Abstract：
Iron (hydr)oxides as a kind of natural mineral actively participate in the transformation of organic pollutants, but there is a large knowledge gap in their impacts on photochemical processes of microplastics (MPs). This study is the first to examine the degradation of two ordinary plastic materials, polyethylene (PE) and polypropylene (PP), mediated by iron (hydr)oxides (goethite and hematite) under simulated solar light irradiation. Both iron (hydr)oxides significantly promoted the degradation of MPs (particularly PP) with a greater effect by goethite than hematite, related to hydroxyl radical (•OH) produced by iron (hydr)oxides. Under light irradiation, the surface Fe(II) phase catalyzed the production of H2O2 and promoted the release of Fe2+, leading to the subsequent light-driven Fenton reaction which produced a large amount of •OH. As the iron (hydr)oxides were modified with NaF at various concentrations, the activity of the surface Fe(II) as well as the release of Fe2+ were greatly reduced, and thus the •OH formation and MP degradation were depressed remarkably. It is worth noting that the surface hydroxyl groups (especially ≡FeOH) affected the reaction kinetics of •OH by regulating the activity of Fe species. These findings unveil the distinct impacts and intrinsic mechanisms of iron (hydr)oxides in influencing the photodegradation of MPs.
摘要：
氧化铁作为一种天然矿物,积极参与有机污染物的转化,但是它们对微塑料（MPs）光化学过程的影响存在很大的知识差距。本研究首次考察了两种普通塑料材料的降解，聚乙烯（PE）和聚丙烯（PP），在模拟太阳光照射下由铁（氢）氧化物（针铁矿和赤铁矿）介导。两种铁（氢）氧化物均显着促进了MP（特别是PP）的降解，针铁矿的作用比赤铁矿更大。与铁（氢）氧化物产生的羟基自由基（·OH）有关。在光照下,表面Fe(II)相催化生成H2O2,促进Fe2+的释放,导致随后的光驱动Fenton反应产生大量的·OH。当铁（氢）氧化物用各种浓度的NaF改性时，表面Fe（II）的活性以及Fe2的释放大大降低，从而显著抑制了·OH的形成和MP的降解。值得注意的是，表面羟基（尤其是=FeOH）通过调节Fe物种的活性来影响·OH的反应动力学。这些发现揭示了铁（hydr）氧化物在影响MPs光降解方面的独特影响和内在机理。
