Removal of Cr(VI) from wastewaters in a tubular electrochemical reactor.

This work aimed at studying the electrochemical reduction of the hexavalent chromium Cr(VI) by means of a tubular reactor operating under both continuous and batch regimes. It is shown that chromium (VI) reduction to chromium (III) was exerted not only by the oxidation of iron to Fe(II) released from the steel sacrifice anodes immersed in an acid solution to aid the overall process. Also, it is shown that there was an additional contribution to chromium reduction from an ancillary reaction at the cathode, where Fe(III) ions generated after the Cr(VI) reduction are again reduced to Fe(II), this being interpreted as a catalytic effect taking place. The results are presented at pH values of 1, 1.3, 1.7, and 2: it became clear that the variable affected the solubility of the species generated in solution. The initial chromium hexavalent concentration was 1000 mg L(- 1) and it was found that after treatment times ranging from 320 to 25 minutes this could reach values as low as 0.5 mg L(- 1), depending on the operating conditions.