Recovery of Chromium (III) from Tannery wastewater

Three aqueous oxidants, Hydrogen peroxide, Sodium Hypochlorite and Calcium Hypochlorite were employed independently in oxidizing Chromium (III) containing tannery wastewaters to soluble chromate (CrO_42-) under alkaline conditions. The amount of chromate recovered was determined via spectrophotometry. Hydrogen peroxide was potentially a suitable oxidant as it could recover chromate (CrO_4^2-) up to 98% (from synthetic Cr³⁺ solution) and 88% (from effluent I). The percentage recoveries by the hypochlorites were lower than those by hydrogen peroxide i.e. for NaOCl the recoveries were up to 94% (from synthetic Cr³⁺ solution) and 67% (from effluent I), similarly for Ca(OCl)₂ 90% (from synthetic Cr³⁺ solution) and 49% (from effluent I). For all three oxidants complete (100%) recovery could not be achieved despite different experimental conditions (temperatures and oxidation time). The results clearly indicate that hydrogen peroxide is the most efficient among the three oxidants @ JASEM.