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Insights into the Properties and Adsorption–desorption Behaviors of Aged Microplastics with Different Colors
Summary
Researchers aged black tire wear particles and white polyethylene microplastics under UV light in the presence and absence of algal organic matter, finding that aging increased their adsorption capacity for the antibiotic tetracycline hydrochloride, with the degree of aging and adsorption behavior differing by particle color and composition. This reveals that weathered microplastics in real aquatic environments act as amplified vectors for antibiotic transport, posing compounded risks to aquatic ecosystems and potentially human health through contaminated water sources.
Microplastics (MPs) act as vectors for antibiotics in aquatic environments; however, their adsorption capacities, influenced by their color and the concentration of algal organic matter (AOM) in water, remain poorly understood. Herein, black tire wear particles (B-TWPs) and white polyethylene (W-PE) MPs were selected as model MPs. To accurately compare property differences between the two MP types in water environments, MPs particles subjected to ultraviolet aging (30 w) in ultrapure water, water with 5 mg/L AOM, and freshwater were analyzed. Further, changes in the structure, functional groups, and adsorption–desorption behaviors of tetracycline hydrochloride (TCH) on these MPs were studied. Results revealed that the hydrophilic properties of both the MPs developed with oxygen-containing functional groups, which enhanced their adsorption capacity after aging. AOM inhibited the aging extent of B-TWPs and W-PE MPs, with B-TWPs exhibiting a greater degree of aging than W-PE. These alterations substantially influenced the adsorption–desorption behavior of TCH, as confirmed by adsorption and desorption kinetic studies. The adsorption process of aged B-TWPs and W-PE MPs in the presence of AOM was best described by a second-order kinetic model (R2 > 0.97). The isothermal adsorption results confirmed that the Freundlich model better described the adsorption of antibiotics on the MPs with and without AOM present (R2 > 0.98). This study is the first to underscore the critical role of AOM in the aging of MPs with different colors. AOM modifies the adsorption and desorption behaviors of co-occurring antibiotics in the environment.