Production of Cr(VI) from CrxFe1–x(OH)3 precipitates and NOM-Cr(III) colloids upon reaction with H2O2 under oxic conditions

Li，Binrui1; Zhang，Shaojian2; Liao，Peng2; Liu，Peng3; Ye，Zhihang3; Liu，Chongxuan1

2022-12-30

10.1016/j.chemgeo.2022.121177

CHEMICAL GEOLOGY   Impact Factor & Quartile

0009-2541

Cr(III)-Fe(III) hydroxides (CrFe(OH) precipitates) and NOM-Cr(III) colloids are common products of Cr(VI) reduction during remediation and natural processes. However, re-oxidation of Cr(III) to Cr(VI) can undermine remediation efforts. Nevertheless, until now, less is known about the oxidation of Cr(III) from naturally occurring Cr(III) (i.e., CrFe(OH) precipitates and NOM-Cr(III) colloids) by HO. Here, we examined the oxidation of Cr(III) from CrFe(OH) and NOM-Cr(III) colloids by HO under oxic conditions. Batch experiments demonstrated that Cr(VI) generation via Cr(III) oxidation from both CrFe(OH) and NOM-Cr(III) colloids increased with increasing HO concentration. Increasing pH and addition of Fe promoted Cr(III) oxidation, but the promoting effect of pH was more significant on CrFe(OH), whereas the promoting effect of Fe was significant on NOM-Cr(III) colloids. By evaluating the effects of Fe species on Cr(VI) generation from CrFe(OH) and NOM-Cr(III) colloids, we proposed that an intermediate reactive Fe species formed during the reaction with HO activated Cr(III) oxidation. X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) analyses collectively supported that the surface structural Fe in CrFe(OH) precipitates might contribute to the formation of reactive Fe species that promoted Cr(III) oxidation. In contrast, the decomposition of complexed NOM from NOM-Cr(III) colloids enabled the formation of Cr(III)-HO complex that is favorable for subsequent Cr(III) oxidation. Results gained from this study provide a complete understanding of the long-term stability of naturally occurring Cr(III) under environmentally relevant conditions.

Cr(III) oxidation Cr(VI) generation CrxFe1–x(OH)3 precipitates Hydrogen peroxide NOM-Cr(III) colloids

English

First

GEOSCIENCES

2-s2.0-85140046096

Scopus

1.State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control,School of Environmental Science and Engineering,Southern University of Science and Technology,Shenzhen,518055,China
2.State Key Laboratory of Environmental Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang,550081,China
3.School of Environment,China University of Geosciences,Wuhan,388 Lumo Road,430074,China

Li，Binrui,Zhang，Shaojian,Liao，Peng,等. Production of Cr(VI) from CrxFe1–x(OH)3 precipitates and NOM-Cr(III) colloids upon reaction with H2O2 under oxic conditions[J]. CHEMICAL GEOLOGY,2022,614.

Li，Binrui,Zhang，Shaojian,Liao，Peng,Liu，Peng,Ye，Zhihang,&Liu，Chongxuan.(2022).Production of Cr(VI) from CrxFe1–x(OH)3 precipitates and NOM-Cr(III) colloids upon reaction with H2O2 under oxic conditions.CHEMICAL GEOLOGY,614.

Li，Binrui,et al."Production of Cr(VI) from CrxFe1–x(OH)3 precipitates and NOM-Cr(III) colloids upon reaction with H2O2 under oxic conditions".CHEMICAL GEOLOGY 614(2022).