Selective binding of Cd2+by natural and synthetic organic macromolecules investigated by113Cd‐NMR spectroscopy

Poly(methacrylic acid) or humic acids were added in increasing quantities to aqueous CdCl2 solutions (5.25 × 10‐2 M, pH = 6), and the changes in the concentrations of both the free cadmium and chloride ions remaining in the supernatant were measured from the peak intensity and chemical shift data of the 113Cd NMR spectra. The decrease in the cadmium concentration was not accompanied by any changes in the chloride concentration, suggesting that only the Cd2+ ion is selectively bound by the synthetic and naturally occurring organic macromolecules.