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Title: Effects of citrate on hexavalent chromium reduction by structural Fe(II) in nontronite

Abstract

Iron-bearing clay minerals and organic matter are two important components in natural environments that influence hexavalent chromium (Cr(VI)) reduction. Previous studies have shown that organic ligands could influence Cr(VI) reduction by aqueous Fe2+ and pyrite. However, the effects of organic ligands on Cr(VI) reduction by structural Fe(II) in clays are not well understood. In this study, the effects of citrate on Cr(VI) reduction by nontronite (NAu-2) were investigated under near neutral pH condition (pH=6). Our results showed that the presence of citrate decreased the rate but increased the amount of Cr(VI) reduction by structural Fe(II) in NAu-2. The decreased reaction rate was likely due to competitive sorption of citrate and polyanionic dichromate (Cr2O7- ), because sorption of dichromate appeared to be the first step for subsequent Cr(VI) reduction. The increased amount of Cr(VI) reduction in the presence of citrate was likely because citrate provided additional reducing power through ligand-metal electron transfer in the presence of soluble Fe 3+ derived from dissolution of reduced NAu-2. Soluble Cr(III)-citrate complex was the possible form of reduced chromium when citrate was present. In contrast, nanometer-sized Cr2O3 particles were the product of Cr(VI) reduction by reduced NAu-2 without citrate. Our study highlights the importance ofmore » organic ligands on Cr(VI) reduction and immobilization when iron-bearing clay minerals are applied to treat Cr(VI) contaminant in organic matter rich environments.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1416673
Report Number(s):
PNNL-SA-127651
Journal ID: ISSN 0304-3894; 49562; KP1704020
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Hazardous Materials
Additional Journal Information:
Journal Volume: 343; Journal Issue: C; Journal ID: ISSN 0304-3894
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory

Citation Formats

Liu, Xiaolei, Dong, Hailiang, Yang, Xuewei, Kovarik, Libor, Chen, Yu, and Zeng, Qiang. Effects of citrate on hexavalent chromium reduction by structural Fe(II) in nontronite. United States: N. p., 2018. Web. doi:10.1016/j.jhazmat.2017.09.038.
Liu, Xiaolei, Dong, Hailiang, Yang, Xuewei, Kovarik, Libor, Chen, Yu, & Zeng, Qiang. Effects of citrate on hexavalent chromium reduction by structural Fe(II) in nontronite. United States. doi:10.1016/j.jhazmat.2017.09.038.
Liu, Xiaolei, Dong, Hailiang, Yang, Xuewei, Kovarik, Libor, Chen, Yu, and Zeng, Qiang. Thu . "Effects of citrate on hexavalent chromium reduction by structural Fe(II) in nontronite". United States. doi:10.1016/j.jhazmat.2017.09.038.
@article{osti_1416673,
title = {Effects of citrate on hexavalent chromium reduction by structural Fe(II) in nontronite},
author = {Liu, Xiaolei and Dong, Hailiang and Yang, Xuewei and Kovarik, Libor and Chen, Yu and Zeng, Qiang},
abstractNote = {Iron-bearing clay minerals and organic matter are two important components in natural environments that influence hexavalent chromium (Cr(VI)) reduction. Previous studies have shown that organic ligands could influence Cr(VI) reduction by aqueous Fe2+ and pyrite. However, the effects of organic ligands on Cr(VI) reduction by structural Fe(II) in clays are not well understood. In this study, the effects of citrate on Cr(VI) reduction by nontronite (NAu-2) were investigated under near neutral pH condition (pH=6). Our results showed that the presence of citrate decreased the rate but increased the amount of Cr(VI) reduction by structural Fe(II) in NAu-2. The decreased reaction rate was likely due to competitive sorption of citrate and polyanionic dichromate (Cr2O7- ), because sorption of dichromate appeared to be the first step for subsequent Cr(VI) reduction. The increased amount of Cr(VI) reduction in the presence of citrate was likely because citrate provided additional reducing power through ligand-metal electron transfer in the presence of soluble Fe 3+ derived from dissolution of reduced NAu-2. Soluble Cr(III)-citrate complex was the possible form of reduced chromium when citrate was present. In contrast, nanometer-sized Cr2O3 particles were the product of Cr(VI) reduction by reduced NAu-2 without citrate. Our study highlights the importance of organic ligands on Cr(VI) reduction and immobilization when iron-bearing clay minerals are applied to treat Cr(VI) contaminant in organic matter rich environments.},
doi = {10.1016/j.jhazmat.2017.09.038},
journal = {Journal of Hazardous Materials},
issn = {0304-3894},
number = C,
volume = 343,
place = {United States},
year = {2018},
month = {2}
}