Adsorption/desorption behavior of degradable polylactic acid microplastics on bisphenol A under different aging conditions

Abstract

As emerging pollutants, microplastics have attracted significant attention in recent years. To evaluate the potential carrier effect of degradable microplastics on coexisting contaminants, we used UV light at different wavelengths, 254 nm and 340 nm, to simulate laboratory-accelerated aging and natural noon direct solar aging, respectively. A study was carried out to analyze the adsorption and desorption properties of polylactic acid (PLA) on bisphenol A (BPA) before and after aging. Compared to the UV-340 nm aged PLA (Aged-PLA 2), the UV-254 nm aged PLA (Aged-PLA 1) showed a significant yellowing phenomenon, the original larger PLA particles cracked into smaller ones, and more pronounced changes were observed in surface functional groups and physicochemical properties. The zeta potential of Aged-PLA 1 exhibited a decrease from −24.75 mV to −30.35 mV. By contrast, there was no fixed trend in the Zeta potential changes of Aged-PLA 2. In adsorption experiments, the original PLA and Aged-PLA 2 showed similar adsorption capabilities for BPA, which were higher than those of Aged-PLA 1. Desorption experiments showed that aged PLA desorbed from BPA to an extent greater than that of the original PLA, indicating that the aged PLA had a greater capacity for the pollutant to migrate. The desorption of BPA was found to be higher in simulated intestinal fluid than in ultrapure water, suggesting that PLA adsorbed on BPA faces a higher ecotoxicological risk in organisms. Overall, these results will contribute to the comprehension of the carrier effect and potential ecological risk of MPs on coexisting pollutants.