Zero-valent copper nanoparticles for effective dechlorination of dichloromethane using sodium borohydride as a reductant

Abstract

Dichloromethane (DCM) is a recalcitrant groundwater contaminant that shows nearly no reactivity with zero-valent iron (ZVI) nanoparticles. In this study, an effective dechlorination of DCM has been demonstrated using zero-valent copper (Cu0) nanoparticles as a catalyst under sodium borohydride reduction conditions. The average diameter of Cu0 nanoparticles was about 50nm and the specific surface area was about 19m2g−1. Batch experiments revealed that 90% of DCM (26.4mgL−1) was rapidly degraded within 1h in the presence of Cu0 nanoparticles (2.5gL−1) and sodium borohydride (1gL−1). The observed pseudo-first-order rate constant (kobs) was 2.19h−1, corresponding to a surface area normalized rate constant of 0.052Lm−2h−1, which is 2–3 orders of magnitude higher than for other zero-valent metals. The DCM degradation rate is a function of the Cu0 nanoparticle dose. Increasing the dose increased the observed reaction rate. Product analysis indicated that the degradation of DCM involved hydrodechlorination. Soluble copper ions generated by the dissolution of Cu0 nanoparticles are lower than the World Health Organization drinking water standard, which suggests that the use of Cu0 nanoparticles under reduction conditions may be potentially useful for the treatment of recalcitrant contaminants that are unable to be degraded by ZVI technology.