Department of Chemistry, Ball State University, Muncie, IN, 47306, USA.
Department of Chemistry, Ball State University, Muncie, IN, 47306, USA.
Chemosphere. 2022 Jan;287(Pt 1):131953. doi: 10.1016/j.chemosphere.2021.131953. Epub 2021 Aug 25.
Colloids, such as natural particulate matter and microplastics, can play a significant role in the fate and transport of organic contaminants. Specifically, these small nano-to micron-sized particles provide large surface area; thus, particle-aqueous interfacial chemistry becomes significant. In this work, we present an experimental investigation of interfacial photokinetics of malachite green cation (MG) adsorbed at the surface of polystyrene carboxyl (PSC) microspheres suspended in aqueous solution. Second harmonic generation (SHG), an interfacial selective laser spectroscopic tool, has been used to probe the buried interface. It is revealed that relative to the bulk, photoinduced degradation of MG is accelerated by approximately 10-fold at this noncatalytic particle surface. By measuring the SHG-based surface electronic spectra, we have also demonstrated that N-demethylated intermediates of MG remain at the interface until they are further decomposed. MG exhibits a bathochromic shift at the interface. Together with strong binding affinity and faster initial rate of photodegradation of MG at the interface, this work highlights that adsorption and surface photolysis are important pathways by which organic compounds can be transformed within the aquatic environment. Moreover, this research also stimulates further questions on the enrichment of reactive species at the colloidal-aqueous interface and their influence on facilitating decompositions of organic pollutants.
胶体，如天然颗粒物和微塑料，可以在有机污染物的命运和迁移中发挥重要作用。具体来说，这些纳米到微米大小的小颗粒提供了较大的表面积；因此，颗粒-水界面化学变得非常重要。在这项工作中，我们展示了在悬浮于水溶液中的聚苯乙烯羧酸（PSC）微球表面吸附的孔雀石绿阳离子（MG）的界面光动力学的实验研究。二次谐波产生（SHG），一种界面选择性激光光谱工具，已被用于探测埋藏界面。结果表明，与体相相比，在这个非催化颗粒表面，光诱导的 MG 降解大约加速了 10 倍。通过测量基于 SHG 的表面电子光谱，我们还证明了 MG 的 N-去甲基化中间产物在界面上一直存在，直到它们进一步分解。MG 在界面处表现出红移。与界面处 MG 的强结合亲和力和更快的初始光降解速率一起，这项工作强调了吸附和表面光解是有机化合物在水环境中转化的重要途径。此外，这项研究还引发了关于胶体-水界面上反应性物种的富集及其对促进有机污染物分解的影响的进一步问题。
