Degradable plastics could help to protect the marine environment: proof based on pollutant surface behaviors

Information regarding adsorption–desorption of pollutants on degradable microplastics in marine environments is limited. Biodegradable microplastics including polylactic acid (PLA), polyhydroxyalkanoate (PHA), and polybutylene adipate (PBAT) as well as non-biodegradable microplastic controls including polypropylene (PP) and polyethylene (PE), were selected to investigate the adsorption and desorption behaviors of phenanthrene on biodegradable microplastics in seawater. The results showed that PP (5.3%) and PE (5.5%) had relatively high adsorption and desorption capacity for phenanthrene, while PBAT had similar phenanthrene adsorption but lower desorption capacity (desorption rate 3.8%). PLA had the lowest adsorption capacity (118 μg g−1), while PHA had the lowest desorption rate (3.1%) for phenanthrene. Adsorption of phenanthrene by PLA was sensitive to the salinity, while that of PBAT, PP and PE was not affected by the salinity. The high adsorption and weak desorption of phenanthrene on PBAT were mainly affected by π–π interactions and the low crystallinity of PBAT, while those on PLA and PHA were mainly affected by hydrophilicity. The replacement of non-degradable plastics by degradable plastics could modify the adsorption–desorption behaviors of phenanthrene in marine environments. These findings provide new insights into the environmental friendliness of degradable plastics in marine environments.