Release mechanisms of plasticizers from emerging biodegradable plastics and their aging behavior

While the increasing use of biodegradable plastics (BDPs) raises concerns over the release of additives like phthalate esters (PAEs), their leaching behavior during photoaging is unclear. This study investigated how UV aging influences PAE release dynamics from three major BDPs, including poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and two types of polylactic acid (PLA), in aquatic environments. Through controlled leaching experiments coupled with diffusion modeling and mass transfer analysis, we found that photoaging increased the plastic-water partition coefficients while decreasing PAE diffusivities. Contrary to expectations, cumulative PAE release was lower under UV exposure than in the dark, attributable to enhanced volatility, altered diffusivity, and in-situ photodegradation. Leaching kinetics were plastic- and compound-specific, and increased water flow universally accelerated release, shortening half-lives. These results demonstrate the complex interplay of diffusion, sorption, and photochemistry during BDP aging, underscoring the need to incorporate photoaging effects in environmental risk assessments.