Chemical and Electrocoagulation for Chromium (VI) Removal from Galvanic Effluents

Industrial effluents usually contain 10 to 500 mg/l Cr(VI); that according to international environmental rules must be set at permissible levels before being discharged into the environment. The upper permitted levels of chromium are 0.5 mg/l for effluent discharge and 0.01 mg/l for drinking water respectively. Hexavalent chromium is a very toxic heavy metal moiety occurring in various industrial wastewaters, such as electroplating, anodizing, tanning and dyeing effluents. Industrial effluents may contain hundreds of mg/l of Cr(VI), whereas the upper allowed limit for effluent discharge to aquatic systems is 0.5 mg/l. In the present study, the removal of chromium from industrial electroplating effluents is presented using the chemical coagulation with addition of iron sulfate coagulant and the electrocoagulation process with iron electrodes. Both processes achieved a rapid and effective chromium removal of over 99.9%, with the electrochemical process being superior in terms of the total operational costs.