Selective preconcentration of trace thorium from aqueous solutions with Th(IV)-imprinted polymers prepared by a surface-grafted technique

Abstract

A novel ion-imprinted adsorbent for selective solid phase extraction of thorium(IV) based on the surface of silica gel was prepared by a surface-grafted technique with methacrylic acid (MAA) as a functional monomer. After removal of Th(IV) ions with 3 mol L⁻¹ HCl solution, the obtained imprinted particles for Th(IV) exhibited specific recognition and relatively rapid kinetic process. The maximum static and total dynamic adsorption capacity of the ion-imprinted polymers (IIPs) for Th(IV) was 33.2 and 17.3 mg g⁻¹, respectively. A comparison of the selectivity coefficient of the imprinted polymers with that of non-imprinted polymers showed that the imprinted matrix for Th(IV)/U(VI), Th(IV)/Ce(III), Th(IV)/La(III) and Th(IV)/Zr(IV) was 58.8, 107, 106.4 and 151.7 times greater than non-imprinted matrix, respectively. With a series of samples loading flow rate of 3 mL min⁻¹ for preconcentration, an enrichment factor of 14.6 and the detection limit of 0.59 µg L⁻¹ were obtained. The relative standard deviation of the method under optimum conditions was 2.1% (n = 7). The developed method was successfully applied to the determination of trace Th(IV) in real water samples with satisfactory results.

Keywords:

• ion-imprinted polymers
• solid phase extraction (SPE)
• thorium(IV)
• silica grafting
• spectrophotometric determination