Abstract
A solvent impregnated resin (SIR) containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) as the extractant was tested for zinc removal from aqueous solutions, including the real electroless nickel plating bath employed for an aluminum alloy substrate, in order to extend the bath life. The SIR effectively and selectively adsorbed zinc over nickel without any pH adjustment from the plating bath, although the adsorption was significantly suppressed by the complexation of the zinc ion by the hydrogen phosphite and dihydrogen phosphite ions. The Langmuir adsorption isotherm was used to correlate the zinc adsorption data and the SIR containing 30 wt% EHPNA, exhibited the maximum adsorption capacity of 0.51 mmol/g-dry-SIR corresponding to a zinc- to-EHPNA molar ratio of 1:2. Repeated column adsorption and elution tests for 15 cycles showed that the adsorption ability of the SIR gradually decreased suggesting that the durability of the resin should be improved.
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