Study On The Effect Of Photoaging Of Microplastics In Water On Their Leachate And The Properties Of Antibiotic Adsorption

In recent years,Microplastics(MPs)have attracted much attention as a kind of emerging environmental pollutants.The latest research shows that MPs not only causes direct harm to the ecological environment,but also further aggravates the pollution to the environment through the leaching of MPs in the water environment and the formation of complex pollutants after absorbing other pollutants.MPs in natural aquatic environment will be subjected to physical,chemical and biological effects to aging.Aging will change the physicochemical properties,leaching characteristics and adsorption behavior of MPs with pollutants,which will affect their harm characteristics to the ecological environment.At present,the research on this field is emerging,but no unified conclusion has been reached.The aim of this study was to investigate the effects of photoaging on the physicochemical properties,leaching behavior and antibiotic adsorption performance of MPs in water.In this study,acrylonitrile-butadiene-styrene(ABS),polycarbonate(PC),polyethylene terephterate(PET)and polyvinylidene fluoride(PVDF)with high detection frequency in water were selected as typical MPs.The photoaging process of four MPs in pure water was simulated in the laboratory.The effects of photoaging on physicochemical properties,leaching behavior and ofloxacin adsorption performance of typical MPs were studied.The main research contents and results were as follows:(1)A 14-day simulated photoaging experiment was conducted on four kinds of MPs.Then,scanning electron microscopy,X-ray diffractometer,infrared spectrometer,nitrogen adsorption desorption instrument and contact Angle tester were used to observe or measure the surface morphology,lattice structure,surface functional groups,specific surface area and hydrophilicity of MPs before and after aging.The results showed that,the surface properties of the four MPs were changed by light exposure.At the same time,the extracts of MPs in water under dark and light conditions were studied,and the dissolved organic carbon(DOC)of the extractives was quantitatively determined by the total organic carbon analyze r,qualitatively analyzed by infrared spectroscopy and three-dimensional fluorescence spectroscopy,and the possible components were detected and analyzed by liquid-mass spectrometer.The results showed that photoaging induced MPs to release more dissolved organic matter into water,and the main organic matter was low molecular weight.(2)The adsorption experiments of ofloxacin on MPs without aging and after aging were carried out respectively,and the adsorption kinetics model,internal diffusion model and isothermal adsorption model were established successively to investigate the adsorption kinetics and isothermal adsorption process.The results show that the adsorption of ofloxacin by four MPs before and after aging conforms to the quasi-second-order kinetic model,and photoaging increases the adsorption capacity of MPs to ofloxacin and speeds up the adsorption rate.At the same time,the adsorption of ABS and PET conforms to Freundlich isothermal adsorption model before aging,and Langmuir isothermal adsorption model after aging,indicating that the adsorption of ofloxacin on ABS and PET changes from multi-layer to single layer adsorption.In addition,the study also found that environmental factors such as salinity,p H,temperature,etc.,affect the adsorption capacity of MPs to ofloxacin,and its influence on MPs after aging is more significant.