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Updated: May 30, 2025
Removal of Arsenic Using a Cationic Polymer Gel Impregnated with Iron Hydroxide
Published on: June 28, 2019
Quantitative Enhancement of Arsenate Immobilization Induced by Vacancy Defects on Various Exposed Lattice Facets of
Juan Liu1, Jingtao Hou1, Juan Xiong1
1State Environmental Protection Key Laboratory of Soil Health and Green Remediation, Hubei Key Laboratory of Soil Environment and Pollution Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
Abstract:
Defects are common features in hematite that arise from deviations from the perfect mineral crystal structure. Vacancy defects have been shown to significantly enhance arsenate (As) immobilization by hematite. However, the contributions from vacancy defects on different exposed facets of hematite have not been fully quantified. In this study, hematite samples with various morphologies were pretreated with sodium borohydride (NaBH4) to generate oxygen vacancy defects (OVDs), analyzed quantitatively using extended X-ray absorption fine structure (EXAFS) and thermogravimetric analysis (TG). Batch experiments revealed that the OVDs on different exposed facets showed significant variations in improving arsenate adsorption, i.e., the quantitative enhancement of arsenate adsorption amount per unit OVD concentration (ΔQm/Cdefect) followed the sequence of (110) facet (80.05 μmol/mmoldef) > (001) facet (31.85 μmol/mmoldef) > (012) facet (13.14 μmol/mmoldef). The underlying mechanism by which OVDs affect arsenate adsorption across different exposed facets of hematite was studied. The results reveal that the tremendous improvement of arsenate adsorption caused by OVDs on the (110) facet compared to (001) and (012) facets was attributed to their stronger bonding strength of As to under-coordinated Fe atoms, thus significantly promoting the immobilization of arsenate. The findings of this study enhance our ability to precisely understand the migration and fate of As while also aiding in the design of highly efficient iron mineral materials for mitigating As pollution.
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