Study On The Performance And Mechanism Of Ionic Liquid-based Imprinted Photocatalyst For Selective Photodegradation Of Levofloxacin Hydrochloride Residues

Levofloxacin hydrochloride is a commonly used antibiotic germicidal drug for human and livestock.As a typical fluoroquinolone antibiotic,the long-term existence of its high toxicity,low concentration residue and its transformation products will lead to a series of environmental and human health problems.However,there are not only highly toxic and low concentration pollutants in the water environment,but also some non-toxic,harmless and even reusable substances.However,sedimentation,coagulation,photocatalysis and other technologies can not selectively remove highly toxic and low concentration pollutants from public substances,resulting in limited removal of these pollutants,which is not conducive to the efficient treatment of the water environment.Therefore,it is of great significance to remove levofloxacin hydrochloride residues among many substances.For this reason,the imprinted photocatalysis technology is introduced,which combines the imprinted technology with the photocatalysis technology.The imprinted photocatalytic material has imprinted cavities,and the existence of the imprinted cavities can realize the specific adsorption of the target molecules,and then realize the selective degradation and removal of levofloxacin hydrochloride residues in the water environment under light.However,the traditional imprinted photocatalysts are mostly synthesized in highly toxic organic solvents,which not only cause secondary pollution,but also go against their selective adsorption because of the difference between water molecules and swelling.Therefore,it is necessary to develop imprinted photocatalysts for preparation and application in aqueous media.At the same time,it is very important to select functional monomers with good water solubility.Therefore,in this paper,a series of ionic liquid-based imprinted photocatalysts were designed using green solvent ionic liquids（IL）and their polymers（polyionic liquids,PIL）as functional monomers to achieve efficient and selective degradation of levofloxacin hydrochloride residues in aqueous environment.The main research work is as follows:（1）Using IL as functional monomer,P25 as matrix material and levofloxacin hydrochloride as template molecule,IL-P25 imprinted photocatalyst（I-IL-P25）was prepared by aqueous phase microwave polymerization.The structure,composition,morphology and photoelectrochemical properties of I-IL-P25 were investigated by FI-IR,XPS,TEM,EIS and PL.The degradation activity and selectivity of I-IL-P25 were investigated by photocatalytic degradation experiment and selectivity experiment,and its selective photodegradation mechanism was clarified.The results showed that the type II heterostructure formed between IL and P25 improved the separation performance of electron-hole pairs,and then improved the photocatalytic activity of the materials.under visible light irradiation,the degradation rate of levofloxacin hydrochloride residue by I-IL-P25 was 50.69%,which was 2.33 times higher than that of matrix material P25（21.80%）.The selectivity coefficient of I-IL-P25 compared with P25 and IL-P25 non-imprinted photocatalysts was 2.69 and 2.26 respectively,showing excellent selective photodegradation ability.（2）Using PIL as functional monomer,TiO₂ as matrix material and levofloxacin hydrochloride as template molecule,PIL-TiO₂ imprinted photocatalyst（I-PIL-TiO₂）was prepared by microwave-assisted aqueous phase in-situ polymerization.The structure,composition,morphology and photoresponse of I-PIL-TiO₂ were investigated by FT-IR,XPS,HRTEM,EIS and PL.The photodegradation selectivity of I-PIL-TiO₂ was investigated in two different water environments:simulated wastewater and swine wastewater,and the factors of water quality parameters（p H and NH₃-N）were investigated.The results showed that the Z-type heterostructure constructed by PIL and TiO₂ can effectively promoted the separation of photogenerated carriers in TiO₂ and further improved the photocatalytic activity of I-PIL-TiO₂.In the simulated wastewater,the degradation rate of levofloxacin hydrochloride residue by I-PIL-TiO₂ reached 73.06%and 58.75%in swine wastewater.At the same time,I-PIL-TiO₂ showed good directional degradation performance in simulated wastewater and swine wastewater.In the simulated wastewater,the selectivity coefficient of I-PIL-TiO₂ to TiO₂,PIL-TiO₂ and PIL-TiO₂non-imprinted photocatalyst was 2.05,2.00 and 2.02,respectively.In swine wastewater,the selectivity coefficient of I-PIL-TiO₂ for TiO₂,PIL-TiO₂ and PIL-TiO₂non-imprinted photocatalyst was 1.90,1.97 and 2.27,respectively.（3）Using TiO₂ as the matrix material,the PIL layer was coated by the self-polymerization of IL,and the template molecule（levofloxacin hydrochloride）was introduced and removed in the process of preparing PIL layer by IL self-polymerization,so that the self-polymerized PIL-TiO₂ imprinted photocatalyst（Self-I-PIL-TiO₂）was prepared in aqueous medium.The structure,composition,morphology and photoresponse of Self-I-PIL-TiO₂ were investigated by FT-IR,XPS,HRTEM,EIS and PL.The photodegradation selectivity of Self-I-PIL-TiO₂ was investigated in two different water environments:simulated wastewater and swine wastewater,and the factors of water quality parameters（p H and NH₃-N）were investigated.The results showed that the Z-type heterostructure formed between PIL and TiO₂ was beneficial to the transfer and separation of photogenerated carriers.Under UV-visible light irradiation,the degradation of levofloxacin hydrochloride residue in simulated wastewater by Self-I-PIL-TiO₂ was as high as 91.52%.At the same time,Self-I-PIL-TiO₂ showed good directional degradation performance in simulated wastewater and swine wastewater.In the simulated wastewater,the selectivity coefficient of Self-I-PIL-TiO₂ to TiO₂ and PIL-TiO₂ non-imprinted photocatalysts was 2.35 and 2.44,respectively.In swine wastewater,the selectivity coefficient of Self-I-PIL-TiO₂ to TiO₂ and PIL-TiO₂ non-imprinted photocatalyst was2.57 and 2.71,respectively.