Cr(Vi) Removal by Sodium Borohydride in the Presence of Small Molecular Organic Ligand: Involvement of Citrate and Edta Chemical Transformation

作     者：Njoya, Ousmanou Wang, Zhehao Shen, Jimin Zhao, Shengxin Tan, Qiang Qu, Yanfeng Chen, Zhonglin 

作者机构：State Key Laboratory of Urban Water Resource and Environment School of Environment Harbin Institute of Technology Harbin150090 China Institute of Agricultural Research for Development P.O. Box 415 Garoua Cameroon School of Food Engineering Harbin University Harbin150086 China 

出 版 物：《SSRN》 

年 卷 期：2023年

核心收录：

主　　题：Hydrogen bonds 

摘      要：The use of chemical reduction to convert highly toxic Cr(VI) in water into low toxic and weakly mobile Cr(III) is considered the most feasible. Carboxylic acids (CAs) as clean regent widely coexists in multiples types of wastewater with Cr(VI). The influence of coexisting CAs during Cr(VI) reduction process should be widely studied. In this investigation, the role of coexisting CAs including Citrate and EDTA in Cr(VI) reduction was clarified. The results indicated that Citrate and EDTA could significantly promote Cr(VI) reduction by NaBH4. EDTA had a better promoting effect, exhibiting that 10 mM EDTA obtained similar 90.31% and 87.67% of Cr(VI) reduction at initial pH 4 and 5, respectively, reducing the requirement for low initial pH for Cr(VI) reduction. Regarding the improvement mechanism of Cr(VI) by NaBH4, Citrate and EDTA did not directly transfer their electrons to Cr(VI), while the addition of BH4- resulted in their degradation or transformation. Citrate and EDTA had two effects on Cr(VI) reduction by NaBH4. On the one hand, they provided a strong buffering effect, providing H+ to the reaction system for resisting OH- from NaBH4 self-hydrolysis and alleviate H+ requirement for Cr(VI) reduction;On the other hand, it might be attributed to the fact that Citrate or EDTA could eliminate some of hydrogen radical (•H) producing from homolysis of B–H bonds induced by Cr(VI), which exhibited a slight inhibitory of Cr(VI) reduction due to the competition with Cr(VI) for •H. However, the promoting effect was greater than the inhibitory effect. The findings provided new insights into Cr(VI) reduction by NaBH4 mediated by CAs, which is of interest for systems engineered for Cr(VI) remediation. © 2023, The Authors. All rights reserved.