Separation of zinc ions from aqueous solutions using modified silica impregnated with CYANEX 272

Abstract
Di-2,4,4-trimethylpentyl phosphinic acid (CYANEX 272) was immobilized on a silica surface after it was treated with dichlorodimethylsilane and chlorotripropylsilane. The resulting adsorbent prepared showed an excellent selectivity for zinc ion in aqueous solutions and was stable under acidic conditions. Change in surface and pore structure were investigated by means of FT-IR and BET, respectively. The metal ion adsorption capacity order of the resulting adsorbent (silica powder impregnated with CYANEX 272 after silanization of dichlorodimethylsilane, SPDC) was in the pH range of 2–5. Fixed bed tests were conducted in order to evaluate the efficiency of removal of metal ions using the SPDC, and a breakthrough curve was obtained for the zinc solution. The adsorbed zinc ions could be recovered by treatment with 0.1 M HCl, which permits cyclic use after regeneration.