Preparation and properties of double-template magnetic molecularly imprinted polymers for removal of nitrophenol from drinking water

In order to efficiently remove 4-nitrophenol (4-NP) and 2,4-dinitrophenol (2,4-DNP), 4-NP and 2,4-DNP were used as template molecules and double-template magnetic molecularly imprinted polymers (D-MIPs) were prepared by surface molecular imprinting technology using itaconic acid as functional monomer, Fe3O4@SiO2 as carrier, ethylene glycol dimethacrylate as crosslinking agent and azodiisobutyronitrile as initiator. The morphology of D-MIPs was characterized using FT-IR and SEM. The adsorption specificity, regenerability, and applicability of D-MIPs were studied in detail. The results show that D-MIPs successfully coated the surface of the Fe3O4@SiO2 carrier and had a good polymerization effect, specific recognition sites, and good imprinting performance, with a diameter of 90 nm and homogeneous shape. The theoretical adsorption capacities of 4-NP-MIPs, 2, 4-DNP-MIPs, and D-MIPs for target molecules were 103.97, 73.14 and 123.99 mg/g, respectively. There were many adsorption sites with different adsorption energies. D-MIPs reached the optimal adsorption equilibrium state in 30 min. The best fitting models for the MIPs were the Freundlich adsorption and pseudo-second-order kinetic models, indicating that adsorption of MIPs occurred via a chemical adsorption process. Test results show that MIPs had highly specific recognition and selective adsorption capacity in different water samples. After eight regeneration cycles, the adsorption capacity of D-MIPs decreased by 7.51%, confirming that MIPs had excellent regeneration.