Cobalt electrowinning is an intensive energy-consuming process, and allied to the increasing demand for pure cobalt, has led to the need for optimization. Based on a statistical approach, the effects of additives, including sodium lauryl sulfate (SLS), boric acid (H3BO3), and cobalt chloride (CoCl2) on the current efficiency of electrowinning have been studied using the cyclic voltammetry (CV). CV tests indicated the concentration range of the more appropriate additives to be used in the factorial design study of electrowinning. Regarding the electrowinning tests, the addition of 0.05 g L-1 SLS, 10 g L-1 H3BO3, 50 g L-1 Na2SO4, and 1 g L-1 CoCl2 led to a current efficiency of 96% and energy consumption of 1.95 kWh kg-1, along with a smooth metallic deposit without evident pits and other defects. SLS in its higher concentration level led to the formation of compact structures, while the higher concentration level of H3BO3, lightens the deposits.

Foram investigadas as influências do tempo de eletrólise, da área anódica, da densidade de corrente e do tipo de eletrólito na degradação de fenol e de seus subprodutos de oxidação em anodo de Ti/RuO2. Foi observado que na presença de cloreto ocorreu rápida degradação de fenol e de seus subprodutos. Resultados de cromatografia gasosa/espectroscopia de massa (GC/MS) mostraram que a presença de cloreto levou à formação inicial de clorofenóis através do Cl2 e/ou OCl¯ gerados durante a eletrólise. Entretanto, eles posteriormente atuaram na degradação dos clorofenóis. As concentrações limites estabelecidas pelo Órgão Ambiental Brasileiro (CONAMA) para descartes de fenol e clorofenóis foram obtidas após 360 min de eletrólise a uma densidade de corrente fixa de 10 mA cm-2.Voltamogramas cíclicos obtidos antes e após 436 h de eletrólise em condições severas de salinidade (2 mol L-1) e densidade de corrente (800 mA cm-2) mostraram que o eletrodo de Ti/RuO2 não perdeu suas propriedades eletrocatalíticas

The influences of electrolysis time, anodic area, current density and supporting electrolyte on phenol and its byproducts degradation on a Ti/RuO2 anode were investigated. It was observed that phenol and its byproducts were rapidly broken down in the presence of chloride ions. Gas chromatography/mass spectrometry (GC/MS) data have shown that the presence of chloride ions lead to chlorophenols formation, due to reactions with Cl2 and/or OCl¯ generated during electrolysis. However, these intermediate products were also degraded later by the oxidizing agents. The standards established by the CONAMA (Brazilian National Council for the Environment) for phenols and chlorophenols in effluents were achieved after 360 min of electrolysis with a current density of 10 mA cm-2. Cyclic voltammograms obtained with the anodes before and after 436 h of electrolysis under severe salinity conditions (2 mol L-1) and current density (800 mA cm-2) showed that Ti/RuO2 did not lose its electrocatalytic properties. This fact indicates that Ti/RuO2 can be used for the treatment of effluents containing phenols in a chloride environment