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  • Field-scale transport and transformation of carboxymethylcellulose-stabilized nano zero-valent iron.

Field-scale transport and transformation of carboxymethylcellulose-stabilized nano zero-valent iron.

Environmental science & technology (2013-01-15)
Richard L Johnson, James T Nurmi, Graham S O'Brien Johnson, Dimin Fan, Reid L O'Brien Johnson, Zhenqing Shi, Alexandra J Salter-Blanc, Paul G Tratnyek, Gregory V Lowry
ABSTRACT

The fate of nano zerovalent iron (nZVI) during subsurface injection was examined using carboxymethylcellulose (CMC) stabilized nZVI in a very large three-dimensional physical model aquifer with detailed monitoring using multiple, complementary detection methods. A fluorescein tracer test in the aquifer plus laboratory column data suggested that the very-aggressive flow conditions necessary to achieve 2.5 m of nZVI transport could be obtained using a hydraulically constrained flow path between injection and extraction wells. However, total unoxidized nZVI was transported only about 1 m and <2% of the injected nZVI concentration reached that distance. The experimental data also indicated that groundwater flow changed during injection, likely due to hydrogen bubble formation, which diverted the nZVI away from the targeted flow path. The leading edge of the iron plume became fully oxidized during transport. However, within the plume, oxidation of nZVI decreased in a fashion consistent with progressive depletion of aquifer "reductant demand". To directly quantify the extent of nZVI transport, a spectrophotometric method was developed, and the results indicated that deployment of unoxidized nZVI for groundwater remediation will likely be difficult.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Carboxymethylcellulose sodium salt, High viscosity
Sigma-Aldrich
Carboxymethylcellulose sodium, meets USP testing specifications, Medium viscosity
Sigma-Aldrich
Carboxymethylcellulose sodium salt, Medium viscosity
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Carboxymethylcellulose sodium salt, low viscosity
Sigma-Aldrich
Sodium carboxymethyl cellulose, average Mw ~250,000, degree of substitution 0.7
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Sodium carboxymethyl cellulose, average Mw ~250,000, degree of substitution 0.9
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Sodium carboxymethyl cellulose, average Mw ~250,000, degree of substitution 1.2
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Sodium carboxymethyl cellulose, average Mw ~90,000
Sigma-Aldrich
Sodium carboxymethyl cellulose, average Mw ~700,000