| Microplastics(MPs)are a kind of emerging marine pollutants due to their stable chemical properties and can exist in the marine environment for a long time.They not only endanger the health and stability of marine ecosystems,but also threaten the safety of marine food and even human health.At the same time,MPs can experience aging in nature,which may enhance their adsorption performance to pollutants.Due to the abuse of antibiotics in marine aquaculture systems,their residues may induce antibiotic resistance genes(ARGs),thereby threatening human health.The characteristics of the combined pollution effects of microplastics and antibiotics are still unclear.Therefore,this study carried out a study on the adsorption behavior of MPs to LEV before and after aging to further evaluate the ecological and environmental risks of the two.This study selected the more common types of polyvinyl chloride(PVC)and polymethyl methacrylate(PMMA)MPs in daily life.with levofloxacin(LEV)as the target antibiotic,through a series of batch adsorption equilibrium experiments,the adsorption behavior,adsorption change trend,adsorption influence factors and action mechanism of PVC and PMMA to LEV were studied.Secondly,indoor UV lamp aging method and Fenton aging method were used to simulate the aging process of PVC and PMMA under natural light conditions and oxidation reaction conditions respectively,and the adsorption behavior,adsorption change trend,adsorption influencing factors and action mechanism of PVC and PMMA MPs to LEV after Ultraviolet and Fenton aging were also studied.The main conclusions of this research are as follows:(1)The adsorption kinetics and isotherm experiment results of LEV on the surface of microplastics show that the pseudo-second-order kinetic model can fit the adsorption kinetics data of PVC and PMMA to LEV before and after Fenton and UV aging well,and the adsorption rate is controlled by both internal and external diffusion of particles.Both Langmuir and Freundlich models can fit the adsorption isotherm data of PVC and PMMA to LEV before and after Fenton and UV aging well,and the Freundlich model can fit the experimental data of PVC before and after Fenton and UV aging better;The value of the fitting parameter n is basically between 0.3 and 0.5,indicating that the adsorption process has significant nonlinear characteristics.The fitting results of D-R model show that the adsorption process of PVC and PMMA to LEV before and after Fenton and UV aging is mainly physical adsorption.In the pure water system,both PVC and PMMA have a certain enrichment capacity to LEV before and after Fenton and UV aging.The enrichment capacity of five particle sizes PMMA to LEV before and after Fenton and UV aging is as follows:1?m>75?m>125?m>250?m>500?m,all of which show a weakening trend with the increase of particle size.The seawater environment has a significant inhibitory effect on the enrichment behavior of LEV on PVC and PMMA before and after Fenton and UV aging compared with the pure water system.(2)Both UV irradiation and Fenton reaction oxidized PVC and changed the physical properties of PMMA.Ultraviolet aging has a significant enhancement effect on the adsorption performance of LEV on PVC and PMMA,and it has a higher promotion effect on PVC.The results of Fenton aging of PVC and PMMA are similar to that of UV aging.The promoting effect of UV aging on the adsorption performance of PMMA increases with the increase of particle size.Fenton aging has a weaker promotion effect on the adsorption performance of PVC compared with UV aging,and its promotion effect on PMMA is roughly equivalent to that of UV aging.(3)The presence of Cu2+,Zn2+,Cr3+significantly promotes the adsorption performance of LEV on PVC before and after Fenton and UV aging;while the presence of Cd2+and Pb2+significantly inhibits the adsorption behavior of LEV on PVC before and after Fenton and UV aging.The presence of Zn2+,Cr3+,and Pb2+promotes the adsorption behavior of LEV on PMMA before and after Fenton and UV aging to a certain extent,while the presence of Cu2+and Cd2+has a certain inhibitory effect on the adsorption behavior of LEV on PMMA before and after Fenton and UV aging.(4)The total amount of adsorption(mg)of PVC and PMMA to LEV before and after Fenton and UV aging increases with the increase of the adsorbent mass,but the adsorption capacity(mg/g)per unit of microplastics decreases with it.Ionic strength has a significant inhibitory effect on the adsorption behavior of LEV on PVC and PMMA before and after Fenton and UV aging.Humic acid has a significant inhibitory effect on the adsorption properties of LEV on PVC and PMMA before and after Fenton and UV aging. |
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