Synthesis and Application of Zwitterionic Magnetic Molecularly Imprinted Polymer for Selective Removal of Fluoroquinolones from Aqueous Solution

Abstract

Background: Although molecularly imprinted polymers (MIPs) have now been widely utilized for the sample pretreatment, chromatography separation and removal of pollutants, conventional MIPs are still lack of satisfactory compatibility with water, thus leading to poor molecular recognition for target analytes in aqueous solutions. This aim of study was to prepare the watercompatible MIPs. Methods: The zwitterionic MMIPs were synthesized on vinyltrimethoxysilane-coated Fe3O4 (Fe3O4-VTMS) through a surface imprinting process by using levofloxacin (LEV) as a template, [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SPE) as a functional monomer, N, N-methylene-bis-acrylamide (MBA) as a crosslinker and potassium persulfate as an initiator. Results: The prepared zwitterionic LEV-MMIPs were characterized by Fourier transform infrared spectrometry, X-ray diffraction, vibrating sample magnetometry, scanning electron microscopy and water contact angle test. The characterization results showed that zwitterionic LEV-MMIPs exhibited good magnetic responsiveness and super-hydrophilicity (the contact angle is 0°). The optimum pH for binding LEV was found to be 6.0 and the binding isotherm followed the Langmuir isotherm model of monolayer adsorption. The binding process was very fast and the pseudo-second-order model fitted well with the kinetic data. The adsorption capacity of these zwitterionic MMIPs was 54.30 mg g-1 with a selectivity factor of 1.6 compared to the magnetic non-imprinted polymers (MNIPs). Their feasibility for removing fluoroquinolones (FQs) from the environmental sample was demonstrated using pearl river water spiked with LEV, gatifloxacin, ciprofloxacin and lomefloxacin. The zwitterionic LEV-MMIPs could be reused at least five times with a removal efficiency of more than 80% for the selected FQs. Conclusion: The prepared zwitterionic LEV-MMIP is a promising sorbent for rapid, selective and efficient removal of fluoroquinolones from aqueous medium.