Wang Anqi, Hou Jun, Tao ChunMei, Miao Lingzhan, Wu Jun, Xing Baoshan
Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing210098, China.
Lianyungang Water Conservancy Bureau (Director of Engineering Technology Center), 9 Lingzhou East Road, Haizhou District, Lianyungang22206, China.
Environ Sci Technol. 2023 Feb 28;57(8):3323-3333. doi: 10.1021/acs.est.2c07289. Epub 2023 Feb 2.
Chemical sulfidation has been considered as an effective strategy to improve the reactivity of zero-valent iron (S-ZVI). However, sulfidation is a widespread biogeochemical process in nature, which inspired us to explore the biogenetic sulfidation of ZVI (BS-ZVI) with sulfate-reducing bacteria (SRB). BS-ZVI could degrade 96.3% of trichloroethylene (TCE) to acetylene, ethene, ethane, and dichloroethene, comparable to S-ZVI (97.0%) with the same S/Fe ratio (i.e., 0.1). However, S-ZVI (0.21 d) exhibited a faster degradation rate than BS-ZVI (0.17 d) based on pseudo-first-order kinetic fitting due to extracellular polymeric substances (EPSs) excreted from SRB. Organic components of EPSs, including polysaccharides, humic acid-like substances, and proteins in BS-ZVI, were detected with 3D-EEM spectroscopy and FT-IR analysis. The hemiacetal groups and redox-activated protein in EPS did not affect TCE degradation, while the acetylation degree of EPS increased with the concentration of ZVI and S/Fe, thus inhibiting the TCE degradation. A low concentration of HA-like substances attached to BS-ZVI materials promoted electron transport. However, EPS formed a protective layer on the surface of BS-ZVI materials, reducing its TCE reaction rate. Overall, this study showed a comparable performance enhancement of ZVI toward TCE degradation through biogenetic sulfidation and provided a new alternative method for the sulfidation of ZVI.
化学硫化被认为是提高零价铁（S-ZVI）反应活性的有效策略。然而，硫化是自然界中一种广泛存在的生物地球化学过程，这启发我们探索用硫酸盐还原菌（SRB）对零价铁进行生物成因硫化（BS-ZVI）。BS-ZVI能将96.3%的三氯乙烯（TCE）降解为乙炔、乙烯、乙烷和二氯乙烯，与具有相同S/Fe比（即0.1）的S-ZVI（97.0%）相当。然而，基于伪一级动力学拟合，由于SRB分泌的胞外聚合物（EPSs），S-ZVI（0.21天）的降解速率比BS-ZVI（0.17天）更快。通过三维荧光光谱（3D-EEM）和傅里叶变换红外光谱（FT-IR）分析检测了BS-ZVI中EPS的有机成分，包括多糖、类腐殖酸物质和蛋白质。EPS中的半缩醛基团和氧化还原激活蛋白不影响TCE的降解，而EPS的乙酰化程度随ZVI浓度和S/Fe的增加而增加，从而抑制了TCE的降解。附着在BS-ZVI材料上的低浓度类腐殖酸物质促进了电子传输。然而，EPS在BS-ZVI材料表面形成了一层保护层，降低了其TCE反应速率。总体而言，本研究表明通过生物成因硫化，ZVI对TCE降解的性能增强相当，并为ZVI的硫化提供了一种新的替代方法。
