This bench scale study compares the performance of copper-amended nanoscale zero valent iron (Cu-nZVI) with unamended nZVI particles. where both particle types were stabilized with carboxymethylcellulose (CMC). This study evaluated the degradation kinetics, byproduct distribution and mass-balance of select chlorinated hydrocarbons (CHCs), including chloroform, 1,1,1- trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1,2,3-trichloropropane, and various chlorinated ethenes (perchloroethene, trichloroethene, cis-1,2-dichloroethene) with nZVI and Cu-nZVI in batch reactors. A pseudo first-order degradation rate model was used to evaluate the kinetics of CHC degradation. The effect of Cu loading and Cu-nZVI concentration on chloroform degradation showed faster degradation kinetics at increasing Cu loading and Cu-nZVI concentrations. Greater Cu loading in Cu-nZVI systematically increased methane byproduct production. The pseudo first-order degradation rate constants (kobs) were faster and the byproduct distributions were more favorable for Cu-nZVI than nZVI for all CHCs studied. Cu-nZVI outperformed most other bimetallic nZVI reductants reported in the literature for chloroform and chlorinated ethanes treatment. The degradation byproducts of chloroform and 1,1,1-trichloroethane with Cu-nZVI suggest the formation of reactive carbene intermediates that degraded further into methane, ethene and ethane through α-elimination and hydrogenolysis pathways. In comparison to nZVI, Cu-nZVI also showed a more effect treatment potential for 1,2,3-trichloropropane. However, Cu-nZVI did not show much improvement over nZVI in degrading chlorinated ethenes. Longevity investigations have shown that the reactivity of unstabilized and CMC-stabilized Cu-nZVI towards 1,1,1-trichloroethane decreased with nanoparticles aging. Unstabilized Cu-nZVI particles showed a linear decline in reactivity (kobs) with time, whereas CMC-stabilized Cu-nZVI particles showed a more rapid, power-function, decline in reactivity with time. The kobs for 1,1,1-trichloroethane with unstabilized Cu-nZVI particles were 12-fold greater in comparison to stabilized Cu-nZVI particles 24 hr after synthesis. Even with decline in reactivity, 1,1,1-trichloroethane was rapidly degraded (over a few hours) 7 days after nanoparticle synthesis by both unstabilized and CMC-stabilized Cu-nZVI.

More effective treatment of chlorinated solvents by Cu-amended nanoscale zero-valent iron stabilized with carboxymethylcellulose

251st National Meeting (2016)

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