Kinetics and Mechanism of Carbon Tetrachloride Rapid Reduction by Nanoscale Ni-Fe Using Scanning Electron Microscope

The nanoscale iron particles have high specific surface area and high reactivity, can be used to rapidly reduce chlorinated alkene to the non-toxic chloride ions, chlorine-free end products ethene and ethane. But nanoscale iron particle degrades chlorinated alkanes with much toxic intermediate or end products. A small amount of a second metal deposited on the iron surface has proved to enhance the reactivity of metal particles. In this paper, laboratory-synthesized nanoscale Ni-Fe (2% by weight) particles have diameters on the order of 20-60 nm using Scanning Electron Microscope. In batch experiments, the kinetics, products, stability of performance, and mechanism of carbon tetrachloride (CT) by Ni-Fe nanoparticles were investigated. CH₄ (~42%) and CH₂Cl₂ (~17%) in nanoscale Ni-Fe system were the major end products. Compared to nanoscale iron and the cast iron scarp, a major benefit of the nanoscale Ni-Fe particles for treatment of CT is the low yield of chlorinated by-product. Due to the presence of catalyst (Ni) on the surface, dechlorination rate was significantly increased and production of chlorinated byproducts was notably reduced. Catalytic metal Ni from the nanoscale Ni-Fe particles would not dissolve into water so that it would not form a secondary contamination of water body. The laboratory-synthesized nanoscale particles are quite stable under ambient conditions. For nano-scale Ni-Fe particles system, the end-product CH₄ were reduced by 13% compared with nanoscale Pd-Fe particles. Although tnano-scale Pd-Fe particles are effective in dechlorination of chlorinated organic compounds, nano-scale Ni-Fe particles are more economically viable which made it possible for the large scale remediation of water and soil contaminated by chlorinated organic compounds.