Catalytic Ozonation of Nitrobenzene by Manganese-Based Y Zeolites

Jingze Hu; Yiming Li; Shaoshuai Nan; Brandon A Yoza; Yifan Li; Yali Zhan; Qinghong Wang; Qing X Li; Shaohui Guo; Chunmao Chen

doi:10.3389/fchem.2020.00080

Catalytic Ozonation of Nitrobenzene by Manganese-Based Y Zeolites

Front Chem. 2020 Feb 12:8:80. doi: 10.3389/fchem.2020.00080. eCollection 2020.

Authors

Affiliations

¹ State Key Laboratory of Petroleum Pollution Control, China University of Petroleum-Beijing, Beijing, China.
² Hawaii Natural Energy Institute, University of Hawaii at Manoa, Honolulu, HI, United States.
³ Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI, United States.

Abstract

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 Mn²⁺ 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 (Mn²⁺, Mn³⁺, and Mn⁴⁺) 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 Mn²⁺ 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.

Keywords: Mn oxides; Y zeolites; catalytic ozonation; ozonation; wastewater treatment.