Removal Of Chromium From Electroplating Wastewater By Simple Chemical Treatment And Ion Exchange

Abstract

Wastewater from metal plating works was treated with lime - watersuspensions at relatively small concentrations with continuous stirring.Experiments were designed to allow a direct contact of lime suspensionwith the wastewater constituents for a period of time followed by settlingand filtration through a sand filter. The heavy metal content could beprecipitated efficiently from the mother liquor by two mechanisms: reactionwith calcium ions to yield calcium chromate and the precipitation of thechromium hydroxides in the alkaline medium. Various parameters werestudied to reach the optimum conditions for the removal of chromium fromthe wastewater. It appeared that reasonable removal of chromium (80 –85%) could be achieved with lime: wastewater ratio of 40 mg/ L and 50 mincontact time. After the removal of most of the chromium from wastewater,the level of the pollutant needed to be reduced to the acceptable limit bypassing water through ion exchange column. This final treatment gavetreated water samples with chromium levels as low as 0.6 - 1.3 mg/L.