A recoverable magnetic surface ion-imprinted polymer based on graphene oxide for fast and selective adsorption of Ni(ii) from aqueous solution: experimental and DFT calculations

Abstract

A novel magnetic graphene oxide-based surface imprinted polymer (Fe₃O₄@GO@IIP) was synthesized using the surface imprinting technology to selectively adsorb Ni(II) from aqueous solution. The imprinted polymer was characterized by FT-IR, XRD, SEM, TEM, VSM, TGA and XPS. The results showed that the sorbent exhibited good thermal and mechanical stability, and can be quickly separated from the solution by applying an external magnetic field. The adsorption performance indicated that the prepared imprinted material had a short adsorption equilibrium time (16 min) and a high adsorption capacity (35.31 mg g⁻¹) for Ni(II) at an optimal pH of 6.0. The selectivity coefficients of the imprinted material were 17.57, 16.27, 10.86, 14.27 and 17.65 for Ni(II)/Co(II), Ni(II)/Cu(II), Ni(II)/Pb(II) Ni(II)/Cd(II), and Ni(II)/Zn(II), respectively. Reusability studies indicated that the adsorption capacity of the prepared polymer did not decrease significantly after repeated use ten times. Moreover, the adsorption mechanism of Ni(II) by the imprinted polymer was also studied. The adsorption process was spontaneous and endothermic, and followed the pseudo-secondary kinetic model and the Langmuir model. The results of the Scatchard model indicated the presence of two Ni(II) strong binding sites on Fe₃O₄@GO@IIP, where the single-bond O atom of the sulfonic acid group and the N atom of the –N–CO group in AMPS played a dominant role in Ni(II) adsorption, as conformed by both DFT calculations and XPS.