Pitting corrosion of chloride ions in electrocoagulation for Cr(VI) removal: optimization by response surface methodology

This work observed an interesting phenomenon of pitting corrosion by chloride ions (Cl-) in electrocoagulation (EC) for Cr(VI) removal. High Cr(VI) removal capacity was achieved by initiating pitting corrosion on iron surface with Cl- over 50 mg L-1, as showed by environmental scanning electron microscope analysis (ESEM). Then response surface methodology (RSM) was applied to optimize the Cr(VI) removal in the case of Cl-. RSM suggested that the optimal operation conditions were initial pH at 5.24, applied currents at 0.914 A and Cl- concentration at 54.37 mg L-1. The verification test showed 99.98 % of Cr( VI) removal efficiency under the above optimal condition. Our study indicated that Cl- can act as an enhancement factor by pitting corrosion in EC for Cr(VI) removal.