Dissertationen zum Thema „Ammonia separation“

The effective separation of ammonia from the synthesis loop in ammonia synthesis plants is an important step in its manufacture. This work presents the use of nanocomposite MFI zeolite membranes prepared by a pore-plugging method for this separation process. Performance of a zeolite membrane is highly dependent on the operating conditions. Therefore, the influences of differential pressure, temperature, sweep gas flow, feed gas flow and gas composition are studied experimentally. Transport of NH3 in this membrane is by surface diffusion in the intracrystalline (zeolite) pores in parallel with capillary condensation in the intercrystalline (non-zeolite) pores. The separation of NH3 from a mixture with H2 and N2 is by preferential adsorption of NH3, which hinders the permeation of weakly adsorbed H2 and N2. Differential pressure has only relatively small effects in the pressure range 300kPa – 1550kPa. Increase in sweep flow rate has little effect on NH3 gas permeance, but H2 and N2 permeances increase thereby decreasing the selectivities. Increase in feed flowrate also has little effect on NH3 permeance. However, the N2 and H2 permeances increase and there is a subsequent decrease in selectivities. Membrane performance was found to be highly dependent on temperature. NH3 permeance in the mixture increases linearly with temperature. NH3 selectivity was found to increase with temperature up to 353K after which it starts to decrease due to N2 and H2 permeances increasing with temperatures beyond 353K (αNH3/N2 = 46 and αNH3/H2 = 15) and is therefore the optimum temperature for separation. A potential barrier model is developed to describe the hindering effect of NH3 on H2 and N2 permeance. The model fails to predict correctly H2 and N2 permeances in the ternary mixture using pure gas (H2 and N2) permeances. Binary mixture permeation H2/N2 studies showed that there are diffusion effects (single file diffusion) that have not been taken into account in the potential barrier model. When permeances of the individual components in the binary mixture are used in the model instead of the pure gas permeances, there is an improved agreement between experimental and predicted results.

ENGLISH ABSTRACT: Leaching of nickel laterite was conducted with a solution of ammonia and ammonium carbonate in a closed vessel. The vessel used in this study was designed to leach and perform solid-liquid separation at the same time. For solid-liquid separation, stainless steel sintered metal filter media were used. The sintered metal filter medium was selected for its high strength to withstand pressure, chemical resistance to caustic solution and back flushing properties. Optimum leaching conditions were determined by varying temperature, ammonia concentration, ammonium carbonate concentration and oxygen pressure. After leaching and filtration, the pH of the leach liquor was measured and samples were analyzed for dissolved metals (Ni, Fe and Co) using atomic absorption spectrophotometry. The most significant variable effect on leaching of nickel was the ammonia concentration. The maximum dissolution of nickel from the unroasted ore was 11.90% at 4 M NH3, 100oC, 2 M (NH4)2CO3 and 2 bar O2 pressure. Optimization from the leaching data was done using response profiling and desirability in Statistica software. Optimum leaching conditions were determined to be 3 M NH3, 2 M (NH4)2CO2, 100oC and 2 bar O2 pressure. The mineralogy of the ore before and after leaching was studied to understand why nickel extraction from unroasted ore was poor. XRF analysis of solids after leaching showed that iron, silicon, and magnesium remained the same. The only metal which showed significant decrease from solids was nickel. XRD analysis of solids after and before leaching showed that most mineral phases present in the ore are not affected by the leaching solution. SEM with EDS detection was used to determine nickel distribution within the ore. The results showed that nickel is mostly associated with iron. The iron is surrounded by magnesium and silicon. Silicate minerals do not react with ammonia and ammonium carbonate solution. From filtration experiments, the filtration differential pressure had no significant effect on the filtration rate. An average filtration rate of 0.29±0.07 ml/min.cm2 was obtained. The filtration rate from these experiments was very low. The main reason was due to quick pore clogging of sintered metals. Pore clogging was found to be mainly on the surface of the filter medium. Laterites have been found to have low permeability due a lot of clay present in the ore. Rheological studies on this ore showed that the ore has shear thickening behavior. However, a very clear filtrate was obtained. After each leach and filtration experiment, the sintered metals was unblocked by back flushing with water and air. Back flushing was successful because all 18 experiments were carried out using the same sintered filter medium. The effect of roasting the ore prior to leaching was investigated using optimum conditions obtained when leaching the unroasted ore. There was a slight improvement in nickel extraction when the ore was roasted. The average percentage extraction of nickel from 3 experimental runs was 19.25%±0.19 at 100oC, 3M NH3, 2M (NH4)2CO3, and 5 bar oxygen pressure. Some part of nickel in the ore was unextractable due to association of nickel with recrystallized silicate minerals in the reduced ore. Roasting improved permeability of the ore. The filtration rate improved significantly after roasting the ore. The average filtration rate was 2.60±0.05 ml/min.cm2. Dissolution kinetics of the unroasted and roasted saprolitic laterite were investigated with regard to the effects of temperature, ammonia concentration, ammonium carbonate concentration, and oxygen pressure. For the unroasted ore, it was found that dissolution rate and degree of nickel extraction increases with increasing temperature. Increase in ammonia concentration improves the degree of nickel extraction. Nevertheless, nickel extraction does not depend entirely on ammonia concentration because even when ammonia concentration is high and ammonium carbonate concentration is zero nickel extraction is low. An increase in ammonium carbonate concentration also increases the degree of nickel extraction. Ammonium carbonate is critical for the extraction, since ammonium ions in the solution prevent hydrolysis of the nickel ammine complex. Oxygen did not have a significant effect on the degree of nickel extraction. The leaching of nickel laterite was found to be a two stage leaching process. In the first stage, the dissolution of nickel is faster but after 15 minutes, the reaction rate is reduced. The reaction rate is reduced by inert minerals which host nickel. These minerals contain iron magnesium and silicon. The fast dissolution of nickel in the first stage represents leaching of free nickel in the ore. The data for the second stage of leaching was analyzed by the shrinking core model, and the results suggested that the dissolution rate is controlled by mixture kinetics (ash layer diffusion and surface reaction control). The activation energy for the dissolution reaction was calculated as 56.5 KJ/mol. The reaction order with respect to ammonia and ammonium carbonate were determined to be 0.3 and 0.26 respectively. For the roasted ore, the highest degree of nickel extraction was obtained at 60oC, 3M NH3, 2M (NH4)2CO3, and 5 bar oxygen pressure. The percentage extraction under these conditions was 28.7%. Temperature did not have a significant effect on the leaching rate. An increase in NH3 and (NH4)2CO3 increased the final extraction of nickel but did not have any effect on leaching rate in the first stage of leaching. In the absence of ammonium carbonate, nickel extraction is almost zero. The experimental data did not give linear fit to the shrinking core models investigated for the unroasted ore. The reason for this could be due to the sampling time interval which was too far apart, or the leaching behavior of roasted nickel is complicated and cannot explained by shrinking core model alone. Leaching experiments demonstrate that for a high degree metal extraction and improved reaction kinetics with ammonia and ammonium carbonate, the solution temperature should be high (>100oC) for the unroasted ore. In order to leach at high temperature with ammonia and ammonium carbonate a closed vessel is required to prevent reagent loses. The reaction kinetics showed that the reaction is controlled mostly by ash layer diffusion; this indicates that a low degree of nickel extraction in the unroasted saprolitic laterite is due to inert minerals (ash layer) which host nickel within the ore. In order to obtain a high degree of nickel extraction, the ore needs to be roasted under reducing conditions. Roasting conditions need to be carefully controlled to ensure high dissolution of nickel. In fact optimum roasting conditions which will give maximum dissolution of nickel, must be determined before working with the bulk of the ore.
AFRIKAANSE OPSOMMING: Logingstoetse van saprolitiese lateriet met 'n oplossing van ammonia en ammonium karbonaat is gedoen in 'n druk houer. Die logingsvat vir hierdie studie is ontwikkel om die loging sowel as die vloeistof – vastestof skeiding te doen. Gesinterde metaal filter medium was gebruik vir die vloeistof – vastestof skeiding aangesien dit die volgende eienskappe vertoon; die vermoë om druk te weerstaan, die chemiese weerstand teen bytsoda oplossing, asook voordelige terugspoel eienskappe. Optimum loogkondisies is bepaal deur die temperatuur, ammoniak konsentrasie, ammonium karbonaat konsentrasie, en suurstof druk te varieer. Na loging en filtrasie is die pH van die loogvloeistof gemeet en monsters is deur atoom absorpsie spektrofotometrie geanaliseer vir opgeloste metale (Ni, Fe en Co). Die veranderlike wat die grootste effek op die loging van nikkel gehad het was die ammoniak konsentrasie. Die maksimum herwinning van nikkel van uit ongeroosterde erts was 11.9 % by 4 M NH3, 100 oC, 2 M (NH4)2CO3 en 2 bar O2 druk. Optimisering van die loogdata is gedoen deur die respons profiel te analiseer met Statistica sagteware. Optimum loogkondisies was bepaal as 3 M NH3, 2 M (NH4)2CO2, 100 oC en 2 bar O2 druk. Die mineralogie van die erts voor en na loging is bestudeer om te bepaal waarom die nikel opbrengs van ongeroosterde erts so laag was. XRF analise van die vastestof na loging het gewys dat yster, silikon en magnesium nie deur loging affekteer is nie. Slegs nikkel het 'n merkwaardige afname getoon. XRD analsiese van die vastestof voor en na loging wys dat die meeste mineraal fases teenwoordig in die erts nie deur die loogoplossing affekteer is nie. SEM met EDS deteksie is gebruik om die nikkel verspreiding in die erts te bepaal. Die resultate wys dat nikkel meestal met yster assosieer. Die yster is omring deur magnesium en silikon. Silikaat minerale reageer nie met ammoniak en ammonium karbonaat oplossing nie. In filtrasie eksperimente is daar gevind dat die filtrasie differensiële druk geen noemenswaardige effek op die filtrasie tempo gehad het nie. Die gemiddelde filtrasietempo was 0.29+0.07 ml/min.cm2. Die filtrasie tempo van hierdie eksperimente was baie laag, hoofsaaklik as gevolg van blokkasie van porieë van die sinter metaal filter medium. Dit is gevind dat blokkasie van porieë hoofsaaklik op die oppervlak van die filter medium plaasvind. Lateriedes toon 'n lae deurlaatbaarheid as gevolg van die erts se hoë klei inhoud. Rheologiese studies op hierdie erts wys dat die erts skuif verdikking (“shear thickening”) gedrag vertoon. 'n Baie helder filtraat is egter verkry. Die gesinterde metale is na elke loog en filtrasie eksperiment skoongemaak deur terugspoeling met water en lug. Hierdie procedure was suksesvol, aangesien al 18 eksperimente met dieselfde filter medium uitgevoer is. Die effek van erts roostering voor loging is ondersoek by die optimum kondisies wat verkry was vir die loging van ongeroosterde erts. Nikkel ekstraksie het effens verbeter met geroosterde erts. Die gemiddelde persentasie ekstraksie van nikkel van drie eksperimentele lopies was 19.25 % + 0.19 by 100 oC, 3 M NH3, 2 M (NH4)2CO3, en 5 bar suurstofdruk. 'n Gedeelte van die nikkel in die erts was onherwinbaar as gevolg van die assosiasie van nikkel met her-gekristaliseerde sillikaat-minerale in die gereduseerde erts. Die porositeit van die erts is verbeter deur dit te rooster. Die filtrasie tempo het merkwaardig verbeter nadat die erts gerooster is. Die gemiddelde filtrasie tempo was 2.6+0.05 ml/min.cm2. Kinetika vir die oplossing van ongeroosterde en geroosterde saprolitiese lateriet is ondersoek, met in ag geneem die effekte van temperatuur, ammonia konsentrasie, ammonium karbonaat konsentrasie en suurstofdruk. Vir ongeroosterde erts is gevind dat die oplossingstempo en graad van nikkel ekstraksie toeneem met toenemende temperatuur. Toename in ammoniak konsentrasie lei tot 'n toename in nikkel ekstraksie, maar nikkel ekstraksie is nie alleenlik afhanklik van ammoniak nie. 'n Toename in ammonium karbonaat konsentrasie lei ook tot 'n toename in nikkel ekstraksie. Ammonium karbonaat is krities vir die ekstraksie, aangesien ammonium ione in die oplossing die hidrolise van die nikkel-amien kompleks verhoed. Suurstof het nie 'n merkwaardige effek op die totale nikkel ekstraksie gehad nie. Vir die bepaling van reaksie kinetika is 100˚C gebruik as die logingstemperatuur. Die loging van saprolitiese nikkel lateriet vind in twee stadia plaas. In die eerste fase is die oplossing van nikkel vinnig, maar na 15 minute neem die reaksietempo af. Die reaksietempo word verlaag deur inerte minerale wat teenwoordig is in die nikkel erts. Hierdie minerale bevat yster, magnesium en silikon. Die vinnige oplossing van nikkel in die eerste fase verteenwoordig die loging van vry nikkel in die erts. Die data vir die tweede stadium is geanaliseer deur die krimpende kern model, en die resultate dui aan dat die oplossingstempo deur 'n gemengde meganisme beheer word (as laag diffusie en oppervlak reaksie beheer). Die aktiveringsengergie vir die oplossingsreaksie was bereken as 56.5 kJ/mol. Die reaksieorde ten opsigte van ammoniak en ammonium karbonaat is onderskeidelik bepaal as 0.3 en 0.26. Die hoogste graad van nikkel ekstraksie vir die geroosterde erts is verkry by 60oC, 3 M NH3, 2 M (NH4)2CO3, en 5 bar O2 druk. Die persentasie ekstraksie by hierdie kondisies was 28.7 %. Temperatuur het nie 'n merkwaardige effek op loogtempo gehad nie. 'n Toename in NH3 en (NH4)2CO3 het die graad van nikkel ekstraksie laat toeneem, maar het nie enige effek op die loogtempo gehad nie. In die afwesigheid van ammonium karbonaat het byna geen nikkel ekstraksie plaasgevind nie. Die eksperimentele data het nie 'n lineêre passing vir die krimpende kern model soos vir die ongeroosterde erts ondersoek gegee nie. Die rede hiervoor is dat die monsternemings interval te groot was, of dat die logings karakteristiek van geroosterde nikel gekompliseerd is en nie alleen deur die krimpende kern model voorspel kan word nie. Logings eksperimente wys dat die temperatuur hoog moet wees (> 100 oC) om 'n hoë graad van nikkel ekstraksie te verkry met die ongeroosterde erts. 'n Geslote reaktor word benodig om by 'n hoë temperatuur met ammoniak en ammonium karbonaat te loog om reagens verliese te verhoed. Die reaksie kinetika word grootliks deur aslaag diffusie beheer. Hieruit kan gesien word dat 'n lae graad van nikkel ekstraksie uit die ongeroosterde saprolitiese lateriet die gevolg is van nie-reaktiewe minerale (aslaag) waarin die nikkel binne die erts bevat word. Om 'n hoë graad van nikkel ekstraksie te verkry moet die erts onder reduserende kondisies gerooster word. Rooster kondisies moet versigtig beheer word om hoë oplossing van nikkel te verseker. Optimum rooster kondisies om maksimum nikkel oplossing te verkry, moet bepaal word voordat daar met groter hoeveelhede erts gewerk kan word.

This diploma thesis deals with the solution of ammonia separation from waste raw materials of agricultural production. It focuses on determining the efficiency of desorption from an experimental stripping device depending on the measurement temperature. Ammonia water solutions and liquid digestate samples from technical practice were used to verify the functionality of the equipment. Increasing separation efficiency with increasing temperature has been demonstrated. The device was gradually improved during the measurement for a better profitability of the separation process. The results of the experiments are discussed concerning the theoretical assumptions and compared with other methods of ammonia separation.

A proposta deste trabalho é estudar a tecnologia para a remoção de amônia do lixiviado através do processo físico-químico de arraste com ar e a sua caracterização por processos de fracionamento com membranas de MF e UF. Foram analisados no processo de arraste de ar os parâmetros pH, vazão de ar e tempo de operação. Foi verificada a remoção de nitrogênio amoniacal de 93,5% em um tempo de operação de 6 horas, com ajuste de pH igual a 11 e vazão de ar 100 L/h. Após a remoção do nitrogênio amoniacal, os lixiviados foram submetidos a processo de fracionamento com membranas de microfiltração (MF) e ultrafiltração (UF), sendo investigadas a remoção de amônia, a condutividade, DQO, COD, cloreto e pH. Obtiveram-se resultados praticamente constantes à medida que o lixiviado permeou nas membranas de MF e UF. Ademais, empregaram-se testes de toxicidade e ensaios de tratabilidade biológica com amostras de lixiviado bruto, lixiviado tratado (baixa concentração de amônia) e lixiviados fracionados com membranas de MF e UF. Nos ensaios de tratabilidade biológica os resultados mostraram que não houve uma remoção significativa de matéria orgânica e nos testes de toxicidade com organismos Danio rerio, embora tenha ocorrido uma redução na toxicidade na sequência dos experimentos, foi constatado que o lixiviado bruto, lixiviado tratado com remoção de amônia e fracionados com membranas de MF e UF mantiveram elevada toxicidade.
The proposal of present work is to study the technology for removing ammonia from leachate by physico-chemical process of air stripping and its characterization after fractionation processes with MF and UF membranes. Were analyzed the process of entrainment of air pH, air flow rate and operating time. Moreover, there was the removal of ammonia nitrogen from 93.5% in a running time of 6 hours, with pH adjustment equal to 11 and air flow rate 100 L / h. Soon after the first treatment the leachate were characterized in the process of fractionation with membranes (MF and UF) and were investigated the remotion of ammonia, conductivity, COD, COD, chloride and pH. Getting results were nearly constant as the leachate permeated the membranes of MF and UF. Moreover, were employed for toxicity tests and biological treatability tests on samples of raw leachate, leachate treatment group (low ammonia concentration) and leachates fractionated with the MF and UF membranes. In tests of biological treatability results showed no significant removal of organic matter and toxicity tests with organisms Danio rerio, besides the occurrence of a reduction in toxicity, it was found that the raw leachate, leachate treated with removal of ammonia and fractionated with the MF and UF membranes maintained high values of toxicity.

Municipal wastewater contains a significant amount of nutrients such as phosphorus (P) and nitrogen (N). Therefore have the interest of recovering these nutrients at wastewater treatment plants (WWTP) increased. Nutrient recovery would generate revenue for the WWTP, as it is possible to sell the products as fertiliser. Today, there are several techniques on the market to recover P as magnesium ammonium phosphate (MAP) and N as ammonium sulphate (AMS). Urine is the fraction contributing with the highest concentration of nutrients. Techniques to separate urine from the rest of the wastewater have been developed. These techniques enable the possibility to recover nutrients from the urine fraction separately; this is beneficial since the nutrient concentration would be higher. The purpose with this study was to examine the possibility for increased nutrient recovery at centralised WWTPs through urine separation.   Different techniques for nutrient recovery were compared by their recovery efficiency, chemical demand, and hydraulic retention time (HRT). A WWTP with enhanced biological P removal was modelled with Danish Hydraulic Institute’s (DHI) software WEST. Eight scenarios, with different percentage of the population equivalents using urine separation techniques, were simulated. The P recovery was calculated from phosphate (PO4) in the hydrolysed excess sludge and the separated urine. The N recovery was calculated from the ammonium (NH4) in the supernatant from the anaerobe digester. The theoretical biogas production was also calculated, from the modelled sludge.    The comparison of P recovery techniques showed no substantial differences in their recovery efficiency, chemical demand, and HRT. The comparison of N recovery techniques showed three techniques with a higher efficiency than the other methods. Ekobalans Fenix AB, CMI Europe Environment, and Organics developed these techniques. To determine which method to use, requests for proposal from different providers are recommended. As the urine separation increased, the influent P and N load decreased. When the urine separation increased and the operational parameters were kept constant, the effluent concentration of P and N decreased. The ratio of total Kjeldahl nitrogen (TKN) and total nitrogen (TN) however increased as the urine separation increased. The total MAP production calculated from the modelled hydrolysis showed that the production increased as the urine separation increased. On the other hand, the total MAP production from calculated hydrolysis showed a decrease in production as the urine separation increased. The difference in these results could be because of the performance of the modelled hydrolysis was better with a smaller nutrient load, resulting in a larger release of PO4 as the urine separation increased. The total AMS production increased as the urine separation increased. This, due to the increase of the TKN:TN ratio. The biogas production was not substantially affected by the increased urine separation.

Several commercially available reverse osmosis (RO) membranes were characterized with aqueous solutions of ammonium sulfate, potassium triphosphate, and mixtures of these two salts at different feed concentrations, compositions and pressures. The objective of this study was to investigate the rejection of these solutes, in particular the ammonium ion (NH4+), by different RO membranes. The aqueous solutions were assumed to come from an anaerobic digester via a process, currently under investigation by CHFour Biogas Inc., to maintain low concentrations of ammonia in the digester in order to maximize the biogas production. The ammonium ions present in the liquid produced from the process are then concentrated using membrane separation. The concentrated ammonium solution would be a valuable fertilizer that could be used by agriculture. The membranes were characterized with three models: the solution-diffusion model, the Kedem-Katchalsky model, also known as the irreversible thermodynamics model, and the Donnan Steric Pore Model (DSPM). The solution-diffusion and irreversible thermodynamics models were found to be inadequate for proper membrane characterization and the use of the DSPM model yielded membrane properties in good agreement with those found in already existing literature. The pore radius of investigated membranes ranged from 0.39 to 0.51 nm. The effect of pH on membrane surface charge was also studied, with the conclusion that increases in pH led to increasingly negative surface charges. This affected the transport of individual ions through the membrane due to preferential passage of the counter-ions. The effects of applied pressure on the stoichiometric nature of salt rejections were also studied. The minimal observed rejection from the range of experiments carried out using ammonium sulfate was 93%Non-stoichiometric rejections of ions were also observed in the experiments with single and multiple solutes. Furthermore, the rejection of ammonium ions in the presence of other ions (K+, SO42-, PO43-) increased as feed concentration increased, which was a result of the synergistic effects of feed pH and ionic interactions. The minimum NH4+ rejection in the presence of other ions was 95.4%, which suitability using RO membranes for concentration of ammonium from dilute aqueous solutions.

Concentrating quaternary (positive) charge at polymer surfaces is important for applications including layer-by-layer polyelectrolyte deposition and antimicrobial coatings. Prior techniques to introduce quaternary charge to the surface involve grafting of quaternary ammonium moieties to a substrate or using polyurethanes with modified hard segments however there are impracticalities involved with these techniques. In the case of the materials discussed, the quaternary charge is introduced via polyurethane based polymer surface modifiers (PSMs) with quaternized soft segments. The particular advantage to this method is that it utilizes the intrinsic phase separation between the hard and soft segments of polyurethanes. This phase separation results in the surface concentration of the soft segments. Another advantage is that unlike grafting, where modification has to take place after device fabrication, these PSMs can be incorporated with the matrix material during device fabrication. The soft segments of these quaternized polyurethanes are produced via ring opening copolymerization of oxetane monomers which possess either a trifluoroethoxy (3FOx) side chains or a quaternary ammonium side chain (C12). These soft segments are subsequently reacted with 4,4’-(methylene bis (p-cyclohexyl isocyanate)), HMDI and butanediol (BD) to form the PSM. It was initially intended to increase the concentration of quaternary ammonium charge by increasing PSM soft segment molecular weight. Unexpectedly, produced blends with surface microscale phase separation. This observation prompted further investigation of the effect of PSM soft segment molecular weight on phase separation in PSM-base polyurethane blends and the subsequent effects of this phase separation on the biocidal activity. Analysis of the surface morphology via tapping mode atomic force microscopy (TMAFM) and scanning electron microscopy (SEM) revealed varying complexities in surface morphology as a function of the PSM soft segment molecular weight and initial annealing temperature. Many of these features include what are described as nanodots (100-300 nm), micropits (0.5-2 um) and micropeaks (1-10 um). It was also observed that surface morphology continued to coarsen with time and that the larger features were typically observed in blends containing PSMs with low molecular weight soft segments. This appearance of surface morphological feature correlates with decreased biocidal activity of the PSM blends, that is, the PSM blends exhibit little to no activity upon development of phase separated features. A model has been developed for phase separation and concomitant reduction of surface quaternary charge. This model points the way to future work that will stabilize surface charge and provide durability of surface modification.

The isolation of individual enantiomers of drugs is an important subject of interest in the pharmaceutical and medical fields, because stereochemistry can have a significant effect on the biological activity of the drug. Therefore, it is important to develop enantiomeric separation methods for the determination of the optical purity of drugs, since the undesired enantiomer is regarded as one of the impurities. The available single isomer anionic cyclodextrins (CD) can resolve the enantiomers of only a few weakly acidic analytes. To rectify this problem, the chloride salts of heptakis(6-deoxy-6-morpholinio)-cyclomaltoheptaose (HMBCD), and mono(6- deoxy-6-N,N,N r,N r,N r-pentamethylethylenediammonio)-cyclomaltoheptaose (PEMEDA-BCD), the first members of the permanently charged, single-isomer cationic cyclodextrin family, have been synthesized. The purity of process intermediates and final products was determined by HPLC-ELSD and indirect UV-detection capillary electrophoresis. Structural identity was verified by 1D and 2D NMR and massBoth cationic CD derivatives have been used for the separation of the enantiomers of strong acid, weak acid, weak base, ampholytic, and neutral analytes by capillary electrophoresis. Because the charge state of these cationic chiral resolving agents is independent of the pH of the buffer, separation could be performed in both low and high pH buffers without compromising the charge density of the resolving agent. Contrary to expectation, the multiply charged HMBCD showed poor complexation with the newly synthesized strong electrolyte test analytes. The weak binding between the analytes and HMBCD resulted in separation of enantiomers of only three strong electrolyte analytes. Strong complexation was observed between PEMEDA-BCD and the anionic and nonionic analytes in both low and high pH buffers, though complexation was stronger in the high pH buffer. Due to strong complexation between the anions and PEMEDA-BCD, only low concentrations of the resolving agent were required to effect good enantiomer resolutions. spectrometry.

Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 15, 2008) Vita. Includes bibliographical references.

The principal aim of this research was to determine the optimum conditions of extraction and separation of niobium and tantalum with octanol as solvent, from Mozambican tantalite using ammonium bifluoride as an alternative to hydrofluoric acid. The extraction of niobium and tantalum from tantalite can be divided into three activities, viz., acid treatment of the ore to bring the niobium and tantalum values into solution, separation of niobium and tantalum by solvent extraction and preparation of pure niobium pentoxide and tantalum pentoxide by precipitation followed by calcination. An initial solution was prepared by melting a mixture of tantalite and ammonium bifluoride followed by leaching of the soluble component with water and separation of the solution by filtration. The solution filtered was successfully used after adjustment of the acidity for the extraction and separation of niobium and tantalum. After liquid-liquid extraction highly pure niobium pentoxide and tantalum pentoxide were obtained through precipitation with ammonium hydroxide and calcination. Comparative experiments were performed modifying the following variables: decomposition temperature; decomposition time of the digestion of niobium and tantalum; acid concentration of feed solution; solvent agent; and stripping agent. From the experimental results it was determined that the decomposition temperature, decomposition time of the digestion of niobium and tantalum, the acidity of the feed solution, the solvent agent, and stripping agent, all have an important effect on the extraction and separation of tantalum and niobium. The optimal conditions were determined to be: tantalite-to-ammonium bifluoride 1:30; decomposition temperature 250°C; decomposition time 3 hours; and a water leach period of 10 minutes. Under these conditions the leach recovery of niobium and tantalum was about 95.07% and 98.52%, respectively. For nearly complete extraction of tantalum and niobium with 2-octanol, two and three equilibrium stages, respectively, are required. The equilibrium data were obtained at an aqueous-to-organic ratio (A/O) of 1:1 using: 100% 2 octanol; 6 M H2SO4; 10 minutes contact time at room temperature for tantalum; and 100% 2 octanol, 9 M H2SO4, 10 minutes contact time at room temperature for niobium. Different stripping agents were used and water seems to give good result for both. For the nearly complete stripping process four equilibrium stages are required. From the results obtained an optimum stripping efficiency is achieved after 15 minutes for a 1:1 ratio. Niobium and tantalum were then neutralized using 28% ammonium hydroxide. The precipitate obtained was dried and placed in a muffle furnace for 4 hours at 900°C. After calcinations, pure tantalum pentoxide and niobium pentoxide were obtained and characterized using XRD and SEM. Tantalum pentoxide and niobium pentoxide synthesized contain trace impurities such as iron and titanium which can be removed by incorporating an appropriate intermediate treatment.
Dissertation (MSc)--University of Pretoria, 2012.
Chemical Engineering
unrestricted

In this modern age, society has become much more aware of the danger bacteria can have on people's health. Personal and household antimicrobial formulations are commonly used within the home to lower the levels of harmful bacteria such as E. Coli, Salmonella and Pseudomonas. The active which kills the bacteria within the formulation is described as a biocide. This research looks at the often neglected potential of cationic polyelectrolyte as a biocide, firstly within solution and secondly in creating an antimicrobial surface. The solution properties and antimicrobial activity for a range of commercially available cationic polyelectrolytes (polymeric quaternary ammonium compounds (QAC) and biguanides) of differing molecular weights were investigated. All polyelectrolytes were observed to have some level of antimicrobial activity. The second phase of this research investigated polyelectrolyte/surfactant/water mixture of similar charge (cationic). Two QAC surfactants were investigated: Alkyl (C12 70%; C14 30%) dimethyl benzyl ammonium chloride (BAC) and Didecyldimethylammonium chloride (DDQ). At a critical concentration, these mixtures segregatively phase separate into a surfactant rich upper phase and polyelectrolyte rich lower phase. This phase separation phenomenon was investigated in respect of surfactant and polyelectrolyte type as well as polyelectrolyte molecular weight. Surfactant type was observed to be the dominant factor in determining the onset of phase separation and by mixing different ratios of surfactants the ability to tune this phase separation concentration was shown. Dilute solutions of these mixtures well below their respective phase separation concentration were then deposited onto glass substrates via a drop cast or inkjet printer method. The surfactant/polyelectrolyte film composites left after drop evaporation ranged from an amorphous film to nodular like structures. The ability to order/structure actives onto a surface could alter active adhesion and surface roughness properties of the film. This change in surface property could consequently affect antimicrobial performance.

Aujourd’hui, les combustibles fossiles sont largement brûlés pour répondre aux besoins énergétiques croissants des populations humaines et aux enjeux industriels. De grandes quantités de gaz à effet de serre sont ainsi rejetées dans l’atmosphère et contribuent au réchauffement de la planète. Pour cette raison, des techniques d’atténuation du dioxyde de carbone (CO2) efficaces et respectueuses de l’environnement sont nécessaires, comme le captage et de stockage du carbone (CCS) en post-combustion, notamment à l’aide du processus de séparation à base d’hydrates (HBSP). Le HBSP consiste en l’encapsulation de petites molécules de gaz (e.g. CO2, azote (N2), méthane (CH4)) dans des composés cristallins semblables à de la glace, formant des hydrates de clathrate ou hydrates. Des travaux antérieurs ont montré que l’ajout de promoteurs tels que le bromure de tetrabutylammonium (TBAB) améliore considérablement le mécanisme de piégeage du gaz dans l’hydrate de semi-clathrate (sc). C’est pourquoi le HBSP peut s’avérer être une technique appropriée pour le captage sélectif du CO2 et la récupération d’énergie, bien qu’il soit encore nécessaire d’approfondir les connaissances fondamentales que nous avons des processus impliqués avant de pouvoir considérer un déploiement routinier à grande échelle. Ce travail vise à mieux comprendre les processus de séparation et de capture du CO2 à l’aide de l’hydrate sc, ainsi qu’à explorer les processus d’échange dans les hydrates de clathrate pour ouvrir une perspective vers les applications industrielles.Tout d’abord, une revisite des propriétés vibrationnelles de clathrates de CO2 est effectuée par spectroscopie Raman ex-situ à haute résolution pour révéler la distribution de cette molécule dans les hydrates en fonction des paramètres composition, pression et température. Seule une étude a rapporté la répartition des molécules de CO2 dans les petites et grandes cages des hydrates, mais avec une interprétation contestable, probablement due à l’effet de la résonance de Fermi qui en complique l’interprétation. Une des nouveautés de ce travail est l’identification des changements de fréquence en fonction de l’environnement structurel du CO2, améliorant ainsi notre connaissance des mécanismes d’encapsulation. De plus, des analyses Raman à haute résolution corroborées par mesures de diffraction de neutrons sont effectuées sur des sc de TBAB à base de CO2 à des fins de caractérisation.Par la suite, l’étude se concentre sur l’influence du protocole de formation (cristallisation rapide ou lente) sur les mécanismes d’encapsulation, la structure et la sélectivité de CO2+N2-TBAB par mesures Raman in-situ. Un nouveau point de dissociation est obtenu et nos résultats Raman mettent en évidence une performance variable du système sur la sélectivité en CO2 loin de ce point, alors qu’un meilleur résultat est obtenu proche de la dissociation. De même, les facteurs de séparation atteignent leurs plus grandes valeurs proches de la dissociation, en fonction toutefois de la structure du cristal de sc. La variation morphologique de la surface est suivie par microscopie optique et présente une transformation continue avec la température (cristaux polygonaux ou empilés évoluant en cristaux de TBAB-sc cylindriques). De plus, l’influence de la cinétique de formation sur la séparation et la sélectivité du CO2 est explorée.Enfin, une application potentielle de la séparation et du captage du CO2 par HBSP est abordée en étudiant le mécanisme d’échange lors de l’exposition d’un hydrate de clathrate de CO2 à l’azote gazeux. Même si les hydrates de CO2 et de N2 cristallisent respectivement dans les structures sI et sII, après injection de N2, ils forment une structure sI avec une occupation préférentielle des petites cages par les molécules de N2. Ensuite, la cinétique d’échange est analysée avec une perspective supplémentaire de récupération de méthane par injection de CO2 et de CO2+N2
Nowadays, fossil fuels are constantly burnt to fulfill the increasing human and industrial demand in energy, and as a consequence, large quantities of greenhouse gases such as carbon dioxide (CO2) are released in the atmosphere and contribute to global warming. It is therefore pressing to develop efficient post-combustion CO2 mitigation techniques that are also efficient and environment-friendly, and as such, Carbon Capture and Storage (CCS) technologies involving the Hydrate-Based Separation Process (HBSP) have attracted a lot of attention. HBSP consists in encapsulating small gas molecules (e.g. CO2, nitrogen (N2), methane (CH4)) within crystalline ice-like compounds known as clathrate hydrates or hydrates. Previous works have shown that promoters like tetra-n-butyl ammonium bromide (TBAB) considerably improves the guest-gas trapping mechanism in semi-clathrate hydrate (sc). Hence, while HBSP proves to be a suitable technique for selective CO2 capture and energy recovery, advancing the fundamental understanding of processes at play is still needed before large-scale practical applications can be routinely considered. This work aims to better comprehend CO2 separation and capture processes using sc-hydrate technology, while also exploring exchange processes in hydrates to open a perspective towards industrial applications.First, the guest distribution in the hydrate phases of CO2¬-based clathrate hydrates as a function of parameters (initial composition, p, T) is revisited and elucidated by ex-situ high-resolution Raman spectroscopy. Up to now, there is a gap in the literature regarding the discrimination of the contribution of the small and large cages in CO2-based hydrates, mainly due to the Fermi resonance effect. So far, only a single study has attempted to distinguish these contributions in CO2-clathrates, however with a questionable interpretation. One of the novelties of the present work is to revisit the vibrational properties of CO2-clathrates to identify distinct frequency shifts depending on the structural environment of CO2 molecules, thereby improving our knowledge of CO2 encapsulation mechanisms in hydrates. High-resolution Raman analysis and neutron diffraction analyses are additionally performed in CO2-based TBAB-semi-clathrates for characterization purposes.Second, the influence of two different formation protocols (quick and slow crystallization protocols, commonly used in hydrate formation) on the encapsulation mechanisms, the structure, and the selectivity of CO2+N2-TBAB compounds is investigated by in-situ Raman spectroscopy. A new dissociation point (pressure and temperature) is obtained and our results highlight that slow hydrates formation rates exert a variable performance on CO2 selectivity at temperatures far from the dissociation point, while a better performance is observed when approaching dissociation. Similarly, separation factors reach their greatest values close to the dissociation, depending however on the sc crystal structure formed. Surface morphology variation is monitored by optical microscopy and exhibits a continuous transformation with temperature, starting from a rough surface coated with polygonal or stacked shaped crystals to the formation of columnar TBAB-sc crystals near dissociation. Moreover, the influence of the formation kinetics on CO2 separation and selectivity is explored.Finally, a potential application of CO2 separation and capture by HBSP is addressed through the investigation of the exchange mechanism when exposing CO2 clathrate hydrates to N2 gas. Even though CO2 and N2 hydrates crystallize in structure sI and sII, respectively, it is a CO2-N2 mixed hydrate with a preferential occupation of the small cages by N2 molecules that forms upon N2 injection. The exchange kinetics is analyzed from the perspective of methane recovery from CO2 and CO2+N2 injections

Etude thermodynamique et cinetique de la corrosion electrochimique dans les melanges hf-mf(m=k ou nh::(4)) du cuivre metal entrant, soit pur, soit sous forme d'alliage (monel) dans la construction des cellules industrielles d'electrolyse. Mise en evidence de la formation d'une couche de fluorure de cuivre passivante. Evaluation de l'epaisseur limite de la couche. Etablissement de l'influence de la densite de courant sur le caractere passivant de la couche formee. Proposition d'un mecanisme de corrosion du cuivre

Synthèse de divers 18-crowns-6 porteurs d'une partie ose condensée aptes à être fixes sur un support chromatographique ; greffage de silice pour HPLC ; synthèse de supports chromatographiques porteurs de motifs halogénure de benzyle et étude de leur fonctionnalisation par les composés crowns préparés ; complexation des éthers crowns par le potassium, le phenylglycinate d'éthyle, l'éthyl phényl ammonium ; séparation chromatographique de la phénylglycine

碩士
國立中興大學
環境工程學系所
104
Mixed matrix membranes (MMMs) consisting of organic and inorganic phase was raised much attention due to its mechanical strength, thermal ability, and good permselectivity compared to polymer membrane. However, the separation performance of MMMs was influenced by the dispersion of inorganic and the interfacial adhesion between the organic and inorganic phase. Therefore, the choice of suitable materials and the applicable methods to synthesis a defect-free MMMs with good performance have been discussed in the recent works. In this study, the symmetric and asymmetric MMMs were prepared by incorporated ZIF-8 as filler. In the design of green procedure, ZIF-8 crystals were synthesized at the minimum stoichiometric ratio of Zn : Hmim = 1 : 2 with micro-aqueous solution. The ammonia was added as a catalyst to assist in the growth of ZIF-8 crystal. To examine the effect of molar ratio of NH4+ = 0.22-0.42 mol on the morphology and pore arrangement of ZIF-8. Further, the separation performance of MMMs was evaluated by single gas permeation test at different feed pressure. The results indicated that the ZIF-8 crystals can be synthesized by micro-aqueous solution with different NH4+/DIW ratio. Increasing with the molar ratio of NH4+/DIW is benefit to the grain growth of ZIF-8 crystal as well as the improvement of ZIF-8 pore structure development, such as total pore volume and surface area. Moreover, the ZIF-8 fillers have a well adhesion to the organic phase, which effectively increased the gas separation performance of polymer membrane. The CO2 and O2 permeability increased from 16.39 Barrer to 20.89 Barrer and 4.32 Barrer to 5.88 Barrer, respectively. The selectivity of CO2/N2 and O2/N2 reached to 18.43 and 5.77, respectively when adding 10 wt% ZIF-8. Moreover, the addition of ZIF-8 could avoid to the CO2-induced plasticization phenomena of membrane in gas permeation. Thus, CO2/N2 separation performance of MMMs was improved by the additive ZIF-8 at high feeding pressure. However, O2/N2 selectivity of MMMs was not significantly influenced at high permeability due to the pore size of ZIF-8 was not benefit to the transport of O2 and N2 molecules.

This thesis is focused on the selected methods of calculating basic runoff on a small catchment basin known as the P6, which belongs to the basin Kopaninsky flow and assess the impact on the basic runoff concentration of nitrate nitrogen in the total runoff. The thesis also analyzes the total, surface and subsurface runoff with its detailed division. There are also described in detail the chosen methods used for the separation of basic drainage. There is shown their mutual comparison too. We dealt with the nitrogen in groundwater. The methods for separation of basic runoff are described with regard to the content of nitrogen compounds, which are practically the most common type of pollution of groundwater used as drinking water sources.

博士
國立臺灣科技大學
化學工程系
97
Selective separation of phosphate and ammonium from fluoride-containing wastewater of semiconductor manufacturing was studied utilizing magnesium salts. The characteristics of raw wastewater influence the treatment process. In the presence of excess NH4, simultaneous separation of phosphate and ammonium as struvite (MgNH4PO4.6H2O) was investigated. Magnesium chloride (MgCl2.6H2O) was used as precipitation reagent. When at molar ratio ([Mg]:[PO4]) of 2.5:1 and pH 9, total of 84.2% of phosphate and 33.5 % of ammonium were removed. Addition of excess ammonium was beneficial for struvite precipitation, as revealed from experimental results and model prediction. Characterization of solid precipitates using X-ray diffraction (XRD) confirmed the presence of struvite, and other minerals mostly bobierrite ((Mg)3(PO4)2.8H2O). When at lower concentration of ammonium and phosphate, results showed that MgCl2 is a better selective precipitation reagent compared with MgO. In the first stage, total of 41.72 % of phosphate was recovered at molar ratio ([Mg]:[PO4]) of 3:2 and pH 10. Recovery of phosphate increased with increasing molar ratio, and 66.12% of phosphate was recovered when molar ratio ([Mg]:[PO4]) was 3:1. Recovery of phosphate increased as pH increased from 8 to 10. However, it decreased as pH further increased to 12. Solid precipitates in range pH of 8 to 10 were dominantly bobierrite and some amorphous precipitates. Results in this study showed that fluoride and sulfate did not affect precipitation reactions. In the second stage, CaCl2 was used to induce precipitation of calcium fluoride and calcium phosphate. Residual fluoride concentration at pH 10 was 9.9 mg/L. Sodium dodecylsulfate (SDS) was an effective collector for subsequent solid-liquid removal via dispersed air flotation. Theoretical equilibria were modeled with PHREEQC and compared with experimental results. The advantages of selective separation of phosphate, ammonium and fluoride include recovery of struvite and bobierrite as reusable minerals, better control of dosing systems, and higher separation efficiency.

碩士
國立中央大學
化學研究所
91
Abstract This investigation describes the simultaneous separation of two major non-chromophoric quaternary ammonium surfactants, alkytrimethyl and dialkydimethyl ammonium compounds ( ATMACs and DADMACs, respectively ), by capillary electrophoresis ( CE ) with indirect UV detection. The most effective separation condition was 10 mM phosphate buffer with 57.5% tetrahydrofuran and 3 mM SDS at pH 4.35, and the sample hydrodynamic injection of up to 20 sec at 1 psi ( approximately 59.33 nL ), and an applied voltage 25 kV. The selection of appropriate chromophore and internal standard to improve the peak identification and quantitation was systematically investigated. Decylbenzyldimethyl ammonium chloride ( C10-BDMAC ) as a chromophore wih 3 mM SDS provided the best detectability for all homologues. The reproducibility of the migration time and quantitative analysis can be improved by using tetraoctylammonium bromide ( TOA+B- ) as an internal standard, giving the relative standard deviation ( RSD ) less than 0.8% for the relative migration times, and 2.5 to 5.5% for the relative peak areas. A good linearity of CE analysis was obtained in the range of 1.0 to 2.0 μg/mL with r2 values of above 0.999. The analysis of cationic surfactants in commercial products of hair conditioners and fabric softeners was also performed. Electrospray mass spectrometric method ( ESI-MS ) was applied to evaluate the CE method , and the compatible results were obtained.

Tetra-n-Butyl Ammonium Bromide (TBAB) forms semi-clathrate hydrates which can incorporate small gas molecules, such as methane and nitrogen at ambient temperatures and atmospheric pressure. Such favourable stability conditions, combined with ease of formation could make semi-clathrates particularly attractive for a large variety of applications. These hydrates have recently been investigated for their use in the separation of gases, and it is proposed that the same technology could potentially be used for storage and transportation of gases. To evaluate the feasibility of using TBAB hydrates for separation and storage purposes, an extensive test programme was conducted to determine: phase stability of the semi-clathrates, gas storage capacity, and composition of the stored gas. The results show that TBAB semi-clathrates have very favourable stability conditions. They can store considerable quantities of gas, and favour small molecules in their structures. These experiments suggest that semi-clathrate hydrates, such as TBAB, could have a significant potential as an alternative for industrial separation, storage, and transportation of natural gas.

碩士
中原大學
化學工程研究所
100
In ethanol fermentation, the major limitation of the continuous process comes from product inhibition, generally inhibition becoming important as ethanol concentration greater than 10 wt % . The integration of a fermenter with membrane distillation has been investigated as a tool for the continuous removal of ethanol from fermentation broths. In addition, membrane distillation has received attention in recent years for the removal of volatile compounds like ammonia for recycling and reuse of industrial wastewater, especially for which has a relatively low level of ammonia. In this study, simulation and experiments are carried out in the study to analyze the effects of operating conditions on the performances of ethanol and ammonia removal from aqueous streams by membrane distillation. Direct contact membrane distillation(DCMD) and vacuum membrane distillation(VMD) two different membrane distillation processes are considered in the study. Comparison between the simulation result in the study and the experimental data from literatures of VMD ammonia separation showed that simulation analysis with considering free ammonia (FA) factor is better to estimate selectivity of ammonia. Simulation showed that the selectivity of ammonia increases with the vacuumed pressured of the permeated side and the pH of the solution in the pH range of 9~11. Under some conditions given in the study, high ammonia selectivity up to 11 is estimated. Experimental results of DCMD with feed of 5~ 15 wt% ethanol and at 40 oC showed that 0.12μm PTFE membrane gives an ethanol enrichment factor 20~40 % higher than that by 0.45 μm PTFE membrane. As the feed temperature and ethanol concentration increase, ethanol flux increases as a result, while lower ethanol enrichment factors are obtained. It is noted that the PVDF membrane will be wetted when the feed has a higher ethanol concentration as 15 wt % . Comparison between the simulation and the measured fluxes in DCMD showed that the effect of interaction between water and ethanol molecules on effective diffusivity of water can be ignored in calculation of water flux. However, the model with considering the interaction between the two molecules will give a better result in simulation of ethanol flux . Experimental and simulation results at the given conditions of 50~60 oC and 5~15 wt % ethanol concentration showed that ethanol flux and ethanol enrichment factor of VMD are higher than the DCMD operation. But, when the feed temperature is at 40 oC and concentration of 10 ~ 15wt%, the DCMD will produce a higher enrichment factor for ethanol. Simulation results of membranes in the pore size range of 0.01~0.2 m showed that the use of membranes with smaller pore size can enhance the selectivity of the ethanol in DCMD. However, the membrane pore size can only give a slight effect on the ethanol enrichment factor under the conditions given in the study.