Facile preparation of a novel Hg(ii)-ion-imprinted polymer based on magnetic hybrids for rapid and highly selective removal of Hg(ii) from aqueous solutions

Abstract

A novel magnetic ion-imprinted polymer (MIIP) with incorporated Fe₃O₄@SiO₂ nanoparticles was synthesized via a surface imprinting technique using allylthiourea (ATU) as a functional monomer. The MIIP has an excellent saturation magnetization of 15.9403 emu g⁻¹. Solution pH values had an immediate influence on the Hg(II) adsorption capacity with optimal removal occurring at pH 6. The adsorptivity of MIIP towards Hg(II) ions (78.3 mg g⁻¹) was approximately twice that of a magnetic non-ion-imprinted polymer (39.5 mg g⁻¹). The adsorption indicated that the adsorption mechanism closely agreed with a pseudo-second-order adsorption process, with a correlation coefficient (R²) of 0.998, which could be attributed to the soft acid–soft base interaction of Hg(II) and allylthiourea. The relative selectivity coefficients of MIIP for Hg(II)/Ni(II), Hg(II)/Cu(II), Hg(II)/Co(II) and Hg(II)/Cd(II) were 623, 355, 623 and 155, respectively. The recovery in rebinding capacity for Hg(II) was found to be decreased by only approximately 10.4% up to the 6th cycle, which suggests an excellent stability of MIIP. The application of MIIP in real samples shows a removal rate for Hg(II) of more than 99% to well below U.S. EPA mercury limits for wastewater, indicating that the MIIP has wide application prospects for Hg(II) removal in environmental water samples.