Thermo-responsive ion imprinted polymer on the surface of magnetic carbon microspheres for identification and removal of low-concentrations of Cu2+

Abstract

Environmental context Because of the multiple industrial applications of metals, contamination by metal ions is widespread and can at times endanger the environment and the health of human beings. We prepared ion-imprinted adsorbents to achieve selective recognition and smart separation of low-concentrations of copper ions from water. These smart imprinted materials have high potential for selective adsorption and removal of contaminant copper ions, particularly at very low concentrations. Abstract A temperature-responsive magnetic adsorbent (poly(N-propyl acrylamide) grafted magnetic carbon microspheres, Cu2+-IIP) was synthesised by ion imprinting technology for low concentration Cu2+ removal. Cu2+-IIP was prepared by using N-propyl acrylamide as a thermo-sensitive functional monomer, N,N-methylene-bis-acrylamide as a cross-linker and ammonium persulfate as an initiator. The morphologies and microstructures of samples were characterised by transmission electron microscopy, Fourier transform infrared spectrometry, thermogravimetry and vibrating sample magnetometry. Adsorption experiments were conducted in terms of kinetics, isotherms and selective recognition adsorption at low feed concentrations. Results indicate that Cu2+-IIP possesses good recognition selectivity and affinity for Cu2+, and can be separated from the treated solution quickly by applying an external magnetic field. The adsorption capacity towards Cu2+ depends on temperature and reaches a maximum value of 45.46 mg g-1 at 35 °C, higher than that of the non-imprinted polymer. The adsorption behaviour of Cu2+ on Cu2+-IIP can be well defined with both the pseudo-second-order kinetic model and Langmuir isotherm model. Cu2+-IIP performs good adsorption selectivity towards Cu2+ because the relative selectivity factors of Cu2+ with respect to Ni2+, Zn2+ and Cd2+ are 7.14, 7.60 and 6.77, respectively. The adsorption capacity of Cu2+-IIP remained 88.41 % after five cycles.