Sorption characteristics of chelating resins

Chelating resins are used for preconcentrating metal ions in trace analysis. As part of a systematic study of sorption characteristics of the chelating resin Chelex 100, the sorption of Zn(II) and Cd(II) in different aqueous media was investigated. The distribution coefficient (DC) values for both Zn(II) and Cd(II) were extremely low (<4) in 0.5 to 6M HNO₃ and H₂SO₄ solutions. In HCl solution, theDC values for both Zn(II) and Cd(II) were higher, reaching a peak of nearly 40 in 3M HCl solutions. TheDC values for both Zn(II) and Cd(II) increased with increasing pH in chloride, nitrate, and sulfate solutions (0.1M); the value was nearly 10⁴ for both Zn(II) and Cd(II) between pH 5 and 7 and pH 6 and 8, respectively.