Synthesis and application of ion-imprinted interpenetrating polymer network gel for selective solid phase extraction of Cd2+

• Cd2+-imprinted IPN sorbent was prepared by hybrid photopolymerization.
• The Cd2+-imprinted gel showed excellent selectivity for Cd2+.
• The developed method was successfully applied to the determination of trace Cd2+.

In the present work, a new Cd2+-imprinted sorbent with interpenetrating polymer network (IPN) structure has been prepared by free radical/cationic hybrid photopolymerization. The ability of the imprinted gel to adsorb Cd2+ was assessed using a batch adsorption technique. The sorption equilibrium data agreed well with the pseudo-second-order kinetic model and the Freundlich isotherm. The study on thermodynamic parameters suggested that the Cd2+ sorption was a spontaneous, exothermic process with further decrease in the degree of freedom. The adsorption mechanism studied by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated that Cd2+ adsorption was mainly through interactions with the NH, OH, CO and CO groups. In addition, the imprinted gel was examined as a column packing material for solid phase extraction of Cd2+. The imprinted gel showed higher selectivity for Cd2+ in comparison to the non-imprinted gel. Relative selectivity coefficients for Cd2+/Cu2+, Cd2+/Ni2+ and Cd2+/Pb2+ were 7.64, 7.58 and 7.59 respectively. The relative standard deviation of the seven replicate determinations of Cd2+ was 1.7%. With preconcentration of 100 mL samples, detection limit of 0.5 μg/L was determined. The developed method was successfully applied to the determination of trace Cd2+ in various natural water samples with satisfactory results.