Abstract Organic matter-in-aqueous entrainment is a serious problem in the hydrometallurgical extraction of copper from ore. Current inefficiencies, changes in the morphology and orientation of cathode deposit are some of the problems when organic matter is present in the advance electrolyte. In addition, negative effects upon metabolic activity of bioleaching microorganisms are reported due to entrained organic matter in the raffinate electrolyte. In view of these problems, the objective of this study was to evaluate ozonation as an alternative method for the removal of entrained organic matter present in an advanced electrolyte. For this purpose, ozonation during 30 min of synthetic solutions using a bubble glass column reactor at different ozone concentrations, flow rates and temperatures were studied. It was found that the increase in all of these operating parameters is not necessarily associated with an increase of the removal efficiency, and their effects on the mass transfer rate, chemical reaction rate, ozone solubility and contact time play a decisive role in the ozonation process. Thus, the best operating conditions were found at 6.7 wt.%, 1 L min-1 and 27 °C and reached a removal efficiency of 94.5%. This result demonstrated that removal of entrained organic matter in strongly acid solution by ozonation could be an alternative technology.

Abstract The focus of this study is to evaluate the efficiency of oxidation processes in the treatment of a solution containing Rhodamine-B (RhB) used in various industrial applications. The advanced oxidation processes of electrooxidation (EO) and photoelectrooxidation (PEO) were used. At the same time, direct photolysis (DP) was also applied. Total organic carbon (TOC) reduction and color removal were evaluated. There was an efficient color removal when DP was performed, and the color removal efficiency was the highest when NaCl was used as supporting electrolyte for PEO and EO. However, the TOC reduction was low, indicating that the degradation of the color does not correspond to the pollutant mineralization.

Nos dias atuais, há uma infinidade de modelos, tamanhos e configurações de equipamentos eletro-eletrônicos disponíveis para o consumo. Visando a realizar a reciclagem e o reaproveitamento dos metais preciosos encontrados nas placas de circuito impresso (PCI) dos celulares, esse trabalho tem o objetivo de caracterizar o ouro presente nas PCI dos aparelhos celulares e desenvolver uma rota de reciclagem para o ouro e a prata, utilizando reagentes alternativos ao cianeto, como o tiossulfato de sódio e tiossulfato de amônio. Esses reagentes agridem, numa menor intensidade, o meio ambiente e a saúde do trabalhador. Primeiramente realizou-se uma caracterização com água-régia. Os resultados mostraram 86.26g Au/tonPCI e 123.85g Ag/tonPCI. Na segunda caracterização, foi utilizado o reagente comercial a base de cianeto e o resultado foi de 112.02g Au/tonPCI e 26.13gAg/tonPCI. Para a lixiviação com tiossulfato de sódio, chegou-se ao resultado de 9.02g Au/tonPCI, na lixiviação do ouro, e de 33.88g Ag/tonPCI, na lixiviação da prata, comparando com os resultados da caracterização usando reagentes a base de cianeto.

Nowadays there is a wide variety of models, sizes and configurations of mobile phones available for consumption. After the life cycle of this equipment, the recycling and reuse of the precious metals found in the printed circuit boards (PCB) of the mobile phones are principal objectives. Thus, the objective of this work was to characterize the gold and silver present in a PCB and develop a recycling route using alternative reagents for cyanide, such as sodium and ammonium thiosulfate. These reagents are less harmful to the environment and worker health. The first characterization of gold and silver was performed with aqua regia. The results show 86.26g Au/ton of PCBs and 123.85g Ag/ton of PCBs. The second characterization was performed with a commercial cyanide-based reagent and 112.02g Au/ton of PCBs and 26.13g Ag/ ton of PCBs were obtained. A leaching study with solutions based on thiosulfate was performed and an extraction of 9.02g Au/ton of PCBs and 33.88g Ag/ton of PCBs was obtained, compared to characterization results using a cyanide-based reagent.

Considerando-se a preocupação crescente com a toxicidade dos efluentes, pela presença de metais e a ocorrência de novos poluentes orgânicos, esse estudo aplicou o Processo Oxidativo Avançado (POA) de fotoeletrooxidação (FEO) como polimento para o efluente após o processo convencional de tratamento de efluentes da indústria metalomecânica, que, muitas vezes, não remove, satisfatoriamente, metais e aditivos orgânicos. A FEO associou, à degradação de aditivos orgânicos, a remoção do níquel. Foram avaliados efluentes sintéticos com composição similar a efluentes do processo de eletrodeposição de níquel contendo aditivos. Empregando o ânodo de Ti revestido com 70%TiO2/30%RuO2 sob incidência de radiação UV de uma lâmpada de vapor de mercúrio de 250 W e um cátodo de aço inox, 2,5 L de efluente foram tratados em um reator de 1,6 L, com vazão de recirculação de 1 L.min-1. Aplicando diferentes densidades de corrente, observou-se redução da DQO de até 83% e remoção de Ni acima de 90%. Os ensaios de citotoxicidade indicaram que a FEO não gerou intermediários mais tóxicos, pois não ocorreu aumento do efeito tóxico na comparação das soluções antes e após a FEO.

Considering the growing concern about effluent toxicity, generated by the presence of metals and the occurrence of new organic pollutants, this study applied an advanced oxidation process (AOP), denominated the photo-electro-oxidation (PEO), for polishing after the effluent passed through the conventional wastewater treatment from the metal finishing industry that often does not satisfactorily remove metals and organic additives. PEO associated organic additive degradation with nickel removal. A synthetic wastewater, whose composition is similar to a nickel bath containing additives, was evaluated. Employing a Ti anode coated with 70%TiO2/30%RuO2 under an incidence of UV radiation from a mercury vapor lamp of 250 W and a stainless steel cathode, 2.5 L of wastewater were treated in a 1.6 L reactor, at a flow rate of 1L.min-1. Applying different current densities, there was a reduction of up to 83% COD and removal of Ni above 90%. The cytotoxicity assays indicated that PEO did not generate more toxic intermediates because there was no increase in the toxic effect when the solutions were compared before and after PEO.

O crescimento constante na geração de resíduos sólidos em todo o mundo tem estimulado estudos para os mais variados tipos de resíduos. Nesse trabalho, foram estudadas as Placas de Circuito Impresso (PCI), que fazem parte das sucatas eletrônicas e que são encontradas nos equipamentos eletroeletrônicos. As PCI são compostas de polímeros, cerâmicos e metais, o que dificulta o seu processamento. Na primeira etapa desse trabalho, foi utilizado processamento mecânico, como moagem, separação granulométrica, magnética e eletrostática para se obterem uma fração concentrada em metais (principalmente Cu) e uma outra fração contendo polímeros e cerâmicos. Na segunda etapa, a fração concentrada em metais foi dissolvida e enviada para uma eletroobtenção a fim de recuperar o cobre. O teor de cobre alcançou mais de 50% em peso nas frações condutoras e significativos teores de chumbo e estanho. No segundo estágio, as frações concentradas em metais foram dissolvidas com ácidos e tratadas em um processo eletroquímico, a fim de se recuperarem os metais separadamente, especialmente o cobre. Os resultados demonstram a viabilidade técnica para se recuperarem cobre usando processamento mecânico seguido de uma técnica eletrometalúrgica. O conteúdo de cobre, em solução decaiu rapidamente em todos os experimentos e o cobre obtido por eletroobtenção apresentou teores acima de 97% na maioria dos testes.

The constant growth in the generation of solid residues in the world stimulates studies for most types of residual recycling. In this work Printed Circuit Boards, that are part of electronic scraps and are found in electro-electronic equipment, were studied. Printed Circuit Boards are composed of polymers, ceramics and metals, making their processing difficult. During the first stage of this work, mechanical processes, such as comminution, sizing, magnetic and electrostatic separation were used to obtain two concentrated fractions”one with metals (mainly Cu) and the other with polymers and ceramics. During the second stage, the metal-concentrated fraction was dissolved with acids and treated in an electrochemical process to separate the metals. The results were that there was more than a 50% copper content in most of the conductive fractions and also, a significant content of Pb and Sn. This demonstrated the technical feasibility of copper recovery using mechanical processing followed by an electrometallurgical technique. The copper content in solution decayed quickly in all the experiments and the copper obtained by electrowinning was above 97% in most of the tests.