Recognizing removal of norfloxacin by novel magnetic molecular imprinted chitosan/γ-Fe2O3 composites: Selective adsorption mechanisms, practical application and regeneration

A novel magnetic molecular imprinting composites (MICs) were successfully synthesized through cross-linked chitosan and γ-Fe2O3 particles, and the selective removal of aqueous NOR was demonstrated. The γ-Fe2O3 particles embedded in MICs were still of intrinsic crystal and complexed with both amino and hydroxyl groups of chitosan. Adsorption behavior of NOR onto MICs could be described by the pseudo-second-order kinetic and the Langmuir isotherm model. Excellent selective NOR adsorption was identified with competition of sulfadiazine (SD), ofloxacin (OFL) and phenol, respectively. It could be ascribed to the memory cavities for NOR molecules, as well as the formation of triple intermolecular hydrogen bonds with suitable angle and length. Furthermore, application feasibility of MICs in NOR-spiked municipal wastewater treatment plant (WWTP) effluent was investigated. Competing with the effluent organic matters (EfOM), effective adsorption performance of NOR could be still obtained. Effect of humic and fulvic acid-like organics could be effectively reduced, while adsorption of tryptophan-like substances was slightly enhanced. In addition, it was found that Fenton-like oxidation instead of NaOH washing would be more appropriate for the multiple regenerations of MICs. The former would reserve more memory cavities and lead to oxidative decomposition of the desorbed NOR into micromolecular organics of low environmental impacts.