ABSTRACT A mechanism to convert Fe(III) to Fe(II) by a reduction process could be a solution to the problem of selective separation of metals in extraction processes by using the ion-exchange process. The aim of this research was to reduce Fe(III) to Fe(II) present in leachate from nickel mining waste. Reducing agents used were sodium dithionite and sodium metabisulfite. The potential was decreased in order to quantify the minimum reducing agent that was necessary for conversion. Reaction time, pH, stirring speed and temperature were also studied. Results indicated dithionite was a better reducing agent than metabisulfite and complete conversion was possible by reducing the potential to 590mV at pH 0.5-2 and 240mV at pH 2.5. Stirring speed had no influence on the reduction process at 2 hours; however, conversion decreased after 24 hours, perhaps due to oxygen present in air. The analyses were conducted by ion chromatography and voltammetry.

Abstract This work aims to verify the possibility of using depleted batteries as a source of manganese dioxide applying the electrolytic process. An electrolyte solution containing the following metal ions was used: Ca (270 mgL-1), Ni (3.000 mgL-1), Co (630 mgL-1), Mn (115.3 mgL-1), Ti (400 mgL-1) and Pb (20 mgL-1). The production of electrolytic manganese dioxide (EMD) was performed through electrolysis at 98 °C (± 2 °C) applying different current densities (ranging from 0.61 A.dm-2 to 2.51 A.dm-2). The materials obtained were analyzed through X-ray fluorescence spectrometry, X-ray diffraction, specific surface area (BET) and scanning electron microscopy (SEM). The best results regarding the current efficiency, purity grade and specific surface area were obtained with a current density ranging between 1.02 A.dm-2 and 1.39 A.dm-2. The allotropic εMnO2 variety was found in all tests.

Abstract Membrane separation techniques have been explored for treating industrial effluents to allow water reuse and component recovery. In an electrodialysis system, concentration polarization causes undesirable alterations in the ionic transportation mechanism. The graphic construction of the current voltage curve is proposed for establishing the value of the limiting current density applied to the cell. The aim of this work was to determine the limiting current density in an electrodialysis bench stack, the function of which was the treatment of an electroplating effluent containing HEDP. For this, a system with five compartments was used with a working solution simulating the rinse waters of HEDP-based baths. The results demonstrated correlation between the regions defined by theory and the experimental data.

Este trabalho visou o estudo da produção de lã de rocha utilizando escória da produção de ligas de ferro silício manganês. O resíduo em questão possui características químicas que indicam a possibilidade de adição deste resíduo em formulações de lãs minerais. Procedeu-se a fusão da escória em um forno elétrico a arco, em escala de laboratório. A escória foi fundida e vazada na temperatura de 1450 ºC em um recipiente com água, visando um resfriamento brusco e com isso uma aproximação do método de produção das lãs de rocha. Amostras da lã de rocha produzida foram caracterizadas por técnicas de análise química, difração de raios X, microscopia eletrônica de varredura e análise térmica diferencial sendo que, os resultados obtidos foram comparados aos valores encontrados na literatura. Os resultados encontrados mostram que a reciclagem dos resíduos para a produção de lãs de rocha é promissora, pois o reaproveitamento da escória de ferro silício manganês permite a transformação destes resíduos em subprodutos através da incorporação dos resíduos na produção de lã de rocha, que possui amplo mercado como isolante térmico, acústico e inibidor de propagação de chamas.

This study aimed to investigate the production of rock wool using slag from the production of ferrosilicon manganese alloys. The waste in question has chemical characteristics that indicate the possibility of adding this in formulations of mineral wool. There has been melting the slag in an electric arc furnace in laboratory scale. The slag was melted and poured at a temperature of 1450 ºC in a container with water, aiming at a rapid cooling and thus an approximation of the method of production of rock wool. Samples of rock wool produced were characterized by techniques of chemical analysis, X-ray diffraction, scanning electron microscopy and differential thermal analysis is that the results were compared to those found in the literature. The results show that the recycling of waste for the production of rock wool is promising, for the reuse of slag from ferrosilicon manganese allows the conversion of waste products through the incorporation of waste in the production of rock wool, which has broad market as insulation thermal, acoustic and inhibiting the spread of flames.

Foram investigados os efeitos da adição de um lodo de estação de tratamento de água nas características físicas e mecânicas de uma cerâmica preparada com massa argilosa (cerâmica vermelha). O lodo "bruto" apresentou partículas grossas e angulares (tamanho médio ~200 µm), elevado teor de ferro (73,0% Fe2O3 para 12,6% SiO2, 8,6% Al2O3, 5,2% CaO) e predominância de composto com estrutura amorfa. O lodo calcinado a 1000 °C transformou-se principalmente nas fases hematita e magnetita e as partículas mantiveram a forma original. O lodo bruto foi adicionado em uma massa cerâmica industrial em frações de 0 (controle), 2, 5 e 10% em peso. Os corpos prensados foram sinterizados a 950, 1000 e 1050 °C em forno elétrico. A adição de lodo causou diminuição da resistência à flexão do corpo seco, devido à redução da retração linear de secagem. A temperatura máxima de sinterização da cerâmica com lodo, para a não ocorrência de retração linear excessiva, foi diminuída para ~1000 °C. Até esta temperatura, a incorporação do lodo pouco afetou a retração linear da cerâmica, mas aumentou a absorção de água e diminuiu a resistência à flexão. Os efeitos deletérios da incorporação do lodo foram associados à formação de microtrincas ao redor das partículas do lodo, que pouco interagiu com a matriz argilosa. A calcinação ou a cominuição do lodo possibilitou aumentar a resistência à flexão, pela diminuição da severidade das microtrincas.

The effect of addition of sludge from water treatment plant on the physical and mechanical properties of a structural clay ceramic (red tile) was investigated. Raw sludge presented large and angular particles (average size of ~200 µm) with high iron content (73.0% Fe2O3, 12.6% SiO2, 8.6% Al2O3, 5.2% CaO), and predominantly amorphous structure. After heating at 1000 °C the sludge presented hematite and magnetite as predominant phases, and the particles remained with original shape. Raw sludge was added to an industrial clay in the fractions of 0 (control sample), 2, 5, and 10 mass%. Pressed bodies were sintered at 950, 1000, and 1050 °C in an electric furnace. The sludge addition caused the lowering of flexural strength of dried body because of the decreasing of linear shrinkage of drying. The maximum sintering temperature of samples, in order to avoid over-firing, was reduced to 1000 °C. Up to this temperature, sludge addition did not affect significantly the linear shrinkage of the ceramic, but tend to increase the water absorption and lower the flexural strength. The deleterious effects of sludge addition were associated to the formation of microcracks around the sludge particles. Sludge did not react very much with the clay matrix. Calcining or milling the sludge resulted in an increase of flexural strength, by the lowering of microcrack severity.