A Novel Technique for Hexavalent Chromium Reduction

This study presents a novel technique for the reduction of Cr(VI) to Cr(III) in an acidic aqueous medium. This technique is a batch treatment that utilizes an iron rotating disc as the reductant metal. The removal of the Cr(VI) under various conditions, including retention time, rotation rate, ion initial concentration and the initial pH of the solution, was investigated in this study. The effect of the shape of the rotating iron piece on the Cr(VI) reduction was also examined. It was found that the efficiency of removal of Cr(VI) initially, increased with increasing rate of rotation, retention time and the surface area of the disc until the dichromate ions were totally consumed or a state of equilibrium was reached. Conversely, the removal efficiency of Cr(VI) was found to decrease with the increasing of the solution pH and the initial concentration of Cr(VI). Almost the complete removal of Cr(VI) was achievable in a retention time of fifteen minutes at pH being 1.5 and the initial concentration reaching 100 ppm. Practically, the removal of the Cr(VI) become independent of the rotation rates above 600 rpm with the retention time being more than fifteen minutes. The use of a fan-shaped iron piece, unexpectedly, showed insignificant advantages over the rotating disc as the retention time increased.