KMnO4氧化降解雌酮反应动力学与氧化产物

Oxidation of estrone by aqueous permanganate:reaction kinetics and oxidation products

摘要:

为探讨KMnO₄氧化降解雌酮（E1）的效能和反应机理，在假一级条件下，研究KMnO₄氧化降解E1的动力学规律，利用三重四级杆串联线性离子阱液相-质谱联用仪（LC-MS/MS）对KMnO₄氧化降解E1的产物进行分析.结果表明，KMnO₄氧化降解E1符合假一级动力学规律，且假一级动力学常数K_obs（s^-1）随着KMnO₄浓度的增加呈线性增加，二级反应动力学常数k（L·mol^-1·s^-1）随着pH的升高而增大.通过与HOCl和O₃氧化E1对比，在中性pH附近，KMnO₄氧化E1的二级反应动力学常数与HOCl相当，但远低于O₃.然而，实际水体中KMnO₄的除污染效能明显高于HOCl和O₃，主要是由于HOCl和O₃在实际水体中的消耗速度比较快，有效剩余浓度低，而KMnO₄在实际水体中的消耗速度比较慢.LC-MS/MS测定KMnO₄氧化降解E1产物的结果表明，KMnO₄易氧化进攻E1苯环上的活性位酚羟基，形成一系列羟基化、醌型、羧酸化芳香开环产物，并且有效降低其内分泌干扰活性.

Abstract:

The purpose of this article was to investigate the effectiveness and mechanism for the oxidation of estrone by aqueous potassium permanganate. Experiments were conducted to examine the reaction kinetics of potassium permanganate with estrone under the condition with potassium permanganate in excess over a wide pH range. Then, reaction products of estrone with potassium permanganate were identified with liquid chromatography tandem mass spectrometry (LC-MS/MS). The results showed that the loss of estrone followed the pseudo-first-order kinetics with potassium permanganate, suggesting that the reaction is first-order with respect to estrone. The pseudo-first-order rate constant (K_obs, s^-1) increased linearly with the increase of potassium permanganate concentration. The degradation of estrone of the second-order rate constants (k, L·mol^-1·s^-1) increased with the increase of pH. Estrone was shown to exhibit similarly appreciable reactivity toward potassium permanganate with the second-order rate constant at near neutral pH comparable to chlorine but much lower than that of ozone. In comparison with these oxidants, however, potassium permanganate was much more effective for the oxidative removal of estrone in real waters, mainly due to the relatively high stability of potassium permanganate therein. Identification of oxidation products suggested the initial attack of potassium permanganate at the hydroxyl group in the aromatic ring of estrone, leading to the formation of a series of quinone-like and aromatic ring-opening products and thus the elimination of its estrogenic activity.