School of Environment, Tsinghua University, Beijing 100084, China.
School of Environment, Tsinghua University, Beijing 100084, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Sci Total Environ. 2021 Sep 1;785:147328. doi: 10.1016/j.scitotenv.2021.147328. Epub 2021 Apr 25.
Manganese dioxide has been widely recognized as catalyst in catalytic ozonation for organic pollutants removal from wastewater in recent decades. However, few studies focus on the structure-activity relationship of MnO and catalytic ozonation mechanism in water. In the present study, the oxidative reactivity of three different crystal phases of MnO corresponding to α-MnO, β-MnO and γ-MnO towards metoprolol (MET) and ibuprofen (IBU) were evaluated. α-MnO was found to contain the most abundant oxygen vacancy and readily reducible surface adsorbed oxygen (O, O, OH), which facilitated an increase of ozone utilization and the highest catalytic performance with 99% degradation efficiency for IBU and MET. α-MnO was then selected to investigate the optimum key operating parameters with a result of catalyst dosage 0.1 g/L, ozone dosage 1 mg/min and an initial pH 7. The introduction of α-MnO promoted reactive oxygen species (O, O, OH) generation which played significant roles in IBU degradation. Probable degradation pathways of MET and IBU were proposed according to the organic intermediates identified and the reaction sites based on density function theory (DFT) calculations. The present study deepened our understanding on the MnO catalyzed ozonation and provided reference to enhance the process efficiency.
二氧化锰在过去几十年中被广泛认为是催化臭氧化去除废水中有机污染物的催化剂。然而，很少有研究关注 MnO 的结构-活性关系和水相中的催化臭氧化机制。在本研究中，评估了三种不同晶相的 MnO（α-MnO、β-MnO 和 γ-MnO）对美托洛尔（MET）和布洛芬（IBU）的氧化反应性。发现 α-MnO 含有最丰富的氧空位和易于还原的表面吸附氧（O、O、OH），这促进了臭氧利用率的提高和最高催化性能，对 IBU 和 MET 的降解效率达到 99%。然后，选择 α-MnO 来研究最佳的关键操作参数，结果表明催化剂用量为 0.1 g/L，臭氧用量为 1 mg/min，初始 pH 值为 7。α-MnO 的引入促进了活性氧物种（O、O、OH）的生成，这对 IBU 的降解起着重要作用。根据鉴定的有机中间体和密度泛函理论（DFT）计算的反应位点，提出了 MET 和 IBU 的可能降解途径。本研究加深了我们对 MnO 催化臭氧化的理解，并为提高该过程的效率提供了参考。
