Effects of pH and Temperature on the Leaching of Di(2-Ethylhexyl) Phthalate and Di-n-butyl Phthalate from Microplastics in Simulated Marine Environment

This study aims to examine the influences of pH and temperature on the leaching of bis(2-ethylhexyl) (DEHP) and di-n-butyl phthalate (DBP) from microplastics in pseudo-seawater. This study consisted of two parts. In the first part, DEHP and DBP in three common microplastics (polyethylene (PE), polyethylene terephthalate (PET), and polyvinyl chloride (PVC)) were experimentally leached into pseudo-seawater at pH values of 5, 7, and 9 respectively with simulated waves. High-performance liquid chromatography was used to detect the leached DBP and DEHP in the samples. The concentrations of DBP leached from PE, PVC and PET from Day-4 to Day-16 were in the ranges of 0.558 - 0.711 mg/L, 0.518 - 0.760 mg/L and 0.540 - 0.791 mg/L respectively. The effect of pH on the amount of DBP leached could not be concluded with different polymers having different optimal pH of leaching. In the second part, DEHP and DBP in six common microplastics (PE, PET, PVC, plastic wrap, disposable gloves, disposable plastic bag) were leached into pseudo-seawater at 25. and 45 degrees C. DBP and DEHP were not detected at 25 degrees C, and a small amount of DBP was detected at 45 degrees C. Higher temperatures promoted the leaching of DBP. This study provides important insight into the leaching behaviors of phthalates from microplastics in the marine environment, which is currently understudied.