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The goal of this work is to optimize the electrochemical reduction of hexavalent chromium using synthetic solutions employing doped diamond electrodes (BDD) as a cathode material. The rate of Cr(VI) reduction was measured as a function of treatment conditions, the sludge generated in the process was characterized by SEM, EDS and XPS to provide insight into the mechanism of the reduction on the cathode material proposed. Also cyclic voltammetry was used to confirm the cathodic Cr(VI) reduction is taking place.

In this study we present the Cr(VI) reduction in synthetic wastewater using an electrochemical cell using boron doped diamond electrodes (BDD). The best conditions were found when Fe-DDB configuration was used. It is observed that when more current is applied into the electrochemical cell faster reduction rates are achieved. To confirm the experimental data, cyclic voltammetry was used and it was found that the cathodic Cr(VI) reduction is taking place.

Electrochemical methods are a novel approach for Cr(VI) reduction due their high capability, ease and inexpensive use. It was found that Cr(VI) reduction can be done using iron (Fe2+): electro-generated and galvanic production. The behavior of copper was examined as cathode material for optimized continuous reactors, determining copper-iron ratio surface areas (3.5:1) in batch studies of corrosion tests. Results of Cr(VI) reduction capacity showed that copper-iron galvanic systems offers advantages over traditional and even iron electro-generative copper-iron systems and moreover include no energy or chemical input into the system and no sludge generation. On the other hand electro-generative reactor showed a strong correlation between current density and Cr(VI) reduction capacity.

In this work an aqueous solution containing a concentration of the dye 5,5',7-indigo trisulfonic acid of 100 mg L-1 have been degraded by an environmentally friendly electrochemical method. Two different supporting electrolytic media, phosphoric acid and sodium sulfate, were used to investigate their contribution in the efficiency of the degradation process. The electrochemical process used is electrochemical peroxidation (ECP), which uses an undivided cell with iron sheets as cathodes and requires the addition of hydrogen peroxide. As a result, the system promotes the production of hydroxyl radicals (.OH) from the Fenton's reaction that takes place between electro generated Fe (II) and the added H2O2. Under optimal conditions a complete color removal is achieved whereas the COD removal is 97%. The sludge generated from the treatment carried out in phosphate media is a fine white powder composed by oxihydroxi Fe-phosphate species. ECP is a highly efficient method for the degradation of the synthetic indigoid dye.

The aim of this paper is to investigate the effectiveness of a coupled system electrocoagulation - activated sludge processes, in the removal of contaminant from industrial wastewater. An electrochemical treatment provides the elimination of recalcitrant compounds from wastewater, and an activated sludge removes the dissolved pollutants. The electrochemical process reduced 69% of chemical oxygen demand (COD) and the biological removed 55% COD, the global efficiencies were 86% COD, 85% color and 82% turbidity.