鹼活化過硫酸鹽氧化法對含氯有機物去除成效及機制評估

Evaluation of the efficiency and mechanism of chlorinated organics removal by alkaline-activated persulfate

林翊民(Yi-Min Lin)

指導教授 ： 陳谷汎

國立暨南國際大學/科技學院/土木工程學系/碩士(2017年)

摘要

本研究以鹼活化過硫酸鹽程序針對 1,2- 二氯乙烷 (1,2-dichloroethane, 1,2-DCA)及三氯乙烯(trichloroethylene, TCE)進行去除成效及機制評估，主要目的如下：(1)評估過硫酸鹽在不同pH及鹼活化下自由基生成物種及強度；(2)探討以鹼活化過硫酸鹽對1,2-DCA及TCE之降解能力與機制；(3)探討在不同pH值下過硫酸鹽對1,2-DCA及TCE之降解能力；(4)評估不同環境條件對過硫酸鹽降解1,2-DCA及TCE之影響；及(5)評估鹼活化過硫酸鹽條件下應用於現地之可能性。
批次實驗結果顯示，鹼活化過硫酸鹽程序(pH > 12)能有效加速 1,2-DCA 之降解，但對 TCE 之降解效能較差，1,2-DCA 及 TCE 之去除，皆符合擬一階降解反應動力。在高 pH 條件下，1,2-DCA 會因脫氯化氫反應(dehydrochlorination)加速其降解，並產生副產物氯乙烯(vinyl chloride, VC)，氯乙烯隨後亦被過硫酸鹽氧化去除。因此鹼媒介的降解反應(base-mediated degradation)可能為鹼活化過硫酸鹽去除某些污染物的重要機制。
陰離子對鹼活化過硫酸鹽去除含氯有機物影響之實驗結果顯示，在鹼性條件下，碳酸鹽抑制含氯污染物降解效果大於氯鹽，氯鹽在酸性條件下抑制含氯污染物降解效果較明顯。在1,2-DCA和TCE共降解實驗結果顯示，在pH值3的條件下，過硫酸鹽降解1,2-DCA的效果有被抑制趨勢，然而pH值13條件下，過硫酸鹽降解TCE的效果有被抑制的趨勢。添加現地土壤批次實驗結果顯示，鹼活化過硫酸鹽程序組別降解1,2-DCA效果明顯優於未活化組別，而TCE則相反，未活化組別優於鹼活化組別，未來在應用於現地時應謹慎評估。本研究成果將有助於鹼活化過硫酸鹽程序應用於受含氯污染物整治之用。

關鍵字

1,2-二氯乙烷 ； 三氯乙烯 ； 鹼活化過硫酸鹽 ； 脫氯化氫反應 ； 陰離子

並列摘要

In this study, the efficiency and mechanism of 1,2-dichloroethane (1,2-DCA) and trichloroethylene (TCE) removal by alkaline-activated persulfate was evaluated. The objectives of this study were to: (1) evaluate the species and intensity of radicals produced by persulfate under different pH and alkaline conditions; (2) evaluate the ability and mechanism of 1,2-DCA and TCE removal by alkaline-activated persulfate; (3) evaluate the ability of 1,2-DCA and TCE removal by persulfate at different pH value; (4) evaluate the effience of 1,2-DCA and TCE removal by persulfate under different environmental conditions; and (5) assess the feasibility of alkaline persulfate for in situ application.
The results of batch experiments indicate that alkaline-activated persulfate (pH>12) could effectively accelerate the degradation of 1,2-DCA, but alkaline-activated persulfate reduced the degradation rate of TCE. Results show that the removal of 1,2-DCA and TCE followed pseudo first-order kinetics. Under high pH conditions, the dehydrochlorination enhanced 1,2-DCA degradation, which produced vinyl chloride (VC). VC could be then removed by persulfate oxidation. Therefore, base-mediated degradation may be an important mechanism for the removal of some pollutants when alkaline-activated persulfate is applied.
Carbonate had a more significant effect on the inhibition of the removal of chlorinated organics under alkaline conditions while chloride caused more retardation of the contaminant removal under acid conditions. In the experiments of the coexistence of 1,2-DCA and TCE, TCE degradation was inhibited under alkaline conditions while the removal of 1,2-DCA was suppressed under acid conditions. The results of the batch experiments with the addition of in situ soil show that the efficiency of 1,2-DCA removal by alkaline-activated persulfate better than that of un-activated persulfate. In contract, the efficiency of TCE removal by un-activated persulfate was better than that of alkaline-activated persulfate. The results of this study will be helpful for the application of alkaline-activated persulfate to remediate chlorinated compound-contaminated groundwater.

並列關鍵字

1,2-dichloroethane (1,2-DCA) ； trichloroethylene (TCE) ； alkaline-activated persulfate ； dehydrochlorination ； anion

參考文獻

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