Removal of Ni, Cu and Cr from a galvanic wastewater in an electrocoagulation system with Fe- and Al-electrodes

The performance of an electrocoagulation system for Ni, Cu and Cr removal from a galvanic wastewater in laboratory scale was studied systematically. Several parameters – such as electrode material and arrangement, initial pH, charge loading and applied current – and their influence on the cleaning results and on the electrocoagulation efficiency were investigated. The results with the galvanic wastewater (2 g/l Ni, 2.5 g/l Cu and 0.7 g/l Cr at pH 1.5) revealed that the best cleaning results and the most effective removal could be achieved with a combination of Fe- and Al-electrodes and an pHinitial > 5.0. This approach combined the advantages of both the single set-ups: the pH increase with the Al-electrodes at high currents, the possibility of a Cr(VI)-reduction by Fe2+ and probably a better co-precipitation by Al- and Fe-hydroxides, respectively. An increase of the current accelerated the removal process. With Fe-electrodes at 0.2 A, Al-electrodes at 1.5 A and pHinitial of 5.0, the residual metal concentrations after 180 min were 1.5 mg/l Cr, 6.5 mg/l Cu and 65.3 mg/l Ni at a power consumption of 9.0 kWh/m3.