Extraction of Hexavalent Chromium from Wastewater of Chromium Production Plant

The experiments on sorption treatment of chromium-containing wastewaters were carried out with anionite Purolite A500/4994. The exchange capacity of anionite was determined at different pH level. The pH of 7.0 was found as the optimal for hexavalent chromium recovery from wastewater. It allows to decrease chromium (VI) concentration to the limits established by the legislation of the Russian Federation (<= 0.02 mg/L). In this case Cr(VI) is extracted as HCrO4- ion and it provides the maximum exchange capacity of the anionite. The sorption from model solution shows 58.1 mg/L exchange capacity and the sorption from real wastewater gives 56.3 mg/mL exchange rate. The chromium(VI) content in effluents is 5-10 times higher than established limits at higher alkalinity of initial solution and the exchange capacity of anionite is two times less than at pH 7. The efficiency of suggested method of hexavalent chromium extraction from wastewater was confirmed by the pilot scale tests.