作者：Sun, ZY (Sun, Zhaoyue) ; Huang, MY (Huang, Meiying) ; Liu, C (Liu, Cun) ; Fang, GD (Fang, Guodong) ; Chen, N (Chen, Ning) ; Zhou, DM (Zhou, Dongmei) ; Gao, J (Gao, Juan)
题目：The formation of center dot OH with Fe-bearing smectite clays and low-molecular-weight thiols: Implication of As(III) removal
刊物：WATER RESEARCH，卷: 174 文献号: 115631
出版年: MAY 1 2020
Low-molecular-weight thiols (LMWTs) are widely occurring in waters and soils, which can act as electron shuttles in biogeochemical cycles. It is interesting to study the interactions between LMWTs and clay minerals, which would produce free radicals on clay surfaces and influence As(III) transformation. Batch experiments and spectroscopic analysis in combined with computational modeling were conducted with three Fe-bearing clay minerals (Na-NAu-1, Na-NAu-2 and Na-SAz-2) and four LMWTs (t-cysteine, cysteamine, homocysteine, and glutathione) to investigate the reaction mechanisms of LMWTs with Febearing clay minerals and influences of clay types and LMWT structures on the interactions. The results showed that Fe-bearing clay minerals can improve 2.4-3.7 times of center dot OH formation in 96-h LMWTs oxidation. Quenching experiments confirmed surface-Fenton-like reactions were the main pathways of center dot OH formation in the presence of Fe-bearing smectite clay minerals. The most possible hypothesis is that structural Fe (III) can accept electrons from LMWTs through proton-coupled transfer from -SH functional group, which was supported by FTIR, XRD and Mossbauer spectroscopies. The results of DFT calculations suggested that clay surfaces could accelerate RS. formation and stabilize the radicals. The addition of Na-NAu-2 in the cystein solution could increase As(III) oxidation to As(V) from 16.3% to 42.0%. The results imply that in-situ center dot OH formation in the presence of LMWTs and smectite clays may be an important geochemical process for the transformation of environmental contaminants. (C) 2020 Elsevier Ltd. All rights reserved.