Antimony release from e-waste-derived microplastics in aqueous environments: Effect of plastic properties and environmental factors

Antimony (Sb) is an emerging contaminant widely concerned by researchers recently. SbO, the flame-retardant synergist extensively used in plastics for electronic products, is an important source of Sb pollution. It can be released into the environment from e-waste, especially from the formed microplastics (MPs). However, the behavior and mechanisms of Sb release remain unclear. This study investigated the release behavior of Sb from two typical e-waste-derived MPs, acrylonitrile-butadiene-styrene (ABS) and high-impact polystyrene (HIPS). The effects of particle size, plastic aging, and environmental conditions (pH, humic acid, and inorganic ions) on Sb release were explored. It was found that HIPS exhibited higher total Sb (Sb) release than ABS, due to differences in their hydrophilicity and crystallinity. When the particle size was reduced from 2 mm to 0.15 mm, Sb release from HIPS and ABS increased by 620% and 350%. UV aging increased hydrophilicity and decreased crystallinity of MPs, further enhancing Sb release. Notably, there were about 40% Sb(III) in Sb released by pristine MPs, whereas in the leachate from the UV-aged MPs, Sb was exclusively Sb(V). Sb release was greatly enhanced by acidic and alkaline environments, especially at extreme pH levels, while humic acid has an inhibitory effect on the Sb release. These results suggest considerable amounts of Sb can be released into the environment from e-waste-derived MPs, and affected by various environmental factors. These findings improve understanding of Sb release from MPs in e-waste areas under various environmental conditions, providing insights into environmental risks tied to additive release from MPs.