Removal Of Tetracycline Hydrochloride From Aqueous Environment By TiO₂ Molecularly Imprinted Polymers

As urbanization and industrialization accelerates,the problem of water environment pollution is increasing,among which antibiotic pollutants as one of the new pollutants,the traditional water treatment process is difficult to remove antibiotic drugs efficiently and is urgent to solve.Tetracycline hydrochloride is a tetracycline broad-spectrum antibiotic,its long-term presence in the water environment will pose a threat to human health and water ecological stability.Photocatalytic oxidation is a kind of advanced oxidation method,which is widely used because of its better effect on the treatment of hard-to-degrade pollutants.TiO₂ is one of the most widely used photocatalysts because of its high chemical stability,high catalytic activity,and environmental friendliness,but the photocatalytic degradation reaction is a process dominated by free radicals,so it does not have molecular selectivity in the degradation process,and the pollutants adsorbed on the surface of the material preferentially react with The pollutants adsorbed on the surface of the material react with the free radicals preferentially.The actual wastewater is usually a mixture of highly toxic and non-biodegradable organic pollutants and less toxic and easily biodegradable organic pollutants.The introduction of molecular imprinting technology in combination with photocatalysis can enhance the selectivity of catalysts and improve the biochemical degradability of wastewater.Molecularly imprinted polymers have specific cavities designed for the target molecules and can specifically identify and separate the target molecules from other structured molecules.Therefore,the rational design and preparation of TiO₂ molecularly imprinted polymers can achieve efficient and selective degradation of antibiotics.TiO₂ molecularly imprinted polymers were synthesized by sol-gel method using tetrabutyl titanate as the titanium source and tetracycline hydrochloride as the template molecule without using functional monomers,avoiding the disadvantages of the surface molecular imprinting method which may cover the active site and prone to degradation.A series of characterization tests proved that the material possesses good adsorption and photocatalytic properties,and can degrade 72.94%of tetracycline hydrochloride within 60 min of light exposure,which is 1.3times of non-molecularly imprinted TiO₂,and still has good removal rate after five cycles of experiments.To obtain abundant imprinted cavities with active sites,the SiO₂@TiO₂ core-shell structure was introduced.The SiO₂ microspheres were prepared by Stober method,and the TiO₂ layer with molecularly imprinted cavities was synthesized on the surface of SiO₂ microspheres by sol-gel method using tetrabutyl titanate as the titanium source and tetracycline hydrochloride as the template molecule.According to the characterization test results,the composite formed a core-shell structure as expected from the design,and the adsorption and photocatalytic performance of the material was significantly improved.The degradation rate of tetracycline hydrochloride was as high as 82.18%within 60 min of light exposure,and the high removal rate was still maintained after five cycles.The weak visible light activity of TiO₂ restricts its development and application,and the doping of nitrogen is used to reduce the forbidden bandwidth of the material and broaden the light response range of the composite.Nitrogen-doped TiO₂ layers with molecularly imprinted cavities of tetracycline hydrochloride were synthesized on the surface of SiO₂ microspheres using urea as the nitrogen source.The results of characterization and performance tests confirmed that the nitrogen doping reduced the forbidden band width of TiO₂ without affecting the morphology and structure of the composites,and enhanced the visible light activity of the materials,with the degradation rate of tetracycline hydrochloride reaching 95.64%within 60min of light exposure.The composite photocatalyst showed good stability in the cycling test,and the degradation mechanism of the material was studied by the burst experiment,which provided a reliable data reference and theoretical support for the removal of antibiotics from an aqueous environment by TiO₂ molecularly imprinted polymers.