研究奈米光觸媒之合成及處理染料之效率及降解機構

Synthesis of nano-photocatalysts using hydrothermal method and its efficiencies, mechanisms of photocatalytic degradation with triphenylmethane dyes

劉守靜(Shou-Ching Liu)

指導教授 ： 林昭田 ； 麥富德

中山醫學大學/健康管理學院/應用化學系碩士班/碩士(2008年)

https://doi.org/10.6834/CSMU.2008.00001

摘要

本研究使用高級氧化過程之光觸媒催化程序來降解難分解染料，並探討其降解情形及影響催化的因子。此外，選擇鈦板及鋅板為底材經由水熱法合成奈米級的光觸媒在底材表面，研究其材料特性及光催化之效果。
探討五種三苯甲烷類陰陽離子染料(CV、EV、MG、BG、SB)同時在含有二氧化鈦光觸媒懸浮液中，當光催化降解過程改變參數如：pH值、觸媒濃度、照光與否、鹽類的加入，觀察染料的競爭情形。由實驗可知，在二氧化鈦表面帶正電荷時陰離子染料(SB)有較好的降解效率；而在二氧化鈦表面帶負電荷時，陽離子染料(CV、EV、MG、BG)則有較佳的降解效率。在不同的pH值可以觀察到含有乙基的染料其降解效率比含有甲基的染料佳(EV>CV；BG>MG)；在酸性條件下加入鹽類對大部分的染料離子有加強降解效率的作用，然而，在鹼性條件下加入鹽類，反而造成降解效率變差的情形。
利用高純度的鈦板以10M NaOH水溶液迴流過程製備成多孔性二氧化鈦薄膜，在不同迴流條件下，其晶體性質和孔洞的結構也不同，孔洞的直徑約在1.0 μm左右。實驗結果顯示，迴流24小時之鈦板製成之二氧化鈦薄膜對於染料Ethyl Violet (EV)有最佳的光催化降解能力。此外，再以HPLC-PDA-ESI-MS來鑑定其中間產物，發現有25個中間產物在染料EV的光催化降解中被鑑定出來，如開環後產生的DDBP和DAP；以及隨後利用GC-MS所測得分子量較小的中間產物如醋酸、氨基苯等。並依據所產生的中間物進一步的推測可能的反應途徑。
用高純度的鋅板作為固定化奈米光觸媒的基材，同樣以10M NaOH溶液，利用簡單的水熱法製備奈米氧化鋅。由實驗結果可知，在不同的迴流條件下，所產生的氧化鋅不僅具有不同的奈米結構結晶型態，且同時也具有很強的光催化活性。這些合成出來的氧化鋅的結晶顆粒小，在處理染料EV時，有很高的降解效果。

關鍵字

光觸媒 ； 二氧化鈦 ； 氧化鋅 ； 高級氧化法 ； 光催化降解

並列摘要

In this study, we use the photocatalytic degradation of Advanced Oxidation Processes (AOPs) to decompose the dyes, also discussed the condition of degradation and the factors which can influence the degradation rate. Besides, we employed selected material as substrates to synthesize nano-size photocatalysts.
A completive photodegradation study of the triphenyllmethane dyes is reported in aqueous TiO2 suspensions. The effect of various adsorbed dye in TiO2 aqueous suspension was studied. The adsorption and photodegradation have been investigated in illuminated TiO2 suspension for five dyes, including cationic dyes, Crystal Violet (CV), Ethyl Violet (EV), Malachite Green (MG), Brilliant Green (BG), and an anionic dye, Sulfan Blue (SB). Our results indicate that factors such as, UV illumination, pH value of the aqueous solution, concentration of TiO2, and salt addition, all determine the rate of photodegradation. The photocatalytic activities of adsorbed dyes prepared under different pH values were examined that on the positively charged TiO2 particle surface by a sulfonate group, anionic dye (SB) has better degradation rate. On the other hand, on the negatively charged TiO2 particle surface, cationic dyes (CV, EV, MG, and BG) have better degradation rate by a dialkylamino group. The cationic dye including di-ethylamino groups have better degradation rate than the cationic dye including di-methylamino groups (EV>CV; BG>MG) at different pH values. When addition salt under acid aqueous solution, most of the five dyes tends to positive effect, but under base aqueous solution, they tend to negative effect. For photodegradation of dyes, the degradation rate were proposed and discussed in this research.
Porous TiO2 films were fabricated onto Ti substrates by reflux process in 10 M NaOH solution. A TiO2 film with porous structure and crystallization was obtained. The crystallization and porous structure of TiO2 film were dependent on the time and temperature of the reflux process. The pore diameter is ca. 1.0μm. TiO2 film showed high photocatalytic activity towards degradation of Ethyl Violet (EV). TiO2 film has been successfully applied to degrade dye pollutants. In order to obtain a better understanding on the mechanistic details of this TiO2-assisted photodegradation of the EV dye with UV irradiation, decomposed intermediates of the process were separated, identified and characterized by HPLC-PDA-ESI-MS technique in this study. The results indicated that the N-de-ethylation degradation of EV. Moreover, the hydroxyethylated intermediates formed by the N-de-ethylated EV, 4-(N,N-diethylamino)-4'-(N',N'-diethylamino)benzophenone (DDBP), and 4-(N,N-diethylamino)phenol (DAP) processes were separated and identified. Several probable photodegradation pathways were proposed and discussed.
In order to develop efficient photocatalytic ZnO films for application wastewater treatment and reuse systems, there is a great need to tailor-design the structural properties of ZnO material and enhance its photocatalytic activity. Through a simple synthesized hydrothermally by the reaction of ZnO plate and NaOH solution, we have fabricated nanostructured crystalline ZnO thin films with simultaneous photocatalytic properties. The highly ZnO crystal exhibited different structures, narrow pore size distribution, and small crystallite size. These ZnO materials were highly efficient in the decomposition of ethyl violet dye. Here, we report results on the synthesis, characterization, and environmental application and implication of photocatalytic ZnO films.It was shown that the obtained ZnO film possess high photocatalytic activity in a model reaction of Ethyl Violet (EV) dye.

並列關鍵字

photocatalyst ； TiO2 ； ZnO ； Advanced Oxidation Processes (AOPs) ； photocatalytic degradation

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