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The adsorption of arsenic oxyacids to iron oxyhydroxide columns

including studies of weakly hydrated ions and molecules in aqueous solution

Mähler, Johan (2013). The adsorption of arsenic oxyacids to iron oxyhydroxide columns. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2013:54
ISBN 978-91-576-7846-1
eISBN 978-91-576-7847-8
[Doctoral thesis]

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Abstract

The fundamental side of this project includes determination of ionic radii and plausible hydration numbers for the weakly hydrated alkali metal ions in solution, as well as an investigation of the intramolecular bond lengths of arsenic oxyacid species and orthotelluric acid. Experimental methods such as EXAFS, XANES and LAXS have been used for these purposes, as well as thorough screening for relevant structures in crystal structure databases. The improved ionic radius for the sodium ion in six-coordination is of particular interest as current literature data to a large extent is derived from structures not representative for aqueous solutions. The improved larger value is 1.07 Å in six-coordinated crystal structures and increases to 1.09 Å in aqueous solution due to hydration effects. Furthermore it has been discussed how alkali metal ions affect the three-dimensional network of hydrogen bound water molecules in aqueous solution, based on investigations with double difference infrared spectroscopy. Only the lithium ion was found to be a true structure making ion, even though the status of the border-line sodium ion can be discussed.

The applied studies have focused on the rapid removal of arsenic from aqueous solution using columns filled with iron oxyhydroxide based adsorbents, complemented with additional batch experiments. Atomic absorption spectrophotometry has been used to determine concentrations of arsenic in the effluent of columns and iron content of the adsorbent material. Experiments have shown that adsorption does occur rapidly and since there is no need for reaching equilibrium in practical water cleaning applications, short empty bed contact times are sufficient for removing practically all arsenic. However, somewhat longer empty bed reaction times are desirable for a more efficient material utilization, as both diffusion into porosities and desorption of competing species are kinetic hindrances. Adsorption capacity in a column is quite dependent on the presence of competitors such as phosphate, hydrogen carbonate and fluoride, as well as on pH, possibly due to desorption kinetics. Scanning electron microscopy as well as XANES and EXAFS have been used to study the structural and chemical status of the adsorbents. The arsenic part of the project can be seen as an initiation of a future project, aiming at developing a simple but efficient adsorption filter for arsenic removal from drinking water in Burkina Faso.

Authors/Creators:Mähler, Johan
Title:The adsorption of arsenic oxyacids to iron oxyhydroxide columns
Subtitle:including studies of weakly hydrated ions and molecules in aqueous solution
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :2013
Volume:2013:54
Number of Pages:116
Papers/manuscripts:
NumberReferences
I.Mähler, J.; Persson, I. (2012). A Study of the Hydration of the Alkali Metal Ions in Aqueous Solution. Inorganic Chemistry 51, 425-438.
II.Mähler, J.; Persson, I.; Herbert R.B. (2013). Hydration of Arsenic Oxyacid Species. Dalton Transactions 42, 1364-1377.
III.Mähler J.; Persson I. Rapid Adsorption of Arsenic from Aqueous Solution by Ferrihydrite Coated Sand and Granular Ferric Hydroxide. Applied Geochemistry, in press. DOI 10.1016/j.apgeochem.2013.07.025
IV.Mähler J.; Persson I. Competition for Adsorption Sites on Iron Oxyhydroxide based Column Adsorbents for the Removal of Arsenic Oxyacid Species. Manuscript
Place of Publication:Uppsala
Publisher:Institutionen för kemi, Sveriges lantbruksuniversitet
Associated Programs and Other Stakeholders:SLU - Environmental assessment > Programme Non-Toxic Environment
SLU - Agricultural Sciences for Global Development > Land use and climate change
SLU - Agricultural Sciences for Global Development > Scale issues in relation to food security and poverty alleviation
ISBN for printed version:978-91-576-7846-1
ISBN for electronic version:978-91-576-7847-8
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:P Natural resources > P10 Water resources and management
T Pollution > T01 Pollution
X Agricola extesions > X50 Chemistry
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Inorganic Chemistry
(A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Other Chemistry Topics
(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Environmental Sciences (social aspects to be 507)
(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Geochemistry
(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 204 Chemical Engineering > Other Chemical Engineering
(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 208 Environmental Biotechnology > Water Treatment
Agrovoc terms:arsenic, adsorption, water, water purification, chemistry, geochemistry, experimentation, methods, microscopy, burkina faso
Keywords:column, adsorption, arsenic, arsenous, oxyacid, arsenic removal, arsenic enriched water, Burkina Faso, ionic radii, alkali ions, iron oxyhydroxide, GFH
URN:NBN:urn:nbn:se:slu:epsilon-e-1600
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-1600
ID Code:10752
Department:(NL, NJ) > Dept. of Chemistry (until 131231)
External funders:Swedish International Development Cooperation Agency and Swedish Research Council
Deposited By: Johan Mähler
Deposited On:22 Aug 2013 14:13
Metadata Last Modified:14 Dec 2014 03:21

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