Study of reducing Chromium (VI) to Chromium (III) ion using reduction and coagulation methods for electroplating industrial waste

The electroplating industrial waste is the primary source of environmental pollution due to heavy metal chromium (VI). The method commonly used in treating chromium (VI) metal waste in industry is by reduction and coagulation. Chromium (VI) metal is very toxic because it is very unstable compared to chromium (III). Therefore, chromium (VI) waste must be reduced to chromium (III) before it will be discharged into the environment. The purpose of this study is to find the optimum conditions in reducing levels of chromium (VI). The method used is reduction with sodium metabisulfite, coagulation with Polyaluminium chloride (PAC), and a combination of both. The percentage of reduction obtained in the reduction, coagulation, and combined methods is 96.36%; 20.57%; and 98.57%, with the optimum dose of reducing agents and coagulants of 330 mg/L and 300 mg/L. The best method to reduce the level of chromium (VI) is the combined method at a percentage reduction of 98.57% with a standard deviation of 0.0046 and %RSD of 0.43%. The electroplating waste has reduced percentage until 98,39% at using combination methods. (paper)