Arsenic entrapment by nanocrystals of Al-magnetite: The role of Al in crystal growth and As retention

Freitas, Erico T. F., Stroppa, Daniel G., Montoro, Luciano A., de Mello, Jaime W. V., Gasparon, Massimo and Ciminelli, Virginia S. T. (2016) Arsenic entrapment by nanocrystals of Al-magnetite: The role of Al in crystal growth and As retention. Chemosphere, 158 91-99. doi:10.1016/j.chemosphere.2016.05.044

Author Freitas, Erico T. F.
Stroppa, Daniel G.
Montoro, Luciano A.
de Mello, Jaime W. V.
Gasparon, Massimo
Ciminelli, Virginia S. T.
Title Arsenic entrapment by nanocrystals of Al-magnetite: The role of Al in crystal growth and As retention
Journal name Chemosphere   Check publisher's open access policy
ISSN 1879-1298
Publication date 2016-09-01
Year available 2016
Sub-type Article (original research)
DOI 10.1016/j.chemosphere.2016.05.044
Open Access Status Not Open Access
Volume 158
Start page 91
End page 99
Total pages 9
Place of publication Kidlington, Oxford, United Kingdom
Publisher Pergamon Press
Collection year 2017
Language eng
Abstract The nature of As-Al-Fe co-precipitates aged for 120 days are investigated in detail by High Resolution Transmission Electron Microscopy (HRTEM), Scanning TEM (STEM), electron diffraction, Energy Dispersive X-Ray Spectroscopy (EDS), Electron Energy-Loss Spectroscopy (EELS), and Energy Filtered Transmission Electron Microscopy (EFTEM). The Al present in magnetite is shown to favour As incorporation (up to 1.10 wt%) relative to Al-free magnetite and Al-goethite, but As uptake by Al-magnetite decreases with increasing Al substitution (3.53-11.37 mol% Al). Arsenic-bearing magnetite and goethite mesocrystals (MCs) are formed by oriented aggregation (OA) of primary nanoparticles (NPs). Well-crystalline magnetite likely formed by Otswald ripening was predominant in the Al-free system. The As content in Al-goethite MCs (having approximately 13% substituted Al) was close to the EDS detection limit (0.1 wt% As), but was below detection in Al-goethites with 23.00-32.19 mol% Al. Our results show for the first time the capacity of Al-magnetite to incorporate more As than Al-free magnetite, and the role of Al in favouring OA-based crystal growth under the experimental conditions, and therefore As retention in the formed MCs. The proposed mechanism of As incorporation involves adsorption of As onto the newly formed NPs. Arsenic is then trapped in the MCs as they grow by self-assembly OA upon attachment of the NPs. We conclude that Al may diffuse to the crystal faces with high surface energy to reduce the total energy of the system during the attachment events, thus favouring the oriented aggregation.
Keyword Al magnetite
Arsenic immobilization
As partitioning
As speciation
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Publications
HERDC Pre-Audit
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 0 times in Thomson Reuters Web of Science Article
Scopus Citation Count Cited 0 times in Scopus Article
Google Scholar Search Google Scholar
Created: Sun, 31 Jul 2016, 00:16:52 EST by System User on behalf of Learning and Research Services (UQ Library)