Catalytic Ozonation of P-nitrophenol by Metal Oxide
|School||Wuhan University of Technology|
|Keywords||Metal Oxide p-nitrophenol NiO Catalytic Ozonation|
P-Nitrophenol (PNP) is an important fine chemical intermediate which is widely used in the production of pesticides, synthetic dyes and herbicides. It is a kind of toxic and bio-refractory pollutant which can do considerable damage to ecosystem and human health. In recently years, heterogeneous catalytic oxidation is widely used in the control of organic pollutants based on its numerous advantages, such as high efficiency, stabilization, no secondary pollution and so on.In the paper, transition metal oxide (NiO, Mn2O3and Fe2O3), complex metal oxides (Ni1.43Fe1.7O4, NiFe2O4, NiMnO3and NiMn2O4) and mixed metal oxides (FeMnOx) were prepared by precipitation method and characterized by XRD which indicated that the expectation catalysts were synthesized successfully. The as prepared samples were used for catalytic ozonation of PNP in aqueous solution and NiO shows the highest PNP degradation ratio (99%degradation in70min) than other samples. This result showed that there was no improvement on the catalytic activity of bicomponent catalysts, which indicted that no synergetic effect occurred between the two transition metals in the bicomponent catalysts.Effects of some preparation conditions (calcination temperature, calcination time and molar ratio of dispersant/Ni2+) on the catalytic activity of NiO were studied. The as prepared samples and precursor (NiCO3) were characterized by SEM, FT-IR and TG-DSC. SEM analysis showed that NiO showed a very coarser surface. FT-IR analysis indicated that plenty of hydroxyl exhibited on NiO surface. TG-DSC analysis indicated that the decomposition of NiCO3precursor began at258℃and completed at400℃during the calcinations process.In order to improve the practical application of the catalyst powders, NiO/ceramic filtration media catalyst was prepared by impregnation method and used for catalytic ozonation of PNP (97%degradation in70min). In the fourth cycling test,87%of PNP was degraded in70min which indicated that NiO/ceramic filtration media catalyst was high stability in the catalytic ozonation of the organic pollutant molecules.In the paper, reaction temperature, ozone dosage, catalyst dosage, initial concentration and initial pH in degradation of PNP were studied. An obvious decrease of PNP removal ratio was observed in the presence of radical scavenger t-BuOH alcohol, which indicated that?OH was the active group in the reaction. A possible mechanism of the catalytic ozo nation over the NiO was proposed.