Study of iron oxide nanoparticles in soil for remediation of arsenic |
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Authors: | Heather J Shipley Karen E Engates Allison M Guettner |
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Institution: | (1) Department of Civil and Environmental Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA |
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Abstract: | There is a growing interest in the use of nanoparticles for environmental applications due to their unique physical and chemical
properties. One possible application is the removal of contaminants from water. In this study, the use of iron oxide nanoparticles
(19.3 nm magnetite and 37.0 nm hematite) were examined to remove arsenate and arsenite through column studies. The columns
contained 1.5 or 15 wt% iron oxide nanoparticles and soil. Arsenic experiments were conducted with 1.5 wt% iron oxides at
1.5 and 6 mL/h with initial arsenate and arsenite concentrations of 100 μg/L. Arsenic release occurred after 400 PV, and 100%
release was reached. A long-term study was conducted with 15 wt% magnetite nanoparticles in soil at 0.3 mL/h with an initial
arsenate concentration of 100 μg/L. A negligible arsenate concentration occurred for 3559.6 pore volumes (PVs) (132.1 d).
Eventually, the arsenate concentration reached about 20% after 9884.1 PV (207.9 d). A retardation factor of about 6742 was
calculated indicating strong adsorption of arsenic to the magnetite nanoparticles in the column. Also, increased adsorption
was observed after flow interruption. Other experiments showed that arsenic and 12 other metals (V, Cr, Co, Mn, Se, Mo, Cd,
Pb, Sb, Tl, Th, U) could be simultaneously removed by the iron oxide nanoparticles in soil. Effluent concentrations were less
than 10% for six out of the 12 metals. Desorption experiment showed partial irreversible sorption of arsenic to the iron oxide
nanoparticle surface. Strong adsorption, large retardation factor, and resistant desorption suggest that magnetite and hematite
nanoparticles have the potential to be used to remove arsenic in sandy soil possibly through in situ techniques. |
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