Aging Of Microplastics And Their Adsorption Behavior Of Antibiotics In Water

Currently,the interaction behavior of microplastics with pollutants is an important research hotspot.In this study,artificial accelerated aging method was used to simulate the natural aging of microplastics in environment,and the adsorption behaviour of microplastics on antibiotics was studied.Two different types of microplastics traditional microplastics polyethylene terephthalate(PET)and biodegradable microplastics polylactic acid(PLA)were selected.The“carrier"effects of different types of microplastics on pollutants were evaluated using laboratory chemical aging methods.The influence patterns of environmental factors on their adsorption behaviors were investigated to further elucidate the interaction mechanisms between microplastics and antibiotics.Considering the presence of surfactants in aqueous environment,anionic surfactant sodium dodecyl benzene sulfonate(SDBS),cationic surfactant cetyl trimethyl ammonium bromide(CTAB)and nonionic surfactant Tralatone X-100(TX-100)were selected to investigate the effects on the adsorption of tetracycline(TC)by two microplastics in the presence of different types of surfactants.The main conclusions are as follows:(1)The physicochemical properties of microplastics changed after aging.Compared with the original microplastics,the surface of the aged microplastics was rougher,and the specific surface area of PET and PLA microplastics increased from0.6158 m~2/g and 0.1122 m~2/g to 1.3018 m~2/g and 0.6096 m~2/g,respectively,and the intensity of the-C=O functional group absorption peak increased significantly.The crystallinity of PLA microplastics varied most significantly with contact angle,demonstrating that the surface of biodegradable microplastics is more susceptible to be damaged by free radicals.(2)The property changes caused by chemical aging increased the adsorption capacity of the microplastics.The adsorption capacities of PET and PLA after aging were 1.3 and 1.7 times those of before aging,respectively.The adsorption process of PET and PLA microplastics and cephalexin is uniform single molecular layer physical adsorption.Environmental factors such as temperature,p H,salinity and humic acid had different degrees of influence on the adsorption capacity of aged microplastics.The adsorption capacity of microplastics on cefadroxil gradually increased with the increase of temperature,but too low or too high p H,concentrations of Na Cl and humic acid inhibited the adsorption capacity of microplastics.The adsorption mechanism indicated that hydrophobic interaction and electrostatic interaction played a crucial role in the adsorption mechanism of degradable microplastics and conventional microplastics.(3)Surfactants significantly promoted the adsorption of tetracycline on microplastics.The order of the tetracycline adsorption potential of PET in the presence of surfactant was PET-SDBS>PET-CTAB>PET-TX100>PET,and the same trend was observed for tetracycline adsorption on PLA microplastics.Compared with no surfactant addition,the addition of SDBS had significant promotion effect on tetracycline adsorption on PET and PLA microplastics,which increased by 1.43 and1.96 times,respectively.The surfactants affected the ability of microplastics to accumulate environmental pollutants by improving the polarity of their surfaces.Fourier transform infrared spectroscopy detection showed that in the absence of surfactant,the adsorption process of PET and PLA microplastics with tetracycline was mainly based on physical adsorption,and the addition of surfactant enhanced the adsorption of tetracycline by microplastics by electrostatic and hydrogen bonding interactions.