Oak Ridge Institute for Science and Education (ORISE) Fellow, Office of Superfund Remediation and Technology Innovation, U.S. Environmental Protection Agency, 2777 Crystal Drive, Arlington, Virginia 22202, United States.
OHSU-PSU School of Public Health, Oregon Health & Science University , 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States.
Environ Sci Technol. 2017 Nov 21;51(22):13070-13085. doi: 10.1021/acs.est.7b04177. Epub 2017 Nov 1.
Iron-based materials used in water treatment and groundwater remediation-especially micro- and nanosized zerovalent iron (nZVI)-can be more effective when modified with lower-valent forms of sulfur (i.e., "sulfidated"). Controlled sulfidation for this purpose (using sulfide, dithionite, etc.) is the main topic of this review, but insights are derived by comparison with related and comparatively well-characterized processes such as corrosion of iron in sulfidic waters and abiotic natural attenuation by iron sulfide minerals. Material characterization shows that varying sulfidation protocols (e.g., concerted or sequential) and key operational variables (e.g., S/Fe ratio and sulfidation duration) result in materials with structures and morphologies ranging from core-shell to multiphase. A meta-analysis of available kinetic data for dechlorination under anoxic conditions, shows that sulfidation usually increases dechlorination rates, and simultaneously hydrogen production is suppressed. Therefore, sulfidation can greatly improve the efficiency of utilization of reducing equivalents for contaminant removal. This benefit is most likely due to inhibited corrosion as a result of sulfidation. Sulfidation may also favor desirable pathways of contaminant removal, such as (i) dechlorination by reductive elimination rather than hydrogenolysis and (ii) sequestration of metals as sulfides that could be resistant to reoxidation. Under oxic conditions, sulfidation is shown to enhance heterogeneous catalytic oxidation of contaminants. These net effects of sulfidation on contaminant removal by iron-based materials may substantially improve their practical utility for water treatment and remediation of contaminated groundwater.
用于水处理和地下水修复的铁基材料 - 特别是微纳米级零价铁 (nZVI) - 在经过低价硫形式（即“硫化”）改性后可以更有效。为此目的进行的受控硫化（使用硫化物、连二亚硫酸盐等）是本综述的主要主题，但通过与相关且特征较好的过程（例如，在硫化水中的铁腐蚀和铁硫化物矿物的非生物自然衰减）进行比较得出了一些见解。材料特性表明，不同的硫化方案（例如协同或顺序）和关键操作变量（例如 S/Fe 比和硫化持续时间）导致具有从核壳到多相的结构和形态的材料。对缺氧条件下脱氯的可用动力学数据进行的荟萃分析表明，硫化通常会提高脱氯速率，同时抑制氢气生成。因此，硫化可以大大提高去除污染物所需的还原当量的利用效率。这种好处很可能是由于硫化抑制了腐蚀。硫化也可能有利于去除污染物的理想途径，例如 (i) 通过还原消除而不是氢解进行脱氯，以及 (ii) 将金属螯合作为硫化物，这些硫化物可能对再氧化具有抗性。在有氧条件下，硫化被证明可以增强污染物的多相催化氧化。通过铁基材料进行硫化对污染物去除的这些净效应可能会大大提高其在水处理和受污染地下水修复中的实际应用。
