Sorption of Thiocyanate Ions on Cr–Polymer Composite and Obtaining a New Sorbent

The sorption of thiocyanate ions under various conditions on a Cr–polymer composite and, for comparison, on a strongly basic anion exchanger Purolite A-400(Cl) was studied. Temperature has a significant effect on sorption on the composite and a minor effect on Purolite A-400(Cl). The sorption of thiocyanate ions on both sorbents practically does not depend on the pH of the solution in the range 2–12. The rate of thiocyanate ion sorption is limited by mixed intra-particle and boundary layer diffusion. The sorption isotherms obtained at 18 and 60°C on Purolite A-400 are well described by the Langmuir sorption model, and on the Cr–polymer composite – by the Freundlich model. The difference in the magnitude of sorption on these composites is explained by the fact that on Purolite A-400(Cl) the retention of thiocyanate ions occurs as a result of ion exchange, while on the Cr–polymer composite it occurs as a result of ion exchange and complex formation. The Cr–polymer composite loaded with thiocyanate ions becomes a sorbent with selective sorption properties in relation to heavy metal cations, which is confirmed by the retention of Hg2+ ions from solution.