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Zinc Ion Removal from Aqueous Solutions Using Modified Silica Impregnated with 2-Ethylhexyl 2-Ethylhexyl Phosphonic Acid

2-Ethylhexyl 2-ethylhexyl phosphonic acid was immobilized on a silica surface after treatment with dichlorodimethylsilane. Batch and fixed-bed tests were conducted in order to evaluate the metal ion removal capabilities using the prepared adsorbent (SDSP). Equilibrium isotherm data showed that the amount of adsorption is dependent on solution pH. The adsorption of zinc and the elution rate of the SDSP were examined, thus permitting a breakthrough curve to be obtained for the zinc solution. The adsorbed zinc ions were eluted with 0.1 M HCl. The elution ratio using a fixed bed was 91%. The selective recovery of zinc ion from Cu2+, Cd2+, and Co2+ was also investigated. The results showed that the SDSP adsorbed zinc ions selectively in the presence of Cu2+, Cd2+, and Co2+ in the 2–4 pH range. The effects of Mg2+, Ca2+, Na+, Cl−, NO3 −, and SO4 2− on the removal of zinc were relatively small.