Removal of chromium (VI) using synergistic liquid–liquid extraction through LIX63/Cyanex 302 system

Abstract

The use of single carrier system in liquid–liquid extraction (LLE) offers a slow kinetic extraction and low capacity of targeted solute in the organic phase which adversely affects the extraction efficiency. Hence, throughout this work, a mixed carrier system containing of 8-diethyl-7-hydroxyldodecane-6-oxime (LIX63) and Di-2,4,4-trimethylpentyl mono-thio-phosphinic acid (Cyanex 302) has been investigated for the synergistic LLE of chromium (VI) from electroplating wastewater. An organic phase consists of a mixture of known concentration of LIX63 and Cyanex 302 in kerosene. Meanwhile, the aqueous phase represents an electroplating wastewater containing of 40 ppm of chromium (VI). Results demonstrated that about 98% of chromium (VI) have been synergistically extracted using a binary mixed carrier system consisting of 0.05 M Cyanex 302 + 0.05 M LIX63 with maximum synergistic factor, Rmax of 27.6. Both LIX63 and Cyanex 302 behaved as a carrier and synergist carrier, respectively. Besides, the stripping performance of chromium from loaded organic phase containing LIX63/Cyanex 302 system showed that Cr could be stripped using 7.0 M of sulfuric acid solutions. It can be concluded that that the synergism behavior of LIX63/Cyanex 302 system in LLE appears as a new formulation which significantly improved the removal of toxic Cr(VI) from electroplating wastewater as well as reducing the use of the expensive and toxic organophosphorus extractants.