. This work has focused on toxic organic compounds such as trichloroethylene (TCE) degradation in aqueous phase, using titanium dioxide nanoparticles as photo-catalyst in a UV radiation system. Photo-catalytic decomposition of TCE was studied under UV illumination in batch reactor. Removal efficiency of TCE was investigated in the terms of different photo-catalysts and initial TCE concentrations, different temperature, presence of surfactant and ultrasonic. Several pH were examined in order to evaluate the feasibility of method. The pollutant and decomposition products were monitored. TCE degradation was achieved more than 80% with an increase the TiO 2 concentration up to 0.9g/l. However, larger TiO 2 concentration causes a decrease in TCE degradation efficiency. The photo-catalytic degradation of TCE appeared to be more effective in acidic media and near the neutral pH conditions than alkaline pH. In the acidic pH conditions, decrease in pH did not have a significant effect on the TCE degradation. Greater degradation of TCE was achieved with an increase of initial concentration of TCE (up to 100 ppm) in solution, but larger TCE concentrations results in a decrease in removal efficiency. In presence of non-ionic surfactant, removal efficiency was improved to more than 99% witch increases by surfactant concentration. Ultrasonic affect the degradation rate and promise complete decomposition of TCE in short time(less than 60 min). The effects of different pH, photocatalyst and initial TCE concentrations on removal efficiency were also investigated in direct analysis photocatalytic system. Approximately the same results with photocatalytic batch reactor system were observed. Afterwards, reduction of TCE by zero-valent iron nanoparticles was studied in batch reactor system. Reduction of TCE appeared to be more effective in acidic pH than neutral and alkaline pH. Catalyst concentration affects the removal efficiency and increasing the catalyst concentration improves the removal efficiency. Increase in initial concentration of TCE cuases a decreas in degradation efficiency.
