Potential use of synergist D2EHPA/Cyanex 302 in kerosene system for reactive extraction: Zinc recovery and organic phase regeneration

Abstract

The extraction of Zn(II) from aqueous solution was studied using extractants mixture in organic base kerosene by reactive extraction. The extraction process was conducted by evaluating some base and synergistic extractants, followed by back-extraction using several types of stripping agents. Around 99% of zinc extraction was achieved at pH 9 using 9 mM D2EHPA as a base and 1 mM Cyanex 302 as a synergistic extractant with a synergistic coefficient of 2.9. Such findings proof to the intensification of reactive extraction compared to the single system. So, the mixture system produced synergistic and productive extraction with minimum use of extractants. The reaction between Cyanex 302-D2EHPA and Zn was studied, and its stoichiometry, as well as the possible structure of Zn(II)-extractant complexes in the extract phase, were investigated. FTIR and the slope analysis method both produced similar findings that Zn•A2•2HB is the zinc form complex with 2 mol D2EHPA (HA) and 2 mol Cyanex 302 (HB) extracted species. Meanwhile, the back-extraction revealed that 0.45 M acidic thiourea is the most effective stripping agent, which achieved almost 100% stripping efficiency. For recycling, the organic phase can be recycled/reused successfully up to 4 times with almost 100% stripping performance.