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O objetivo do presente trabalho foi estabelecer um processo eletrolítico para remover metais de efluentes aquosos usando um catodo tridimensional de carbono vítreo reticulado. Durante o desenvolvimento do trabalho foi estudado a influência do fluxo do eletrólito e da porosidade do eletrodo. A célula eletrolítica utilizou potenciais tais que a reação de redução ocorreu sob controle de transporte de massa. A célula demonstrou eficiência na remoção de chumbo, zinco e cobre, reduzindo a concentração desses metais de 50 mg.L -1 a 0,1 mg.L -1 em 20 min de recirculação da solução.The aim of the present study was to establish an electrolytic method for the removal of metals from wastewater using a three dimensional, reticulated vitreous carbon cathode. During the development of the experimental set up, particular attention was paid to the electrolyte flow rate and to the cathode porosity. The electrolytic cell employed potential values in such a way that the metals reduction reaction occurred under mass transport control. These potentials were determined by hydrodynamic voltammetry on a vitreous carbon rotating disc electrode. The cell proved to be efficient in removing copper, zinc and lead and it was able to reduce the levels of these metals from 50 mg/L to 0.1 mg/L.

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Both glassy carbon electrodes and carbon fibre microelectrodes were shown to accumulate Pb 2+ ions at open circuit, the amount of Pb 2+ accumulated being determined by anodic stripping voltammetry in 0.1 M HCl following the accumulation step. The mechanism of Pb 2+ accumulation was investigated by studying the effects of the pH of the solution, the concentration of Pb 2+ and the preconcentration time on the amount of Pb 2+ accumulated. For a 5 min preconcentration time at open circuit, using a glassy carbon electrode (4 mm diameter) and a carbon fibre microelectrode (8 mm diameter), detection of around 10 nM Pb 2+ was obtained for both electrodes. The pH dependence of the amount of Pb 2+ accumulated suggests that the Pb 2+ ions are complexed by carboxylate groups at the surface of the carbon electrodes. This conclusion is supported by results obtained using basal plane and edge plane pyrolytic graphite electrodes and by studies of the effects of electrochemical oxidation of the glassy carbon surface on the magnitude of the lead stripping peak.