Industrial water treatment plant. The electrochemical method of wastewater treatment is primarily used for extraction of chromium.
The chromium is removed by sedimentation and by electrolysis with iron anodes.
The process is based on the oxidation of trivalent to hexavalent chromium at the anode. The solution is pumped through electrolytic cell. The electrodes (anode / cathode ratio is (30/1) are energized with direct current. This electrochemical process keeps the concentration of trivalent chromium in the range of 60-75 g / l and hexavalent chromium concentration of 1069-1137 g / l. This technology allows multiple reuse of chromic acid. But with all its appeal (heavy metals come in pure form, no septic tanks or bulky chemical plant needed) this electrolysis method is not widely used, as the metal is obtained in powder form and requires additional processing for recycling. More promising is the method of direct electrolysis for recycling the recovered metal from draining solution.
Since the chromium effluents, apart from chromium (III, VI), also contain iron, copper, lead and zinc, complete purification requires extraction of these metals. For this purpose reagent method is used. However, this method does not provide a high degree of purification because of its inability to simultaneously sediment all metals in the effluent.