ ion. Next, several voltammetric experiments, in the absence and presence of increasing aliquots of biodiesel and standard solution of the metallic ion, were performed to optimize the analysis conditions. The results indicate that the Square Wave Adsorptive Stripping Voltammetry (VAdRSWV) appeared suitable for measurements of trace metal in Biodiesel (B100) in concentrations up to 10-8 mol L-1. The experiments carried out by successive addition of aliquots of a standard solution of Ni2+ ions provided a linear response of peak current with the concentration of metal ion. Each sample of biodiesel was analyzed in triplicate, with very satisfactory results from the analytical point of view, once we were dealing with trace element analysis, especially in terms of accuracy (recovery 105%) and precision (RSD 9.61%) for the Ni2+ metal ion, using a confidence limit of 98%.
A presença de metais no biodiesel pode estar relacionada com a matéria-prima, com o processo utilizado para a obtenção do biodiesel ou com sua estocagem e pode provocar reações de oxidação, corrosão e entupimento em motores, além de causar riscos à saúde humana e ao meio ambiente. Neste trabalho, é proposto um procedimento voltamétrico com base em condições experimentais adequadas para a determinação do íon Ni2+ em biodiesel (B100) por Voltametria Adsortiva de Redissolução no modo Onda Quadrada, usando o eletrodo de Filme de Mercúrio preparado no modo ex situ. Inicialmente, o filme de mercúrio foi preparado e a seguir realizaram-se as análises com amostra de biodiesel pré-tratada (digerida). A digestão da amostra foi realizada com forno de micro-ondas em sistema fechado, na presença de ácido nítrico ultra-puro e peróxido de hidrogênio. Após essa etapa, foi adicionado tampão amônia 0,01 mol L-1 pH 9,23 e NaOH 0,46 mol L-1 na célula para ajustar o pH da amostra para um valor final de aproximadamente 9,2. Por fim, foi adicionado o quelante dimetilglioxima (DMG) 0,01mol L-1 que funciona como complexante para captura do íon Ni2+. Após esta etapa, vários experimentos voltamétricos, na ausência e presença de alíquotas crescentes de biodiesel e solução padrão do íon metálico foram realizados para otimizar as condições de análise. Os resultados obtidos indicam que a Voltametria Adsortiva de Redissolução no modo Onda Quadrada (VAdRSWV) apresentou resultado satisfatório para medidas do metal traço em Biodiesel (B100), em concentrações de até 10-8 mol L-1. Os experimentos realizados pela adição sucessiva de alíquotas de uma solução padrão do íon Ni2+ proporcionaram uma resposta linear da corrente de pico com a concentração do íon metálico. Cada amostra de biodiesel foi analisada em triplicata, apresentando resultados bastante satisfatórios do ponto de vista analítico por se tratar de análise de elementos traços, principalmente, em termos de exatidão (recuperação de 105 %) e precisão (DPR de 9,61%), para o íon metálico Ni2+, utilizando um limite de confiança de 98%.
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Albuquerque, Luiza Gimenes Rodrigues. "Estudo de métodos para determinação total, fracionamento e análise de especiação elementar em fertilizantes base orgânica." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-12042018-102440/.
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A aplicação de fertilizantes aos solos é frequente devido à atual demanda mundial pela produção de alimentos e às projeções feitas para o futuro. Fertilizantes orgânicos têm sido uma opção amplamente explorada devido ao seu preço, possibilidade de reuso de resíduos agriculturais e urbanos, além do caráter sustentável. Podem ser provenientes de diversas origens como lodo de esgoto, estercos e restos de animais e vegetais submetidos a processos de compostagem. Neste trabalho, foi desenvolvido método para determinação elementar total em fertilizantes orgânicos, substratos e condicionadores de solo, e realizados estudos de fracionamento e análise de especiação em fertilizante orgânico. Assim, foi realizada a caracterização geral das amostras com fracionamento por tamanho de partícula, análises dos teores de C e N, difração de Raios-X e determinação elementar total. Para este último, foi desenvolvido método de digestão assistida por radiação micro-ondas, com análise por ICP OES. O procedimento foi otimizado para diferentes misturas ácidas, as quais foram avaliadas quanto aos erros relativos para diversos elementos em CRM de lodo de esgoto, utilizando PCA como ferramenta estatística. A mistura escolhida, constituída por 3 mL HNO3 + 1 mL HBF4 + 2 mL H2O, foi utilizada para digestão das amostras. Apenas a concentração total não traz informações a respeito da mobilidade e disponibilidade dos elementos, então estudos de fracionamento elementar também foram realizados. Na primeira abordagem foi executado fracionamento por tamanho de partícula, no qual foi observado que quanto menor o tamanho de partícula menor o teor de C e maior o teor de N, e maior a concentração de micronutrientes e contaminantes (Cr, Cu, Fe, Mn, Pb e Zn), indicando que estes elementos podem estar mais associados a frações com mais características inorgânicas e maior teor de humificação (dado pela razão C/N). A segunda abordagem refere-se à associação dos elementos com diferentes componentes da matriz seguindo o procedimento de extração sequencial do BCR e extrações em etapa única para avaliar a mobilidade, sendo os extratos analisados por ICP-MS. O elemento Cr mostrou baixa mobilidade e bioacessibilidade. Cu está associado, principalmente, à fração orgânica da matriz, porém também pouco móvel. Fe e Pb também apresentaram baixa mobilidade e associados, principalmente, a óxidos da amostra. Mn e Zn mostraram alta mobilidade, sendo também associados a matéria orgânica e aos óxidos. A análise de especiação dos extratos obtidos foi realizada por SEC-ICP-MS, de modo a investigar a associação dos elementos extraídos com ácidos húmicos e fúlvicos. Nenhum sinal de Cr estava relacionado com a matéria orgânica, enquanto que os elementos Cu, Fe e Pb mostraram associação com ácidos húmicos. Mn apresentou espécies associadas a ácidos fúlvicos, enquanto que o Zn, não está associado a espécies orgânicas.Fertilizers are frequently applied to soils due to actual global food demand and its future projections. Organic fertilizers have been extensively employed due to its price, as a reuse possibility to agricultural and urban wastes, and its sustainable character. They can be prepared from various sources, such as sewage sludge, manure and plants and animal scraps, submitted to composting process. In this work, it was developed a total elements determination method, as well as fractionating studies and speciation analysis of organic fertilizer. Thus, organic fertilizer samples were generally characterized using particle size fractionating, C and N content analysis, X-Ray diffraction and total elements determination. To the last, it was developed a sample preparation method by microwave-assisted digestion and ICP OES analysis. Digestion procedure was optimized using various acid mixtures, which were evaluated due to its relative errors related to sewage sludge CRM values, using PCA as a statistical tool. The chosen acid mixture constituted of 3 mL HNO3 + 1 mL HBF4 + 2 mL H2O was applied to samples digestion and their total elements determination. As total concentration is not enough to predict elements mobility and bioavailability, fractionation studies were conducted. The first approach was the particle size fractionation, were it was observed that the smaller the particle size the higher the micronutrients and contaminants concentration (Cr, Cu, Fe, Mn and Zn), along with lower C contents and higher N contents, indicating that these elements are associated with inorganic fractions, or with highly humified compounds (due to the lower C/N ratio). A second approach refers to elements association with various matrix components, using BCR and single-step extraction procedures to investigate elements mobility and bioavailability, with ICP-MS analysis of extracts. Cr was poorly mobile and bioavailable. Cu was bound to organic fraction, but also poorly mobile and bioavailable. Fe and Pb were also weakly mobile, and were mostly associated with oxides on matrix. Mn and Zn were greatly mobile and bioavailable, and were also mainly associated with oxides on matrix. Speciation analysis of extract was performed by SEC-ICP-MS, investigating elements association with humic and fulvic acids on previous extracts. Cr could not be associated with any humic substance, as expected with previous extractions results. Cu, Fe and Pb had identifiable species associated with humic acids, while Mn was associated with fulvic acids. Zn, even though high mobile, was not associated with any organic species.
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Moraes, Diogo Pompéu de. "Decomposição de elastômeros por combustão iniciada por microondas em sistema fechado." Universidade Federal de Santa Maria, 2006. http://repositorio.ufsm.br/handle/1/10376.
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A rapid digestion procedure for further determination of inorganic elements in carbon black-containing elastomers has been developed using sample combustion in closed quartz vessels with oxygen pressure. Microwave radiation was used for the ignition step. Samples containing high levels of carbon black (up to 30%) were digested using the proposed procedure: nitrile-butadiene rubber (NBR) and ethylenepropylene-diene monomer (EPDM). A quartz device was used simultaneously as a sample holder and for the protection of vessel cap. Sample was pressed as pellet
and placed together a small piece of low-ash content paper in the holder. Ammonium nitrate solution (50 ml of 50% m/v) was added to the paper as aid for ignition. The influence of the absorption solution (nitric acid or water) and the necessity of an additional reflux step were evaluated. Determination of Al, Fe, Mn, Sr and Zn was performed by inductively coupled plasma optical emission spectrometry. A reference method (ASTM D 4004-064) based on conventional dry ashing followed by flame atomic absorption spectrometry determination was used for results comparison (Mn and Zn). Results were also compared to those obtained by using wet acid digestion in closed systems. As no certified reference elastomers were available analyte spikes were made for NBR and EPDM digests. Concentrated and diluted (4 mol l-1) nitric
acid, with 5 min for reflux step after the combustion process, gave better recoveries for all analytes (from 97 to 101%). For Al and Mn recoveries were bellow 90% for both open and closed vessels using HNO3 and H2SO4 mixture. For dry ashing
quantitative recoveries were found only for Zn (for Al recovery was 14%). Residual carbon content was bellow 0.5% for the proposed procedure. With the proposed procedure further determination of Al, Mn, Sr and Zn is feasible with only the combustion step but for Fe a reflux with diluted HNO3 was necessary. Then, using the proposed procedure complete sample digestion is obtained is less time than other procedures and no need of concentrated acids was considered necessary.Neste trabalho foi proposto um procedimento para a decomposição de elastômeros (Etileno-propileno-dieno monômero e borracha do tipo nitrílica) em sistema fechado por combustão iniciada por microondas. Após a decomposição das amostras foram determinados Al, Fe, Mn, Sr e Zn por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES). Para Mn e Zn, a metodologia proposta foi comparada com a metodologia oficial ASTM D 4004-064 para a decomposição de elastômeros e posterior determinação por espectrometria de absorção atômica com chama (F AAS). Os resultados obtidos foram concordantes com a metodologia oficial para a determinação de Mn e Zn. Adicionalmente, ensaios de recuperação foram empregados para Al, Fe, Mn, Sr e Zn para avaliação do método proposto. Além disso, foram estudados dois tipos de solução absorvedora (H2O e HNO3 diluído e concentrado), além da variação do emprego do tempo de aquecimento com microondas (1 min ou 5 min). Entretanto, para se obter recuperações quantitativas para todos os elementos, em ambas as amostras, é necessário que se utilize HNO3 4 molar ou concentrado como solução absorvedora e uma etapa adicional de refluxo ao procedimento de combustão. Cabe destacar que outras condições podem ser utilizadas, como por exemplo, HNO3 concentrado sem a etapa adicional de refluxo, entretanto nestas condições as recuperações podem ser quantitativas para todos os elementos com exceção de ferro. Cabe salientar que, o procedimento proposto foi comparado com o procedimento da norma ASTM, onde os valores encontrados para Zn e Mn nas amostras foram concordantes pelas duas técnicas. O teor de carbono residual é baixo e comparável aos do sistema de decomposição por via seca em mufla. Desta forma é possível propor este procedimento para a decomposição de elastômeros do tipo EPDM e NBR, sendo adequado para a posterior determinação de Al, Fe, Mn, Sr e Zn.
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Consonni, João Luiz. "Valores de referencia de elementos inorgânicos potencialmente tóxicos em solos do Estado de São Paulo." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/8023.
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The use of guiding values has been the practice in countries with tradition in monitoring the quality of natural resources. The first step of a pollution monitoring program is to establish the natural concentrations of potentially toxic elements (PTEs) in uncontaminated soil to the development of background values. Mean values of total PTE concentration in worldwide are very heterogeneous and resulting from different soils, extraction methods and techniques of analytical determination. The background values recommended by CETESB were obtained from samples of 13 soils, submitted to USEPA SW 846 3050 protocol, whose PTE contents were determined by atomic absorption spectrometry. The objective of this work was to contribute to the improvement of background values of Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, V and Zn in tropical soils, using topsoil samples (0-20 cm) of 30 representative soils of State of São Paulo, Brazil, collected in areas without human disturbance. The soil samples were submitted to the USEPA SW 846 3051, 3051 A and 3052 protocols, with microwaveassisted acid digestion. Natural contents of PTEs were determined by inductively coupled plasma optical emission spectrometry (ICP OES). Extraction protocols were evaluated using the certified soil sample NIST SRM 2709 San Joaquin. Arithmetic means were adopted to describe the central tendency and the variation of results from the different acid digestions and to set the background values into 75 and 90 percentiles. Regardless the extraction method, the average contents of EPT were in the following range of variation (mg kg-1): Al - 27118-42865; Ba - 78-101; Fe - 6318- 35888; Cd - ND - 2.2; Co - 18 to 37; Cr - 39-59; Cu - 43-61; Mn - 176-623; Ni - ND - 61; V - 111-193 and Zn - 63 to 68. The contents of Al, Co, Cu, Fe, Mn, V and Zn correlated with clay, amorphous (Feox) and crystalline (FeDCB) iron oxides contents. The method 3052 resulted in PTEs recovery levels within the limits considered acceptable for certified sample. Within recommended methods by CONAMA Resolution n.420 / 2009, the 3051 A was the best correlated with the method 3052 and was considered the protocol with high potential to improve soil background values. The new soil background values were (mg kg-1): a) percentile 75: Al - 66,700; BA - 68; CD - 1.53; Co - 16; Cr - 47; Cu - 20; Fe - 24,830; Mn - 333; Ni - 57; V - 66; Zn - 61; percentile 90: Al - 99 820; Ba - 113; CD - 1.78; Co - 30; Cr - 62; Cu - 32; Fe - 39 280; Mn - 480; Ni - 113; V - 119; Zn - 65. Since new background values differed from those currently practiced by CETESB, the use of ICP OES to determine natural PTE levels extracted by USEPA 3051 A, from a larger and more representative set of soils, supported the improvement of background values and may contribute to the improvement of the environmental risk assessment estimates for edaphoclimatical conditions of the State of São Paulo.
O emprego de listas com valores orientadores tem sido prática nos países com tradição no monitoramento da qualidade dos recursos naturais. A primeira etapa de um programa de monitoramento de poluição é o estabelecimento das concentrações naturais dos elementos potencialmente tóxicos (EPTs) em solos não contaminados, para a definição de valores de referência de qualidade (VRQs). Valores médios da concentração total de EPTs no âmbito mundial são muito heterogêneos e decorrem da diversidade dos solos, dos métodos de extração e das técnicas de determinação analítica. Os valores de referência preconizados pela CETESB foram obtidos de amostras de 13 solos, submetidas ao protocolo USEPA SW 846 3050, cujos teores foram determinados por espectrofotometria de absorção atômica (AAS). O objetivo deste trabalho foi contribuir para o aprimoramento dos VRQs de Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, V e Zn em solos paulistas, utilizando amostras superficiais (0-20 cm) de 30 solos representativos dos limites estaduais, coletadas em áreas isentas de perturbação antrópica. As amostras de solo foram submetidas aos protocolos USEPA SW 846 3051, 3051 A e 3052, com digestão ácida assistida por forno micro-ondas. Os teores naturais de EPTs foram determinados por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES). Os métodos de extração foram avaliados utilizando a amostra certificada de solo NIST SRM 2709 San Joaquin. Médias aritméticas foram adotadas para descrever a tendência central e a variação dos resultados provenientes das diferentes digestões e para definir os VRQs nos percentis 75 e 90. Independentemente do método de extração, os teores médios de EPTs apresentaram a seguinte amplitude de variação (mg kg-1): Al - 27.118 a 42.865; Ba - 78 a 101; Fe – 6.318 a 35.888; Cd – ND a 2,2; Co – 18 a 37; Cr – 39 a 59; Cu – 43 a 61; Mn – 176 a 623; Ni – ND a 61; V – 111 a 193; Zn – 63 a 68. Os teores de Al, Co, Cu, Fe, Mn, V e Zn correlacionaram-se com os teores de argila, de óxidos de ferro cristalinos (FeDCB) e de óxidos de ferro amorfos (FeOX) dos solos. O método 3052 resultou em teores percentuais de recuperação dentro dos limites considerados aceitáveis para a amostra certificada. Dentre os métodos recomendados pela Resolução CONAMA n.420/2009, o 3051 A foi o que melhor se correlacionou com o método 3052, sendo considerado o método com maior potencial para aprimorar os VRQs de solos do Estado de São Paulo. Os novos VRQs sugeridos para solos do Estado de São Paulo foram (mg kg-1): a) percentil 75: Al – 66.700; Ba – 68; Cd – 1,53; Co – 16; Cr – 47; Cu – 20; Fe – 24.830; Mn – 333; Ni – 57; V – 66; Zn – 61; percentil 90: Al – 99.820; Ba – 113; Cd – 1,78; Co – 30; Cr – 62; Cu – 32; Fe – 39.280; Mn – 480; Ni – 113; V – 119; Zn – 65. Os VRQs diferiram daqueles atualmente praticados pela CETESB, indicando que o uso do ICP OES para determinar teores naturais EPTs, extraídos pelo método USEPA 3051 A, a partir de um conjunto maior e mais representativo de solos, subsidiou o aprimoramento dos VRQs, podendo contribuir para a melhoria das estimativas de avaliação de risco ambiental para as condições edafoclimáticas do Estado de São Paulo.
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Gabriel, Coelho Nuno Miguel. "Application of Microwaves and Thermophilic Anaerobic Digestion to Wastewater Sludge Treatment." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22763.
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Anaerobic digestion of waste activated sludge can be improved if hydrolysis of particulate substrates is enhanced and available substrate is made more accessible by both breakup of the sludge matrix floc and rupture of the cell wall. Microwave (MW) pretreatment was suggested and studied as a way to improve digestion efficiency. The work done focuses on the effects of MW pretreatment on the characteristics of the sludge, due to thermal and athermal effects. It also evaluates the effects some process variables in the activated sludge process have on the pretreatment efficiency as well as the effect operating conditions in the downstream anaerobic digestion process have on the biodegradability efficiency of those sludges.
Effects of athermal and thermal MW radiation were measured by use of a customized MW oven capable of providing MW radiation with uncoupled thermal and athermal effects. Athermal radiation was capable of increasing substrate present in the soluble phase of sludge, and had a positive effect in the digestion of athermal samples. The increases in biogas production and substrate solubilisation were smaller in magnitude than the increases measured for MW thermal tests. Further refining of the tests with athermal and thermal sludge, involved separation by size class of the solubilized substrate by means of ultrafiltration (UF), and revealed that changes in particle size distribution were significant not only for MW thermal tests, but also for athermal tests, with a particular emphasis in proteins in athermal tests. These changes had an effect on the biodegradability of the sludges by class size, with thermally pretreated sludge producing more biogas for smaller particles size classes but also exhibiting more inhibition.
Tests were made with several combinations of sludge with different ages and subject to different MW pretreatment temperatures. The work showed that sludge age or solids retention time (SRT) has a significant effect on the pretreatment efficiency with maximum biogas improvements measured at different MW pretreatment temperatures depending on the SRT of the sludge tested, and with different behaviour for mesophilic and thermophilic digestion. Mesophilic tests showed greater improvements in terms of digestion effiency on average, but thermophilic tests showed more uniform performance, with a higher baseline efficiency. The presence of an optimum of MW pretreatment temperature and sludge SRT for maximal biogas production is more defined for mesophilic conditions than for thermophilic conditions.
Semi-continuous studies were conducted with several combinations of single and two stage mesophilic and thermophilic digestors treating MW pretreated sludge and non-pretreated sludge. Staging and thermophilic digestion allowed the maintenance of a stable digestion process with high biogas productions and high solids removal efficiencies with production of sludge with good bacteriological characteristics for an very low residence time (5 d).
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Almeida, Joseany de Moraes Santos. "PROCEDIMENTO ELETROANALÍTICO PARA DETERMINAÇÃO DE CÁLCIO EM BIODIESEL." Universidade Federal do Maranhão, 2013. http://tedebc.ufma.br:8080/jspui/handle/tede/980.
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Previous issue date: 2013-06-05Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Metal traces are often detected in biodiesel samples due to its presence in the raw materials or solubilization during its manufacturing. Thus, this work aims to propose an electroanalytical methodology for the direct determination of Ca²⁺ in biodiesel using with a glassy carbon electrode. The metal quantification was developed according to Anodic Stripping Voltammetry Mode square-wave (SWASV) technique applying EDTA as the complexing agent. Thus, all samples were pretreated according to wet acid digestion processing and microwave radiation. Therefore, a solution of 4 mL of ultrapure nitric acid (HNO₃), 2 mL of hydrogen peroxide (H₂O₂) and 1 mL deionized water were added to 300 mg sample of biodiesel. Later, such mixtures was thermal treated at 90 °C using 300 W (10 min) and 450 W (5 min) of microwave radiations. The analytical determinations were carried out using ammonium buffer (0.01 mol Lˉ¹, pH = 9.4) as supporting electrolyte and EDTA (1x10ˉ² mol Lˉ¹) as ligand. The optimized voltammetric conditions were EDEP = -1000 mV; tpre = 120 s; Frequency = 30 Hz; Amplitude = 100 mV and ΔEstep = 15 mV. The accuracy was verified by recovery tests. In all cases, the metal quantizations were statistically consistent considering the t-test student for a confidence level of 95%. The CV values were lower than 11%, the recoveries were between 102.9% to 102.4% and the values of the detection limits were 1.9 x 10ˉ⁸ and 1.6 x 10ˉ9 mol Lˉ¹ for the samples, showing good accuracy and sensitivity of the proposed method. The values obtained for the samples ranged from 2.8 x 10ˉ⁸ ± 5.0 x 10ˉ⁸ mol Lˉ¹ and 3.4 x 10ˉ7 ± 5.0 x 10ˉ9 mol Lˉ¹ for Ca²⁺ in evaluated biodiesel.
A presença de metais no biodiesel está diretamente relacionada com a matéria-prima utilizada e também com o processo utilizado para a obtenção do biodiesel. Este trabalho apresenta um procedimento eletroanalítico simples para a determinação direta de Ca2+ em biodiesel com um eletrodo de carbono vítreo. A determinação foi feita com a técnica Voltametria de Redissolução Anódica no modo onda quadrada (SWASV), usando-se o EDTA como agente complexante. As amostras de biodiesel foram submetidas a um processo de digestão ácida por via úmida por radiação, em sistema fechado, com o uso de um microondas. O procedimento para digestão das amostras foi realizado pela adição de 4 mL de ácido nítrico ultrapuro (HNO₃), 2 mL de peróxido de hidrogênio (H₂O₂) e 1 mL de água deionizada em 300 mg de amostra de biodiesel. As amostras foram aquecidas a uma temperatura de 90 oC, durante 10 minutos, em potência de 300 W e 5 minutos em potência de 450 W. As determinações foram feitas utilizando-se tampão amônio (0,01 mol Lˉ¹), pH 9,4, como eletrólito suporte e EDTA 1 x 10ˉ² mol Lˉ¹ como ligante, nas seguintes condições: potencial de deposição (Edep) = -1000 mV; tempo de pré-concentração (tpré) = 120 s; frequência (Freq.) = 30 Hz; amplitude (Amp) =100 mV e potencial de escada (ΔEescada) =15 mV. A exatidão do método foi verificada através de testes de recuperação. Os resultados foram concordantes, estatisticamente, considerando o teste-t de student para um nível de confiança de 95%. Os valores de CV foram menores que 11%, as recuperações foram entre 102,9 % e 102,4 % e os valores dos limites de detecção foram de 1,9 x 10ˉ⁸ e de 1,6 x 10ˉ9 mol Lˉ¹ para as amostras analisadas, mostrando boa exatidão e sensibilidade do método proposto. Os valores obtidos para as amostras analisadas situaram-se entre 2,8 x 10ˉ6 ± 5,0 x 10ˉ⁸ mol Lˉ¹ e 3,4 x 10ˉ7 ± 5,0 x 10ˉ9 mol Lˉ¹ para Ca²⁺ nas amostras de biodiesel.
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Ghisi, Mirela. "Determinação de Cu e Fe em Biodiesel por Espectrometria de Absorção Atômica com Atomização Eletrotérmica e Estudo do Efeito Catalítico destes Metais sobre a Estabilidade Oxidativa do Biodiesel." Universidade Federal do Maranhão, 2011. http://tedebc.ufma.br:8080/jspui/handle/tede/918.
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Previous issue date: 2011-05-16Conselho Nacional de Desenvolvimento Científico e Tecnológico
The metals content in biodiesel is directly related with the raw material used and also with the utilized biodiesel production method. In this work, an evaluation of the main metals present in biodiesel samples from different sources was done. The qualitative analysis of the metal content was assessed using the Inductively Coupled Plasma Mass Spectrometry technique after sample digestion in microwave oven. The main metals identified in the analyzed biodiesel samples were Al, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr and Zn. Metals like Ag, As, Ba, Cd, Co, Tl and V have not significant presence in the samples. Among these, Cu and Fe were selected due to their relevance and importance in oxidative process of biodiesel, to the development of an analytical methodology to be used in the determination by Electrothermal Atomic Absorption Spectrometry, and also evaluate the effect of these metals over the oxidative stability of the soy biodiesel. The samples were prepared with tetramethylammonium hydroxide (TMAH), and the pyrolysis and atomization temperatures were optimized pyrolysis and atomization curves. The high pyrolysis temperature adopted, 1000 oC, certainly minimized potential interferences, but calibration had to be carried out with aqueous standard solutions in the presence of the TMAH. The detection limits in the sample (3s, n=10), were quite low 15 ng g-1 and 24 ng g-1 for Cu and Fe, respectively. Seven biodiesel samples, produced from different raw materials, including vegetable seed, waste frying oil and animal fat were analyzed. Accuracy was validated by applying the recovery test (recoveries from 105% to 120%) and through comparison with the obtained results by High Resolution Continuum Source Electrothermal Atomic Absorption Spectrometry. The precision, expressed by the relative standard deviation, was better than 3% for Cu and than 7% for Fe. Copper could be quantified in two and Fe in three of the seven samples. The biodiesel sample from fodder turnip was especially rich in the analytes in comparison to the other samples. The influence of metals Cu and Fe on soy biodiesel oxidative stability was evaluated by Rancimat method through induction period, according with the Standard EN 14112. The metals Cu2+ and Fe3+ were added to the biodiesel samples in the form of theirs salts, and different storage times of the samples were evaluated. Due to the catalytic behaviour of these metals, the oxidative stability of the samples was affected, even under low metal concentrations. Compared to Cu2+, the effect over the biodiesel stability was higher when Fe3+ was added.
A presença de metais no biodiesel está diretamente relacionada com a matéria-prima utilizada e também com o processo utilizado para a obtenção do biodiesel. Neste trabalho realizou-se uma avaliação dos principais metais presentes em amostras de biodiesel provenientes de diferentes fontes. A análise semi-quantitativa nas amostras de biodiesel foi realizada utilizando a técnica de Espectrometria de Massa com Plasma Indutivamente Acoplado após a digestão das amostras em micro-ondas. Os principais metais identificados nas amostras de biodiesel analisadas são Al, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr e Zn. Metais como Ag, As, Ba, Cd, Co, Tl e V não estão presentes em concentrações significativas nessas amostras. Em função de sua relevância e importância em processos oxidativos do biodiesel, selecionou-se Cu e Fe para o desenvolvimento de uma metodologia analítica para a determinação destes por Espectrometria de Absorção Atômica com Atomização Eletrotérmica e também a avaliação do efeito destes metais sobre a estabilidade oxidativa do biodiesel de soja. As amostras foram preparadas com hidróxido de tetrametilamônio (TMAH), e as temperaturas de pirólise e atomização foram otimizadas através de curvas de pirólise e atomização. A alta temperatura de pirólise adotada, 1000 oC, certamente ajudou a minimizar possíveis interferências; porém, a calibração teve de ser realizada com padrões aquosos na presença de TMAH. Os limites de detecção (3s, n = 10), na amostra, foram baixos, 15 ng g-1 e 24 ng g-1 para Cu e Fe, respectivamente. Sete amostras de biodiesel, produzidas de diferentes matérias-primas, incluindo óleos vegetais, óleo de fritura e gordura animal foram analisadas. A exatidão foi avaliada através do teste de recuperação (recuperações de 105% a 120%) e através da comparação com os resultados obtidos por Espectrometria de Absorção Atômica de Alta Resolução com Fonte Contínua e Atomização Eletrotérmica. A precisão, expressa pelo desvio padrão relativo foi melhor que 3% para Cu e que 7% para Fe. Cobre pôde ser quantificado em duas e Fe em três das sete amostras. A amostra de biodiesel proveniente do nabo forrageiro era especialmente rica nos analitos comparada às outras amostras. A influência dos metais Cu e Fe sobre a estabilidade oxidativa do biodiesel de soja foi avaliada pelo método Rancimat através do período de indução, de acordo com a Norma EN 14112. Os metais Cu2+ e Fe3+ foram adicionados nas amostras de biodiesel na forma de seus sais, e foram avaliados diferentes tempos de armazenamento das amostras. Devido ao efeito catalítico destes metais, a estabilidade oxidativa das amostras analisadas foi reduzida mesmo na presença de baixas concentrações dos metais. O efeito do Fe3+ sobre a estabilidade do biodiesel foi significativamente maior quando comparado ao Cu2+.
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Tarantino, Taiana do Bomfim. "Desenvolvimento de um procedimento alternativo para determinação de elementos traço em arroz empregando digestão assistida por micro-ondas com ácido nítrico diluído." reponame:Repositório Institucional da UFBA, 2012. http://www.repositorio.ufba.br/ri/handle/ri/11755.
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CAPES
O arroz (Oryza sativa) é um dos cereais mais produzidos e consumidos, sendo o alimento básico na dieta de mais da metade da população mundial. A digestão ácida assistida por radiação micro-ondas usando ácidos diluídos vem sendo bastante utilizada, principalmente, por reduzir a concentração ácida mantendo a eficiência da digestão, gerando menor volume de resíduo e diminuindo o fator de diluição antes da análise. A determinação dos teores de nutrientes é de grande relevância devido à capacidade nutricional do arroz, que pode conter espécies essenciais ou contaminantes a saúde humana. O objetivo deste trabalho foi propor um procedimento de digestão com HNO3 diluído empregando forno de micro-ondas com cavidade para determinação de macro, micro e elementos traço (As, Ca, Cd, Fe, K, Mg, Mn, Mo, P, Se, Zn) em amostras de arroz por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) e espectrometria de massas com plasma indutivamente acoplado (ICP-MS). Foi realizado um planejamento fatorial 32 e Box-Behnken e as variáveis investigadas foram: volume de HNO3 destilado, temperatura e tempo, ambos no último patamar do programa de aquecimento. As condições otimizadas foram 2 mL de HNO3 e temperatura de 200 ºC durante o tempo de 20 minutos. O volume de H2O2 30%, a massa e a granulometria da amostra foram fixados em 1,0 mL, 250 mg e 500 m, respectivamente. A exatidão foi avaliada com o material de referência certificado NIST 1568a e do teste de recuperação para os analitos investigados, que variaram entre 80,1 e 102,1 % e 96,6 e 109,8 %, respectivamente. A precisão foi verificada pelo desvio padrão relativo, sendo sempre inferior a 10%, inclusive no teste de repetitividade. O procedimento proposto foi aplicado na determinação dos elementos em 23 amostras de arroz submetidas a três tipos de processamentos (polido, parboilizado e integral). As faixas de concentração para os elementos traço, em μg g-1, foram: Al (<2,4-15,3); As (<0,2-0,32); Cd (<0,004–0,017); Cu (0,2-2,2); Fe (<0,2- 17,4); Mn (2,8-34,9); Mo (<0,20-0,81); Se (<0,2-0,271) e Zn (4,8-14,9). De modo geral, os resultados obtidos encontram-se concordantes com as faixas de concentração descritas na literatura.
Salvador
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Lopes, Monica Aparecida Ferreira de Souza Bindes Gomes. "Digestão nitro-sulfúrica de fígado de peixe Mugil liza em forno de micro-ondas com radiação focalizada para determinar elementos de interesse ambiental por ICPMS." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2771.
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O presente estudo propõe uma metodologia para dissolução de tecidos biológicos em sistema de micro-ondas com radiação focalizada e posterior análise elementar por espectrometria de massas com plasma acoplado indutivamente (ICPMS). Foram determinados os elementos arsênio (As), cádmio (Cd), cobre (Cu), chumbo (Pb), níquel (Ni), vanádio (V) e zinco (Zn). A matriz nitro-peroxo-sulfúrica foi comparada com outra sem o ácido sulfúrico e apresentou melhor padrão de recuperação (acima de 90%) na quantificação dos elementos certificados no material de referência TORT-2. As interferências causadas pela presença do ácido sulfúrico na matriz digestora foram contornadas com o uso da célula de reação/colisão com gás hélio (He) e adição deste ácido na composição da curva de quantificação. O ganho analítico proporcionado pelo método de digestão em matriz sulfúrica, em sistema não pressurizado, baseia-se no incremento da temperatura reacional e na degradação completa da matéria orgânica. As digestões tradicionalmente realizadas para quantificação por ICPMS, compostas unicamente de ácido nítrico (HNO3) e peróxido de hidrogênio (H2O2), não apresentam a mesma eficiência na degradação da matéria orgânica em sistemas abertos. Por fim, este método foi aplicado satisfatoriamente em amostras de tecido hepático de peixe Mugil liza (tainha), comprovando sua eficiência em monitorar a bioacumulação, utilizando-se da sensibilidade da técnica multielementar de ICPMSThis study proposes a methodology for dissolution of biological tissues in microwave system with focused radiation and subsequent elemental analysis by mass spectrometry with inductively coupled plasma (ICPMS). The elements arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni), vanadium (V) and zinc (Zn) were identified and quantified. The nitro-peroxo-sulfuric acid matrix was compared to another without sulfuric acid and showed better recovery (above 90%) in the quantification of elements in certified reference material TORT-2. The interferences caused by the presence of sulfuric acid in digesting matrix were bypassed by the use of ORS (octapole reaction system) with helium (He) gas and the addition of this acid in the composition of the quantification curve. The gain provided by the analytical method of digestion with sulfuric acid matrix in non-pressurized system, is based on increasing the reaction temperature and the complete degradation of organic matter. Digestions traditionally performed for quantification by ICPMS, composed only with nitric acid (HNO3) and hydrogen peroxide (H2O2), are not as efficient in the degradation of organic matter in open systems. Finally, this method was satisfactorily applied in samples of liver tissue of fish Mugil liza (mullet), proving its effectiveness in monitoring the bioaccumulation, using the sensitivity of multielemental ICPMS technique
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Shan, Tan Chun. "Uso de microfrascos de digestão em forno de microondas focalizadas como uma alternativa para a preparação de amostras." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-15022018-113536/.
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Este trabalho propõe o uso de microfrascos de polipropileno adaptados a um forno de microondas focalizadas como um procedimento alternativo para a preparação de amostras. O pré-tratamento de amostras em microfrascos digestores agrega algumas características importantes como aumento da freqüência analítica, pequena massa de amostra e baixo consumo de reagentes. A eficiência do sistema de digestão foi verificada com o desenvolvimento de metodologia para a determinação de cobre, ferro, manganês, selênio e zinco em cabelo por espectrometria de absorção atômica com atomização por chama ou eletrotérmica em forno de grafite. Os elementos selecionados são essenciais para os seres humanos e são indicadores nutricionais e do bom funcionamento enzimático. O sistema de digestão é constituído de um forno de microondas focalizadas e um tubo de vidro com 30 cm de comprimento e 4 cm de largura, ao qual são colocados quatro ou cinco microfrascos de polipropileno com capacidade para respectivamente 4,0 mL e 2,0 mL. Esses microfrascos foram adaptados a um suporte de Teflon® e fixado a uma haste de vidro, facilitando a introdução e retirada do interior do tubo de vidro. O sistema proposto possibilitou uma drástica redução no tempo de preparo de amostra e melhor eficiência de decomposição (menor teor de carbono residual) em comparação com os procedimentos convencionais. O sistema \"quase fechado\" associado a baixas temperaturas atingidas evitou perdas de elementos por volatilidade, além de apresentar uma ótima homogeneidade de aquecimento entre os microfrascos. A exatidão da metodologia foi verificada através de ensaios de recuperação da análise de um material de referência certificado (IAEA-086) e da análise de amostra com adição e recuperação dos analitos apresentando recuperações de 90 a 103%.In this work the use of polypropylene vials adapted at focused m1crowaves, as alternative method for sample preparation is proposed. The sample pre-treatment in digestion vials include some desirable characteristics like increase of analytical frequency, low sample mass and low reagents consumption. To check the efficiency of the digestion system the development of a methodology for copper, iron, manganese, selenium and zinc determination using graphite furnace or flame atomic absorption spectrometry was performed. The selected elements are essential for human individual, nutritional indicators and required for enzymatic working. The digestion system is constituted of a focused microwave oven, a glass tube with 30 cm length and 4 cm width, where are setting four or five polypropylene vials with capacity for 4.0 mL and 2.0 mL, respectively, through a Teflon® support assisted by glass haste. The proposed system allowed a drastic reduction of sample preparation time and improved the decomposition efficiency (lower carbon residual content) comparing with conventional methods. The \"almost closed\" system associated with the low temperature avoids elements losses and improve heating homogeneity among the vials. The accuracy of the methodology was ascertained through good recoveries for a certificate reference material (IAEA-086) analysis and good recovery of spiked sample analysis, presenting recovery 90 to 103%.
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Mesquita, Glenda Máris. "Metodologias de preparo de amostras e quantificação de metais pesados em sedimentos do Ribeirão Samambaia, Catalão-GO, empregando Espectrometria de Absorção Atômica." Universidade Federal de Goiás, 2014. http://repositorio.bc.ufg.br/tede/handle/tede/4128.
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Ensuring water quantity and quality for all human beings has been a very discussed topic nowadays. The River Samambaia, watershed that supplies the city of Catalão, has been suffering with anthropogenic actions and the consequences of human intervention. To evaluate the quality of water may be used: water, particulates and sludge. The sediments can store dangerous substances and then can act as a secondary source of pollution by releasing contaminants into the aquatic environment. Within this context, the aim of this study was to evaluate the potential for contamination and the quality of the River Samambaia, located in Catalão-GO. For this, samples of water and sediment were collected at seven sampling sites along the river and the metals arsenic, cadmium, lead, chromium, manganese and nickel, which are considered toxic, were quantified. Was also performed, on the sampling sites, the analysis of physico-chemical water parameters: pH, conductivity, dissolved oxygen, temperature and salinity. For the extraction of metals fixed in the sediment samples was employed three methods of opening: ultrasound assisted extraction, digestion in digester block and microwave digestion. The quantification of metals was done by Atomic Absorption Spectrometry, by Flame or by Electrothermal Atomization in Graphite Furnace. The three methods opening samples used were effective, but the microwave digestion excelled in all cases. Among the physico-chemical parameters analyzed, pH showed values outside those permitted by law in all sampling points and dissolved oxygen showed the value below allowed only in point 7. In measurements of metals in water samples, cadmium, lead and chromium showed concentrations above the maximum allow by CONAMA. Already for the quantification of metals in the sediment samples, only chromium showed a concentration above the permitted limits. The results presented here indicate that human activities carried out in the river have contributed to adverse effects on local biota and humans.
A garantia de água com quantidade e qualidade para todos os seres humanos tem sido um assunto muito abordado na atualidade. O Ribeirão Samambaia, manancial que abastece a cidade de Catalão, vem sofrendo com as ações antrópicas e com as consequências dessa intervenção humana. Para avaliar a qualidade da água podem ser utilizados: água, materiais particulados e sedimentos. Os sedimentos podem estocar substâncias perigosas e, então, atuar como uma fonte secundária de poluição pela liberação de contaminantes no meio aquático. Dentro desse contexto, o objetivo deste trabalho foi avaliar o potencial de contaminação e a qualidade do Ribeirão Samambaia, localizado em Catalão-GO. Para isso, foram coletadas amostras de água e de sedimento em sete pontos de amostragem ao longo do ribeirão e os metais arsênio, cádmio, chumbo, cromo, manganês e níquel, os quais são considerados tóxicos, foram quantificados. Também foi realizada, nos locais de amostragem, a análise dos seguintes parâmetros físico-químicos da água: pH, condutividade, oxigênio dissolvido, temperatura e salinidade. Para a extração dos metais fixados nas amostras de sedimento foi empregado três métodos de abertura: extração assistida por ultrassom, digestão em bloco digestor e digestão em forno de microondas. A quantificação dos metais foi feita por Espectrometria de Absorção Atômica, por Chama ou por Atomização Eletrotérmica em Forno de Grafite. Os três métodos de abertura de amostras utilizados se mostraram eficientes, porém a digestão em forno de microondas se destacou em todos os casos. Dentre os parâmetros físico-químicos analisados, o pH apresentou valores fora do permitido pela legislação em todos os pontos de amostragem e o oxigênio dissolvido mostrou valor abaixo do permitido apenas no ponto 7. Nas quantificações dos metais nas amostras de água, cádmio, chumbo e cromo apresentaram concentrações acima do limite máximo permito pelo CONAMA. Já para as quantificações dos metais nas amostras de sedimento apenas o cromo apresentou concentração acima do permitido. Os resultados apresentados nesse trabalho indicam que as atividades antrópicas realizadas no ribeirão têm contribuído com efeitos negativos para biota local e aos seres humanos.
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Huang, Yu-Shan, and 黃鈺珊. "Study of Microwave Effect on Enzymatic Digestion." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/36355582579527304874.
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Chen, Chih-Hao, and 陳志豪. "Microwave-Assisted Protein Digestion and Qualitative Analysis." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/46845598186919982420.
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Tasi, Chin-Lian, and 蔡錦蓮. "Using microwave digestion for pretreatment of lead, manganese." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/03878241170353561076.
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碩士高雄醫學院
職業安全衛生研究所
86
Lead, manganese and arsenic are widely used in industry. However, long-term exposure to the metals may induce pathophysiological changes in workers.The environmental monitoring of these metals is used as an index of earlyexpoure risk. One previous 5 year study has shown increasing levels of bloodlead in workers taking place over 5 years in a lead battery factory, while leadin their environment assessment remained normal. Generally, a wet digestionmethod involving a heater is used to the pretreatment of lead, manganeseand arsenic. However, this method evaporates the solutions,wastes time andseems to be somewhat hazardous. So, our study was to comparean alternativeprocedure using microwave digestion with heater digestion in sample pretreatmentfor analysis of heavy metals in air samples of the workplace. The methods were taken from the NIOSH Manual of Analytical Methods: Elements by ICP 7300,Arsenic 7900, and Lead by Flame-AAS 7082.,and SOP :Arsenic 3002, Lead 3009,Manganese 2303. The selected filter was SKC MCE 37mm 0.8 μ m, P/N 255-5 forthe prepared sample. The standard solution concentration refersto the 2 TLV and 1/2 TLV added to the filter, which was then air dried.This dried concentrationwas completely digested by acid prior to analysis byflame-AAS and HG-AAS.The results of this study show that the wet digestion by both heater andmicrowave had average recovery rate of lead, manganese and arsenic are more than 90 %.Using the heater , the digested solution volume was 11 ml, however usingthe microwave, the volume was 3 ml, saving four times the acid solution volume. Digestion by heater took 4 to 5 hours, but digestion by microwave only took5 to 15 min, saving five times the time. The same results wereobtained in both the lead factory particle and in the laboratory with standard solutionaddition to cellulose filter.Our study shows the using a microwave for wet digestion is preferable to a heater in the pretreatment of particles for for analysis heavy metal particle in the workplace.
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Kao, ChengChing, and 高澄慶. "Determination of heavy metals in harbor sediments by open system digestion and microwave-assisted digestion." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/48519201562168843322.
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碩士國立高雄海洋科技大學
海洋環境工程研究所
100
This research focuses on different characteristics of sediment, took 20 samples in Kaohsiung Harbor, including estuaries, waterways and harbors, to determine of heavy metals (copper, zinc, nickel, lead, chromium, cadmium, silver, mercury, arsenic) content with the open system digestion (OSD) and microwave-assisted digestion (MAD). Base on the result, evaluate the difference between the two digestion procedures on the metal content. Furthermore, evaluate to the impact factor between OSD and MAD. According the result of analysis, detection limits of OSD and MAD range from 0.03 mg/kg (Hg) - 2.08 mg/kg (Pb) and 0.02 mg/kg (Hg) - 2.18 mg/kg (Pb), there are no significant differences between all the metal. Duplicate sample analysis of OSD and MAD range from 2.5±2.6% (Cr) - 12±2.3% (Ag) and 2.9±2.2% (Pb) - 8.8±0.1% (Ag), the metal all in the control, but MAD is lower than OSD about 2.0 - 5.6%. Spiked sample analysis of OSD and MAD range from 81±3.5% (Hg) - 111±1.7% (Pb) and 91±5.5% (Cr) - 102±9.1% (Cu), the metal all in the control, but MAD is better than OSD about 9 - 21%. Certified reference material analysis range from 71 - 90% and 90 - 125%, the recoveries of MAD are higher than OSD about 19 - 35%. It's possible that MAD use a variety of digestive, so that sediment mineral digest more complete. Determination of metal concentrations based on OSD and MAD, the result of analysis range from 0.5±0.2 mg/kg (Cd) - 352±572 mg/kg (Zn) and 0.4±0.2 mg/kg (Cd) - 399±597 mg/kg (Zn), the recoveries of MAD are higher than OSD. The level of differences between OSD and MAD range from Hg (118±18%) >As (67±32%) >Cr (45±33%) >Cu (36±21%) ≅Cd (28±25%) >Zn (21±21%) ≅Pb (21±25%) ≅Ag (22±16%) >Ni (18±11%). Mercury have a large number of volatile in open acid digestion resulting in difference.The correlate test of the sediments characteristics to the RSD of OSD and MAD shows that, water content and organic matter are significant correlated with Copper, zinc, nickel, lead, chromium and silver. It's possible that one of the main impact factor to the difference between the two methods. The results of research show that, it is recommended that use the microwave-assisted acid digestion, if investigate the heavy metal of Geological. Because it uses hydrofluoric acid and a variety of inorganic acid with the closed system, it can obtain total metal to the sediment. If it involves assessment of hazard, it is recommended that use the open system digestion. Because it is heavy metal from man-made. In addition, it's possible that the ratio and types of digestive is the key of difference of two digestion procedures. Because different minerals must use different digestive to carries the mineral dissolve. So it must use Sequential extraction, etc. to determine the composition of sediment mineral, by the result of analysis to determine the composition of digestive is the main impact factor to the differences in two digestion procedures.
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Hu, Jun-Fu, and 胡竣富. "Improving the Digestion Efficiency of Microwave-assisted Proteolytical Reactions." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/fd8fwu.
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碩士國立東華大學
化學系
95
The development of proteomics technology has allured increasingly greater investments of financial and human capitals to improve its applicability and performance in clinical research. Among all research programs, high-resolution mass spectrometry is being used to probe, in a large scale, the molecular identity of many proteins. In addition, matrix-assisted laser desorption ionization time-of-flight mass spectrometry has proved its unique and indispensable role in the analysis of large biomolecules such as proteins for its accuracy, shorter analysis time and high-sensitivity. Recent literature has shown that the microwave-assisted digestion reaction can be applied to the qualitative analysis of proteins within a short period of time. However, compared to conventional digestion, microwave-assisted digestion reactions often yields some miss-cleavaged peptides, resulting from incomplete hydrolysis reactions between enzymes and substrates. In this research, we investigated the effects of different solvents, different protein / enzyme molar ratios and varying microwave temperatures in the digestion completeness. We have concluded that a protein / enzyme molar ratio of 1：5 in a 50 mM Tris buffer at a microwave temperature of 60℃ is the optimized experimental condition.
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Wu, Tsung-Hsun, and 吳宗勳. "Reduction of Lead Metal Leaching from Flyash by Microwave Digestion." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/v5r8uc.
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碩士國立臺北科技大學
環境規劃與管理研究所
94
The TCLP result of Flyash often exceeds the regulation control standards, because of lead and cadmium, and it produces many restrictions to follow-up treatment and recycling treatment. Flyash emitted from a large-scale refuse incinerator in the north was sampled and analysed in this research. Due to the TCLP result, it was discovered that the concentration of lead exceeded the standard most frequently (up to 11 times while studying), and therefore lead was targeted mainly in this study. The TCLP result of Flyash often exceeds the regulation control standards, because of lead and cadmium, and it produces many restrictions to follow-up treatment and recycling treatment. Flyash emitted from a large-scale refuse incinerator in the north was sampled and analysed in this research. Due to the TCLP result, it was discovered that the concentration of lead exceeded the standard most frequently (up to 11 times while studying), and therefore lead was targeted mainly in this study. The purpose of this research that Flyash is treated with auxiliary acid by microwave digestion, we hope that it can reduce lead metal content and TCLP leachate, and made it follow-up treatment and recycling treatment. The research used microwave power 600W,and S/L is 1/10, with the suitable microwave operation condition (nitric acid concentration 9.0 mole/L, digesting time 8 minute, and digesting temperature 140 ℃), by microwave digestion lead leaching rate is 94.11%, if it used microwave power 600W,and S/L is 1/10, with the best microwave operation condition (nitric acid concentration 0.8 mole/L, digesting time 6 minute, and digesting temperature 120 ℃), by the result of study, after Microwave Digestion Treatment, the TCLP leachate of lead in reaction ash might could be reduce to 4.83 mg/L from 7.10 mg/L, and the TCLP leachate could keep under the regulation control standards. Under the best microwave condition, prevention efficiency of Pb TCLP can reach 32.0%. This research finding prevention efficiency of Pb TCLP that is dependence about microwave factors, such as nitric acid concentration, digesting time and digesting temperature. The prevention efficiency of Pb TCLP can be expressed as η= 4.15×10-4 (CM)0.30 (T)1.19 (t)0.48, application which it can have as the project in the future.
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Tsai, Tsuey-Lin, and 蔡翠玲. "Research on the Kinetics of Polymer Decomposition Using Microwave Digestion System." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/35257156017351268271.
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博士國立清華大學
生醫工程與環境科學系
97
A simplified and novel kinetic model was firstly developed in this study by way of characterization of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), high performance liquid chromatography (HPLC) with refractive index detector (RID) and the weight-loss method for PMMA decomposition under microwave assisted digestion system. By Newton’s approximation method, the experimental results of the remaining weight of PMMA were closely fitted by the model combined with zero-order and first-order kinetics, in which the former dominated the reaction at lower temperatures (423-443K) and the latter at higher temperatures (≥453K). Kinetic parameters of PMMA decomposition under 423-453K including rate constants and the mass fractions (α) via main-chain (453K) and side-chin (423K-443K) scission were determined by this empirical model. The average activation energies of PMMA 996,000 g/mol decomposition estimated by Arrhenius equation were 2.63 and 25.25 kcal/mol for the zero- and first-order reactions, respectively. For PMMA 350,000 g/mol, 0.76 and 35.97 kcal/mol were estimated for the zero- and first-order reaction, respectively. For PMMA 120,000 g/mol, 1.79 and 29.18 kcal/mol were obtained for the zero- and first-order reaction, respectively. In addition, the average pre-exponential factors of the respective zero- and first-order reactions for PMMA 996,000 g/mol were 2.4×10-2 g min-1 and 2.50×1012 min-1 respectively. For PMMA 350,000 g/mol, 2.33×10-3 g min-1 and 9.31×1017 min-1 were calculated for the respective zero- and first-order reactions. For PMMA 120,000 g/mol, 8.5×10-3 g min-1 and 3.72×1014 min-1 were obtained for the zero- and first-order reaction, respectively. Effect of HNO3 volume on PMMA decomposition was further investigated at 423-473K for three different molecular weights of PMMAs. At 473K, the digestion efficiency increased to 100% as HNO3 volume was ≥3 mL for PMMA 996,000 and 350,000 g/mol, respectively. This was due to the increase of oxidizing potential of HNO3. For PMMA 120,000 g/mol, the decomposition was also almost completely digested (100%) when the amount of HNO3 was >3 mL. The estimated α values for the decomposition of PMMA 350,000 g/mol with 2-7 mL of HNO3 were increasing with HNO3 volume at 423, 443K and 453K, yet varying insignificantly at 473K. The predicted α values for the decomposition of PMMA 996,000 and 120,000 g/mol were also increasing with HNO3 volume at 423 and 443K, but not apparently varied at 453 and 473K.
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Lee, I.-Sheng, and 李奕昇. "Enzymatic digestion completeness in nanoparticle solutions under microwave and conventional heating." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/74645384529393195204.
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Lo, Chen-Yu, and 羅振宇. "Study on Characteristics of Sintered MSWI Flyash with Microwave Digestion Treatment." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/wsf9z4.
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碩士國立臺北科技大學
環境工程與管理研究所
98
In all processing technologies for incineration flyash, the sintered processing is the most possible to turn incineration flyash into sources. However, the content of heavy metal and Dioxin in sintered MSWI flyash which generated in the sintering process is higher than incineration flyash by the evaporation of heavy metals and the synthesis of Dioxin in the sintered process. To understand the characteristics of sintered MSWI fly ash, so the object of this study is sintered MSWI flyash. This study explored the characteristics of sintered incineration flyash, and processed the sintered MSWI flyash by microwave digestion treatment (MDT). According to the results of experiments in this study, the sintered MSWI flyash was high alkaline substance. The average pH of sintered MSWI flyash was about 11.18. The water content of sintered MSWI flyash was about 5.12%. And the fixed carbon of sintered MSWI flyash was about 4.87. In chemical composition, CaO was the highest component of sintered MSWI flyash. The highest content of heavy metals in sintered MSWI flyash was lead, then zinc and copper. And the results of sintered MSWI flyash TCLP (toxicity characteristics leaching procedure) test showed that the highest heavy metal concentration was dissolved for lead than copper and zinc. When the MDT experimental conditions were 800 W, liquid-solid ratio 1/20, digested acids H2SO4 (8.9M) + HNO3 (7.8M), the efficiency of destroying Dioxin could reach 91.41%. The result showed that it was helpful to destroy Dioxin by MDT. Overall, when the concentration of acid increased, the weight-loss ratio of sintered MSWI flyash also increased. But whatever the concentration of acid was high or low, the weight-loss ratio of sintered MSWI fly ash was more than 91%.
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Pickel, Jessica Lee. "An Evaluation of Alternatives for Enhancing Anaerobic Digestion of Waste Activated Sludge." Thesis, 2010. http://hdl.handle.net/10012/5149.
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Waste activated sludge (WAS) is one of the largest by-products of biological wastewater treatment. Anaerobic digestion of WAS is beneficial for several reasons. In an ever increasingly energy conscientious world the production of renewable energy resources is becoming more important, and thus the production of methane has been seen as a valuable product. To achieve efficient conversion of organic matter to methane, the biomass in the digester must be provided optimal operating conditions, as well as adequate retention times, that will allow for substrate metabolism and prevent bacteria washout. Two approaches have been taken in this research to achieve improved biodegradation. Initially microwave pretreatment was employed to improve the biodegradability of the sludge, then the addition of a submerged hollow fibre membrane separation unit was used to allow for a longer SRT while maintaining the hydraulic residence time (HRT).
The impact of microwave pretreatment on WAS characteristics was assessed for both the low temperature operations and the high temperature operations. An increase due to pretreatment on the filtered to total COD ratio when comparing the feed to the microwaved feed was established to be 200 % for low temperature operations and 254 % for high temperature operations.
For the low temperature operations, CODT destruction, VS destruction, and organic nitrogen destruction were all higher for the test digester than the control digester indicating that the microwaving of the WAS increased the biodegradation in the anaerobic digester. For the high temperature operation, CODT destruction and organic nitrogen destruction were improved with microwave application, however VS destruction did not support this. The measured biogas data indicated that microwaving did influence the volume of biogas produced during anaerobic digestion of WAS for both the low and high temperature operations, and hence the VS destruction data for the high temperature operations was determined to be incorrect.
For the membrane operations both the CODT and the VS destruction calculations indicated that at the same SRT the test digester was capable of more biodegradation than the control digester. The control digester organic nitrogen reduction was calculated to be higher than for the test digester, suggesting that the control digester removed more organic nitrogen than the test digester, however, these results were likely due to the lower HRT of the test digester compared to those of the control digester.
A greater volume of biogas was produced by the test digester than the control digester; however, the composition of the gas from both digesters was similar, although the percentage of methane produced by the test digester was higher than that produced by the control digester. The higher destruction by the test digester indicated that the presence of the membrane unit and the decoupling of the HRT and SRT improved the biodegradation capability of the digesters.
The results of the membrane performance study indicated that for a hollow fibre anaerobic membrane bioreactor, stable operations could be achieved with a total solids concentration of 2.01 %+/-0.34, an HRT of 15 days and an SRT of 30 days. With a constant flux of 14 L/m2-h +/-0.68 the average TMP was 0.079 kPa/min+/-0.08. No cleaning was required to achieve this, however the operations consisted of 20 minutes of permeation followed by 5 hours and 40 minutes of relaxation. The critical flux was determined to be in the range of 18 to 22 L/m2-h.
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"Phosphorus Recovery from Microbial Biofuel Residual Using Microwave Peroxide Digestion and Anion Exchange." Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15859.
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abstract: Biofuel from microbial biomass is a viable alternative to current energy production practices that could mitigate greenhouse gas levels and reduce dependency on fossil fuels. Sustainable production of microbial biomass requires efficient utilization of nutrients like phosphorus (P). P is a limited resource which is vital for global food security. This paper seeks to understand the fate of P through biofuel production and proposes a proof-of-concept process to recover P from microbial biomass. The photosynthetic cyanobacterium Synechocystis sp. PCC 6803 is found to contain 1.4% P by dry weight. After the crude lipids are extracted for biofuel processing, 92% of the intercellular P is found within the residual biomass. Most intercellular P is associated with nucleic acids which remain within the cell after lipids are extracted. Phospholipids comprise a small percentage of cellular P. A wet chemical advanced oxidation process of adding 30% hydrogen peroxide followed by 10 min of microwave heating converts 92% of the total cellular P from organic-P and polyphosphate into orthophosphate. P was then isolated and concentrated from the complex digested matrix by use of resins. An anion exchange resin impregnated with iron nanoparticles demonstrates high affinity for P by sorbing 98% of the influent P through 20 bed volumes, but only was able to release 23% of it when regenerated. A strong base anion exchange resin sorbed 87% of the influent P through 20 bed volumes then released 50% of it upon regeneration. The overall P recovery process was able to recover 48% of the starting intercellular P into a pure and concentrated nutrient solution available for reuse. Further optimization of elution could improve P recovery, but this provides a proof-of-concept for converting residual biomass after lipid extraction to a beneficial P source.Dissertation/Thesis
M.S. Civil and Environmental Engineering 2012