Journal
JOURNAL OF HAZARDOUS MATERIALS
Volume 265, Issue -, Pages 208-216Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jhazmat.2013.11.068
Keywords
Mine drainage; As redox stability; As immobilization; Surface precipitation; Iron oxyhydroxy sulphate
Categories
Funding
- German Academic Exchange Service (DAAD)
- Geotechnologien programme (BMBF) [03G0714A]
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As(III)-enriched mine discharge often drains through Fe(III)-mineral abundant land covers which makes the understanding of its fate and redox behaviour extremely important. We therefore conducted batch kinetic and equilibrium studies at pH 3.0 +/- 0.05 in anoxic media coupled with spectroscopic and microscopic examinations at variable conditions to understand possible As(III) binding mechanisms and the redox stability of As(III) on schwertmannite, a prominent ferric mineral in acid mine drainage environments. Schwertmannite acted as an efficient scavenger for As(III) compared to goethite at identical sorbent:solute ratios. As K-edge X-ray absorption near-edge structure (XANES) demonstrated partial oxidation of sorbed As(III) to As(V) on both the minerals depending on the Fe(III)/As(III) ratios (goethite acted as a better oxidant than schwertmannite). Sorbed As(III) and As(V) coordinated in a bidentate binuclear binding mechanism with As(III)/As(V)-O and As(III)/As(V)-Fe interatomic distances as 1.78/1.69 and 3.37/3.31 angstrom, respectively. Scanning (SEM-EDX) and transmission (TEM) electron microscopic, and IR spectroscopic measurements revealed the formation of As-containing surface coatings by sorbed As on schwertmannite. (C) 2013 Elsevier B.V. All rights reserved.
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