Adsorption and desorption of nonylphenol on the biodegradable microplastics in seawater

Biodegradable plastics have been widely used and their interaction with endocrine disrupting chemicals in the environment is worth exploring. This study selected poly (butylene adipate-co-terephthalate), poly (butylene succinate), polylactic acid (PLA) and a non-biodegradable microplastics (PE) as control to explore the adsorptiondesorption behavior of nonylphenol (NP) on the biodegradable microplastics in seawater. The adsorption capacity of NP on PLA (60.78 mu g g- 1) was approximately 50% lower than that on PE (116.53 mu g g- 1) which was the non-biodegradable microplastic control. Almost all biodegradable microplastics showed negligible desorption capacity compared to PE, indicating a lower environmental risk of biodegradable microplastics. The pH could influence the interaction between the NP and biodegradable microplastics through the formation of hydrogen bonds. The adsorption-desorption capacity of microplastics might increase at the condition of the high salinity and seawater erosion. Physical adsorption was the major adsorption processes based on the Gibbs free energy changes that calculated. The adsorption mechanism of microplastics was determined by calculating the crystallinity of microplastics, simulating the surface electrostatic potential of microplastics and conducting hydrophilicity tests of microplastics. The adsorption and desorption capacities of NP on biodegradable microplastics were mainly influenced by various mechanisms, including the crystallinity of the microplastics, hydrogen bonding and hydrophobic effects. These results will offer new perspectives on the interaction between biodegradable microplastics and NP in the ocean.