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O tratamento de rejeitos de determinados processos industriais vem ganhando importância, seja pelo impacto negativo do simples descarte no meio ambiente, seja pelo valor econômico de materiais e substâncias que podem ser eventualmente recuperados e reciclados. O rápido empobrecimento de reservas minerais primárias e o aumento de demanda de energia são problemas que merecem atenção especial. Neste contexto, a recuperação de metais existentes nos rejeitos de alguns processos de fabricação assume papel de maior importância. A recuperação do molibdênio presente em soluções nitro-sulfúricas, na forma de rejeitos líquidos do processo de fabricação de lâmpadas incandescentes e fluorescentes, não constitui exceção no que diz respeito à importância da reciclagem. Este rejeito, proveniente da dissolução dos mandris de conformação dos filamentos de tungstênio das lâmpadas, apresenta valores que podem ser recuperados e até reciclados no próprio processo. É o caso dos ácidos nítrico e sulfúrico. Já o molibdênio, presente em concentrações em torno de 40 a 90 g.L-1, pode ser recuperado e utilizado na fabricação de aços especiais, pigmentos, lubrificantes, adubo, etc. Neste trabalho foram desenvolvidos dois processos de recuperação deste rejeito. No primeiro, o rejeito é diluído e por cromatografia de troca iônica o molibdênio é recuperado. Os ácidos efluentes são destilados para a retirada da água. No segundo processo, o rejeito passa por uma destilação e ao mesmo tempo o molibdênio é precipitado. Em ambos os processos, os ácidos recuperados podem voltar à fábrica de lâmpadas para a dissolução dos mandris do filamento de tungstênio e o molibdênio encontra outras diferentes aplicações, além de possuir um valor significativo no mercado. / The waste treatment of certain industrial processes is becoming more important, either by the economic impact of simple disposal in the environment, or by the economic value of materials and substances that can eventually be recovered and recycled. The rapid depletion of mineral reserves and increasing primary energy demand are problems that deserve special attention. In this context, the recovery of metals present in waste of some manufacturing processes assumes a great importance. The recovery of molybdenum present in nitro-sulfur solutions in the form of liquid waste in the manufacturing process of incandescent and fluorescent lamps, is no exception with regard to the importance of recycling. The tailing from the dissolution of the molybdenum mandrel wires used in the conformation of the tungsten filament of electric lamps, has values that can be recovered and recycled to the process itself. Is the case of sulfuric and nitric acids. Molybdenum, present in concentrations around 40 to 90 g.L-1, can be recovered and used in the manufacture of special stainless steel, pigments, lubricants, fertilizer, etc.. In this work two processes for the recovery of this waste were proposed. At the first one, the waste is diluted and molybdenum is recovered by ion-exchange chromatography. The effluent acid from this process was distilled to extract water used in the dilution step. In the second case, the waste goes through a distillation while the molybdenum is precipitated. In both cases, the acids are recovered back to the lamp factory for the dissolution of the molybdenum mandrel wires and molybdenum finds other different applications, as well as having significant value in the market.

M.Sc. (Chemistry) / Please refer to full text to view abstract

Natural materials can be used to remove water contaminants by applying proper physical, chemical, and biological water treatment processes. This study involves using natural materials, as they are considered to be more environmentally benign and cost-effective than synthetic materials. This dissertation concentrates on monitoring five major water quality parameters—ammonia, fluoride, turbidity, pH, and fecal indicator bacteria (FIB) —in two major applications where clean water is needed. The focus is on meeting the water quality requirements for each contaminant. The overall objective of this study is to control the levels of ammonia in aquaculture wastewater, and adjust fluoride, turbidity, pH, and FIB in drinking water by using natural materials. To accomplish this objective, this dissertation study is divided into two parts. Part I is about ammonia removal in aquaculture wastewater. Zeolite was the representative natural material that was used in this study. The methodologies presented include ion exchange and chemical neutralization processes. Part II is about fluoride, turbidity, pH and fecal indicator bacteria control in drinking water. Pumice stone was used in this study. The methodologies utilized in this work include biofiltration and adsorption. In Part I, the methods of ion exchange and chemical neutralization as a function of ammonia removal efficiency, toxicity, and daily cost were compared. All these methods were found to remove ammonia by a simple drop-off system. Chabazite, a natural zeolite, was the ion exchanger source. Similarly, we compared the effectiveness of commercialized neutralizers versus a novel neutralizer prepared for this work. The ion exchanger (chabazite) had the highest ammonia removal in freshwater, but no significant ammonia removal in seawater was observed after in-vivo trials. However, for commercial water neutralizers, the in-vivo trials showed that they are not able to control ammonia levels in either freshwater or seawater. The novel neutralizer was found to have higher ammonia removal efficiencies in both freshwater and seawater. In terms of toxicity, the AmmoSorb can be considered non-toxic. To safely use the novel neutralizer, it is recommended to control its daily dose at 1 g/L/day followed by a two-thirds volume of water change every day. A comprehensive cost analysis also showed that the novel neutralizer was the least expensive ammonia remover. In Part II, drinking water was treated by a bench-scale biosand filter system that included different filtration technologies, biological disinfection, and adsorption. The filtration technologies analyzed in this work include Aluminum Oxide Coated Pumice (AOCP) and sand. The AOCP also works as adsorption media to remove fluoride in water. As results, the AOCP imbedded biosand filter (BSF) can efficiently control fluoride, turbidity, and pH level to meet the WHO standards. In addition, the exhausted BSF can be regenerated by recoating the pumice with additional layers of aluminum oxide. The fluoride, turbidity, pH, as well as fecal indicator bacteria levels controlled by the regenerated BSF also meet the WHO standard for about one-month operation. The overall contribution of this research is providing new methods to treat water at an affordable cost and an easy operational procedure with potential health benefits to the specific applications that require ammonia, fluoride, turbidity, pH, and E. coli levels to be controlled.

M.Sc. (Chemistry) / The storage as solid Ag12BI(s) of reactor produced 12BI (t~ = 1.6 x 107 a) in underground respositories can present an environmental problem due to the potential release of radioactive 12BI into the environment over extended storage periods. One process that causes concern is the solubilization of AgI through complexation when brought into contact with underground water, particularly those with high salt content. In this work the charaqterization of the complexation equilibria in the AgI(s)/I-(aq),CI-(aq) system was studied. Solu- I tions containing high CI- and low 1- concentrations were of special interest with regard to the possible formation of ternary complexes. The presence of AgICI22- was indicated experimentally but no evidence of other ternary species like AgI2CI2- or AgIsCIS- could be established. Solubilities were determined radiochemically by using specially prepared 110mAgI. Solubility curves for AgI in different I-/CI- mixtures were adequately explained in terms of models consisting of the species AgCls2-, AgC14S-, AgIs2-, AgI4s- and AgICI22-. Distribution curves were calculated for different I-/CI- mixtures. As an alternative detection mode for silver-determination a flow injection system incorporating a micro-column of activated alumina was used in conjuntion with flame atomic absorption spectrometry for the pre-concentration and determination of silver in water. The procedure was successfully applied to a range of water samples, but no determination of silver in halide or perchlorate media was possible. The limit of detection based on a sample volume of 15 cms was 4.5 ~gdm-3 and the relative standard deviations at 50 and 5 ~gdm-3 were 5.4 and 19%, respectively. In part B of this work a method for the determination of chloride in organic compounds (oils provided by the Atomic Energy Corporation) by using an Parr oxygen bomb and ion chromatography was studied. The combustion products were absorbed in H20. The solution was injected into an ion chromatograph equipped with an anion analytical column, membrane suppressor and conductivity detector. The instrument response was calibrated using different standard solutions. These were prepared from several organic solutions, an organic salt and from sodiumchloride. Calibration curves were linear over a wide range and presented good reproducibility. It differed however according to the type of standard solution used. The limit of detection was 255 ~gdm-3 and the relative standard deviations at 10, 1 and 0.5 ugcm-3 were 0.52, 1.64 and 3.5%, respectively. As an alternative decomposition method wet decomposition within a sealed system (autoclave) was used. Due to the high blank values in this method no analysis of substances could be made in the lower ugcm-3 range.

M.Sc. / The prevalence of natural organic matter (NOM) in water remains a huge challenge for water treatment companies and municipalities. NOM, however, is not a stand-alone problem as it affects water quality in many ways. NOM is largely responsible for the formation of disinfection by-products (DBPs) via its interaction with disinfectants during water disinfection. It is implicated for the undesirable colour, taste and odour of water and NOM even inhibits precipitation precursors which form the backbone of drinking water treatment. There is therefore no question that NOM, which is either a precursor to or direct cause of the problems highlighted above, should be considered as one of the critical design parameters to be considered for drinking water treatment. In our laboratories, research that involves the use of cyclodextrin (CD) polyurethanes for the removal of organic pollutants from water has been extensively investigated, and the CD polyurethanes have demonstrated the ability to effectively remove the organic species from water at low (ppb) concentrations. CDs, which are cyclic oligomers consisting of glucopyranosyl units linked together through α-1,4 glycosidic linkages, behave like molecular hosts. They are capable of forming inclusion complexes with guest molecules and hence can be utilised for the removal of organic contaminants from water. Their solubility in water, however, limits their application in the removal of organic contaminants from water. This limitation is easily resolved by polymerising the CDs into water-insoluble polymers with bifunctional linkers such as hexamethylene diisocyanate (HMDI). In this study, CD polyurethanes and ion exchange resins were used for the removal of NOM and possibly its DBPs from water. This study first investigated the local NOM source to establish its type and character, hence the study involved the characterization of the bulk water samples and fractionating the NOM using ion exchange resins for further characterization. The water samples were found to consist mainly of humic substances in the form of hydrophobic NOM, with the hydrophilic basic (HpiB) fraction being the most abundant NOM fraction in all samples. Trihalomethanes (THMs) were used as a representative of DBPs in this vii study. THMs formation studies of the individual NOM fractions indicated that all six NOM fractions were found to form THMs but in varying proportions. The HpiB fraction was found to be the most reactive precursor fraction for THMs formation. The ozonation process was also independently evaluated for its ability to remove the NOM fractions from water. Ozonation was found not to be very effective at NOM removal since it only resulted in a 12% overall decrease of the NOM in the water samples. The CD polyurethanes, when used alone, were also not very effective at removing the NOM fractions from water (maximum of 33% NOM removal). On the other hand, the combination method (i.e. the use of CD polyurethanes and ozonation for NOM removal) resulted in a good capability of the CD polyurethanes at decreasing some NOM fractions in water as evidenced by a 73% and 88% decrease of the HpiB and hydrophilic acid (HpiA) fractions, respectively. The 73% reduction of the HpiB fraction demonstrates a great success of the combination approach employed herein, as this study reports this fraction as the most reactive precursor fraction for THM formation.

D.Sc. (Chemistry) / Please refer to full text to view abstract

The characteristics of the ion exchange mechanisms which regulate volume and pH in fish and amphibian erythrocytes were investigated and compared. Experiments were carried out under steady state conditions and also following adrenergic stimulation both in vivo and in vitro. Under steady state conditions, a decrease in extracellular pH caused an increase in the volume of rainbow trout erythrocytes, and a decrease in the intracellular pH. These pH-induced volume changes were mainly associated with movements of chloride across the chloride/bicarbonate exchange pathway. The sodium/proton exchange mechanism is quiescent at all pH's studied under steady state conditions. Beta adrenergic stimulation of rainbow trout erythrocytes promoted cell swelling and proton extrusion from the erythrocytes. Amiloride inhibited both the volume and pH changes associated with adrenergic stimulation indicating that this response is associated with an increase in the activity of the sodium/proton exchange mechanism on the erythrocyte membrane. The adrenergic swelling and pH responses are enhanced by a decrease in extracellular pH. An increase in bicarbonate concentration reduces the adrenergic pH response, but it is still significant even at 10 mM bicarbonate. DIDS markedly enhanced the beta adrenergic effect on the erythrocyte pH, but abolished the increase in erythrocyte volume. The adrenergic response was independent of temperature between 10 and 18°C. These results support a loosely coupled sodium/proton and chloride/bicarbonate exchange model for the adrenergic response in rainbow trout erythrocytes. The increases in erythrocyte pH and volume following adrenergic stimulation are associated with increases in the haemoglobin:oxygen affinity. The oxygen carrying capacity of the blood is, therefore, increased following adrenergic stimulation in rainbow trout. Carbon dioxide excretion, however, was not significantly affected by adrenergic stimulation. The functional significance of the adrenergic response of fish erythrocytes may be to offset the effects of the Root shift on the oxygen carrying capacity of the blood during acute changes in extracellular pH. In contrast to fish erythrocytes, the sodium/proton exchange mechanism in amphibian erythrocytes is active under steady state conditions. In the presence of bicarbonate movements, this exchange significantly affects the erythrocyte volume, but not the erythrocyte pH. Similar to fish erythrocytes, protons are passively distributed in amphibian erythrocytes under steady state conditions and in Donnan equilibrium with chloride ions. The erythrocyte volume also increases with decreases in extracellular pH as in fish erythrocytes, due to changes in the chloride distribution across the erythrocyte membrane. Adrenergic stimulation does not affect the volume or pH of amphibian erythrocytes either in vivo or in vitro. These animals, therefore, do not appear to regulate erythrocyte pH adrenergically. Amphibians are able to efficiently utilize oxygen stores via both central and peripheral shunting. In addition, the blood of these animals does not have a Root shift. Adrenergic regulation of erythrocyte pH in order to enhance oxygen transport during fluctuations in ambient and internal gas tensions, therefore, is probably less important than it would be in fish. / Science, Faculty of / Zoology, Department of / Graduate