Zhao Ling, Peng Ping-an
Department of Soil Biology and Biochemistry, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
Huan Jing Ke Xue. 2008 Apr;29(4):972-7.
Experiments were conducted to determine oxidation kinetics of pentachlorophenol (PCP) using manganese dioxide (MnO2) as an oxidant. The influence of cosolutes (e.g. inorganic ions and organic substances) on the reaction kinetics was also assessed. When simulating the kinetics of PCP with n-order reaction model by a non-linear curve fitting approach, the reaction order n is over 0.999, which suggests that the first order reaction model fit the degradation kinetics of PCP. The apparent rate constant k(obs) values are 2.86 h(-1) for the centrifugation method and 2.14 h(-1) for the ascorbic acid method by non-linear fitting the kinetics of PCP for 0.5 h reaction using pseudo-first-order model under the 95% confidence limits. The addition of bivalent metal ions causes the considerable reduction of the apparent rate constants. The significant effect on the k(obs) of PCP occurs when the concentration of Mn2+ above 2% of the initial MnO2 is added as the co-solute, but no significant influence on the k(obs) of PCP for the presence of other ions. The presence of caffeic acid, syringic acid or gallic acid reduces the reaction rate of PCP significantly. Oppositely, no considerable decrease of k(obs) is observed in experiments with the addition of cinnamonic acid, coumaric acid, ferulic acid or ortho (para)-hydroxybenzoic acid. These experimental results demonstrate that the decrease of PCP adsorbed to MnO2 considerably or the action of competing against PCP reacted with MnO2 is the dominant factor that slows down the transformed rate of PCP oxidation by MnO2.
开展了实验以确定使用二氧化锰（MnO₂）作为氧化剂时五氯苯酚（PCP）的氧化动力学。还评估了共溶质（如无机离子和有机物质）对反应动力学的影响。当通过非线性曲线拟合方法用n阶反应模型模拟PCP的动力学时，反应级数n超过0.999，这表明一级反应模型适合PCP的降解动力学。在95%置信限下，使用伪一级模型对PCP 0.5小时反应的动力学进行非线性拟合，离心法的表观速率常数k(obs)值为2.86 h⁻¹，抗坏血酸法为2.14 h⁻¹。二价金属离子的添加导致表观速率常数显著降低。当作为共溶质添加的Mn²⁺浓度高于初始MnO₂的2%时，对PCP的k(obs)有显著影响，但其他离子的存在对PCP的k(obs)没有显著影响。咖啡酸、丁香酸或没食子酸的存在显著降低了PCP的反应速率。相反，在添加肉桂酸、香豆酸、阿魏酸或邻（对）羟基苯甲酸的实验中，未观察到k(obs)有明显下降。这些实验结果表明，吸附在MnO₂上的PCP大量减少或与MnO₂反应的PCP发生竞争作用是减缓MnO₂氧化PCP转化速率的主要因素。
