Preparation Of Polydopamine/Graphene Imprinted Polymer For Adsorption Removal And DGT Analysis Of Fluoroquinolones

In recent years,antibiotics in environments have gained increasing public concern all over the world.With long-term exposure of low concentration antibiotics,it will induce increased bacterial resistance and produce resistance genes,resulting in great potential threat to ecological environment and human health.The efficient removal and detection of antibiotics in waters is still a challenge due to various antibiotics with low concentration and strong polarity of their molecular structures.In this paper,we focused on efficient removal and in-situ analysis for fluoroquinolone antibiotics in waters by molecularly imprinted polymer（MIP）and thin film diffusion gradient technique（DGT）.The main contents include:Graphene oxide/Fe₃O₄ magnetic materials（GO/Fe₃O₄）were prepared by a hydrothermal method,and the polydopamine coated GO/Fe₃O₄ imprinted nanoparticles（GO/Fe₃O₄@MIP）were further prepared by the self-polymerization of dopamine in weak alkaline solution using sarafloxacin as a template.The resulting GO/Fe₃O₄@MIP nanoparticles were characterized by Transmission electron microscope（TEM）,Fourier transform infrared spectroscopy（FTIR）,N2 adsorption-desorption,elemental analysis,Thermogravimetric analysis,and magnetic hysteresis loop experiments.Results showed that the average size of the nanoparticles was about 130 nm,and the average thickness of the dopamine imprinting layer was 10 nm,with a specific surface area of 46.3 m2/g.The nanoparticles showed superparamagnetic properties and enough thermal stability under 600℃.Adsorption experiments showed that the maximum saturated adsorption capacity of the nanoparticles to sarafloxacin is 70.92 mg/g.The adsorption reached equilibrium within 30 minutes and fitted Langmuir adsorption isotherm and pseudo-second-order kinetics model.The nanoparticles achieved a good performance at pH 7⁹,and salt could reduce the adsorption capacity.The imprinted nanoparticles had a good selectivity to fluoroquinolone compounds,with an imprinting factor of 1.4 versus non-imprinted nanoparticles.The prepared nanoparticles could be used for five adsorption-regeneration cycles for fluoroquinolones in waters without any loss of the adsorption capacity.These results indicated that the prepared GO/Fe₃O₄@MIP could be used for selective removal of fluoroquinolones in waters.Because of the high adsorption capacity,the GO/Fe₃O₄@MIP nanoparticles were used as an adsorbent in DGT for in-situ analysis of antibiotics in waters,in which GO/Fe₃O₄@MIP-polyacrylamide as a binding phase,1.5% agarose gel as a diffusion phase and polyether sulfone membrane as a protective phase.Results showed that the binding capacity was 90¹50 mg/piece to ten fluoroquinolones,and 10 mg/piece to two sulfonamides,indicated that the bing phase had a good selective uptake ability to fluoroquinolones.The diffusion coefficients of fluoroquinolones in the diffusion phase was 1.49⁵.27 ′ 10-6 cm2/s.The elution efficiencies of fluoroquinolones using methanol/acetic acid（v:v = 9:1）as eluent were more than 90%.With a simulated seawater sampling,the sampling amounts of ten fluoroquinolones linearly increased with the sampling time within 5 days,and the sulfonamides achieved low uptake rate.The measured concentrations by the DGT well matched the real concentrations in the samples.This fact indicated that the present method was feasible for in-situ analysis of fluoroquinolones in water.The present work provided a new type of GO/Fe₃O₄@MIP imprinted nanoparticles,which could be used for efficient removal of fluoroquinolone antibiotics in waters,and it also could be used as a binding phase material of DGT for in-situ analysis of fluoroquinolone in water.The results have a good theoretical significance and potential applications.