Chromium(VI) reduction using conducting polymer films

Reduction of highly toxic hexavalent chromium (Cr(VI)) to its trivalent state (Cr(III)) is necessary to enable further treatment of wastewater by precipitation or adsorption. For this purpose, the present study proposes the use of thin polyaniline films deposited on a large surface area substrate reticulated vitreous carbon (RVC). The influence of electric potential, flow velocity and supporting electrolyte on the reaction rate, current efficiency and energy consumption was investigated for bare RVC and polyaniline-covered RVC. The film stability was also evaluated. The polyaniline thickness was not observed to influence the reaction rate. Also, the synthesis conditions must be controlled in order to guarantee that the substrate surface is completely covered by the polymer. The supporting electrolyte was observed to influence the energy consumption, but not the reaction rate. Flow velocity is very important for process optimization since it improves the mass transfer. Finally, the polyaniline-modified electrode is a promising material for use in Cr(VI) reduction as it remained stable after several cycles and no loss in the reduction rate was observed.