Natural attenuation of arsenic in the environment by immobilization in nanostructured hematite

Freitas, Erico T. F., Montoro, Luciano A., Gasparon, Massimo and Ciminelli, Virginia S. T. (2015) Natural attenuation of arsenic in the environment by immobilization in nanostructured hematite. Chemosphere, 138 340-347. doi:10.1016/j.chemosphere.2015.05.101


Author Freitas, Erico T. F.
Montoro, Luciano A.
Gasparon, Massimo
Ciminelli, Virginia S. T.
Title Natural attenuation of arsenic in the environment by immobilization in nanostructured hematite
Journal name Chemosphere   Check publisher's open access policy
ISSN 1879-1298
0045-6535
Publication date 2015-11-01
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.chemosphere.2015.05.101
Open Access Status Not Open Access
Volume 138
Start page 340
End page 347
Total pages 8
Place of publication Kidlington, Oxford United Kingdom
Publisher Pergamon Press
Collection year 2016
Language eng
Abstract Iron (hydr)oxides are known to play a major role in arsenic fixation in the environment. The mechanisms for long-term fixation into their crystal structure, however, remain poorly understood, especially arsenic partitioning behavior during transformation from amorphous to crystalline phases under natural conditions. In this study, these mechanisms are investigated in Fe–Al-oxisols exposed over a period of 10 years to a sulfide concentrate in tailings impoundments. The spatial resolution necessary to investigate the markedly heterogeneous nanoscale phases found in the oxisols was achieved by combining three different, high resolution electron microscopy techniques – Nano-Beam Electron Diffraction (NBD), Electron Energy-Loss Spectroscopy (EELS), and High Resolution Transmission Electron Microscopy (HRTEM). Arsenic (1.6 ± 0.5 wt.%) was unambiguously and precisely identified in mesocrystals of Al-hematite with an As/Fe atomic ratio of 0.026 ± 0.006. The increase in the c-axis (c = 1.379 ± 0.009 nm) compared to standard hematite (c = 1.372 nm) is consistent with the presence of arsenic in the Al-hematite structure. The As-bearing Al-hematite is interpreted as a secondary phase formed from oxyhydroxides, such as ferrihydrite, during the long-term exposure to the sulfide tailings. The proposed mechanism of arsenic fixation in the Al-hematite structure involves adsorption onto Al-ferrihydrite nanoparticles, followed by Al-ferrihydrite aggregation by self-assembly oriented attachment and coalescence that ultimately produces Al-hematite mesocrystals. Our results illustrate for the first time the process of formation of stable arsenic bearing Al-hematite for the long-term immobilization of arsenic in environmental samples.
Keyword Arsenic fixation
As partitioning
As speciation
Long-term stability
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Papers
Official 2016 Collection
 
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