Hu Jingze, Li Yiming, Nan Shaoshuai, Yoza Brandon A, Li Yifan, Zhan Yali, Wang Qinghong, Li Qing X, Guo Shaohui, Chen Chunmao
State Key Laboratory of Petroleum Pollution Control, China University of Petroleum-Beijing, Beijing, China.
Hawaii Natural Energy Institute, University of Hawaii at Manoa, Honolulu, HI, United States.
Front Chem. 2020 Feb 12;8:80. doi: 10.3389/fchem.2020.00080. eCollection 2020.
Catalytic ozonation process (COP) is considered as a cost-efficient technology for the treatment of refractory chemical wastewaters. The catalyst performance plays an important role for the treatment efficiency. The present study investigated efficiencies and mechanisms of manganese (Mn)-based Y zeolites in COPs for removing nitrobenzene from water. The catalysts of Mn/NaY and Mn/USY were prepared by incipient wetness impregnation, while Mn-USY was obtained by hydrothermal synthesis. Mn-USY contained a greater ratio of Mn than Mn/NaY, and Mn/USY. Mn oxides loaded on Y zeolites promoted the COP efficiencies. Mn/NaY increased total organic carbon removal in COP by 7.3% compared to NaY, while Mn/USY and Mn-USY increased 11.5 and 15.8%, respectively, relative to USY in COP. Multivalent Mn oxides (Mn, Mn, and Mn) were highly dispersed on the surface of NaY or USY, and function as catalytic active sites, increasing mineralization. Mn-USY showed the highest total organic carbon removal (44.3%) in COP among the three catalysts, because Mn-USY had a higher ratio of Mn to the total Mn oxides on the surface than Mn/NaY and Mn/USY and the catalytic effects from intercorrelations between Mn oxides and mesoporous surface structures. The hydroxyl radicals and superoxide radicals governed oxidations in COP using Mn-USY. Nitrobenzene was oxidized to polyhydroxy phenol, polyhydroxy nitrophenol, and p-benzoquinone. The intermediates were then oxidized to small organic acids and ultimately carbon dioxide and water. This study demonstrates the potential of Y zeolites used in COP for the treatment of refractory chemical wastewaters.
催化臭氧化工艺（COP）被认为是一种处理难降解化学废水的经济高效技术。催化剂性能对处理效率起着重要作用。本研究考察了基于锰（Mn）的Y型沸石在催化臭氧化工艺中从水中去除硝基苯的效率和机理。通过初湿浸渍法制备了Mn/NaY和Mn/USY催化剂，而通过水热合成法获得了Mn-USY。Mn-USY中Mn的比例高于Mn/NaY和Mn/USY。负载在Y型沸石上的锰氧化物提高了催化臭氧化工艺的效率。与NaY相比，Mn/NaY使催化臭氧化工艺中的总有机碳去除率提高了7.3%，而与催化臭氧化工艺中的USY相比，Mn/USY和Mn-USY分别提高了11.5%和15.8%。多价锰氧化物（Mn²⁺、Mn³⁺和Mn⁴⁺）高度分散在NaY或USY表面，并作为催化活性位点，提高了矿化程度。在三种催化剂中，Mn-USY在催化臭氧化工艺中表现出最高的总有机碳去除率（44.3%），因为Mn-USY表面Mn与总锰氧化物的比例高于Mn/NaY和Mn/USY，且锰氧化物与介孔表面结构之间的相互关联产生了催化作用。在使用Mn-USY的催化臭氧化工艺中，羟基自由基和超氧自由基主导氧化反应。硝基苯被氧化为多羟基苯酚、多羟基硝基苯酚和对苯醌。这些中间体随后被氧化为小有机酸，最终氧化为二氧化碳和水。本研究证明了Y型沸石在催化臭氧化工艺中处理难降解化学废水的潜力。
