| 高铁酸钾氧化降解三氯生的动力学模拟及反应机制研究 |
| 摘要点击 1177 全文点击 1604 投稿时间：2010-10-09 修订日期：2010-12-13 |
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| 中文关键词 高铁酸钾 三氯生 氧化 二级反应动力学 线性自由能关系 |
| 英文关键词 ferrate(Ⅵ) triclosan (TCS) oxidation second-order reaction kinetics linear free-energy relationship |
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| 中文摘要 |
| 对高铁酸钾氧化降解水中微量三氯生（TCS）的反应动力学、反应机制及降解效果进行了实验研究.结果表明，高铁酸钾氧化降解TCS符合二级反应动力学模式，pH 8.5时表观二级反应动力学速率常数为531.9 L·(mol·s)-1，以10 mg·L-1的高铁酸钾计算，反应的半衰期是25.8 s.表观二级反应动力学速率常数随着pH值的增加逐渐降低，这种趋势可由高铁酸钾的各形态分布和TCS的酸碱解离常数来进行模拟.HFeO-4与TCS的非解离态和解离态的反应速率常数分别为(4.1±3.5)×102 L·(mol·s)-1和(1.8±0.1)×104 L·(mol·s)-1，且HFeO-4与解离态TCS的反应占主导作用.线性自由能关系表明其反应机制为亲电氧化反应，反应的初始步骤是HFeO-4亲电攻击TCS的酚羟基.当n［Fe(Ⅵ)］∶n(TCS)>7∶1时，TCS完全去除，低浓度的腐殖酸有助于提高高铁酸钾氧化降解TCS的速率.因此，高铁氧化技术是一种极具应用前景的新型水处理技术. |
| 英文摘要 |
| Triclosan (TCS) is a broad-spectrum antibacterial agent widely used in many personal care products. We investigated oxidation of TCS by aqueous ferrate Fe(Ⅵ) to determine reaction kinetics, interpreted the reaction mechanism by a linear free-energy relationship, and evaluated the degradation efficiency. Second-order reaction kinetics was used to model Fe(Ⅵ) oxidation of TCS, with the apparent second-order rate constant (kapp) being 531.9 L·(mol·s)-1 at pH 8.5 and (24±1) ℃. The half life (t1/2) is 25.8 s for an Fe(Ⅵ) concentration of 10 mg·L-1. The rate constants of the reaction decrease with increasing pH values. These pH-dependent variations in kapp could be distributed by considering species-specific reactions between Fe(Ⅵ) species and acid-base species of an ionizable TCS. Species-specific second-order reaction rate constants, k, were determined for reaction of HFeO-4 with each of TCS's acid-base species. The value of k determined for neutral TCS was (4.1±3.5)×102L·(mol·s)-1, while that measured for anionic TCS was (1.8±0.1)×104L·(mol·s)-1. The reaction between HFeO-4 and the dissociated TCS controls the overall reaction. A linear free-energy relationship illustrated the electrophilic oxidation mechanism. Fe(Ⅵ) reacts initially with TCS by electrophilic attack at the latter's phenol moiety. At a n［Fe(Ⅵ)］∶n(TCS)>7∶1, complete removal of TCS was achieved. And lower concentration of the humic acid could enhance the kapp of Fe(Ⅵ) with TCS. In conclusion, Fe(Ⅵ) oxidation technology appears to be a promising tool for applications of WWTPs effluents and other decontamination processes. |
