Ultrasound mediated reduction of Cr(VI) using sludge obtained during electrocoagulation.

This study presents the ultrasound mediated reduction of toxic hexavalent chromium (Cr(VI)) into non-toxic trivalent chromium (Cr(III)) using sludge obtained during the electrocoagulation of pharmaceutical wastewater (EC sludge). Experiments were carried out with and without ultrasound to explore its influence. The effect of initial concentration of Cr(VI) (100-200 mg/l), pH (6-8) and EC sludge dosage (5-10 g/l) on Cr(VI) reduction was studied. The morphological and functional group changes of EC sludge due to Cr(VI) reduction were analysed with scanning electron microscopy and Fourier transform infrared, respectively. The reduction rates observed in the presence of ultrasound were found to be higher than the rates observed for without ultrasound. The results concluded that the EC sludge can be successfully used for reduction of Cr(VI) at lower cost.