Selective adsorption of metal ions on a chelating resin from hydrochloric acid and its application to the analysis of high-purity zinc

Eporous AS-4 (Miyoshi Oil & Fat Co.) is the trade name given to an arsenic-selective chelating resin of an iminodiacetate polystyrene-divinly benzene copolymer type, which has been modified by successively treating with iron(III) and sodium hydroxide solutions. Iron(III) hydroxide in Eporous AS-4 was removed by washing with 3 mol/l hydrochloric acid to prepare plain Eporous AS-4. The distribution coefficients for Ca-II, Cd-II, Co-II, Cu-II, Fe-II, Mg-II, Ni-II,and Zn-II on plain Eporous AS-4 were measured by a batch method as a function of the hydrochloric acid concentration, and compared with those on other commercially available chelating resins, i.e., Chelex 100 (Bio-Rad Laboratories) and Diaion CR11 (Mitsubishi Chemicals Co.). The distribution coefficients for Cu-II on plain Eporous AS-4 are higher than those on Chelex 100 and Diaion CR11 by a factor of ca.100 in hydrochloric acid media of less than 0.1 M. The selective adsorption of Cu-II and Fe-III on plain Eporous AS-4 has been successfully applied to the separation of copper and iron in high-purity zinc certified reference materials prior to their measurements by flame atomic absorption spectrometry.