Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/4927
標題: UV/TiO2程序中氫氧自由基之生成研究
The study on hydroxyl radicals generation in UV/TiO2 photocatalytic process
作者: 吳致誠
Wu, Chih Cheng
關鍵字: photocatalysis;光催化;hydroxyl radicals;salicylate;tio2;氫氧自由基;水楊酸;二氧化鈦
出版社: 環境工程學系
摘要: 
本研究採用實驗計劃法進行化學沈積法製備二氧化鈦薄膜之探討,並針對光催化反應中各種操作條件對氫氧自由基的反應性及產率的影響進行測試,以期得到氫氧自由基在光催化反應中的最佳產率及氧化比重。在第一部分實驗係探討不同製備條件下所製備的光觸媒,對液相處理有機物時的影響;實驗中對製備條件:氧化溫度、鍛燒溫度、載流氣體流量及高溫轉速,採用實驗計劃法中的直交表法作規劃,分別討論不同操作變因中,各變數對有機物轉化率的貢獻率。實驗結果顯示,在操作變因中以觸媒的氧化及鍛燒溫度在400oC/550oC(高溫/高溫)及30rpm的披覆轉速下所製造的反應器,在水楊酸的分解上有較高的轉化率;而載流氣體的流速,對於水楊酸的轉化率,則沒有太大的影響。
第二部分實驗是研究不同的操作條件(操作pH值、溶氧曝氣量與照光強度),對光催化系統中有機物(水楊酸)轉化率的影響。採用自由基捕捉劑法原理,利用水楊酸作捕捉劑,捕捉光催化系統中所產生的氫氧自由基,討論轉化率與氫氧自由基產率之間的關係,並由三種不同的中間產物(2,5-DHBA、Catechol、2,3-DHBA)的生成趨勢,討論氫氧自由基在不同操作條件下與有機物的反應趨勢及反應動力。實驗結果顯示,在水楊酸劑量250 mg/L時在捕捉氫氧自由基上有較好的效率,而pH值則是控制在pH = 5時有較好的產率;在溶氧曝氣量上,以攪拌與曝氣機制共存(溶氧= 8.1mgO2/L)時有較好的產率;在光照強度的影響上,在2.9μW/cm2的照光強度時所得到的氫氧自由基產率較2.0與1.0μW/cm2時為佳。最後進行反應動力的計算,根據最佳組與中間產物分解實驗的結果,可求得本研究的氫氧自由基產量濃度為1.0 ×10-17M。而在pH影響因子的實驗當中,發現在高pH值時氫氧自由基的產率雖然明顯比在低pH值時低,但在轉化率的表現上,卻比在低pH值時為高,推測可能在高pH值進行非氫氧自由基為主的氧化反應,或是氫氧自由基的產量大增,導致產物的濃度累積趕不上濃度消耗的速率。

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.
URI: http://hdl.handle.net/11455/4927
Appears in Collections:環境工程學系所

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