利用半導體光觸媒來降解重金屬，因其具有反應快、省時及成本較低之優點，因此成為近年來污染防治工程研究及應用發展的重點。在本研究中我們利用二種不同金屬氧化物(二氧化鈦TiO2，氧化鋅ZnO)，來進行光催化反應處理含六價鉻水溶液，利用太陽光催化光觸媒金屬氧化物進而產生電子-電洞對，並且藉由電洞捕抓劑移除帶正電的電洞(h+)，讓電子(e－)有效導引至催化劑表面，處理含六價鉻水溶液。
利用太陽光激發光觸媒處理Cr(Ⅵ)水溶液，其去除效率和效果增加或降低都會受到光觸媒及犧牲試劑的種類、起始pH值及太陽光強度影響。首先，本研究利用七種不同的犧牲試劑來作為比較其輔助的效果發現，當以TiO2作為光觸媒時，添加EDTA的效果為最佳，在10分鐘可以完全去除六價鉻；ZnO則是添加甲酸的效果為最佳，在20分鐘完全去除六價鉻。在控制不同起始pH值(2，3，4，5，6)的實驗中，我們觀察到了氧化鋅和二氧化鈦對六價鉻之光催化效果隨著溶液pH值越低效果越好，反之當pH值越高效果越不好；另外實驗中使用不同光強度分為有強度1(0.6~0.4mW/cm2 )、強度2(0.1~0.01mW/cm2)和暗室來進行實驗，當光強度越高二氧化鈦和氧化鋅處理六價鉻效果也隨之增加。 Because of quick responses, saving time and reduction of cost, using semiconductor photocatalyst for the degradation of metals become the focus of the research and application development of pollution prevention and control engineering in recent years.
In this study, two kinds of metal oxides (TiO2 and ZnO) were used for photocatalysis on the treatment of aqueous chromium (VI). The utilization of solar could induce metal oxides to generate electrons and holes on surface of TiO2 or ZnO powder. The addition of sacrificial reagent could scavenge electric hole (h+) and reduce the recombination rate of photogenerated electrons and holes. The accumulation of photogenerated electrons on the surface of catalysts could improve the removal of chromium (VI) in aqueous solution.
The treatment of Cr(VI) via photocatalysis induced by solar irradiation would be affected by the kinds of photocatalysts and sacrificial reagents, initial pH and solar irradiation intensity. First, seven different sacrificial reagents were used to examine their photoassisting effects. Results reveal that EDTA had the best effect to aid TiO2 to remove aqueous chromium (VI) completely within 10 minutes, whereas formic acid was the best for ZnO to remove aqueous chromium (VI) completely within 20 minutes.
Secondly, the photocatalytic removal effect of aqueous chromium (VI) increased with the lowering pH. Meantime, it was also found that higher solar irradiation intensity could promote the removal effect of aqueous chromium (VI).
