Optimization of Cr(VI) electroreduction from synthetic industrial wastewater using reticulated vitreous carbon electrodes modified with conducting polymers

In order to maintain high values of current efficiency and space–time yield during the electrochemical reduction of Cr(VI) to Cr(III), a new methodology based on the control of the applied current throughout the process was tested. The electrochemical process was carried out using a reticulated vitreous carbon electrode modified with polyaniline. Experiments to determine the reaction rate of Cr(VI) depletion as a function of current and flow velocities were performed in order to establish the relationship between the transition concentration and these operational variables. The transition concentration was the basis of the optimization procedure proposed here and it is defined as being the concentration where the kinetics changes from linear to exponential concentration dependence. The results demonstrate that for a previously optimized flow velocity, control of the current was very effective in maintaining a high space–time yield down to very low concentrations of Cr(VI) and, consequently, the energy consumption was minimized.