水中基質對硫酸自由基降解新興污染物的影響

劉丹丹，周雪飛

(同濟大學 長江水環境教育部重點實驗室，上海 200092)

1 引言

2 硫酸自由基的產生機理

2.1 能量活化

能量活化主要通過外界提供足夠的能量促使過硫酸鹽中的化學鍵發生斷裂，從而形成硫酸自由基，其反應過程可用式(1)和式(2)表示：

(1)

(2)

目前使用最多的是高溫和紫外照射兩種方法。

2.2 過渡金屬離子活化

相對于使用高溫或UV 活化過硫酸鹽，使用過渡金屬活化具有高效、低成本的優點，越來越多的應用于實踐中。在不同價態的過渡金屬離子的催化下，PMS和PS通過下列方程式生成硫酸自由基和其他的一些物質：

(3)

(4)

(5)

(6)

(7)

(8)

金屬離子與氧化劑的反應原理上主要是金屬離子與氧化劑之間的電子轉移過程。Anipsitakis等研究發現，Co(Ⅱ)和Ru(Ⅲ)活化KHSO5效果最好，Ag(Ⅰ)活化K2S2O8效果最好，而Fe(Ⅱ)、Fe(Ⅲ)活化H2O2效果最好[2]。

3 硫酸自由基對污染物的去除研究

4 水中離子對硫酸自由基的影響

4.1 氯離子對硫酸自由基的影響

(9)

(10)

(11)

(12)

(13)

(14)

(15)

(16)

(17)

(18)

(19)

(20)

4.2 溴離子對硫酸自由基的影響

(21)

(22)

4.3 水中碳酸鹽對硫酸自由基的影響

(23)

(24)

同樣的，人們發現在基于硫酸自由基的高級氧化體系中，通常會發生式(25)、(26)、(27)、(28)和(29)的反應過程。

(25)

(26)

(28)

(29)

5 水中有機質對硫酸自由基的影響

(28)

(29)

(30)

6 總結與展望

基于過硫酸鹽的高級氧化技術在環境領域取到了快速的發展，人們越來越關注其在實際應用中環境基質的影響，相信隨著研究的不斷深入，更準確、更全面的過硫酸鹽降解機理將會得到有效的解讀。與其他高級氧化體系相比，基于過硫酸鹽的高級氧化技術在實際應用中還存在著效率不高、使用范圍有限等問題，如何根據硫酸自由基的特異性和其與環境基質物質的反應機理來提高過硫酸鹽的去除有機物的效率是今后研究的一個重要方向。

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