Speciation of adsorbed arsenic(V) on red mud using a sequential extraction procedure

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doi: 10.1180/0026461056950273
Authors:Rubinos, D. A.; Arias, M.; Díaz-Fierros, F.; Barral, M. T.
Author Affiliations:Primary:
Universidade de Santiago de Compostela, Departamento de Edafoloxía e Química Agrícola, Santiago de Compostela, Spain
Other:
University of Reading, United Kingdom
Universidade de Vigo, Spain
Volume Title:Speciation and toxicity
Volume Authors:Hudson-Edwards, K., prefacer; Hodson, M. E.
Source:Mineralogical Magazine, 69(5), p.591-600; Speciation and toxicity, London, United Kingdom, Sept. 13-14, 2004, prefaced by K. Hudson-Edwards and M. E. Hodson. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X
Publication Date:2005
Note:In English. 41 refs.; illus., incl. 3 tables
Summary:The distribution of sorbed arsenic(V) among different geochemical fractions for arsenic(V)-loaded red mud, an oxide-rich residue from bauxite refining that has been proposed as an adsorbent for arsenic, was studied as a function of sorbed arsenic(V) concentration using a sequential extraction procedure. The release of previously sorbed arsenic(V) was also studied as a function of pH and arsenic(V) concentration. Most sorbed arsenic(V) (0.39-7.86 mmol kg-1) was associated with amorphous and crystalline Al and Fe oxides (24.1-43.8% and 24.7-59.0% of total sorbed arsenic, respectively). Exchangeable arsenic was the smallest fraction (0.4-5.2% of total sorbed arsenic). The distribution of sorbed arsenic(V) was related to the arsenic surface coverage. For arsenic surface coverages >approximately 30% the percentage of arsenic(V) associated with the amorphous Al oxide fraction increased and that associated with the crystalline oxide fraction decreased. The arsenic(V) exchangeable fraction increased from 1.4 to 756 µmol kg-1 as surface coverage increased from 388 to 7855 µmol kg-1. The release of sorbed arsenic(V) from red mud was greater at alkaline pH values (maximum release of approximately 33% of previously sorbed arsenic at pH = 12), but for high arsenic(V) initial concentration (0.2 mM arsenic) considerable amounts of arsenic (6.5% of previously sorbed arsenic) were released at pH 4, in accordance with the dissolution of amorphous Al oxides in the red mud. The results obtained suggest a greater mobility of sorbed arsenic(V) as its surface concentration approaches saturation.
Sections:Apparatus and techniques; Environmental studies; Geochemistry
Subsections:Chemical, XRF, and other instrumental methods
Subjects:Adsorption; Arsenic; Bauxite; Chemical fractionation; Clastic sediments; Experimental studies; Laboratory studies; Metals; Mud; Pollution; Sedimentary rocks; Sediments; Sequential extraction; Sorption; Toxic materials
Abstract Numbers:06M/301
Record ID:2006008023
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland, Reference includes data from GeoScienceWorld, Alexandria, VA, United States
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