| 摘要: | 本研究使用二氧化鈦(TiO2)光觸媒進行含六價鉻水溶液的光催化還原處理，利用UV光照射光觸媒進而產生電子-電洞對，藉由電洞捕捉劑填補產生的電洞，進而移除帶正電的電洞(h+)，讓電子(e－)能有效導引至光觸媒表面，還原水溶液中的六價鉻。
本研究分別於控制不同光強度實驗中添加三水合醋酸鈉(Sodium Acetate, NaOAc)、己二酸(Adipic acid, AA)、單水合檸檬酸(Citric acid, CA)、1,2,3,4-丁烷四羧酸(1,2,3,4-Butanetetracarboxylic acid, BTCA)、二乙烯三胺五乙酸 (Diethylenetriaminepentaacetic acid, DTPA)等五種犧牲試劑到反應中，來提高光觸媒進行光催化還原反應處理水中六價鉻的效果。
實驗結果顯示添加犧牲試劑、pH 2的實驗中，添加5mmol TiO2劑量、0.2mmol DTPA的實驗其去除效果最佳，在40分鐘就可以達到完全去除0.04mmol Cr(VI)。此外結果也發現當起始犧牲試劑濃度與Cr(VI) 起始濃度比值(SPR)在5時(即犧牲試劑/Cr(VI) mol數=5/1)，其去除效果比相同Cr(VI)起始濃度的其他SPR時較好，但當Cr(VI)起始濃度達到0.1mmol時，即使比值為5，去除率仍不佳。
在不同起始pH值(2，3，4)的實驗結果可以看出對六價鉻之光催化去除效果隨著溶液pH值越低去除效果越好，當pH值升高至4時效果跟著降低；另外針對不同光強度如UVC、UVA和暗室來進行實驗時發現，當光強度越高TiO2處理六價鉻效果也隨之增加。以UV- TiO2系統光催化Cr(Ⅵ)水溶液，其去除率效果會受到UV強度、光觸媒劑量和所添加的不同犧牲試劑影響。
在所有實驗中也發現到羧基的數量似乎與Cr(VI)去除效果有關，以相同Cr(VI)濃度、相同犧牲試劑濃度、相同TiO2劑量的實驗做比較，可發現當犧牲試劑所含之羧基數量越多，去除效果也越好。
Titanium oxides were used for photocatalysis on the treatment of aqueous Cr(VI) in this study by the assistance of sacrificial reagents. Electrons and holes were generated by inducing TiO2 with UV irradiation. The addition of sacrificial reagents could scavenge electric hole (h+) and reduce the recombination of electrons and holes, as well as improve the reduction of Cr(VI) by photogenerated electrons.
Five sacrificial reagents, including sodium Acetate, adipic acid, citric acid, 1,2,3,4-Butanetetracarboxylic acid, diethylene-triaminepentaacetic acid, were used to enhance the treatment efficiency of Cr(VI) photoreduction under various light intensity.
Results indicate that the optimal condition for remove Cr(VI) with initial 0.04 mmol among 40 minutes was controlled under pH 2 and adding 5 mmol TiO2 and 0.2 mmol DTPA. In addition, the treatment efficiency of Cr(VI) photoreduction was better by controlling the sacrificial reagent to pollutant (Cr(VI)) ratio (SPR) at 5/1 than at other ratios, based on the same Cr(VI) initial concentration. However, even SPR controlled at 5/1, the treatment efficiency of Cr(VI) photoreduction was not good under the initial Cr(VI) controlled at 0.1 mmol.
The efficiency of Cr(VI) photoreduction was affected by UV light intensity, photocatalyst dosing, kinds of sacrificial reagents under UV-TiO2 photocatalysis system. The treatment efficiency of Cr(VI) photoreduction increased with pH decreasing and increasing light intensity. Results also reveal that the efficiency of Cr(VI) photoreduction had good and positive correlation with the amount of carboxylic group in sacrificial reagents under the conditions of the same initial Cr(VI) concentration, sacrificial reagents and TiO2 dosages. |
