Synergetic formulation of Cyanex 272/Cyanex 302 for hexavalent chromium removal from electroplating wastewater

Abstract

Hazardous hexavalent chromium (Cr(VI)) released from the electroplating industry beyond the discharge concentration limit has created great concern worldwide. Solvent extraction (SX) is an effective method for metal separation from an aqueous system. Throughout this work, novel synergistic solvent extraction of Cr(VI) from rinsed electroplating wastewater was performed using a mixture of two organophosphorus acidic extractants containing di-2,4,4-trimethylpentyl phosphinic acid (Cyanex 272) and di-2,4,4-trimethylpentyl mono-thio-phosphinic acid (Cyanex 302) in kerosene. The results showed almost 99±0.816% of Cr(VI) was synergistically reduced and extracted to the less toxic trivalent chromium (Cr(III)) using the total mixture concentration of 0.1 M (0.04 M Cyanex 272+0.06 M Cyanex 302). For recycling, the organic phase was recycled or reused up to 11 times for excellent extraction (99±0.471%) and stripping (99±0.942%) and became stable afterwards until a certain time. The total concentration of the mixture system was reduced by 50% (0.05 M) using 0.01 M Cyanex 272 and 0.04 M Cyanex 302, with almost 100% of Cr(VI) extraction as less toxic Cr(III). The Cr(III) in the loaded organic phase was completely recovered using 7.0 M hydrochloric acid (HCl). It is concluded that the synergistic extraction using Cyanex 272/Cyanex 302 system improved the Cr(VI) extraction and reduced the chemical consumption in the organic phase.