| 摘要: | 一般光觸媒的材料有二氧化鈦（TiO2）、氧化鋅（ZnO）等，其中以二氧化鈦為主流被廣泛的研究，但在實際應用方面，還是受到侷限。氧化鋅與二氧化鈦具相同性質，且鋅金屬較鈦金屬價格低廉，因此氧化鋅為最有潛力替代二氧化鈦的材料之一。製備奈米氧化鋅包含氣相沉積法、物理粉碎法、溶膠凝膠法等，但如何大規模且經濟化的生產是必須要克服的關鍵問題，至目前為止，在大多數的合成報告中，氧化鋅奈米晶體製備成本均非常高。本研究選取二醇類溶劑，利用其會生成分子間氫鍵的特性，控制小聚集的形成，並搭配簡單、低成本的實驗程序，以製備出奈米級氧化鋅晶體，同時探討製備溶劑、前驅物種類、水化反應、製備溫度、製備酸鹼度、反應時間等反應因子與氧化鋅晶體物化性質之關係，並求得其最高光催化效率之反應條件。
本研究實驗結果顯示，提高製備溫度有助於提高比表面積與純度，並增加其光降解效率，以50℃為製備溫度效果最佳；延長製備反應時間，會使氧化鋅晶體粒徑變大，並有助於提高其純度與光降解效率。提高製備氧化鋅之酸鹼度會改變表面結構，同時亦提高其比表面積與晶體成晶狀況，有助於增加污染物的光降解速率。其中，以乙二醇為製備溶劑、氯化鋅為前趨物，在無水、溫度50℃、酸鹼度為12的狀態下反應48小時，可得純度最高、光催化效率最佳之奈米氧化鋅。然而氯化鋅等物質在二醇類或在含水二醇類溶劑中之產物形成機制，與光催化過程中污染物物種的變化情形等有待後續深入研究。;General photocatalyst included titanium dioxide (TiO2), zinc oxide (ZnO) and so on, and titanium dioxide has been main widely studied. However, in practical application, titanium dioxide is still subjected to limitations. Zinc oxide have the same nature with titanium dioxide, and zinc’s price is lower than titanium, therefore, zinc oxide is the one of the potential materials to replace titanium dioxide. Preparation of nano zinc oxide involves many methods, like vapor deposition, physical crushing method, sol-gel method, etc., but how to produce economically large-scale product is the key issue that must be overcome. Preparation of nano zinc oxide has very high cost in the majority of the synthesis report. This study selected glycol as a key solvent, using its characteristic that can generate intermolecular hydrogen bonds controlling the formation of small aggregates. This study used a simple, low-cost experimental procedure to prepare the nano zinc oxide, and also discussed the factors such as solvents, precursor species, hydration, temperature, pH, reaction time, etc., which influenced physical and chemical properties of zinc oxide. The reaction conditions to obtain the highest photocatalytic efficiency are also investigated.
The results showed that as the temperature increased surface area, the purity of zinc oxide and its efficiency of the photodegradation also increased. Thus, it is concluded that 50 ℃ is the optimal temperature. Extending reaction time, the zinc oxide will grain larger size, helping to improve its purity and the efficiency of the photodegradation. Higher pH will not only change the surface structure, but also improve its surface area and crystal growth, helping to increase the rate of photodegradation of pollutants. Among them, ethylene glycol as the solvent, zinc chloride as the predecessor, the absence of water, 50 ℃, pH=12 and 48 hours are the optimal conditions to obtain the nano zinc oxide with highest purity, and inhanced efficiency of the photodegradation. |
