State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering , Tongji University , Shanghai 200092 , P.R. China.
Shanghai Institute of Pollution Control and Ecological Security , Shanghai 200092 , P.R. China.
Environ Sci Technol. 2018 Mar 6;52(5):2988-2997. doi: 10.1021/acs.est.7b06502. Epub 2018 Feb 23.
When zerovalent iron (ZVI) is used in reductive removal of contaminants from industrial wastewater, where dissolved oxygen (DO) competes with target contaminant for the electrons donated by ZVI, both the reactivity and the electron selectivity (ES) of ZVI toward target contaminant are critical. Thus, the reactivity and ES of two sulfidated ZVI (S-ZVI) samples, synthesized by ball-milling with elemental sulfur (S-ZVI) and reacting with NaS (S-ZVI), toward Cr(VI) under aerobic conditions were investigated. Sulfidation appreciably increased the reactivity of ZVI and the ratio of the rate constants for Cr(VI) removal by S-ZVI or S-ZVI to their counterparts without sulfur fell in the range of 1.4-29.9. ES of S-ZVI and S-ZVI toward Cr(VI) were determined to be 14.6% and 13.3%, which were 10.7- and 7.5-fold greater than that without sulfidation, respectively. This was mainly ascribed to the greater improving effect of sulfidation on the reduction rate of Cr(VI) than that of DO by ZVI. The improving effects of sulfidation on the performance of ZVI were mainly due to the following mechanisms: sulfidation increased the specific surface area of ZVI, the FeS layer facilitated the enrichment of Cr(VI) anions on S-ZVI surface because of its anions selective property and favored the electron transfer from Fe core to Cr(VI) at the surface because of its role as efficient electron conductor.
当零价铁（ZVI）用于还原去除工业废水中的污染物时，溶解氧（DO）与目标污染物竞争 ZVI 提供的电子，因此 ZVI 对目标污染物的反应性和电子选择性（ES）都至关重要。因此，研究了两种硫化零价铁（S-ZVI）样品在有氧条件下对 Cr(VI)的反应性和 ES，这两种样品是通过元素硫（S-ZVI）球磨合成和与 NaS 反应（S-ZVI）合成的。硫化显著提高了 ZVI 的反应性，S-ZVI 或 S-ZVI 去除 Cr(VI)的速率常数与不含硫的速率常数之比在 1.4-29.9 范围内。S-ZVI 和 S-ZVI 对 Cr(VI)的 ES 分别为 14.6%和 13.3%，分别比未硫化时提高了 10.7-7.5 倍。这主要是由于硫化对 ZVI 还原 Cr(VI)的速率的改善作用大于 DO。硫化对 ZVI 性能的改善作用主要归因于以下机制：硫化增加了 ZVI 的比表面积，FeS 层由于其阴离子选择性而有利于 Cr(VI)阴离子在 S-ZVI 表面的富集，并由于其作为有效的电子导体而有利于电子从 Fe 核转移到表面的 Cr(VI)。
