T162 Sources, Transport, Fate, and Toxicology of Trace Elements and Organics in the Environment (Posters)

Tuesday, 6 November 2012
9:00 AM - 6:00 PM
Hall B

TRANSPORT BEHAVIOR AND REACTIVITY OF NANOSCALE ZERO VALENT IRON STABILIZED WITH CARBOXYMETHYLCELLULOSE SIMULATED UNDER AQUIFER CONDITIONS IN 1-D REACTOR

Paper number: T162-12
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

Reports of limited mobility of stabilized forms of nanoscale zero valent iron (nZVI) in porous media at bench-scale and simulated field-scale studies have become a key issue in its application for aquifer treatment and groundwater remediation. Changes in hydraulic conductivity of the aquifer medium upon injection of nZVI and its short life-span have also been reported in both large sand tank experiments and field studies. However, zero-valent iron nanoparticles stabilized with carboxymethylcellulose (CMC-nZVI) synthesized by modified borohydride reduction method have shown improved mobility in bench-scale flow-through reactors. Further, the injection of CMC-nZVI at field scale for in situ remediation of drinking water aquifers contaminated with chlorinated organic compounds has shown some success. CMC-nZVI has also shown a modest improvement in its ability to degrade toxic chlorinated hydrocarbons efficiently over other forms of nZVI in bench-scale studies.

This study investigates the transport behavior of CMC-nZVI in 1-D reactor under simulated aquifer conditions through the application of breakthrough curve analysis. The CMC-nZVI will be injected into a 30 cm long borosilicate glass column at a rate of ~ 100 mL min-1 and flushed with a 10 mM NaCl solution at a velocity of 1 m/d. Breakthrough curves based on conductivity measurements before and after CMC-nZVI injection will be helpful in characterizing changes in the hydraulic properties of the porous medium due to H2 evolution or entrapment of iron though the application of CXTFIT, a solute transport modeling software. The analysis of effluent samples from the column for ferrous iron, total iron, and nZVI using a spectrophotometric technique (phenanthroline method for iron determination) will determine the mass retained. Analysis of hydrogen gas (H2) using gas chromatography will be used to evaluate the longevity or the lifespan of CMC-nZVI upon injection through evolution of H2.