Degradation and adsorption behavior of biodegradable plastic PLA under conventional weathering conditions

With the increasing pollution of plastics and the widespread use of polylactic acid (PLA), its weathering process in the natural environment needs to be studied. Hence, we investigated the characteristics of PLA under conventional weathering conditions and the adsorption behavior between PLA and tetracycline (TC). The results showed cracks and holes in the weathered PLA surface, an increase in oxygen-containing functional groups, and a 77.94 % decrease in contact angle, causing more amount of TC to be adsorbed. The maximum adsorption capacity of PLA for TC is approximately 3.5 times higher than before weathering due to multilayer physical adsorption. Nevertheless, the surface of the microplastics weathered by seawater did not change significantly. This work elucidates the weathering mechanism of biodegradable microplastics under abiotic conditions, thus correctly assessing the difference in natural and conventional degradability of biodegradable plastics.