Metal leaching accompanied with natural photo-aging behavior of e-waste plastic derived microplastics in aquatic environment

As the main component of electronic products, plastics contain complex and diverse metal additives. Recycling process is not conducive to stable existence of metal additives in electronic plastics. Once the e-waste plastics enter the environment, they will continue to release harmful metals into environment after aging, causing serious hazards. This study delved into the analysis and comparison of metal content of e-waste plastics, elucidating aging process and metal leaching behavior over a 112-day natural light exposure period. The findings underscored that metal content in recycled plastics surpassed that in their new counterparts. Specifically, Ti content in new plastics remained below 100 mg/kg, while recycled plastics exhibited Ti content surpassing 100 mg/kg threshold. Throughout prolonged natural light exposure, metals such as Zn, Ba and Sb demonstrated a heightened likelihood of release from electronic plastics in comparison to other metals. The aging process during light exposure led to fragmentation of electronic plastics, accompanied by a reduction in particle size. Notably, the particle size reduction was more pronounced in poly acrylonitrile butadiene styrene (ABS) and recycled ABS, experiencing reductions of 40 µm and 85 µm, respectively. This phenomenon was attributed to the presence of polybutadiene structural units, which proved more susceptible to aging. Along with the breaking of plastics, the ABS plastics released metal species such as Pb, Cd, Ni, Al that had not been detected in other plastics solutions. The collective evidence from this study suggested that ABS and recycled ABS electronic plastics might pose a heightened potential environmental risk compared to other electronic plastics.