Abinash Agrawal (Advisor), David Dominic (Committee Member), Sushil Kanel (Committee Member)
Master of Science (MS)
Nanoscale zero-valent iron (nZVI) injections have proven to be a promising approach for the remediation of aquifers contaminated by chlorinated organic pollutants. This study compares the efficacy of nZVI in sulfidated and unamended forms in degrading selected chlorinated hyrocarbons (CHCs). Results show that nZVI amended with iron monosulfide (FeS) increases the rate of dechlorination of CT, CF and 1,1,1-TCA compared to that by unamended nZVI. The focus of this research was to characterize degradation kinetics and degradation byproduct distributions of CT, CF and 1,1,1-TCA by nZVI coated by iron monosulfide, which is represented as nZVI/FeS. To prevent nZVI particles from agglomerating, carboxymethylcellulose (CMC) was used as a stabilizer in all experiments. Results indicated that the nZVI/FeS system was faster and produced less toxic byproducts than nZVI for all CHCs studied. a-elimination in nZVI/FeS system was an important degradation pathway for CF and 1,l,1-TCA: it produces reactive carbene intermediates capable of degrading into benign products such as methane, ethane, and ethene. The effect of sulfide loading on degradation was evaluated with all CHCs studied. Regardless of CHC type, the rate constant (kobs) increased with increasing sulfide loading, reaching the highest amount at 1 wt% sulfide, and then decreased with higher sulfide loading. An additional study focused on the effects of varying of the concentration of nZVI and CMC, and particle longevity on the degradation of 1,1,1-TCA in the nZVI/FeS system with 1 wt.% sulfide. Particle longevity experiments showed that reactivity with 1,1,1-TCA decreases as particles age. nZVI/FeS particles showed a rapid power function decline in reactivity with time. Increasing the amount of iron-reducing chemical during nZVI/FeS synthesis improved reactivity by 43%. The addition of a polyelectrolyte stabilizer at an optimized concentration of 4.0 g/L further increased nZVI/FeS reactivity by 350%. nZVI/FeS shows great potential for treating certain CHCs.
Department or Program
Department of Earth and Environmental Sciences
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