Role of humic acid in the transformation of hexavalent chromium in a sulfidated ferrihydrite system

Jiayi Xu; Hanpei Yang; Jun Hou; Lingzhan Miao; Jun Wu

doi:10.1016/j.scitotenv.2022.160884

Role of humic acid in the transformation of hexavalent chromium in a sulfidated ferrihydrite system

Sci Total Environ. 2023 Mar 10:863:160884. doi: 10.1016/j.scitotenv.2022.160884. Epub 2022 Dec 15.

Authors

Jiayi Xu¹, Hanpei Yang¹, Jun Hou¹, Lingzhan Miao¹, Jun Wu²

Affiliations

¹ Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, People's Republic of China.
² Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, People's Republic of China. Electronic address: junwu@hhu.edu.cn.

PMID: 36528100
DOI: 10.1016/j.scitotenv.2022.160884

Abstract

Ferrihydrite (Fh) often coexists with organic matter (i.e., humic acid (HA)) in the environment; however, its impacts on the transformation of hexavalent chromium (Cr(VI)) is poorly understood during the sulfidation of Fh. Upon exposed to 2 mM sulfide for 12 h, the total amount of Fe(II) (Fe(II)_tot, 0.78 mM) in treatments with HA (300 mg HA/L) was higher than that (0.67 mM) in treatments without HA, since HA could enhance the solubility of Fe(II). After then, the Cr(VI) was reduced by sulfidated Fh. Aqueous Cr(VI) concentration (Cr(VI)_aq) declined from 0.67 to 0.43 mM with the increase of HA concentration from 0 to 400 mg/L, which was partly ascribed to the inhibition of surface passivation by HA. Moreover, the increase in Fe(II) during the sulfidation of Fh also exerted a strong impact on the transformation of Cr(VI) subsequently. In addition of HA, batch experiments suggested that EDTA could also promote the formation of Fe(II) (Fe(II)_tot, 0.80 mM), rendering a lower Cr(VI)_aq (0.59 mM) in EDTA-300 treatments. This study further demonstrated that HA played an important role in the transformation of Cr(VI), hence providing a theoretical basis for in-situ remediation of Cr(VI) in the future.

Keywords: Chromium; Ferrihydrite; Humic acid; Sulfidation.