Synergistic effect of zero-valent copper nanoparticles on dichloromethane degradation by vitamin B12 under reducing condition

While zero-valent iron (ZVI, an electron donor) can degrade many kinds of chlorinated organic contaminants and vitamin B-12 (an electron mediator) is capable of enhancing the degradation, both are ineffective in degrading dichloromethane (DCM). In this study, we found that a combination of zero-valent copper (Cu-0) nanoparticles and vitamin B-12 can catalyze the degradation of DCM effectively under reducing conditions when titanium citrate was used as the reducing agent. Batch experiments were performed to test the effectiveness of the Cu-0-B-12 system in DCM degradation. Approximately 99% of 26 mg/L DCM was degraded rapidly within 2 h by the Cu-0-B-12 system. The observed pseudo-first-order rate constant was 1.35 h(-1), which was five times greater than that of using vitamin B-12 alone. A synergistic effect of Cu-0 nanoparticles on the reductive degradation of DCM by vitamin B-12 was found. Soluble copper ions generated by the dissolution of Cu-0 nanoparticles were lower than the WHO-specified limit for drinking water. It is expected that the combination of Cu-0 nanoparticles and electron mediator system may have the potential for treating recalcitrant groundwater contaminants that cannot be degraded by ZVI technology. (C) 2013 Elsevier B.V. All rights reserved.