Department of Chemistry & Biochemistry, 66 George St., College of Charleston, Charleston, SC, USA.
Department of Chemistry & Biochemistry, 66 George St., College of Charleston, Charleston, SC, USA.
Sci Total Environ. 2020 Jun 10;720:137685. doi: 10.1016/j.scitotenv.2020.137685. Epub 2020 Mar 3.
Silver nanoparticles (Ag NPs) are among the most common forms of nanoparticles in consumer products, yet the environmental implications of their widespread use remain unclear due to uncertainties about their fate. Because sulfidation of Ag NPs results in the formation of a stable silver sulfide (AgS) product, it is likely an important removal mechanism of bioavailable silver in natural waters. In addition to sulfide, the complete conversion of Ag NPs to AgS will require dissolved oxygen or some other oxidant so dispersed metal sulfides may be an important pool of reactive sulfide for such reactions in oxygenated systems. The reaction of Ag NPs with zinc sulfide (ZnS) was investigated using a voltammetric method, anodic stripping voltammetry (ASV). ASV provided sensitive, in situ measurements of the release of zinc (Zn) cations resulting from the cation exchange reaction between Ag NPs and ZnS. The effects of Ag NP size and surface coatings on the initial rates of sulfidation by ZnS were examined. Sulfidation of smaller Ag NPs generally occurred faster and to a greater extent due to their larger relative surface areas. Sulfidation of Ag NPs capped by citrate and lipoic acid occurred more rapidly relative to polyvinylpyrrolidone (PVP) and branched polyethylene (BPEI). This study demonstrates the utility of voltammetry for such investigations and provides insights into important factors controlling Ag NP sulfidation such as availability of dissolved oxygen, Ag NP size and Ag NP surface coating. Furthermore, this work demonstrates the importance of cation exchange reactions between silver and metal sulfides, and how the environmental release of Ag NPs could alter the speciation of other metals of environmental significance.
银纳米粒子（Ag NPs）是消费产品中最常见的纳米粒子形式之一，但由于其命运不确定，其广泛使用对环境的影响仍不清楚。由于 Ag NPs 的硫化会导致形成稳定的硫化银（AgS）产物，因此它很可能是天然水中生物可利用银的重要去除机制。除了硫化物外，Ag NPs 完全转化为 AgS 还需要溶解氧或其他氧化剂，因此分散的金属硫化物可能是含氧系统中此类反应中活性硫化物的重要来源。使用伏安法（阳极溶出伏安法，ASV）研究了 Ag NPs 与硫化锌（ZnS）的反应。ASV 提供了对 Ag NPs 和 ZnS 之间阳离子交换反应导致锌（Zn）阳离子释放的敏感、原位测量。研究了 Ag NP 尺寸和表面涂层对 ZnS 初始硫化速率的影响。由于相对表面积较大，较小的 Ag NPs 的硫化通常发生得更快且程度更大。柠檬酸和硫辛酸包覆的 Ag NPs 的硫化速度相对于聚乙烯吡咯烷酮（PVP）和支化聚乙烯（BPEI）更快。本研究证明了伏安法在这类研究中的实用性，并提供了对控制 Ag NP 硫化的重要因素的深入了解，如溶解氧的可用性、Ag NP 尺寸和 Ag NP 表面涂层。此外，这项工作还证明了银与金属硫化物之间阳离子交换反应的重要性，以及 Ag NPs 的环境释放如何改变其他具有环境意义的金属的形态。
