Effect of particle size and environmental conditions on the release of di(2-ethylhexyl) phthalate from microplastics

The extensive use and improper handling of plastics have caused extensive microplastic (MP) pollution in terrestrial environments. Di(2-ethylhexyl) phthalate (DEHP), the main additive used in plastics, is toxic to organisms and may pose risks to human and animal reproductive functions. However, research on the release behavior of DEHP from MPs is scarce. In this study, the effects of particle size and environmental conditions (temperature, pH, ionic strength, and cation type) on DEHP release from polylactide (PLA), polystyrene (PS), and polyvinyl chloride (PVC) MPs were determined by performing leaching experiments. The results showed that when particle size decreased, the content of DEHP in the MPs and the amount of released DEHP increased though increasing specific surface area. An increase in temperature also promoted DEHP release; when the temperature increased from 15 °C to 45 °C, the amount of DEHP released from PLA, PS, and PVC increased by 38.4%, 71.0%, and 109%, respectively. The lower the crystallinity, the greater the increase in the amount of DEHP released. Ionic strength inhibited the release of DEHP from MPs. When Na⁺ concentration increased from 0 to 200 mM, the amount of DEHP released from PLA, PS, and PVC decreased by 27.4%, 41.6%, and 35.3%, respectively. The effect of Ca²⁺ on DEHP release from MPs was greater than that of Na⁺. In addition, the process of DEHP release from MPs fit well with a pseudo-first-order kinetic model. The results of this study provide a theoretical basis for managing and controlling the risks associated with plastic wastes.