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Prepatation of Pr/Al2O3 and Its Activity in Catalytic Ozonation

Author: ZhangAngLiang
Tutor: SongShuang；HeZhiQiao
School: Zhejiang University of Technology
Course: Environmental Science
Keywords: Pr/Al2O3 Phenol Succinic acid Catalytic ozonation
CLC: X703
Type: Master's thesis
Year: 2011
Downloads: 62
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Abstract


In an attempt to utilize ozone effectively, a series of praseodymium-modifiedγ-Al2O3 （Pr/Al2O3） was prepared via incipient wetness impregnation using Pr（NO3）3·6H2O as the precursor. The structure and properties of the catalysts were studied by X-ray diffraction （XRD）, and the Brunauer–Emmett–Teller （BET） method. Catalytic activity was evaluated by monitoring the degradation of succinic acid （SA） in the presence of ozone. The praseodymium modification can effectively enhance the ozonation activity of ?-Al2O3 upon SA removal. Increasing the calcination temperature of Pr/Al2O3 is disadvantageous for the catalytic process, whereas increasing the load of praseodymium is helpful. After three successive recycles, the Pr/Al2O3 catalyst remained stable in the catalytic ozonation of SA. Overall, the initial degradation rate of SA, as well as the saturated adsorption capacity of SA was found to have a linear relation to changes of the surface hydroxyl groups of the catalyst. On this basis, we conclude that the significant enhancement of SA degradation using Pr/Al2O3 should be because the supported praseodymium, in the form of Pr6O11, promoted the formation of surface hydroxyl groups. Hence, the adsorption was ascended and the degradation rate of SA was then enhanced.The efficiency of catalytic ozonation on removing phenol was studied. The effects of ozone concentration, phenol concentration, pH, on the TOC removal rof phenol were evaluated. pH is the key factor to affect heterogeneous catalytic ozonation reactions. To study the effects of pH on catalytic ozonation, The Pr/Al2O3 powder was used as catalyst on catalyzed ozonation for degradation of phenol in different pH solutions. It was found that the TOC removal efficiency of phenol in Pr/Al2O3 catalytic ozonation showed the same trend as its adsorption process, the TOC removal efficiency of phenol was highest under neutral pH conditions. This result was different from the case of ozonation alone, in which higher pH had positive effect on the degradation of phenol due to the formation of hydroxyl radical. It was assumed that adsorption of organic pollutants on Pr/Al2O3 catalyst was an important step and would have direct influence on the effectiveness of catalytic ozonation. The catalytic ozonation efficiency may be affected by the ionization the dependency of phenol ionization on the pH value and point of zero charge （pHPZC） for Pr/Al2O3 catalyst. This means the phenol was beneficial to adsorb on the catalyst surface by electrostatic adsorption with opposite charge, and further decomposed on the surface of catalyst.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization
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