The mobility and fate of Cr during aging of ferrihydrite and ferrihydrite organominerals

• DOI: 10.1016/j.gca.2023.02.021
• Publication Date: 2023-03-01T22:06:59Z
• Authors: Yao Zhao; Alba Otero-Fariña; Ke-Qing Xiao; Oliver W. Moore; Steven A. Banwart; Fu-Jun Ma; Qing-Bao Gu; Caroline L. Peacock
• Keywords: Ferrihydrite; Redistribution; Lability

The fixation of environmentally hazardous Cr(VI) in soils is largely attributed to its retention by iron (Fe) (oxyhydr)oxides the soil environment, which are prevailingly associated with organic carbon (OC). effect OC different binding strengths on adsorption and mobility fate during aging Fe (oxyhydr)oxide however, unknown. Here we investigate how strength influences ferrihydrite (Fh) organominerals, Fh organominerals subsequent or release as proceeds. We conduct experiments onto apply surface complexation modelling study relative between Cr(VI), then track redistribution Cr(VI). show based that weakly-bound at C loadings has almost no discernable influence adsorption, while strongly-bound significantly suppresses via site blocking and/or electrostatic repulsion. process strongly influenced presence OC. Weakly-bound carboxyl-poor not only near doubles rate retained (i.e., from a fraction) neoformed minerals pH 5.0, but also increases final proportion Cr(VI)strongly-bound, attribute loose porous structure easier replacement More carboxyl-rich higher reduces OC, such similar lower than for pure system, fact less easily replaced hence able access sites pores thus be inside minerals. Overall suggest carboxyl-richness will further suppress overall controlled organominerals.