Selective removal and recovery of Ni(ii) using a sulfonic acid-based magnetic rattle-type ion-imprinted polymer: adsorption performance and mechanisms

Abstract

It is significant to selectively remove Ni(II) ions from wastewater. A novel sulfonic acid-based magnetic rattle-type ion-imprinted polymer (Fe₃O₄@void@IIP-Ni(II)) was designed by taking advantage of the strong interaction between Ni(II) and sulfonic acid groups. Green polymerization was used to synthesize Fe₃O₄@void@IIP-Ni(II), which was then investigated using SEM, TEM, FT-IR, VSM, TGA, EDS, and XPS. The adsorption results indicated that the prepared imprinted material had a short adsorption equilibrium time (10 min), good magnetic responsiveness (about 5 seconds) and high adsorption capacity (44.64 mg g⁻¹) for Ni(II) at the optimal pH of 6.0. The removal rate of Ni(II) was up to 99.97%, and the adsorption process was spontaneous and endothermic, following the pseudo-secondary kinetic model and Langmuir model. The selectivity coefficients of the imprinted material were 4.67, 4.62, 8.94 and 9.69 for Ni(II)/Co(II), Ni(II)/Cu(II), Ni(II)/Pb(II) and Ni(II)/Zn(II), respectively. The regeneration and application of the imprinted material in actual water samples have been verified. Moreover, the mechanism of selective adsorption for Ni(II) was investigated by FTIR, XPS and density functional theory (DFT) calculation. The results showed that the imprinted sorbent has a strong binding ability with Ni(II), and the adsorption of Ni(II) on Fe₃O₄@void@IIP-Ni(II) was the result of the co-coordination of O atoms of the sulfonic acid groups and N atoms of –N–CO groups in AMPS with Ni(II).