MODEL FITTING ANALYSIS OF THE ADSORPTION BEHAVIOR OF AGED POLYLACTIC ACID MICROPLASTICS TO COPPER

As new pollutants, microplastics has been proved to can adsorb the traditional heavy metal pollutants in in the aqueous environment. While microplastics will age continuously in the environment, and their physicochemical properties will change accordingly, but the impact of aging process on adsorption behavior of microplastics are not fully understood. Herein, to explore the aging process of microplastics on the adsorption of heavy metal, the adsorption behavior of Cu2+ on polylactic acid (PLA) microplastics with four treatments of unaged (L0), aged 10 days (L10), 20 days (L20) and 30 days (L30) were investigated. Results showed that the optimal PLA microplastics dosage was 0.025 g/L. The adsorption capacity increased with increasing pH and the optimal pH was 7. The adsorption kinetics of Cu2+ onto aged PLA microplastics was explained well by the pseudo-second order kinetic model and the Langmuir model, respectively, suggesting that chemisorption was possibly the adsorption mechanism. On the other hand, the adsorption capacity of four kinds of aged PLA microplastics for Cu2+ under optimal condition was as follow: L30 > L20 > L10 > L0, indicating that would increase their adsorption affinity towards heavy metals, resulting in potential harm to the environment. The results of this study provide valuable information for studying the environmental behavior of aged microplastics and interaction between microplastics and heavy metals in the real environment.