[Preparation of coated iron nanoparticles for reduction of trichloroethylene]

Nanoscale alpha-Fe particles with size of about 80 nm were prepared with a microemulsion-coated method. The results demonstrated that this kind of iron particles could exist stably in the air for 7 d compared with nanoscale iron particles prepared by liquid-phase and microemulsion methods. The removal rate of trichloroethylene with an initial concentration of 10 mg x L(-1) can reach 90% in 700 h. The reduction kinetics was studied under room temperature, neutral, and anaerobic conditions. Experiments show that the reduction process of TCE by nanoscale iron particles conforms to pseudo first order reaction law. The apparent rate constant (k(obs)) is proportional to concentration of nanoscale iron particles. The k(obs), values 6.49 x 10(-40, 6.64 x 10(-4), 7.10 x 10(-4), 7.43 x 10(-4) min(-1), are corresponding to concentrations of 87.5, 175, 262.5, 350 mg x L(-1) respectively. In the reaction, nanoscale iron particles provides electrons and forms an inner film of Fe3O4, on the surface of which an outer film of Fe2O3 is formed together with water. TCE is degraded by electrons. The principal degradation products were ethene and ethane, and smaller amounts of other chlorinated degradation products were also founded.