老化前后聚乳酸和聚乙烯微塑料对抗生素的吸附解吸行为

作为不可降解塑料的替代品，可降解塑料在不同的领域中被广泛使用.与不可降解塑料相比，环境中的可降解塑料可在短期内产生大量的微塑料.为了探明可降解微塑料的老化过程及其与共存污染之间的相互作用，开展了原始和老化的聚乳酸(polylactic acid，PLA)对磺胺甲恶唑(sulfamethoxazole，SMZ)和阿莫西林(amoxicillin，AMX)的吸附解吸行为研究，并与聚乙烯(polyethylene，PE)进行了比较.结果表明:①原始的PLA和PE具有光滑的表面和疏水性的特征.经热活化过硫酸钾老化后，PLA和PE的粒径变小，表面产生大量的凹坑、裂缝和孔隙，比表面积增大，含氧官能团强度增加，亲水性增强.②抗生素在PLA和PE上的吸附符合准二级动力学模型，原始和老化的PLA、PE的主要吸附方式为表面吸附和颗粒内扩散.③老化后PLA和PE的吸附能力增强，老化PLA对SMZ的最大吸附量为14.7 mg/g，约是原始PLA(1.63 mg/g)的9.02倍，老化PE对SMZ的最大吸附量为5.20 mg/g，是原始PE(1.73 mg/g)的3.01倍，且老化PLA对抗生素的最大吸附量大于PE.④老化后的PLA和PE对抗生素的解吸量和解吸率降低，但原始和老化PLA的解吸量和解吸率均高于PE.研究显示，PLA相对于PE对共存污染物有更强的载体作用，且在生物体中PLA比PE更容易释放出抗生素，从而可能给生物体的生命健康造成更大的威胁. 

Adsorption and Desorption Behavior of Antibiotics on Polylactic Acid and Polyethylene Microplastics before and after Aging

As a substitute for non-degradable plastics, biodegradable plastics are widely used in different fields. Compared with non-degradable plastics, biodegradable plastics will produce large amounts of microplastics in a short period of time in the environment. In order to explore the aging processes of the biodegradable plastics and their interactions with coexisting pollutants, the adsorption and desorption behaviors of sulfamethoxazole (SMZ) and amoxicillin (AMX) on the original and aged polylactic acid (PLA) were investigated, and polyethylene (PE) was studied for comparison. The results showed that: (1) The original PLA and PE had the characteristics of smooth surface and hydrophobicity. After heat-activated potassium persulfate aging, the particle size of PLA and PE decreased, plenty of pits, cracks and pores were produced on the microplastics surface, the specific surface area, the oxygen-containing functional groups, and the hydrophilicity increased. (2) The adsorption of antibiotics on PLA and PE conformed to the Pseudo-second-order model, and the main adsorption modes of original and aged PLA and PE were surface adsorption and intra-particle diffusion. (3) The adsorption capacity of PLA and PE increased after aging. The maximum adsorption capacity of SMZ by aged PLA was 14.7 mg/g, which was about 9.02 times that of original PLA (1.63 mg/g). The maximum adsorption capacity of SMZ by aged PE was 5.20 mg/g, which was about 3.01 times that of the original PE (1.73 mg/g). And the maximum adsorption capacity of aged PLA for antibiotics were greater than that of PE. (4) The desorption amount and desorption rate of the antibiotics of the aged PLA and PE decreased, but the desorption amount and desorption rate of the original and aged PLA were higher than that of PE. The results indicate that PLA has a stronger carrier effect for coexisting pollutants than PE. PLA releases antibiotics more easily than PE in organisms, which may pose a greater threat to the life and health of organisms.