可降解微塑料对铜和锌离子的吸附解吸特性

为了评估可降解微塑料对共存污染物的载体效应，对可降解微塑料PLA（聚乳酸）对重金属污染物（Cu²⁺、Zn²⁺）的吸附和解吸行为进行了探究，同时选择常规微塑料PP（聚丙烯）进行对照实验.在紫外老化过程中，微塑料（MPs）均表现为表面出现裂纹、凹坑，比表面积增大，负电荷增多，含氧官能团强度增强，亲水性增强.较之PP，PLA在紫外老化过程中理化性质的改变尤为明显.老化后MPs的吸附能力远大于老化前，老化PLA对Cu²⁺的最大吸附量可达5.56mg/g，约为新制PLA（2.27mg/g）的2.5倍；老化前后PLA对重金属的吸附量均高于PP.解吸实验表明，老化后MPs对重金属的解吸率均低于老化前，而老化前后PLA对Cu²⁺、Zn²⁺的解吸量及解吸率均高于PP.较之胃液环境，老化前后MPs对金属离子的解吸更易在肠液环境中进行.说明PLA相对于PP对重金属具有更强的载体作用，且PLA更容易将重金属污染物释放到人体内，进而对人体健康造成威胁.

Adsorption and desorption properties of degradable microplastic for Cu2+ and Zn2+

In order to evaluate the carrier effects of degradable microplastics on co-existing pollutants, the adsorption and desorption behaviors of heavy metals (Cu²⁺, Zn²⁺) by degradable microplastics was explored, and conventional microplastics PP were selected for control experiments. During the UV ageing process, microplastics (MPs) showed surface cracks, pits, increased specific surface area, increased of negative charge, increased strength of oxygen-containing functional groups and enhanced hydrophilicity. Compared with PP, the physical and chemical properties of PLA were significantly changed during UV ageing. The adsorption capacity of MPs after ageing was much higher than that before ageing, and the maximum adsorption capacity of Cu²⁺ by aged PLA was 5.56mg/g, which was about 2.5 times that of original PLA (2.27mg/g). The adsorption capacity of PLA to heavy metals before and after ageing was better than that of PP. In the desorption experiment, the desorption rate of MPs to heavy metals after ageing were both lower than before ageing. The desorption capacity and desorption rate of Cu²⁺ and Zn²⁺ by PLA were higher than that of PP. Compared with gastric fluid environment, MPs desorption of metal ions was easier in intestinal fluid environment before and after ageing. The results showed that PLA had a stronger carrier effect on heavy metals than PP. At the same time, the results of desorption experiments (simulating human stomach and intestinal environment) showed that PLA was more likely to release heavy metal pollutants into the human body, thereby posing a threat to human health.