The recycling of lead-acid batteries (LABs) is currently an energy intensive, inefficient and polluting procedure. An alternative hydrometallurgical recycling process is investigated in this study. PbO, PbO2, and PbSO4 were individually reacted with a mixture of aqueous citric acid and sodium hydroxide solution, with hydrogen peroxide being used as a reducing agent for PbO2. Pure lead citrate of either Pb(C6H6O7)·H2O or Pb3(C6H5O7)2·3H2O was the product crystallized in each leaching experiment depending on the initial conditions. Combined spent electroactive paste materials from industry were leached and processed. 2.5 M H2O2, 3.2 M C6H8O7·H2O and 3.5 M NaOH were used for optimal leaching and were successful in synthesising Pb3(C6H5O7)2·3H2O after less than one hour. These amounts could be reduced by individual leaching of plate materials. The combustion-calcination of Pb3(C6H5O7)2·3H2O was successful in generating PbO containing both forms of the polymorph α and β crystal phases together with metallic Pb. A novel method to generate PbO from lead citrate was found through a self-sustaining combustion route where leached waste materials were preheated to 270 °C for ~15 minutes and were found to self-sustain a smouldering reaction to produce PbO with a predominately β phase containing metallic Pb. Electrochemical analysis of PbO from Pb3(C6H5O7)2·3H2O demonstrated the viability in the by-product to be used in an electroactive paste and therefore reused in new LABs. Pure α-PbO was generated from both forms of lead citrate, Pb(C6H6O7)·H2O and Pb3(C6H5O7)2·3H2O using NaOH. Pure β-PbO was also generated from Pb(C6H6O7)·H2O and Pb3(C6H5O7)2·3H2O using NaOH through dissolution/re-precipitation reactions. PbCO3 was successfully generated from Pb(C6H6O7)·H2O and Pb3(C6H5O7)2·3H2O using NaOH, NaHCO3 and an acid in a series of disassociation and re-precipitation reactions. PbCO3 could be used to thermally generate α and β-PbO as well as Pb3O4 by calcination at 350, 600 and 450 °C respectively. Glycerol was entrained in both PbCO3 and α-PbO as an in-situ reducing agent to generate PbO containing metallic Pb. Acid reactivity and absorption characteristics of PbO derived from Pb3(C6H5O7)2·3H2O heated in CO2 were equal to and greater than those used in industry for both automotive and industrial batteries.

<div>In this experiment, swirl injectors were designed and tested to validate their use in spraying liquid </div><div>lead into a Barton pot combustion chamber to produce lead oxide at a smaller particle size than </div><div>the current stream injection. Testing was done with water and air to determine the best design for </div><div>atomization results, and then the injector was fabricated for liquid lead testing. Thermochemistry </div><div>calculations showed that due to lead oxidation being a surface reaction, the combustion process </div><div>was diffusion controlled. These conditions were used to determine residence time inside a Barton </div><div>pot combustion chamber for predicted droplet sizes. Results of the liquid lead testing showed that </div><div>final lead oxide particle size and residence time was reduced when using a swirl atomizer in place </div><div>of a steady feed stream. Further calculations were done to create a model for a standard combustion </div><div>chamber and injection system for lead oxide production.</div>

The scope of this thesis was to study thermodynamics of lead oxide and cobalt oxide as the chemical looping agent for oxygen. Furthermore, the theoretical results were verified experimentally. Ellingham diagrams were constructed for the selected oxides. Then, detailed thermodynamic analysis was conducted for stability analysis at different temperatures and pressures. Equilibrium product compositions for various reactions involving these oxides were calculated via Gibbs free energy minimization analysis. Finally, it was shown that cobalt, lead and their oxide forms can be used for syngas production. In the experimental part PbOx, CoOx, Pt-doped CoOx and Pt-doped cobalt alumina, and mixed lead cobalt oxides were synthesized. In addition, technical grade cobalt oxide and lead rods were also used. XRD analysis indicated that Co3O4, Pb2O3 and &alpha / -PbO were the main crystal structures. Oxygen evolution from mixed oxides was monitored by TPD in a home built system. Re-oxidation of the reduced metals was successfully conducted using CO2 and H2O as oxidizing agents. Oxygen TPD studies indicated that oxygen evolution rates and amounts were higher and started at lower temperatures when two oxides were together. These observations were consistent with the predictions obtained from thermodynamics. In a series packed bed reactor, evolved oxygen from the mixed oxides were used to react with coal packed upstream of the oxides. It was found that coal oxidation can be achieved around 400oC and 600oC by using Pb/Co=3 (wt./wt.) looping media with almost no CO2 formation. It was also found that desired product selectivity (CO) can be increased by controlling reactive agent (O2) concentration in reaction environment.

Os ésteres de ácido ftálico são utilizados como aditivos na manufatura de plásticos e a contaminação do meio ambiente por esses compostos pode ocorrer por diferentes mecanismos. Dado o efeito destes no sistema endócrino de animais e seres humanos, efluentes contendo esses compostos sintéticos devem ser adequadamente tratados antes de qualquer descarte. Os tratamentos convencionais são ineficientes para tratar efluentes aquosos contendo esses ésteres e a oxidação eletroquímica tem sido utilizada como uma opção viável. Assim, neste trabalho foi estudada a degradação eletroquímica de dimetil ftalato (DMFt) utilizando três tipos de ânodos: Ti/Ru0.3Ti0.7O2, F-&beta;-PbO2 e diamante dopado com boro (DDB). Os experimentos foram conduzidos em condições galvanostáticas em células de compartimento do tipo filtro-prensa e vários parâmetros, tais como, eletrólito suporte e a densidade de corrente, foram avaliados. Durante as eletro-oxidações, alíquotas das soluções foram analisadas cromatograficamente e por determinações de carbono orgânico total (COT) e demanda química de oxigênio (DQO). Quando utilizado o ânodo de Ti/Ru0.3Ti0.7O2, foram observados níveis de combustão próximos a 100% em baixos valores de carga elétrica aplicada, indicando um possível processo de incineração direta. Com a incidência de radiação UV incidindo diretamente na superfície do eletrodo, foi obtida a completa remoção de DMFt e 98 % de mineralização em meio ácido, elevadas concentração de cloreto e temperatura. A limitação de ambos os processos foi o transporte de massa e assim, os melhores resultados foram obtidos a baixas densidades de corrente. Com o uso do ânodo de &beta;-PbO2 a remoção de DMFt foi superior na presença de Na2SO4 e em baixas densidades de corrente, com 40 % de mineralização. Com o ânodo de DDB foram realizadas eletro-oxidações na ausência e na presença de radiação UV e ultrassônica. Foi obtida a completa remoção de DMFt, COT e DQO em todas as condições estudadas, com maior eficiência a baixas densidades de corrente, devido a menor limitação por transferência de massa. Ocorreu um efeito positivo na eletrooxidação com aplicação conjunta das duas radiações, no entanto, menor do que o obtido com a aplicação destes processos separadamente. O mecanismo de degradação proposto apresenta a oxidação de DMFt seguida da remoção de grupos metil éster e a quebra do anel aromático para formar ácidos carboxílicos, os quais são mineralizados a dióxido de carbono. Na presença de cloreto, a produção de clorofenóis e ácido tartárico e o aumento na concentração dos intermediários formados são as principais diferenças observadas. / The phthalic acid esters are used as additives in plastics manufacturing and the environmental contamination by these compounds may occur by different mechanisms. Considering its effect on the endocrine system of animals and humans beings, effluents containing these synthetic compounds must be properly treated before any disposal. Traditional methods present limited efficiency for treating wastewater containing these esters and electrochemical oxidation has been proposed as a viable option. In this work, the electrochemical degradation of dimethyl phthalate (DMFt) using three types of anodes: Ti/Ru0.3Ti0.7O2, &beta;-PbO2,F and boron-doped diamond (BDD) was studied. The experiments were performed under galvanostatic conditions using a one compartment filter-press cell and different parameters, such as, electrolyte and current density, were analyzed. During the electro-oxidations, aliquots of the solutions extracted at diffent times were analyzed by liquid chromatography and by variations of total organic carbon (TOC) and chemical oxygen demand (COD). Using Ti/Ru0.3Ti0.7O2 anode, the combustion levels were almost 100% when low values of electrical charge were applied, indicating a possible direct incineration process. Applying UV radiation to the electrode surface, the complete removal of DMFt and 98% mineralization were obtained in acid medium with relative high chloride concentration. Both processes were limited by mass transport and therefore, the best results were obtained at low current densities. Using &beta;-PbO2 anode, the removal of DMFt was higher with 40% of mineralization in the presence of Na2SO4 and at low current densities. Using DDB anode, the electrooxidations were performed in the absence and presence of UV and ultrasonic radiations. The complete removal of DMFT, TOC and COD was obtained for all conditions studied with greater efficiency at low current densities because the smallest mass transfer limitation. A positive effect on the electro-oxidation was observed when UV and ultrasound radiation were applied simultaneously however, lower than that obtained with the application of the processes separately. The degradation mechanism proposed presents the oxidation of DMFt followed by removal of methyl ester groups and breakage of the aromatic ring to form carboxylic acids, which are mineralized to carbon dioxide. In the presence of chloride, the production of chlorophenol and tartaric acid and the increased concentration of the intermediates formed are the majors differences observed.

Os ésteres de ácido ftálico são utilizados como aditivos na manufatura de plásticos e a contaminação do meio ambiente por esses compostos pode ocorrer por diferentes mecanismos. Dado o efeito destes no sistema endócrino de animais e seres humanos, efluentes contendo esses compostos sintéticos devem ser adequadamente tratados antes de qualquer descarte. Os tratamentos convencionais são ineficientes para tratar efluentes aquosos contendo esses ésteres e a oxidação eletroquímica tem sido utilizada como uma opção viável. Assim, neste trabalho foi estudada a degradação eletroquímica de dimetil ftalato (DMFt) utilizando três tipos de ânodos: Ti/Ru0.3Ti0.7O2, F-&beta;-PbO2 e diamante dopado com boro (DDB). Os experimentos foram conduzidos em condições galvanostáticas em células de compartimento do tipo filtro-prensa e vários parâmetros, tais como, eletrólito suporte e a densidade de corrente, foram avaliados. Durante as eletro-oxidações, alíquotas das soluções foram analisadas cromatograficamente e por determinações de carbono orgânico total (COT) e demanda química de oxigênio (DQO). Quando utilizado o ânodo de Ti/Ru0.3Ti0.7O2, foram observados níveis de combustão próximos a 100% em baixos valores de carga elétrica aplicada, indicando um possível processo de incineração direta. Com a incidência de radiação UV incidindo diretamente na superfície do eletrodo, foi obtida a completa remoção de DMFt e 98 % de mineralização em meio ácido, elevadas concentração de cloreto e temperatura. A limitação de ambos os processos foi o transporte de massa e assim, os melhores resultados foram obtidos a baixas densidades de corrente. Com o uso do ânodo de &beta;-PbO2 a remoção de DMFt foi superior na presença de Na2SO4 e em baixas densidades de corrente, com 40 % de mineralização. Com o ânodo de DDB foram realizadas eletro-oxidações na ausência e na presença de radiação UV e ultrassônica. Foi obtida a completa remoção de DMFt, COT e DQO em todas as condições estudadas, com maior eficiência a baixas densidades de corrente, devido a menor limitação por transferência de massa. Ocorreu um efeito positivo na eletrooxidação com aplicação conjunta das duas radiações, no entanto, menor do que o obtido com a aplicação destes processos separadamente. O mecanismo de degradação proposto apresenta a oxidação de DMFt seguida da remoção de grupos metil éster e a quebra do anel aromático para formar ácidos carboxílicos, os quais são mineralizados a dióxido de carbono. Na presença de cloreto, a produção de clorofenóis e ácido tartárico e o aumento na concentração dos intermediários formados são as principais diferenças observadas. / The phthalic acid esters are used as additives in plastics manufacturing and the environmental contamination by these compounds may occur by different mechanisms. Considering its effect on the endocrine system of animals and humans beings, effluents containing these synthetic compounds must be properly treated before any disposal. Traditional methods present limited efficiency for treating wastewater containing these esters and electrochemical oxidation has been proposed as a viable option. In this work, the electrochemical degradation of dimethyl phthalate (DMFt) using three types of anodes: Ti/Ru0.3Ti0.7O2, &beta;-PbO2,F and boron-doped diamond (BDD) was studied. The experiments were performed under galvanostatic conditions using a one compartment filter-press cell and different parameters, such as, electrolyte and current density, were analyzed. During the electro-oxidations, aliquots of the solutions extracted at diffent times were analyzed by liquid chromatography and by variations of total organic carbon (TOC) and chemical oxygen demand (COD). Using Ti/Ru0.3Ti0.7O2 anode, the combustion levels were almost 100% when low values of electrical charge were applied, indicating a possible direct incineration process. Applying UV radiation to the electrode surface, the complete removal of DMFt and 98% mineralization were obtained in acid medium with relative high chloride concentration. Both processes were limited by mass transport and therefore, the best results were obtained at low current densities. Using &beta;-PbO2 anode, the removal of DMFt was higher with 40% of mineralization in the presence of Na2SO4 and at low current densities. Using DDB anode, the electrooxidations were performed in the absence and presence of UV and ultrasonic radiations. The complete removal of DMFT, TOC and COD was obtained for all conditions studied with greater efficiency at low current densities because the smallest mass transfer limitation. A positive effect on the electro-oxidation was observed when UV and ultrasound radiation were applied simultaneously however, lower than that obtained with the application of the processes separately. The degradation mechanism proposed presents the oxidation of DMFt followed by removal of methyl ester groups and breakage of the aromatic ring to form carboxylic acids, which are mineralized to carbon dioxide. In the presence of chloride, the production of chlorophenol and tartaric acid and the increased concentration of the intermediates formed are the majors differences observed.