| Summary: | 碩士 === 國立中興大學 === 環境工程學系 === 90 === This investigation aimed at preparing a titanium dioxide coating film by chemical vapor deposition (CVD) method and Taguchi method, discussing the effect of various preparing parameters for photocatalytic reaction through hydroxyl radicals. It is expected to get the best generation of hydroxyl radicals and the extent of oxidation.
The first prart of experiments discussed the salicylate conversion effect with the different preparing parameters by chemical vapor deposition (CVD) method. The results indicated that the optimum preparing parameters for TiO2 photocatalysis were carrier gas flow rate = 550 ml/min, oxidation temperature/calcination temperature = 400℃/550℃, rotating speed of reactor = 20 rpm. Among the parameters, carrier gas flow rate and oxidation temperature/calcinations temperature were significant in salicylate conversion.
The second part of experiments discused the salicylate conversion effect with the different operation parameters of photocatalysis in solid/liquid photocatalytic system. By Monitoring the derivatives of reactants (2,5-DHBA,2,3-DHBA,Catechol) after trapping the hydroxyl radicals by Salicylate, discussing the hydroxyl radical generation rate and reaction path were discussed. The results indicated that the best operating parameters for photocatalytic reaction were salicylate dosage = 250 mg/L, pH = 5, dissolved oxygen = 8.1 mgO2/L,light density = 2.9mW/cm2.According to the decomposition and the reaction dynamic calculation of the three derivatives the hydroxyl radical concentration was about 1.0 × 10-17 M.
A special condition was observed in the experiments of pH operational parameter. The hydroxyl radicals generation in low pH’s was better then in high pH’s, but the salicylate conversion was better in high pH’s. Conjecturing the salicylate reacted with non-hydroxylation process in high pH’s, or the rapid generation of hydroxyl radicals, the accumulation of product concentration exceeded the consumpition.
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