To obtain information about dechlorination of organochlorine compounds in subcritical water catalyzed by metals assisted with ZrO(2), dechlorination of chlorobenzene has been investigated in the presence of Fe/ZrO(2), Ni/ZrO(2) and Cu/ZrO(2) catalysts. The dechlorination efficiency was increased with increasing residence time, temperature and pressure. The order of effectiveness of the catalysts was Cu/ZrO(2) < Ni/ZrO(2) < Fe/ZrO(2). The dechlorination of chlorobenze obeyed pseudo-first-order kinetics models. The rate constants in subcritical water were much greater than that in ambient-temperature water; the activation energies were obtained. ZrO(2) in the catalyst had the power to absorb chlorobenzene onto the catalyst surface and promoted the dechlorination ability of the metal. The primary mechanism for dechlorinaton of chlorobenzene involved the reduction of chlorobenzene by reaction with nascent hydrogen. The nascent hydrogen reacted with the chlorobenzene, which adsorbed on the catalyst in non-planar and co-planar form, and formed benzene and chloride ions.

Decoloration and mineralization of yeast wastewater were investigated by using Ce-Fe/Alz 0 3 as a heterogeneous photo-Fenton catalyst in fluidized bed reactor in order to solve the problem of yeast wastewater discharge. The experimental results were assessed in terms of total organic carbon(TOC) reduction. The operational and reaction conditions affecting the efficiencies of TOC removal such as initial pH value, Hz Oz concentration, catalyst loading and UV power were studied. The results show that TOC is reduced from 347.6 mg/L to 10.8 mg/L, color is changed from 500 units to 0 under the conditions as follows: initial pH value 6.0, HzOz concentration of 1. 000 g/L, catalyst loading of 5 g/L, reaction duration of 120 min and reaction temperature of 30 °C. The irradiated Ce-Fe/Alz Oa catalyst was complexed with 1,10-phenanthroline and then it was subjected to Fourier transform infrared spectroscopy and diffuse reflectance spectroscopy to confirm the formation of Fe( 11 ) in the solid state. Heterogeneous photo-Fenton reaction proves to be effective for the treatment of yeast wastewater.

Reductive dechlorination of chlorobenzene by Fe/ZrO 2 in supercritical water was investigated. The effects of the operation conditions were studied. The dechlorination of chlorobenzene obeyed pseudo-first-order kinetics models. In supercritical water, the rate constant increases more rapidly with temperature than those in subcritical water. The results showed that the rate-determining step of dechlorination in subcritical water is diffusion; whereas the rate-determining of dechlorination in supercritical water is chemical reaction. The reaction mechanism in subcritical water might involve with an ionic mechanism; whereas the reaction mechanism in supercritical water might involve with a homolytic reaction.

Bifunctional Fe / ZrO 2 was prepared by mechanical mixing method, and its bifunctional effect on reductive dechlorination of chlorobenzene in subcritical water was studied. Dechlorination efficiency increased with increasing iron content in catalyst and catalyst amount. Dechlorination efficiency slowed when the iron content in catalyst reached 30%; bifunctional catalyst of Fe / ZrO 2 was more efficient in dechlorination of chlorobenzene than Fe alone. Catalyst of Fe (30%)/ ZrO 2 was characterized by means of X-ray diffraction (XRD), H 2 temperature programmed desorption ( H 2-TPD), and N 2 adsorption. The possible mechanism of dechlorination in subcritical water by this bifunctional catalyst was proposed. H + produced in the water dissociation formed the highly reactive spillover hydrogen on the surface of catalyst, and then reacted with chlorobenzene adsorbed on the catalyst surface by ZrO 2 to form benzene and chloride ions.