Li Fangbai, Liu Chengshuai, Liang Chunhua, Li Xiangzhong, Zhang Lijia
Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environment and Soil Science, Guangzhou 510650, China.
J Hazard Mater. 2008 Jun 15;154(1-3):1098-105. doi: 10.1016/j.jhazmat.2007.11.015. Epub 2007 Nov 17.
To investigate the oxidative degradation of organic pollutants at the interface of manganese oxides and water, beta-MnO2 was prepared and its crystal structure and the specific surface area were examined by X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) methods, respectively. 2-Mercaptobenzothiazole (MBT) as a model chemical was used to study its oxidative degradation reaction in beta-MnO2 suspension. The experimental results showed that MBT was effectively degraded and mineralized into SO4(2-) and NO3- by beta-MnO2. In the meantime, it was found that beta-MnO2 could be reductively dissolved, and aqueous and adsorbed Mn2+ was generated. The kinetics of MBT degradation by beta-MnO2 is a function of initial MBT concentration, beta-MnO2 dosage and pH value. At pH 4.6, apparent reaction orders with respect to initial MBT concentration and beta-MnO2 dosage were determined to be 0.88 and 0.27, respectively. The initial reaction rate (rinit) is of pH dependence with a reaction order of -0.36. The thermodynamics of MBT degradation by beta-MnO2 was also investigated, and the apparent activation energy was calculated to be 5.62 kJ/mol. The inhibited effect of carboxylic acids (oxalic, citric, tartaric, and malic acids) or metal ions (Ni2+, Ca2+, Mn2+ and Cr3+) on the oxidative degradation of MBT by beta-MnO2 was also investigated. This investigation will give some new insights for understanding the interaction of organic pollutants with manganese oxides in natural soils and sediments.
为了研究锰氧化物与水界面处有机污染物的氧化降解情况，制备了β - 二氧化锰，并分别采用X射线衍射（XRD）和布鲁诺尔 - 埃米特 - 泰勒（BET）方法对其晶体结构和比表面积进行了检测。以2 - 巯基苯并噻唑（MBT）作为模型化合物，研究其在β - 二氧化锰悬浮液中的氧化降解反应。实验结果表明，MBT能被β - 二氧化锰有效降解并矿化为SO4(2-) 和NO3-。同时，发现β - 二氧化锰会发生还原溶解，生成水溶态和吸附态的Mn2+。β - 二氧化锰降解MBT的动力学是初始MBT浓度、β - 二氧化锰用量和pH值的函数。在pH 4.6时，相对于初始MBT浓度和β - 二氧化锰用量的表观反应级数分别确定为0.88和0.27。初始反应速率（rinit）与pH有关，反应级数为 -0.36。还研究了β - 二氧化锰降解MBT的热力学，计算得到的表观活化能为5.62 kJ/mol。此外，还研究了羧酸（草酸、柠檬酸、酒石酸和苹果酸）或金属离子（Ni2+、Ca2+、Mn2+和Cr3+）对β - 二氧化锰氧化降解MBT的抑制作用。该研究将为理解天然土壤和沉积物中有机污染物与锰氧化物的相互作用提供一些新的见解。
