State Key Laboratory of Pollution Control and Resource Reuse , Tongji University , Shanghai 200092 , China.
Department of Civil and Environmental Engineering , University of California , Los Angeles , California 90095 , United States.
Environ Sci Technol. 2018 Jun 5;52(11):6466-6475. doi: 10.1021/acs.est.8b00231. Epub 2018 May 23.
Sulfidation of nanoscale zerovalent iron (nZVI) has shown some fundamental improvements on reactivity and selectivity toward pollutants in dissolved-oxygen (DO)-stimulated Fenton-like reaction systems (DO/S-nZVI system). However, the pristine microstructure of sulfide-modified nanoscale zerovalent iron (S-nZVI) remains uncovered. In addition, the relationship between pollutant removal and the oxidation of the S-nZVI is largely unknown. The present study confirms that sulfidation not only imparts sulfide and sulfate groups onto the surface of the nanoparticle (both on the oxide shell and on flake-like structures) but also introduces sulfur into the Fe(0) core region. Sulfidation greatly inhibits the four-electron transfer pathway between Fe(0) and oxygen but facilitates the electron transfer from Fe(0) to surface-bound Fe(III) and consecutive single-electron transfer for the generation of HO and hydroxyl radical. In the DO/S-nZVI system, slight sulfidation (S/Fe molar ratio = 0.1) is able to nearly double the oxidative removal efficacy of diclofenac (DCF) (from 17.8 to 34.2%), whereas moderate degree of sulfidation (S/Fe molar ratio = 0.3) significantly enhances both oxidation and adsorption of DCF. Furthermore, on the basis of the oxidation model of S-nZVI, the DCF removal process can be divided into two steps, which are well modeled by parabolic and logarithmic law separately. This study bridges the knowledge gap between pollutant removal and the oxidation process of chemically modified iron-based nanomaterials.
纳米零价铁（nZVI）的硫化在溶解氧（DO）刺激的类芬顿反应体系（DO/S-nZVI 体系）中对污染物的反应性和选择性表现出一些基本的改善。然而，硫化修饰纳米零价铁（S-nZVI）的原始微观结构仍未被揭示。此外，污染物去除与 S-nZVI 氧化之间的关系在很大程度上是未知的。本研究证实，硫化不仅在纳米颗粒的表面上赋予了硫代和硫酸盐基团（氧化物壳和片状结构上都有），而且还将硫引入到 Fe(0)核区。硫化极大地抑制了 Fe(0)和氧之间的四电子转移途径，但促进了电子从 Fe(0)转移到表面结合的 Fe(III)，并连续进行单电子转移以生成 HO 和羟基自由基。在 DO/S-nZVI 体系中，轻微的硫化（S/Fe 摩尔比=0.1）几乎能使双氯芬酸（DCF）的氧化去除效率提高一倍（从 17.8%提高到 34.2%），而适度的硫化程度（S/Fe 摩尔比=0.3）则显著提高了 DCF 的氧化和吸附。此外，基于 S-nZVI 的氧化模型，DCF 的去除过程可以分为两步，这两步分别可以用抛物线和对数律很好地模拟。本研究填补了化学修饰铁基纳米材料的污染物去除与氧化过程之间的知识空白。
