HR: 0800h
AN: H21C-1035    [Abstracts]
TI: Arsenic Adsorption Onto Iron Oxides Minerals
AU: * Aredes, S
EM: soniaare@interchange.ubc.ca
AF: Mining Engineering Dept. University of B.C., 5th Floor, 6350 Stores Road , Vancouver, B.C V6T 1Z4 Canada
AU: Klein, B
EM: bklein@interchange.ubc.ca
AF: Mining Engineering Dept. University of B.C., 5th Floor, 6350 Stores Road , Vancouver, B.C V6T 1Z4 Canada
AU: Pawlik, M
EM: pp@mining.ubc.ca
AF: Mining Engineering Dept. University of B.C., 5th Floor, 6350 Stores Road , Vancouver, B.C V6T 1Z4 Canada
AB: The predominant form of arsenic in water is as an inorganic ion. Under different redox conditions arsenic in water is stable in the +5 and +3 oxidation states. Arsenic oxidation state governs its toxicity, chemical form and solubility in natural and disturbed environments. As (III) is found in anoxic environments such as ground water , it is toxic and the common species is the neutral form, H$_{3}$AsO$_{3}$. As (V) is found in aerobic conditions such as surface water, it is less toxic and the common species in water are: H$_{2}$AsO$_{4}$ $^{-}$ and HAsO$_{4}$ $^{- 2}$. The water pH determines the predominant arsenate or arsenite species, however, both forms of arsenic can be detected in natural water systems. Iron oxides minerals often form in natural waters and sediments at oxic-anoxic boundaries. Over time they undergo transformation to crystalline forms, such as goethite or hematite. Both As(V) and As(III) sorbs strongly to iron oxides, however the sorption behavior of arsenic is dependent on its oxidation state and the mineralogy of the iron oxides. Competition between arsenic and others ions, such fluoride, sulphate and phosphate also play a role. On the other hand, calcium may increase arsenic adsorption onto iron oxides. Electrokinetic studies and adsorption experiments were carried out in order to determine which conditions favour arsenic adsorption. Hematite, goethite and magnetite as iron based sorbents were used. Test were also conducted with a laterite soil rich in iron minerals. The focus of this study is to evaluate physical and chemical conditions which favour arsenic adsorption onto iron oxides minerals, the results contribute to an understanding of arsenic behaviour in natural and disturbed environments. Furthermore, results could contribute in developing an appropriate remediation technology for arsenic removal in water using iron oxides minerals.
DE: 1899 General or miscellaneous
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting