Дисертації: "Chemical removal"

1

Bernstein, Howard. "A system for heparin removal." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15291.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1985.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 255-264.
by Howard Bernstein.
Ph.D.

2

Gaulin, Jean-Philippe. "Selective caffeine removal by microbial consortia." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80272.

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Coffee processing presents a considerable waste disposal problem, mainly because of the large volumes generated and the chemical composition of the by-products, particularly the caffeine levels. The use of Pseudomonas putida IF-3, a caffeine-degrading microorganism, in a microbial consortium for bioremediation of caffeine found in coffee wastes was investigated. Caffeine degradation was observed in fed-batch reactor experiments with caffeine as sole source of carbon and nitrogen. Metabolic regulation and caffeine removal potential by Pseudomonas putida IF-3 were investigated by supplementing with other nutrient sources. Diauxic growth was not observed. Nitrogen release from caffeine breakdown was found to be rate-limiting.
Effects of caffeine on microbial consortia were studied using denaturing gradient gel electrophoresis (DGGE), providing a community-scale view of changes in microbial consortia upon caffeine addition. Surprisingly, caffeine removal was achieved indigenously by the microbial consortium. Principal component analysis was used to analyze differences in DGGE banding patterns between control and caffeine-exposed mixed cultures.

3

Roostaei, Nadia. "Removal of phenol from water by adsorption." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ46605.pdf.

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4

Abdulrahman, Aymn. "Removal of mixed acids from aqueous solution." Thesis, The University of Maine, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3662514.

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Carboxylic acids are commonly generated in biorefinery operations such as fermentation or aqueous extraction of hemicellulose feedstocks. In most cases, organic acids are generated as dilute components in aqueous streams. If they can be recovered from solution inexpensively they may find value as pure chemical products or as starting materials for a wide variety of organic products, including biofuels.

Liquid-liquid extraction is a separation method applied to recover mixed carboxylic acids from a fermented wood extract. These acids included: acetic, propionic, butyric, valeric, caproic and heptanoic acids. An organic solution, such as trialkylphosphine oxide (CYANEX 923, a mixture of four trialkylphosphine oxides), was mixed with fermented wood extract to extract these acids. Although the extraction was highly effective, however it was shown that distillation was not able to recover these acids from the extraction solvent.

In this study, after liquid-liquid extraction of the acids from the aqueous phase, the mixed acids are recovered from the organic phase by a back extraction with sodium hydroxide. The mixture is agitated and centrifuged to separate the organic and aqueous phases. Results present the extraction and recovery efficiencies of this method of recovery organic acids.

5

Ng, Dedy. "Nanoparticles removal in post-CMP (Chemical-Mechanical Polishing) cleaning." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/4159.

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Research was performed to study the particle adhesion on the wafer surface after the chemical-mechanical polishing (CMP) process. The embedded particles can be abrasive particles from the slurry, debris from pad material, and particles of film being polished. Different methods of particle removal mechanism were investigated in order to find out the most effective technique. In post-CMP cleaning, surfactant was added in the solution. Results were compared with cleaning without surfactant and showed that cleaning was more effective with the combined interaction of the mechanical effort from the brush sweeping and the chemistry of the surfactant in the solution (i.e., tribochemical interaction). Numerical analysis was also performed to predict the particle removal rate with the addition of surfactants. The van der Waals forces present in the wafer-particle interface were calculated in order to find the energy required to remove the particle. Finally, the adhesion process was studied by modeling the van der Waals force as a function of separation distance between the particle and the surface. The successful adaptation of elasticity theory to nanoparticle-surface interaction brought insight into CMP cleaning mechanisms. The model tells us that it is not always the case that as the separation distance is decreased, the attraction force will be increased. The force value estimated can be used for slurry design and CMP process estimation.

6

Mahmud, Hassan. "Development of pervaporation membrane for volatile organic chemical removal." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9896.

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Pervaporation is a membrane based process which overcomes many of the deficiencies of current technologies for the removal/recovery of volatile organic chemicals (VOCs) from aqueous streams. In this process, VOCs from a liquid stream are driven across a permselective membrane and exit as a vapor due to the vacuum maintained in the downstream side of the membrane. Proven hydrophobic membranes used for pervaporation today suffer from limitations of mechanical stability, while membranes with superior mechanical characteristics do not possess sufficient selectivity to be useful for these applications. To overcome these limitations surface modifying macromolecules (SMMs) have been used as additives in the preparation of polyethersulfone (PES) membranes, which inherently have good mechanical characteristics but are intrinsically hydrophilic. This approach produced membranes with high hydrophobicity (based on contact angles), which were expected to be permselective to VOCs, like chloroform. This thesis investigates the impact of PES/SMM membrane preparation parameters on the reported separation of chloroform from aqueous solutions via pervaporation. These parameters include polyvinylpyrrolidone (PVP) addition levels, solution mixing period, solution age and membrane age. A chemical analysis of the permeate revealed that the permeate contained ethanol but virtually no chloroform. Permeate ethanol concentrations were higher with fresh membranes and decreased both with membrane age and period of use. This indicates that ethanol which was used during the solvent exchange drying step of membrane preparation, was being leached from the membrane. It was concluded that there was in fact no enrichment of chloroform in the permeate as reported earlier and that the surface hydrophobicity introduced was insufficient to dominate over the intrinsic bulk hydrophilic characteristics of the PES membranes. These findings indicate a need to reevaluate the levels of SMM addition and the process parameters to develop a sufficiently dominant hydrophobic surface layer.

7

Omoregie, Henryson Osawaru 1953. "Removal of chemical species by electrically charged bicomponent fibers." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282121.

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A new water deionization method was conceived and investigated. Bench scale reactors were designed and tested. Numerical analysis of ion movement in water in the presence of electrical, hydraulic, and chemical gradients was conducted. The new water treatment technology uses bicomponent fibers (BCF). Ions in water are concentrated near charged bicomponent fibers. Bicomponent fibers are composed of two materials. The outer annulus is made of nylon and has an inside diameter of 10 mum and outer diameter of 50 mum. The inner annulus is composed of carbon powder and has an outer diameter of 10 mum. For the bench scale reactors, approximately one kilometer length of fibers was wrapped around a series of plastic panels and placed in a plexiglass container containing sodium nitrate solution. The ends of the fibers were covered with electrically conductive epoxy and connected to a DC power supply. In experiments which lasted up to 96 h., the solution showed up to 50 percent decrease in nitrate concentration after the power supply was applied. Preliminary studies indicated that distance between panels, polarity of panels and voltage magnitude influenced observed concentration. Two one dimensional analytical solutions and finite element solutions for two dimensions were derived for no flow condition between parallel plates. For the first finite element model, the continuity, Navier-Stokes, and species equations were solved for solute concentration with rectangular coordinates. For the second model, Poisson-Boltzmann equations were included in a finite element scheme. The models were applied to irregular-shaped bodies and the finite element solutions were compared with analytical solutions. The solutions for Poisson-Boltzmann equations were obtained for both linearized and non-linear forms. Boundary conditions included no chemical reactions and no transport across boundaries. The formulations did not solve for concentration in bicomponent fiber reactors because insufficient data and knowledge of the bicomponent fiber process is available. However, future numerical models of the bicomponent fiber treatment process may be based on solutions derived in this research.

8

Sundaram, Hari Prashanth. "SO₂ removal with coal scrubbing." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2035.

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Thesis (M.S.)--West Virginia University, 2001.
Title from document title page. Document formatted into pages; contains vii, 42 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 33-34).

9

Shieh, Marvin Bryan. "Face-up chemical mechanical polishing : kinematics and material removal rate." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36701.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (leaf 27).
A working prototype face-up CMP tool has successfully been completed. Experiments conducted on the face-up CMP machine qualitatively correspond with the theoretical polishing model. Discrepancies in data from the theoretical model could potentially be caused by non-uniform loading of the polishing pad and uneven distribution of slurry over the pad due to the edge effects on fluid flow. Despite the discrepancies, experimental data suggest that the theoretical model used to describe blanket wafer polishing by the face-up CMP tool is at least partially valid.
by Marvin Bryan Shieh.
S.B.

10

Chua, Xiang Le. "Derivatisation of chemical warfare agent degradant without removal of water." Thesis, Chua, Xiang Le (2018) Derivatisation of chemical warfare agent degradant without removal of water. Masters by Coursework thesis, Murdoch University, 2018. https://researchrepository.murdoch.edu.au/id/eprint/42915/.

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Degradation products are distinct chemical signature for the detection of chemical warfare agents and forensic attribution in cases where the parent compound no longer exists. Being the common degradant to nerve agents, methylphosphonic acid serves as an explicit biomarker for the use of nerve agents. However, this non-volatile compound requires derivatisation prior to its detection, which incurs time-limiting factor and error. Therefore, development for a novel rapid and simple approach for identifying these degradants is of high importance to shed light on the use of chemical warfare agents and remediation of impacts. With the success of a recent pilot study for derivatisation of methylphosphonic acid without elimination of water, a subsequent quantitative study can be proceeded to assess on its practicality and efficiency.

11

Rois, Anwar Nurul Zaizuliana. "Removal of crystalline confectionery material from hard surfaces." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6542/.

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Cleaning of surfaces in contact with chocolate is necessary in chocolate manufacturing to ensure high production quality. This research was carried out to study the removal behaviour of solid dark chocolate from three surface materials; stainless steel 316, polycarbonate and polytetrafluoroethylene (PTFE). In order to understand the crystallization behaviour and its relationship with the chocolate rheology, a differential scanning calorimeter (DSC) was used to characterize the polymorphs, while a rheometer was used to study the rheological behaviour of chocolate. The polymorphism was found to be influenced by the tempering and cooling processes, with no dependency on the surface material if cooling is properly controlled. Crystallisation can also be studied from the rheological data. Micromanipulation technique and texture analyser were then used to determine the ease of removal of a solid chocolate layer from the surfaces. Finally, both removal behaviour and time to clean were identified using a flow cell cleaning rig with respect to a number of parameters. It was found that surface roughness of the three materials, crystallization and cleaning conditions affect the removal behaviour of solid chocolate layer from those surfaces. Water alone did not produce a clean surface for all the materials used, thus chemical was added. The results from cleaning work and micromanipulation measurements were found to be comparable.

12

McHarg, Amy Marie. "Optimisation of municipal wastewater biological nutrient removal using computer simulation." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/10479.

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Due to more stringent regulations for secondary municipal wastewater treatment, municipalities are beginning to implement tertiary treatment in their wastewater treatment plants. Tertiary treatment would be the removal of either phosphorous or nitrogen or both from the wastewater before it is discarded from the plant. Biological treatment is becoming an increasingly popular process used to accomplish this extra removal. There are several processes available that will provide acceptable levels of biological nutrient and BOD removal from wastewater. Three well-known processes were considered in this study - the Modified Bardenpho Process, the Modified UCT Process and the A2/O Process. For each of these processes, 2 1evel fractional factorial designs along with least squares analysis were performed in order to determine the optimal operating variables (recycle rates and anaerobic, anoxic and aerobic zone retention times), with respect to the final nitrogen concentration, the final phosphorous concentration and a combination of the final nitrogen and phosphorous concentrations. The analyses were performed at 10°C and 20°C with low, medium and high primary effluent concentrations. Due to the complexity of the processes, lab scale experiments were not feasible. Therefore, a widely accepted calibrated biokinetic model (Activated Sludge Model No 2d) was used in a computer simulation program (GPS-X) to gather the necessary data for analysis. Actual plant data were used to test the validity of the simulation model with respect to organic and nitrogen removal. Using the published kinetic and stoichiometric parameters for both temperature levels, the Activated Sludge Model provided a good estimation of outlet concentration levels. It was found that all three biological nutrient removal (BNR) process were capable of achieving an effluent soluble phosphorous concentration below the required limit of 1 mgP/L at 10 and 20°C with low, medium and high primary effluent concentration when the effluent nitrogen concentration was neglected. Neither the Modified Bardenpho, the Modified UCT nor the A 2/O process were capable of producing an effluent with nitrogen concentrations below the required limit of 5 mgN/L at high primary effluent concentrations. The Modified Bardenpho and the Modified UCT processes were both successful in achieving a combined nitrogen and phosphorous removal below their regulatory limits for low primary effluent concentrations at 10 and 20°C. The Modified Bardenpho process, at 20°C with medium primary effluent concentrations, was found to achieve an effluent with nitrogen and phosphorous concentrations below 5 mgN/L and 1 mgP/L, respectively. After analyzing the effects of individual operating variables, it was found that the anoxic recycle for the Modified UCT process had an insignificant effect on total nitrogen (TN) and soluble phosphorous (sP) removals and did not need to be included in future experimental studies. All of the input variables to the MB and A2/O process proved to be somewhat significant and it is recommended that they be kept within future experimental designs. From this study it was found that both the MB and MUCT process are capable of achieving the TN, sP and cBOD5 removals that ROPEC requires. However only the MB process proved to be a robust system when subjected to storm conditions (i.e., peaks in influent flow rate) with respect to sP and cBOD5 removal. Neither the MB nor the MUCT process provided acceptable TN removals when subjected to storm conditions. It is recommended that ROPEC further evaluate the MB process as a possible means to achieve simultaneous cBOD5, TN and sP removal.

13

Mahmud, Hassan. "Removal of organics from water/wastewater by membrane air-stripping." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ66171.pdf.

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14

Dumortier, Rémy. "Selective removal of gallium from aqueous solutions using organophosphorus ligands." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85157.

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The removal and recovery of gallium (III) from aqueous solutions was investigated using different ligands. Sodium di-(n-octyl) phosphinate was found to be the most effective ligand. The metal-ligand complexes formed had the advantages of being highly insoluble in water and allowing a good regeneration of the ligand at the end of the cycle. The effect of time, pH, mole ratio of ligand to metal, temperature and the presence of other ions, such as Na+, NO3-, Cl- and SO42-, was also studied. At the end of the removal process, gallium was recovered from the insoluble complexes using a solvent. The gallium was concentrated in an aqueous phase. The ligand was extracted in the organic phase and regenerated. Other organophosphorus ligands such as sodium di-(n-dodecyl) phosphinate, sodium mono-octyl ester phosphinate and O,O-di-(octyl) dithiophosphoric acid were also synthesised and studied. They were less efficient for the removal of gallium than the sodium di-(n-octyl) phosphinate ligand. The possibility of using compounds with a carboxylic group on the removal of gallium was also investigated using humic and fumaric acids.
The removal with sodium di-(n-octyl) phosphinate of other metals such as aluminum, indium, iron, calcium and zinc, found in the mining and electronic effluents with gallium, was considered. A good selectivity of the ligand for the gallium over the other metals was obtained. A process was proposed for the electronics industry to treat gallium arsenic effluent.
Finally a mathematical model was established to describe the removal behavior of the metals with the sodium di-(n-octyl) phosphinate ligand.

15

Wibulswas, Ratanawan. "Removal of organic compounds for water using modified Montmorillonite." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368193.

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16

Mortazavi, Saviz. "Removal of arsenic from water using adsorption on alumina/membrane separation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1995. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq22006.pdf.

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17

Prasetyo, Imam. "Removal of toxic metals from aqueous solutions by biosorption." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60713.

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Several non-living algal and fungal biomass types were investigated for biosorption of cadmium, lead and a number of other heavy metal ions in aqueous solution. Marine algae A. nodosum was identified for the highest uptake for these metals, and even better than commercial ion exchange resin. A. nodosum maximum uptake capacities for lead and cadmium were in excess of 2590 mg Pb/(g dried biomass) and 120 mg Cd/(g dried biomass), respectively (pH:3.5-5.5). The adsorption mechanism for this natural material is reversible. Meal ions can be easily eluted from the biosorbent with dilute mineral acids. The biosorption process was investigated for equilibrium batch as well as dynamic packed bed column modes. Two different sorbent immobilization techniques, cross-linking and entrapment were developed for the packed bed studies. It was observed that A. nodosum cross-lined with formaldehyde give the best results for practical use.

18

Chen, Huan 1971 Mar 8. "Electrokinetic removal of zinc and lead from saturated clay." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20198.

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Electrokinetic remediation is an in-situ technique in which a direct current is applied across a water-saturated contaminated soil. As a result, metal ions are transported through the soil from the anode toward the cathode by electromigration, electroosmosis and diffusion. Electrokinetic remediation experiments were performed with Bentonite clay contaminated with Pb and/or Zn under a constant current. The clay bed was cylindrical with a diameter of 5 cm and a length of 15 cm.
The electroosmotic flowrate decreased with time due to a significant increase in the concentration of H+ ions in the bed. Without cathode rinsing the clay bed cracked and the voltage increased. Rinsing the cathode prevented cracking and decreased the voltage applied across the bed. The acid front generated at the anode advanced across the clay bed at a speed of approximately 1.4 mm/hr. When there was no rinsing, most of the metals precipitated in the cathode region. With rinsing, the metals which reached the cathode compartment were removed by the effluent at constant rates over four days. For clay contaminated with Zn, the rate of removal was 15 mg/hr; for clay contaminated with Pb, the rate of removal was 54 mg/hr. For clays with single contaminants and cathode rinsing, the energy consumption was approximately 1.3 x 106 kJ/m3 of clean soil for zinc removal and 1.8 x 106 kJ/m3 for lead removal. For clays contaminated with both metals, the rates of removal were 11 mg/hr for Zn and 26 mg/hr for Pb. After four days, 23% of Pb and 67% of Zn was removed. The efficiency of current utilization was 32% for removal of Zn alone and 40% for removal of Pb alone. For removal of mixed contaminants the efficiency was 40%. (Abstract shortened by UMI.)

19

He, Jiahan. "Removal and degradation of chlorinated organic compounds in groundwater." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280357.

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The first part of this work demonstrates that membrane air-stripping (MAS) is an efficient method for separating volatile organic compounds from water. The introduction of a membrane barrier to separate the air and water phases provides several advantages without increasing the total mass transfer resistance. Efficient removal can be achieved at lower air/water ratios than are typically required in packed-tower. Mathematical models were developed to simulate the performances of both countercurrent-flow and cross-flow contractors. Model simulations indicate that the cross-flow contractor is more efficient than the countercurrent-flow contractor. The second part of this work demonstrates the degradation of aqueous-phase CT in a continuous-flow reactor with a porous copper electrode. Removal of CT increases with more negative cathode potentials until hydrogen evolution becomes excessive. At that point, the increase in solution potential offsets further change in cathode potential and limits further improvement in reactor performance. Removal efficiency was predicted to vary inversely with the liquid velocity. At solution conductivities less than 1.0 S/m, both experiment and simulation showed that reactor performance is seriously handicapped by solution potential. The model predictions were in reasonable agreement with experimental results for high conductivity solutions (≥1.0 S/m). At lower conductivities, the discrepancies between the predictions and experimental results are due to the loss of validity of the zero-solution-potential boundary condition at the downstream end of the cathode. The third part of this work investigates a cylindrical reactor geometry in which the anode is wrapped closely around the cathode. This arrangement eliminates the solution potential limitation encountered in the downstream-anode configuration, making it a promising tool for remediation of low-conductivity groundwater. Higher removals of CT are achieved under more negative cathode potential. Increasing the hydrodynamic residence time by increasing the cathode length is also an efficient way to improve the CT conversion even for low-conductivity solutions. An intrinsic drawback of this configuration is lowered current efficiency due to the high proton concentration at the perimeter of the cathode where most of the current is generated. However, low energy consumption due to small overall potential drop across the reactor at least partially compensates for the drawback.

20

Nadeem, Syed Ahmad. "Aspects of SOâ†2 removal in a fluidized bed combustor." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291078.

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21

Leggett, Graham. "Chemical strategies for removal of trace impurities from gases and solvents." Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.731713.

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22

Conley, LuAnne Simpson. "Removal of complexed iron by chemical oxidation and/or alum coagulation." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03172010-020643/.

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23

Khawaja, Anmol. "High temperature removal of H2S by using MNO." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-233862.

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Förgasning av biomassa är en åtråvärd process då det erbjuder en mängd olika slutprodukter såsom; värme, kraft, biometan, väte etc. Dessa fås från de bildade produkterna från förgasningen, dvs. H2, CO, CO2, CH4 och H2O(g). Det är emellertid även känt att processen producerar orenheter under förgasningssteget såsom NH3, H2S, HCl, tjära och partiklar. En lösning för att avlägsna tjära är genom katalytisk tjärsprickning som sker under höga temperaturer direkt efter förgasaren. Huvudproblemet med detta är att den katalysator som används är känslig gentemot H2S ty gasen deaktiverar katalysatorn. På grund av detta bör H2S avlägsnas före den katalytiska tjärsprickningen. Då förgasaren och den katalytiska tjärsprickningen sker under höga temperaturer, är det önskvärt att avlägsna H2S vid höga temperaturer. Syftet med denna uppsats är att utveckla en experimentelluppställning för avlägsnandet av H2S vid 800°C. Utöver detta, genomfördes det även en dimensionell analys för att förstå hur olika parametrar påverkar omvandlingshastigheten hos metalloxiden, samt utseendet på genombrottskurvan.Från resultaten visade sig att det var möjligt att utveckla en experimentelluppställning för avlägsnande av H2S vid 800°C. Dock bör parametrar som påverkar tryckfallet tas i beaktning för framtida experiment. Dessa parametrar är; bredd på reaktorn, läng på sorbentbädden, partikelstorlek samt magnituden på flödet. Det fattade beslutet för denna studie var att minska på flödet samt öka partikelstorleken. När det kommer till den dimensionella analysen av omvandlingshastigheten, visade det sig att en ökning av kontrollparametern 𝜑 ledde till en ökning av omvandlingshastigheten vilket skedde vi ökande temperatur, partikelstorlek och koncentration av gasreaktanten. Därtill visades det även att diffusion var det fenomen som var hastighetsstyrande. Detta bekräftar SCM, och innebär att den kemiska reaktionen kan försummas vid den dimensionella analysen av genombrottskurvan. Från denna analys visade det sig att när kontrollparametern 𝛽 ökades, minskades diffusionsbegränsningarna och den givna genombrottskurvan blev mer idealiskt. Därför minskade 𝛽 vid ökande Mn-innehåll då det ökar diffusionsbegränsningarna. Dock hade detta ingen signifikant effekt på 𝛽. För de kurvor som hade 𝛽~1, var både konvektion och diffusion är hastighetsstyrande

24

Mbedzi, Ndishavhelafhi. "An investigation into the removal of aluminosilicates scaling species by activated alumina." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/5443.

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Includes abstract.
Includes bibliographical references (leaves 69-74).
Gas condensates from the coal conversion plants contains trace amounts of inorganic species such as Si, Ca and Al ions, which cause scaling in downstream processes. Silica has been identified as the main constituent of the scale materials in geothermal plants. In order to prevent scaling, silica ions need to be removed or reduced. Alumina has been shown to successfully remove both silica and calcium from waste water streams. However, it also causes an increase in the aluminum concentration through dissolution. The mechanism of the silica and calcium uptake by alumina is not fully understood. In this study, the mechanism of silica uptake by alumina was investigated through an extensive literature review and experimental work on the alumina and silica chemistry when in solution. The chemistry of the alumina in suspension can be used to explain its reactions with other species (both inorganic and organic) in solutions. Activated alumina chemistry in suspension under alkaline conditions was investigated. The results showed that small amounts of alumina particles can undergo transformation into its hydrated phases and consequently aluminate (Al(OH)4 -) species are leached out from the pellets and dissolve in solution with subsequent precipitation when in solution. The inorganic species uptake can be attributed to the species interacting with the Al in solution and the hydrated phases of alumina. The results on the inorganic species uptake by alumina showed that a break through point is never attained. This indicates that the inorganic species removal by alumina cannot be attributed exclusively to an adsorption process. Hence, the mechanism of species removal was suggested to be a combination of adsorption and surface precipitation/reaction. Since alumina is costly, its application in wastewater treatment is dependent on its ability to be regenerated. As a result, the second objective of this study was to investigate the regeneration of the alumina by unloading the silica from the loaded alumina using various reagents and subsequently testing the effectiveness of the alumina with a second loading. The reagents used to unload the loaded alumina were sulphuric acid, sodium hydroxide and sodium gluconate at varying concentrations. The three reagents showed an increase in Si unloading with an increase in reagent concentrations. Sulphuric acid showed an unloading capacity of up to about 50% and 70% for batch and continuous unloading respectively. On the other hand, sodium hydroxide showed Si unloading of up to about 50% and 40% for the batch and continuous unloading of loaded alumina respectively under the investigated concentrations. The unloading of Si from saturated alumina using sodium gluconate was only conducted batch-wise as it only achieved a 6% unloading for the concentrations investigated. However, even though the scaling species were eluted from the alumina bed this did not improve/restore the loading capacity of alumina but rather kept the performance of the alumina at the same level that it was before the regeneration process. Also during the unloading of silica from alumina, excessive alumina dissolution was observed when using 0.25M and 0.65M NaOH.

25

Yan, Qingmei. "Biological nitrogen removal of saline wastewater by ammonium oxidizers." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182116.

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26

Whyte, Ian. "Reticulated vitreous carbon cathodes for metal ion removal from process streams." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316472.

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27

Andersson, Mathilda. "Biochar removal of micropollutants in wastewater effluentsfrom Morocco and South Africa." Thesis, Umeå universitet, Kemiska institutionen, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-136632.

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28

Charlson, Alexandra. "Removal of pharmaceuticalcontainingwastewater by bioandhydrochar adsorbents : Adsorption capacity and surface functionalities." Thesis, Umeå universitet, Kemiska institutionen, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-136762.

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29

Saad, Ramzi Fayez. "Selected heavy metal and organic removal from wastewater by precipitation and ozonation processes." Thesis, University of Ottawa (Canada), 1998. http://hdl.handle.net/10393/4545.

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Experiments were conducted to precipitate dissolved copper, zinc, and lead from simulated wastewater solutions as solids which could then be separated by filtration. The precipitants used were hydrated lime, as a slurry and in powdered form, aqueous ammonium hydroxide, ferrous sulphide sludge, and carbon dioxide gas. These five different chemicals, singly or in combination, were used; at least one of which was highly successful in precipitating each of the metals, removing at least 99% of that originally present. Copper and zinc were very effectively precipitated as the hydroxides with lime, whereas lead was not. Considering lead to be the most difficult metal to remove, four other chemical conditions were attempted for lead; these were ferrous sulphide alone, lime with ferrous sulphide, lime with carbon dioxide, and lime with ozone. The precipitation of lead with ferrous sulphide alone, was only partially successful with only 95% removal. The other three combinations of chemicals precipitated more than 99% of the soluble lead, giving excellent results. Furthermore, because lead is usually difficult to remove from solution, it is considered that the three new chemical combinations show strong promise for the removal of other heavy metals from wastewater solutions. Experiments were also conducted to decompose the organic compounds, formaldehyde and pyridine, in simulated wastewater solutions in a mixed reactor, using ozone and UV radiation as oxidants. Although 200 ppm Total Organic Carbon content of each of those chemicals, and a mixture of both, were completely decomposed by ozone-UV oxidation, the time taken for these decompositions ranged from about three to four hours. Such prolonged reaction times are considered too long for most wastewater treating processes. However, low concentrations of organic matter might be successfully treated using ozone/UV processes.

30

Yu, Bo. "Sulfate removal from concentrated sodium chloride brines for chloralkali industry with nanofiltration membranes." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27202.

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Nanofiltration membrane elements have been employed for the treatment of solutions containing raw brine generated by chloralkali industry. This study focused on the selection of appropriate nanofiltration membrane element and the assessment of their performance for the removal of sulfate and the retention of chloride from feed solutions. The influence of membrane type, temperature, pressure and sodium sulfate concentration on the selective removal of sulfate from concentrated sodium chloride brines were investigated. A high passage of sodium chloride and rejection of sodium sulfate were achieved with two different commercial nanofiltration membrane elements, DL2540 produced by GE Osmonics and NF270-2540 manufactured by FilmTec (Dow), suggesting that both membranes can be employed in sulfate removal from sodium chloride brines for chloralkali industry. Operating pressure and temperature showed no significant effects on sulfate rejection under the tested conditions. However permeate flux increased with both temperature and pressure in the tested ranges. The influence of temperature on permeate flux was due to the dependency of the viscosity of salt solution, which follows the Arrhenius model. Sodium concentration in feed had significant effects on permeate flux, sulfate rejection, and sulfate concentration at membrane interface and in permeate. Sulfate rejection and permeate flux reduced sharply with the increase of sulfate concentration in feed.

31

Husein, Maen. "Removal of lead from aqueous solutions with compounds having the sodium carboxylate group." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27228.

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Lead was removed from aqueous solutions using reagents having the sodium carboxylate group. For sodium acrylate and sodium polyacrylate, the removal of lead increased, and the reagent loss decreased when using sodium polyacrylate compared to the monomer, and when using a polymer with higher molecular weight. Sodium propionate did not precipitate lead. Sodium oleate formed a suspension with lead. Sodium caprate formed an easily filterable precipitate. For a feed concentration of 1450 ppm lead, and a mole ratio of caprate to lead of 2, the percentage removal of lead and the percentage loss of caprate were 99.5 $ pm$ 0.2% and 0.8 $ pm$ 0.3%, respectively. The effects of pH, concentrations of lead, calcium, chloride and nitrate in the feed on the removal step were determined. For a certain amount of added caprate, the equilibrium concentrations of lead and caprate were independent of the feed concentration of lead. Decreasing the pH of the feed decreased the removal of lead, but did not affect the loss of caprate. The presence of calcium or nitrate in the feed did not affect the removal of lead. At high chloride concentration, C$ sp circ$(Cl$ sp{-}$) $>$ 0.7 M, the loss of caprate increased slightly. Sodium caprate was recovered by adding HNO$ sb3$ to form capric acid. The sodium caprate was regenerated by adding NaOH. A percentage regeneration of 98.9 $ pm$ 0.3% was achieved.

32

JI, LEI. "Novel Nano-Structured Sorbents for Elemental and Oxidized Mercury Removal from Flue Gas." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212028586.

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33

Nazarian, Reyhaneh. "Advanced Phosphate Removal in Dialysis Employing Lanthanum Impregnated Activated Carbon Fixed-Bed Column." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1515508343971243.

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34

Juneja, Harpreet. "Removal of Adsorbed Moisture and Organics from Surfaces and Nanostructures in Semiconductor Manufacturing." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/193597.

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As the semiconductor industry is moving towards achieving smaller, denser and faster integrated circuits; the issue of contamination control is becoming increasingly important. The current work focuses on the mechanism and kinetics of removal of adsorbed moisture and organics from surfaces and nanostructures.In the first application of this study, a novel approach to the characterization of dynamic interactions of gases with solid surfaces is developed. A model is developed to represent the simultaneous adsorption and desorption processes in these systems. The model can simulate both the non-equilibrium adsorption and desorption processes as well as the equilibrium state (isotherms and isobars). The model is validated using experimental data, and applied to the adsorption of moisture on oxides (ZrO2 and HfO2). Practical application of this work is shown by optimizing the purge recipes for removal of moisture from a ZrO2 film.In the second application, a novel approach is developed and demonstrated to characterize the sampling line effects during dynamic monitoring of fluid concentrations. The "Sampling line" in this study refers to all components between the point of fluid sampling and the point of analyzer sensor. In general, sampling lines introduce errors in measurements by altering the sample properties due to the fluid transport in the line as well as the adsorption and desorption of fluid constituents on the surfaces of the sampling components that come in contact with the sample fluid. A methodology based on a sampling line simulator is developed for taking these effects into account and correcting the measurements. The sampling line simulator can be used to analyze the effect of various sampling configurations and operating conditions.In the last application, experiments were carried out to study the interaction of organics with micro/nano particles representing nanostructures. A process model is developed which gives insight about the mechanism and kinetics of these interactions. The micro/nano particles, due to their large surface area, can adsorb any other species which may result in the change in their properties. This may ultimately affect the process in which they exist. This study will also be helpful in analyzing the Environment, Safety and Health (ESH) effects of nanostructures.

35

Paragano, Matthew Vincent. "Liquid Systems for Carbon Dioxide Removal in Spacecraft Environments." Thesis, Yale University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10783463.

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As humans strive to explore deeper into the solar system, the need for efficient, compact, and reliable life support systems for providing breathable air and drinkable water become critical to mission success. One element of providing breathable air is the removal of metabolic gaseous waste products, primarily consisting of carbon dioxide, from the cabin air. Recent work on human performance has suggested that carbon dioxide has effects on human performance at lower concentrations than previously anticipated and at concentrations lower than presently controlled to on the International Space Station. Such performance requirements represent a substantial challenge and provide the opportunity for an alternative solution to the zeolites presently in use. The present work examines the feasibility of using liquid a bsorbents to perform carbon dioxide absorption in enclosed microgravity environments.

The use of liquid absorbents for carbon dioxide removal (or capture) is well studied in literature. Chief among the absorbents studied is monoethanolamine, an organic base which reacts to neutralize carbon dioxide. The reactivity of bases with amines increases the mass transfer rate, a particularly desirable feature for systems requiring compact architectures. To improve the diffusivity of carbon dioxide and reaction products, amines are typically dissolved in water, which has a low viscosity and solubilizes amines well. However, as analyzed in this work, aqueous sorbents are unattractive in enclosed environments because the water will evaporate into the cabin. As an alternative, an off-the-shelf, non-aqueous mixture of aminoethylethyleneamine and triethylene glycol was developed which shows moderate viscosity characteristics with low-volatility components and full miscibility.

This work investigates for the first time the use of electrospray as a nanoscalegas -liquid contactor to improve the mass transfer while using a viscous liquid absorbent. Experimental investigation of this phenomenon concludes that electrospray shows a high overall mass transfer rate at all loadings than a stationary film. The proposed reason for the continued high mass transfer rate is the continuous refreshing of the gas-liquid interface with unreacted amine. Varying parameters for the concentrations of carbon dioxide and a mine, the liquid flow rate, and the driving electricfield show the data may be collapsed by an empirical dimensionless group which relates to the liquid pool at the bottom of the spray that represents a well-mixed interface. In addition, the influence of carbon dioxide reacting with the surface of the electrospray cone was studied experimentally with monoethanolamine, concluding that emitted current increases with carbon dioxide partial pressure due to production of ionic reaction products changing electrical conductivity.

Finally, the mass transfer of water vapor and carbon dioxide through a microporous polytetrafluoroethylene membrane into aqueous and non-aqueous aminoethylethanola mine solutions. Aqueous solutions show water vapor losses, consistent with expectations, which would impose a condensation risk to cabin environments.

36

Bonner, Alison Lee 1966. "Oxidation and removal of organic impurities from ultrapure water." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277910.

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This study focuses on three aspects of the removal of organic impurities from ultrapure water. The interactions between system components such as ion exchange, UV unit and filter on overall purification are examined. The results indicate that the sequencing of the UV unit and the filter affects the TOC removal efficiency so that greater TOC removal is achieved when filtration precedes UV treatment. Furthermore, a UV unit followed by an ion exchange tank is an effective configuration for the removal of some impurities, but is undesirable for others particularly the charged macromolecules and particles. To further enhance the removal of TOC from the water, the effect of combining dissolved ozone with UV light is examined. A synergistic removal, significantly greater than the additive effect of ozone and UV treatments, is achieved. To predict the removal of organic impurities from ultrapure water, a system model is developed using reaction kinetics and reactor design concepts. (Abstract shortened with permission of author.)

37

Buchanan, Ian 1953. "Kinetic modelling of horseradish peroxidase catalyzed phenol removal for reactor development." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40325.

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Horseradish peroxidase (HRP) catalyzes the polymerization of aromatic compounds. These polymers precipitate from solution and may be removed by filtration or sedimentation. The useful lifetime of the enzyme is limited by inactivation which occurs during the removal process; however, the rate of enzyme inactivation is significantly lower in the presence of high molecular mass polyethylene glycol (PEG).
An empirical model has been developed to relate phenol concentration after complete batch reaction to the initial concentrations of phenol and HRP, both in the presence and the absence of PEG.
A kinetic model has been developed for the removal process. Enzyme inactivation has been modelled as occurring when free radicals, formed during the catalytic cycle, disrupt the enzyme's active site; and when the enzyme becomes entrapped in the polymers as they form.
The model has been adapted to batch, plug-flow (PFR) and continuous stirred tank reactors (CSTR). The model was calibrated by means of a genetic algorithm using data from bench-scale batch reactors, and validated for batch and plug-flow reactors over a range of phenol concentrations which is normally encountered in industrial effluents. The rate constant associated with enzyme inactivation by free radicals was found to be essentially zero in the presence of PEG.
Calibration of the inactivation rate constants for a CSTR confirmed enzyme inactivation in the presence of PEG to be modelled best by entrapment alone. The estimated value of the rate constant associated with enzyme entrapment in a CSTR was 35% lower than the value estimated for a PFR and batch reactor.
Model simulations and experimental results obtained using a bench-scale multiple-stage CSTR in the presence of PEG showed that the efficiency of enzyme use increased with an increasing number of reactor stages.
These results indicate that a multiple-stage CSTR, to which PEG was added to provide maximum enzyme protection, would be the most favourable environment of those tested during this investigation for the implementation of the HRP-catalyzed process.

38

Salvesen, Thomas Alexander. "Sol-gel derived palladium catalysts for the removal of automotive chemical pollutants." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/843351/.

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Sol-gel production of catalyst supports has been investigated in order to produce homogeneous, high surface area alumina/zirconia materials. A novel microwave method of preparing colloidal Pd has been developed and a range of alumina/zirconia supported Pd catalysts has been produced. These have been tested for activity in terms of temperature programmed three way catalysis (simultaneous removal of NO, CO and C3H8 from a simulated car exhaust stream) and from the array of catalysts produced a suitable catalyst was chosen for further investigation. This catalyst had a 3% zirconia / 97% alumina support and contained ~1% Pd by weight and was examined for activity in the NO + CO + O2 system at temperatures below 500°C. Temperature programmed catalytic experiments revealed the reactions to be chemically controlled below ~400°C but diffusion controlled above this. CO temperature programmed reduction was used to examine the oxidation state of the Pd and revealed a complex Pd/PdO system to be present involving bulk PdO and surface oxide. Further kinetic studies showed that the reactions between NO, CO and O2 to have positive orders in all components. The reaction rates were stable over a wide range of conditions and the NO + CO reaction proved to have a low selectivity towards N2O. In-situ DBIFTS experiments alongside transient pulse work were used to illustrate low CO adsorption which indicated that these reactions proceeded via a redox mechanism in which Pd is oxidised by NO or O2 before being reduced by CO. The support material was examined by XRD following extended heating regimes and then compared to an identically treated sol-gel alumina. The zirconia doped alumina was found to possess a far greater thermal resistance to sintering than the pure alumina material and this was attributed to Zr4+ ions preventing the diffusion of Al3+ to form a-alumina.

39

Collins, William D. "Chemical treatment of corroding steel reinforcement after removal of chloride contaminated concrete." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08182009-040410/.

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40

Clark, T. "The impact of chemical addition for phosphorus removal on activated sludge treatment." Thesis, Cranfield University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268135.

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41

Rosendahl, Sara. "Modelling control strategies for chemical phosphorus removal at Tivoli wastewater treatment plant." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-453546.

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Wastewater compose an environmental risk as it contains high levels of nutrients, including phosphorus. Wastewater treatment plants (WWTPs) reduce phosphorus by using coagulants that precipitate soluble phosphate into metal phosphate, which is separated by settling. Coagulant flow is regulated by a control strategy, typically feedforward or feedback control. Feedforward is based on incoming wastewater disturbances whereas feedback control uses outgoing process values. Incoming phosphate is hard to measure and can be estimated using soft sensors. Modelling control strategies can help decide which strategy that is most suitable. Models describing phosphorus removal are Activated Sludge Model, ASM2d, and primary clarifier model. ASM2d models phosphorus precipitation and the primary clarifier model settling of particles. Tivoli WWTP faces challenges to reach effluent requirements of phosphorus. The wastewater flows through an equalisation tank, Regnbågen, before being pumped to Tivoli. Particulate matter settles in Regnbågen, which is removed by reducing the water level in Regnbågen. This rapidly increases incoming particulate load to Tivoli.Tivoli’s current control strategy is feedforward proportional to suspended solids. It is suspected, that this strategy overdose coagulant during the emptying of Regnbågen. The purpose of this thesis was to find the optimal control strategy for phosphorus precipitation at Tivoli WWTP, by using a model-based approach. Control strategies modelled are; feedforward, feedback and these two control strategies combined. Additional issues resolved are 1) calibration of a model that predicts the effect of chemical dosage on effluent phosphorus concentration from the primary clarifier, 2) calibrationof a soft sensor, 3) determination of which control strategy that is most suitable. ASM2d and a primary clarifier model were used to create a model describing chemical phosphorus removal. The calibration matches measured phosphate concentration, but underestimate peaks. The primary clarifier model was calibrated by minimising load differences for phosphate and total suspended solids, and was calibrated satisfyingly. A simplified soft sensor was constructed, described by a linear relationship between phosphate and pH. Three disturbances for feedforward control were analysed; measured phosphate, the soft sensors estimation of phosphate and Tivoli’s current controlstrategy. The optimal control strategy was found through a multi-criteria analysis. The optimal control strategy is the combined control strategy, when feedforward is proportional to incoming measured phosphate. The performance of all analysed feedforward disturbances were significantly improved when combined with feedback control. Furthermore, consequential errors are distinct when the soft sensor miss-predictincoming phosphate concentration. If the phosphate concentration cannot be correctly measured/estimated, feedback control alone has the best performance.

42

Karra, Pavan K. "Modeling and control of material removal and defectivity in chemical mechanical planarization." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3355516.

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43

Lingaraju, Bala P. "Removal of Nitrogen from Wastewater Using Microalgae." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321888338.

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44

Yang, Yang. "Removal Mechanisms of Protective Iron Carbonate Layer in Flowing Solutions." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1339731278.

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45

LIU, Fangzhu. "Integration of Chemical Oxidation and Biotreatment for Removal of TNT from Explosives Contaminated Soil." MSSTATE, 2002. http://sun.library.msstate.edu/ETD-db/theses/available/etd-12032002-152100/.

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2,4,6-trinitrotoluene (TNT) is of environmental concern because it?s a possible human carcinogen and it also remains potentially explosive. The Department of the Army (DA) estimates that there are 540,000 cubic meters (700,000 cubic yards) of explosives-contaminated soil at over 2,000 sites that require remediation. Biological treatment of TNT results in the production of the reduced intermediates (such as aminonitrotoluenes). When using chemical oxidation processes to treat TNT, 1,3,5-trinitrobenzene (TNB) is produced. The by-products of both biological and oxidation treatment processes are resistant to further treatment thus they require extensive treatment times. This study evaluated the use of biotic mechanisms that can be used to reduce TNT into aminodinitrotoluenes, which then are oxidized using Fenton?s Reagent oxidation process. Integration experimental results showed that Fenton?s Reagent was capable of degrading TNT, though not as fast as ADNTs. The optimal Fe2+/H2O2 ratio appears to be less than 10:1. The TNT biodegradation rate was higher than the TNT oxidation rate and was biodegraded at a faster rate compared to the ADNTs. It was concluded that the integrated technology showed promise as an effective and innovative technology for treating TNT contaminated soil.

46

Dube, Vuyiswa. "Study of selective removal of CoS and NiS during purification of MnSO₄ electrolyte." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/13710.

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This research project investigated the selective removal of Co²⁺ and Ni²⁺ from a Co-Ni-Mn system through sulphide precipitation. The Co²⁺ and Ni²⁺ ions have adverse effects on the purity of the manganese product, thus, have to be removed via precipitation in a purification step. The main objective of this research was to understand the influence of local supersaturation on the purification process. This was important for controlling such a process to achieve residual ion concentrations of 0.3 ppm and 1.0 ppm for Co²⁺ and Ni²⁺ ions respectively, with minimum loss of the Mn²⁺ ions.

47

Palabiyik, Ibrahim. "Investigation of fluid mechanical removal in the cleaning process." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4593/.

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The cleaning of pipework from fluids of high viscosity is a significant problem in many food and personal care industries which can cause considerable economic and environmental impact. Three stages are identified in the cleaning of straight pipes; (i) a short core removal stage of product recovery, before water breaks through the filled pipe, (ii) the 1st cleaning stage (film removal stage) when there is a continuous wavy annular film on the wall, and (iii) the 2nd cleaning stage (patch removal stage) in which the material is present as patches on the wall. The product recovery stage is found to influence the overall cleaning process. Conducting product recovery at low temperatures and high flow rates cause the formation of a wavy wall layer which leads to more rapid subsequent removal. A two step CIP protocol is proposed to decrease the environmental impact of cleaning of a viscoelastic material (toothpaste) from pipework. Applying cold water in the 1st cleaning stage and hot water in the 2nd cleaning stage results in 40 % energy saving without affecting the cleaning performance significantly compared to traditional CIP protocols used in plants. Yield stress of deposits is the key effect on the cleaning of deposits. A new dimensionless number is explored. It is physically a ratio of flow energy to the yield stress of a deposit. It has collapsed cleaning time data onto a one curve for different deposits cleaned at different velocities. It can be used to predict cleaning times of deposits or identify the governing cleaning mechanisms in cleaning. It is found that the magnitude of pressure loss in flow can be used to quantify the flow and turbulence effect on cleaning and scale up lab scale data. The results show that although fluid mechanical removal is a complex process, cleaning time of deposits can be predicted by knowing its rheology and fluid mechanical parameters of cleaning fluid.

48

Wang, Bei. "Microalgal Lipids Production and NitrogenPhosphorus Removal Using the Green Alga Neochloris oleoabundans." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28571.

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A Neochloris oleoabundans strain screened in our lab was demonstrated to have the ability to accumulate large quantities of triglycerides, the feedstock of biodiesel production, and to remove nitrogen and phosphorus from wastewater efficiently. Box-Behnken experimental design (BBD) and response surface method (RSM) were used to study the effects of a large number of nutrients on cell growth and lipid accumulation. The optimized medium supported a lipid concentration of 641.4 mg/l and a cell density of 2.54 g/l, which were 4.5-fold and 2.2-fold of that obtained with the basic medium, modified Bristol medium (MBM), respectively. The capacity of the strain for phosphorus removal and nitrogen removal was investigated using artificial wastewater and municipal wastewater effluents. It was demonstrated that the strain could achieve near-zero residual phosphate and nitrogen at the end of cultivation when artificial wastewater contained up to 140 mg N-NO 3-/l and 47 mg P-PO43-/l. The rates of the removal of N-NO3- and P-PO4 3-, are 27.5 mg/l·d, and 9.4 mg/l·d, respectively under optimal conditions. It was observed that the nitrogen content of the wastewater effluent was not sufficient and additional nitrogen source (e.g., NaNO 3) of 70 mg/l was required for optimal cell growth, CO2 fixation, and phosphate removal.

49

Esalah, Jamaleddin. "Removal of heavy metals from aqueous solutions by precipitation with sodium di-(n-octyl) phosphinate." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37715.

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Two organophosphorus compounds: sodium di-(n-octyl) phosphinate and sodium di-(n-dodecyl) phosphinate, were synthesized and purified. Sodium di-(n-octyl) phosphinate was used both as a surfactant to form reverse micelles and as a precipitating agent to remove heavy metals from aqueous nitrate and chloride solutions.
The heavy metals lead, cadmium, and zinc were precipitated from aqueous solutions with sodium di-(n-octyl) phosphinate (NaL) in the form of PbL 2(s), CdL2(s), and ZnL2(s). The mole ratio of NaL to lead in the feed was varied from 0.1 to 6.5, depending on the acidity of the feed. The effects of the feed pH, concentration of chloride, concentration of calcium, and of the chain length of the precipitating agent on the removal of lead, were investigated. Adding acid to the feed solution reduced the removal of lead as some of the phosphinate precipitated in the acid form as HL(s). The presence of chloride or calcium in the feed solution, up to mole ratios to lead of 250 and 2.75, respectively, had no effect on the removal of lead. The solubility of the precipitate PbL 2(s) was reduced by increasing the length of the alkyl group of the phosphinate. The removal of cadmium, zinc, and a mixture of lead, cadmium and zinc was investigated. Behavior similar to that of lead was observed. The selectivity of the precipitating agent for the three metals was in the order Zn > Pb > Cd.
The precipitating agent was completely regenerated by adding NaOH to the precipitate, and then contacted with diethyl ether to extract the reagent. The lead was completely recovered from the PbL2(s). Pure lead-free precipitating agent, and an aqueous solution of lead at a concentration 100 times its concentration in the feed, were obtained.
Using measured solubility products of the precipitates and literature values of the stability constants for the other expected reactions, the removal of metal, the loss of precipitating agent, and the equilibrium pH were predicted.

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Huang, Liangliang. "Computational Study of Toxic Gas Removal by Reactive Adsorption." Thesis, North Carolina State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3538542.

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Growing concerns about the environment and terrorist attacks prompt a search for effective adsorbents for removal of small molecule toxic gases, such as ammonia and hydrogen sulfide, under ambient conditions in the presence of moisture, where physical adsorption is not adequate. We use graphene oxide and CuBTC metal-organic framework as the adsorbents to explore toxic gas removal by reactive adsorption. Using ab initio density functional theory, atomistic reactive molecular dynamics and Monte Carlo simulation strategies, theoretical understanding of the underlying reaction and adsorption mechanisms of ammonia and hydrogen sulfide on graphene oxide and CuBTC metal-organic framework have been gained.

The ab initio calculation results show that ammonia and hydrogen sulfide decompose on carboxyl and epoxy functional groups and vacancy defects of graphene oxide. The existence of water molecules substantially reduces the adsorption/dissociation of ammonia or hydrogen sulfide on graphene oxide because the water molecules either form hydrogen bonds with the functional groups or adsorb more easily on the vacancy defects. Reactive molecular dynamics calculations by the ReaxFF method have been performed to propose realistic graphene oxide models for theoretical calculations. We also use reactive molecular dynamics simulation to study the thermal and hydrostatic stabilities of the CuBTC metal-organic framework and its application for ammonia removal. We predict the collapse temperature for CuBTC crystal structure and observe the partial collapse of CuBTC at lower temperatures upon ammonia adsorption. The results agree well with experiment data and provide insights on the reaction mechanism involved in such an ammonia removal process.

The research in this thesis can provide fundamental understanding, at the electronic and atomistic levels, of the roles of surface defects and functionalities for reactive adsorption of toxic gas molecules. In addition to developing experimental and theoretical algorithms to design effective adsorbents, the results are expected to find applications in air cleaning, energy storage, fuel cell technology and other scientific challenges where the separation of reactive molecules is involved.

Дисертації з теми "Chemical removal"

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