Univ., Diss--Helsinki.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xii, 59 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 53-59).

A crescente necessidade de preservação e/ou manutenção da água disponível para o consumo humano gera uma incessante busca por alternativas e métodos eficientes para o tratamento dos efluentes industriais. O objetivo deste trabalho foi avaliar o processo de eletrocoagulação (EC) para tratamento de efluentes galvânicos cianídricos. Avaliou-se as seguintes variáveis de processo, utilizando-se análises estatísticas: tempo de eletrólise, quantidade de eletrólito suporte (NaCl), densidade de corrente aplicada, distância entre eletrodos e área superficial de eletrodos. Utilizouse uma solução sintética simulando o efluente galvânico cianídrico, um reator construído com acrílico transparente e eletrodos de alumínio ligados a uma fonte de corrente contínua para a geração do agente coagulante, com um inversor de pólos acoplado. Determinou-se a perda de massa dos eletrodos pelo método gravimétrico e a quantidade de alumínio remanescente no efluente por absorção atômica. Avaliou-se o comportamento eletroquímico dos eletrodos de alumínio no efluente galvânico cianídrico através de curvas de polarização potenciostáticas. A morfologia e os elementos químicos presentes nos eletrodos de alumínio após o tratamento, foram avaliados pelas análises de microscopia eletrônica de varredura e espectroscopia de energia dispersiva. O lodo galvânico gerado no processo foi caracterizado pelas técnicas de difração de Raios-X e espectroscopia de infravermelho. Obteve-se as seguintes condições ótimas de operação no experimento denominado ECO: tempo de eletrólise de 30 minutos, 5,0 g/L de NaCl adicionado, 8 mA/cm² de densidade de corrente, 1 cm entre eletrodos e 104 cm²/L de área superficial e as remoções de 99,55% de cianeto total, 22,49% de íons níquel, 52,66% de íons cobre e 100,00% de íons zinco. Os resultados dos parâmetros de turbidez, SST, DQO, pH e, remoção de zinco, atendem aos valores passíveis de descarte, não sendo obtidos para os parâmetros de cianeto total, íons cobre e níquel. Obteve-se 8,50 mg/L de alumínio no experimento ECO, passível de descarte e aumento de 20,00% de eficiência para a remoção de cianeto total, íons níquel e cobre com a utilização do inversor de pólos. A eficiência da EC e da cloração alcalina foram semelhantes para a remoção de cianeto total e íons zinco, obtendo-se remoções superiores à 70,00% e 40,00% para os íons níquel e cobre através da cloração alcalina. Nas análises de MEV observou-se corrosão por pitting nas faces externas dos eletrodos de alumínio e corrosão generalizada nas faces internas. As análises de EDS apontaram a presença de óxido de alumínio e cobre na superfície dos eletrodos. Os resultados eletroquímicos mostraram que, quanto maior a quantidade de NaCl adicionada ao efluente galvânico, maior a dissolução anódica dos eletrodos de alumínio, maior a densidade de corrente no circuito e menor o potencial necessário a ser aplicado. Quanto ao lodo galvânico, nas análises de DRX e FT-IR identificou-se agentes coagulantes na forma de hidróxidos de alumínio, e na análise de FT-IR comprovou-se a presença ds metais cobre, níquel e zinco, cianeto e cianato. Atribui-se os resultados de remoção obtidos àsinergia dos processos de EC e da oxidação eletrolítica dos complexos cianídricos metálicos em função da diferença de potencial aplicado. O processo de EC mostrou-se eficiente para a remoção de contaminantes de efluentes galvânicos cianídricos e se obteve parâmetros finais passíveis de descarte de acordo com as normativas vigentes. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2014-11-24T12:37:56Z No. of bitstreams: 1 Dissertacao Tais Sabedot Pertile.pdf: 4298069 bytes, checksum: aea769b9a9953a1a4957813f5a0e08f9 (MD5) / Made available in DSpace on 2014-11-24T12:37:56Z (GMT). No. of bitstreams: 1 Dissertacao Tais Sabedot Pertile.pdf: 4298069 bytes, checksum: aea769b9a9953a1a4957813f5a0e08f9 (MD5) / The growing need for preservation and/or maintenance of water available for human consumption generates an endless search for alternative and efficient methods for the treatment of industrial effluents. The aim of the present work was to evaluate the process of electrocoagulation (EC) for the treatment of hydrocyanic galvanic effluent. The following process variables were evaluated, using statistical analysis: electrolysis time, amount of supporting electrolyte (NaCl), applied current density, distance between electrodes and electrode surface area. It was used a synthetic solution simulating the hydrocyanic galvanic effluent, an reactor built with transparent acrylic and aluminum electrodes connected to a continuous current source for generation of coagulating agent, coupled with an polarity inverter. The mass loss of the electrodes was determined by gravimetric method and the amount of aluminum remaining in the effluent by atomic absorption. The electrochemical behavior of aluminum electrodes in the hydrocyanic galvanic effluent was evaluated by potentiostatic polarization curves. The morphology and chemical elements present in the aluminum electrodes after treatment were evaluated by analysis of scanning electron microscopy and energy dispersive spectroscopy. The galvanic sludge generated in the process was characterized by the techniques of X-ray diffraction and infrared spectroscopy. The following optimal operating conditions were obtained in experiment named ECO: electrolysis time of 30 minutes, addition of 5.0 g/L NaCl, current density of 8 mA/cm², 1 cm between electrodes and surface area of 104 cm²/L and the removal results of 99.55% total cyanide, 22.49% nickel ions, 52.66% copper ions and 100,00% zinc ions. The results of turbidity, TSS, COD, pH and removal of zinc parameters, meet the amounts subject to disposal of treated effluent, not being obtained for total cyanide, copper and nickel ions parameters. It was obtained 8.50 mg/L of aluminum in the ECO experiment, amenable to disposal and increased by 20,00% the efficiency removal of nickel and copper ions and total cyanide using the polarity inverter. The efficiency of EC and alkaline chlorination removal were similar for total cyanide and zinc ions, obtaining removal greater than 70,00% and 40,00% for nickel and copper ions by the alkaline chlorination. SEM analysis showed pitting corrosion in the external faces of the aluminum electrodes and general corrosion in internal faces. EDS analysis indicated the presence of aluminum oxide and copper on the surface of the electrodes. The electrochemical results showed that the higher the amount of NaCl added to the galvanic effluent, the higher the anodic dissolution of aluminum electrodes, the higher the current density in the circuit and lower the necessary potential to be applied. Regarding the galvanic sludge, in the analyzes of XRD and FT-IR were identified coagulating agents in the form of hydroxides of aluminum, and the FT-IR analyzes proved the presence of the metals copper, nickel and zinc, cyanide and cyanate. The obtained removal results are attributed to the synergy of EC process and the electrolytic oxidation of the metal cyanide complexes as function of applied potential difference. The EC process was efficient for removing contaminants from hydrocyanic galvanic effluent and resulted in final parameters amenable of disposal according to current regulations.

A crescente necessidade de preservação e/ou manutenção da água disponível para o consumo humano gera uma incessante busca por alternativas e métodos eficientes para o tratamento dos efluentes industriais. O objetivo deste trabalho foi avaliar o processo de eletrocoagulação (EC) para tratamento de efluentes galvânicos cianídricos. Avaliou-se as seguintes variáveis de processo, utilizando-se análises estatísticas: tempo de eletrólise, quantidade de eletrólito suporte (NaCl), densidade de corrente aplicada, distância entre eletrodos e área superficial de eletrodos. Utilizouse uma solução sintética simulando o efluente galvânico cianídrico, um reator construído com acrílico transparente e eletrodos de alumínio ligados a uma fonte de corrente contínua para a geração do agente coagulante, com um inversor de pólos acoplado. Determinou-se a perda de massa dos eletrodos pelo método gravimétrico e a quantidade de alumínio remanescente no efluente por absorção atômica. Avaliou-se o comportamento eletroquímico dos eletrodos de alumínio no efluente galvânico cianídrico através de curvas de polarização potenciostáticas. A morfologia e os elementos químicos presentes nos eletrodos de alumínio após o tratamento, foram avaliados pelas análises de microscopia eletrônica de varredura e espectroscopia de energia dispersiva. O lodo galvânico gerado no processo foi caracterizado pelas técnicas de difração de Raios-X e espectroscopia de infravermelho. Obteve-se as seguintes condições ótimas de operação no experimento denominado ECO: tempo de eletrólise de 30 minutos, 5,0 g/L de NaCl adicionado, 8 mA/cm² de densidade de corrente, 1 cm entre eletrodos e 104 cm²/L de área superficial e as remoções de 99,55% de cianeto total, 22,49% de íons níquel, 52,66% de íons cobre e 100,00% de íons zinco. Os resultados dos parâmetros de turbidez, SST, DQO, pH e, remoção de zinco, atendem aos valores passíveis de descarte, não sendo obtidos para os parâmetros de cianeto total, íons cobre e níquel. Obteve-se 8,50 mg/L de alumínio no experimento ECO, passível de descarte e aumento de 20,00% de eficiência para a remoção de cianeto total, íons níquel e cobre com a utilização do inversor de pólos. A eficiência da EC e da cloração alcalina foram semelhantes para a remoção de cianeto total e íons zinco, obtendo-se remoções superiores à 70,00% e 40,00% para os íons níquel e cobre através da cloração alcalina. Nas análises de MEV observou-se corrosão por pitting nas faces externas dos eletrodos de alumínio e corrosão generalizada nas faces internas. As análises de EDS apontaram a presença de óxido de alumínio e cobre na superfície dos eletrodos. Os resultados eletroquímicos mostraram que, quanto maior a quantidade de NaCl adicionada ao efluente galvânico, maior a dissolução anódica dos eletrodos de alumínio, maior a densidade de corrente no circuito e menor o potencial necessário a ser aplicado. Quanto ao lodo galvânico, nas análises de DRX e FT-IR identificou-se agentes coagulantes na forma de hidróxidos de alumínio, e na análise de FT-IR comprovou-se a presença ds metais cobre, níquel e zinco, cianeto e cianato. Atribui-se os resultados de remoção obtidos àsinergia dos processos de EC e da oxidação eletrolítica dos complexos cianídricos metálicos em função da diferença de potencial aplicado. O processo de EC mostrou-se eficiente para a remoção de contaminantes de efluentes galvânicos cianídricos e se obteve parâmetros finais passíveis de descarte de acordo com as normativas vigentes. / The growing need for preservation and/or maintenance of water available for human consumption generates an endless search for alternative and efficient methods for the treatment of industrial effluents. The aim of the present work was to evaluate the process of electrocoagulation (EC) for the treatment of hydrocyanic galvanic effluent. The following process variables were evaluated, using statistical analysis: electrolysis time, amount of supporting electrolyte (NaCl), applied current density, distance between electrodes and electrode surface area. It was used a synthetic solution simulating the hydrocyanic galvanic effluent, an reactor built with transparent acrylic and aluminum electrodes connected to a continuous current source for generation of coagulating agent, coupled with an polarity inverter. The mass loss of the electrodes was determined by gravimetric method and the amount of aluminum remaining in the effluent by atomic absorption. The electrochemical behavior of aluminum electrodes in the hydrocyanic galvanic effluent was evaluated by potentiostatic polarization curves. The morphology and chemical elements present in the aluminum electrodes after treatment were evaluated by analysis of scanning electron microscopy and energy dispersive spectroscopy. The galvanic sludge generated in the process was characterized by the techniques of X-ray diffraction and infrared spectroscopy. The following optimal operating conditions were obtained in experiment named ECO: electrolysis time of 30 minutes, addition of 5.0 g/L NaCl, current density of 8 mA/cm², 1 cm between electrodes and surface area of 104 cm²/L and the removal results of 99.55% total cyanide, 22.49% nickel ions, 52.66% copper ions and 100,00% zinc ions. The results of turbidity, TSS, COD, pH and removal of zinc parameters, meet the amounts subject to disposal of treated effluent, not being obtained for total cyanide, copper and nickel ions parameters. It was obtained 8.50 mg/L of aluminum in the ECO experiment, amenable to disposal and increased by 20,00% the efficiency removal of nickel and copper ions and total cyanide using the polarity inverter. The efficiency of EC and alkaline chlorination removal were similar for total cyanide and zinc ions, obtaining removal greater than 70,00% and 40,00% for nickel and copper ions by the alkaline chlorination. SEM analysis showed pitting corrosion in the external faces of the aluminum electrodes and general corrosion in internal faces. EDS analysis indicated the presence of aluminum oxide and copper on the surface of the electrodes. The electrochemical results showed that the higher the amount of NaCl added to the galvanic effluent, the higher the anodic dissolution of aluminum electrodes, the higher the current density in the circuit and lower the necessary potential to be applied. Regarding the galvanic sludge, in the analyzes of XRD and FT-IR were identified coagulating agents in the form of hydroxides of aluminum, and the FT-IR analyzes proved the presence of the metals copper, nickel and zinc, cyanide and cyanate. The obtained removal results are attributed to the synergy of EC process and the electrolytic oxidation of the metal cyanide complexes as function of applied potential difference. The EC process was efficient for removing contaminants from hydrocyanic galvanic effluent and resulted in final parameters amenable of disposal according to current regulations.

No description available.

The electrolysis of water was evaluated as a potentially efficient, as a low cost means of hydrogen production. The theoretical energy, voltage, current, and energy efficiencies of water electrolysis were considered by using various catalyst materials used in the fabrication of membrane electrode assemblies used in low temperature water electrolysis systems. Traditionally, iridium based catalysts have shown to be the most suitable material for its use on electrocatalysis of water to form hydrogen. This study showed that a combination of various elements as a binary and or ternary mixture in the base catalyst that was applied to the anode and cathode by using the Adam’s method had shown to give comparatively good results to that of using iridium oxide on its own. These catalysts were characterized by cyclic voltammetry, at different temperatures (30oC-80oC) with a range of catalyst loading of 0.2-0.5 mg.cm-2 noble metals. The study showed that the Ir40Co40 mixture as an anode catalyst was found to show highest hydrogen efficiency of 73 percent with a relatively low over potential of 0.925V at higher temperature of 80oC. The mixture also showed to give the best electrocatalytic activity with a low Tafel slope of 30.1mV.dec-1. Whereas the Ir50Pt50 showed a comparatively lower hydrogen efficiency of 65 percent with a lower over potential of 0.6V at 50oC. Ternary mixed oxide of Ir20Ru40Co40 showed an even lower over potential of 0.5- 0.6V over a large range of temperatures with a low hydrogen efficiency of 44 percent but gave good electrocatalytic activity in terms of the Tafel slope analysis. On the other hand, mixtures with relatively cheaper material such as Nickel in binary mixture systems such as Pt50Ni50 as cathode catalyst was found to show promising performance of a relatively low over potential that was less than 1.4 V with a low hydrogen efficiency of 62.1 percent Ternary cathode catalyst materials such as Pt33Ni33Co33 exhibited good performance with higher hydrogen efficiency of 65.2 percent at lower over potential of 1.2 V and a higher Tafel slope of 133.9 mV.dec-1 at 80 0C.

No description available.

No description available.

Water electrolysis is one of the first methods used to generate hydrogen and is thus not considered to be a new technology. With advances in proton exchange membrane technology and the global tendency to implement renewable energy, the technology of water electrolysis by implementation of proton exchange membrane as solid electrolyte has developed into a major field of research over the last decade. To gain an understanding of different components of the electrolyser it is best to conduct a performance analysis based on hydrogen production rates and polarisation curves. The study aim was to compare the technologies of membrane electrode assembly with gas diffusion electrode and the proton exchange membranes of Nafion® and polybenzimidazole in a commercial water electrolyser. To determine which of the components are best suited for the process a laboratory scale electrolyser was to be used to replicate the commercially scaled performance. The effect of feed water contaminants on electrolyser performance was also investigated by introducing iron and magnesium salt solutions and aqueous methanol solutions in the feed reservoir. Components to be tested included different PEM types as well as the base component on which the electrocatalyst layer is applied. The proton exchange membranes compared were standard Nafion® N117 and polybenzimidazole meta-sulfone sulfonated polyphenyl sulfone (PBI-sPSU). A laboratory scale electrolyser from Giner Electrochemical Systems was utilised where different components were tested and compared with one another. Experimental results with commercial membrane electrode assemblies and gas diffusion electrodes demonstrated the influence of temperature on electrolyser performance for the proton exchange membranes, where energy efficiency increased with temperature. The effect of pressure was insignificant over the selected pressure range. Comparison of membrane electrode assembly and gas diffusion electrode technologies showed enhanced performance from MEA technology, this was most likely due to superior electrocatalyst contact with the PEM. Results of synthesised Nafion® N117 and PBI-sPSU MEA showed increased performance for PBI-sPSU, but it was found to be more susceptible to damage under severe conditions. The effect of metal cations in the supply reservoir exhibited reduced energy efficiencies and increased specific energy consumption for the test duration. Treatment with sulphuric acid was found to partially restore membrane electrode assembly performance, though it is believed that permanent damage was inflicted on the membrane electrode assembly electrocatalyst. Use of aqueous methanol solutions were found to increase electrolyser performance. It was also found that aqueous methanol electrolysis occurs at lower current densities, whereas a combination of aqueous methanol and water electrolysis occurred at higher current densities depending on the concentration of methanol. / Thesis (MIng (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013.

Water electrolysis is one of the first methods used to generate hydrogen and is thus not considered to be a new technology. With advances in proton exchange membrane technology and the global tendency to implement renewable energy, the technology of water electrolysis by implementation of proton exchange membrane as solid electrolyte has developed into a major field of research over the last decade. To gain an understanding of different components of the electrolyser it is best to conduct a performance analysis based on hydrogen production rates and polarisation curves. The study aim was to compare the technologies of membrane electrode assembly with gas diffusion electrode and the proton exchange membranes of Nafion® and polybenzimidazole in a commercial water electrolyser. To determine which of the components are best suited for the process a laboratory scale electrolyser was to be used to replicate the commercially scaled performance. The effect of feed water contaminants on electrolyser performance was also investigated by introducing iron and magnesium salt solutions and aqueous methanol solutions in the feed reservoir. Components to be tested included different PEM types as well as the base component on which the electrocatalyst layer is applied. The proton exchange membranes compared were standard Nafion® N117 and polybenzimidazole meta-sulfone sulfonated polyphenyl sulfone (PBI-sPSU). A laboratory scale electrolyser from Giner Electrochemical Systems was utilised where different components were tested and compared with one another. Experimental results with commercial membrane electrode assemblies and gas diffusion electrodes demonstrated the influence of temperature on electrolyser performance for the proton exchange membranes, where energy efficiency increased with temperature. The effect of pressure was insignificant over the selected pressure range. Comparison of membrane electrode assembly and gas diffusion electrode technologies showed enhanced performance from MEA technology, this was most likely due to superior electrocatalyst contact with the PEM. Results of synthesised Nafion® N117 and PBI-sPSU MEA showed increased performance for PBI-sPSU, but it was found to be more susceptible to damage under severe conditions. The effect of metal cations in the supply reservoir exhibited reduced energy efficiencies and increased specific energy consumption for the test duration. Treatment with sulphuric acid was found to partially restore membrane electrode assembly performance, though it is believed that permanent damage was inflicted on the membrane electrode assembly electrocatalyst. Use of aqueous methanol solutions were found to increase electrolyser performance. It was also found that aqueous methanol electrolysis occurs at lower current densities, whereas a combination of aqueous methanol and water electrolysis occurred at higher current densities depending on the concentration of methanol. / Thesis (MIng (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013.