Impact of Microplastics on Sulfate Formation via Different Oxidation Pathways

Abstract

In this paper, the effects of microplastics on sulfate formation under different oxidation paths in atmospheric media were studied. Based on two typical oxidation pathways of hydrogen peroxide (H₂O₂) and ozone (O₃), the regulation of microplastics on sulfate formation mechanism was investigated. The effects of pH value, microplastic dosage and the ratio of S (IV) to oxidant on the promotion of sulfate formation by microplastics were analyzed. The promotion mechanism was discussed by measuring the active species such as hydroxyl radical (•OH) and superoxide radical (•O₂^-), combined with material characterization methods. The results showed that both polyvinyl chloride (PVC) and polystyrene (PS) could promote the formation of sulfate in different degrees under the oxidation conditions of H₂O₂ and O₃, and showed different rules under the influence of the above factors. Both of them can promote the decomposition of H₂O₂ and O₃ to generate free radicals, and the formation mechanism of sulfate is driven by adsorption and free radical reaction. In terms of adsorption characteristics, PVC is more likely to adsorb S (VI), while PS shows a stronger adsorption tendency for S (IV).