| Summary: | 碩士 === 國立交通大學 === 環境工程所 === 87 === The essential purpose of this research was to explore the relevant impact factors and reaction kinetic pattern in the process of the degradation of 2-chlorophenol with hydrogen peroxide and synthesized goethite. The research consisted of three major parts. First, we synthesized different iron oxides, and determined the species individually. Second, the influence caused by the individual surface properties during the system with iron oxide and hydrogen peroxide was interpreted. Finally, using designated goethite as the catalytic in the reaction system to explore the different condition factors involved in the consequence that was by degradation of 2-chlorophenol with the catalytic decomposition of hydrogen peroxide, and the main reaction mechanism.
From the results discovered in the research, the order was determined as ferrihydrite > goethite > hematite, according to the catalytic ability of iron oxides in the decomposition of hydrogen peroxide during the experiment. In comparison with the degradation rate of 2-chlorophenol for the three species under the condition of neutral pH, it was goethite > hematite > ferrihydrite. Under the acidic condition, due to the Fenton reaction resulting from the dissolution of ferric ions at the surface of ferrihydrite, the degradation of 2-chlorophenol was therefore accelerated. At this point, the degradation efficiency with 2-chlorophenol for the three iron oxides will be ferrihydrite > goethite > hematite.
The decomposition of hydrogen peroxide due to the catalysis of goethite could be described as the first-order reaction. When the initial concentration of hydrogen peroxide was low, the decomposition rate increased with increasing its concentration, and there existed a linear relationship between the first order reaction rate constant and the amount of goethite. Besides, the decomposition rate of hydrogen peroxide increased with higher pH value.
The optimal addition amounts of goethite and hydrogen peroxide in the system were 1g/L and 8.8 mM, respectively. Under this condition, 49.2% of 2-chlorophenol was degraded. Before the optimal addition amount was reached, the degradation rate rose with increasing the amount of goethite and hydrogen peroxide. Besides, the pH value did not influence the degradation rate of 2-chlorophenol in this system. Thus the disadvantage caused by the control under the acidic condition of the conventional Fenton synthesis will be improved/avoided to elevate its feasibility for practical application.
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