%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Adra, A.
%A Morin, G.
%A Ona-Nguema, G.
%A Menguy, N.
%A Maillot, F.
%A Casiot, C.
%A Bruneel, Odile
%A Lebrun, S.
%A Juillot, Farid
%A Brest, J.
%T Arsenic cavenging by aluminum-substituted ferrihydrites in a circumneutral ph river impacted by acid mine drainage
%D 2013
%L fdi:010061407
%G ENG
%J Environmental Science and Technology
%@ 0013-936X
%K FRANCE
%M ISI:000327360600023
%N 22
%P 12784-12792
%R 10.1021/es4020234
%U https://www.documentation.ird.fr/hor/fdi:010061407
%> https://www.documentation.ird.fr/intranet/publi/2014/01/010061407.pdf
%V 47
%W Horizon (IRD)
%X Ferrihydrite (Fh) is a nanocrystalline ferric oxyhydroxide involved in the retention of pollutants in natural systems and in water-treatment processes. The status and properties of major chemical impurities in natural Fh is however still scarcely documented. Here we investigated the structure of aluminum-rich Fh, and their role in arsenic scavenging in river-bed sediments from a circumneutral river (pH 6-7) impacted by an arsenic-rich acid mine drainage (AMD). Extended X-ray absorption fine structure (EXAFS) spectroscopy at the Fe K-edge shows that Fh is the predominant mineral phase forming after neutralization of the AMD, in association with minor amount of schwertmannite transported from the AMD. TEM-EDXS elemental mapping and SEM-EDXS analyses combined with EXAFS analysis indicates that Al3+ substitutes for Fe3+ ions into the Fh structure in the natural sediment samples, with local aluminum concentration within the 25-30 +/- 10 mol %Al range. Synthetic aluminous Fh prepared in the present study are found to be less Al-substituted (14-20 +/- 5 mol %Al). Finally, EXAFS analysis at the arsenic K-edge indicates that As(V) form similar inner-sphere surface complexes on the natural and synthetic Al-substituted Fh studied. Our results provide direct evidence for the scavenging of arsenic by natural Al-Fh, which emphasize the possible implication of such material for scavenging pollutants in natural or engineered systems.
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