Arsenic Scavenging by Aluminum-Substituted Ferrihydrites in a Circumneutral pH River Impacted by Acid Mine Drainage.

详细信息    查看全文

• 作者：Areej Adra ; Guillaume Morin ; Georges Ona-Nguema ; Nicolas Menguy ; Fabien Maillot ; Corinne Casiot ; Odile Bruneel ; Sophie Lebrun ; Farid Juillot ; Jessica Brest
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：November 19, 2013
• 年：2013
• 卷：47
• 期：22
• 页码：12784-12792
• 全文大小：478K
• 年卷期：v.47,no.22(November 19, 2013)
• ISSN：1520-5851

文摘

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鈥?) 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鈥?0 卤 10 mol %Al range. Synthetic aluminous Fh prepared in the present study are found to be less Al-substituted (14鈥?0 卤 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.