(2021) Journal of Environmental Chemical Engineering_Enhanced reduction of bromate in water by 2-dimensional porous Co₃O₄ via catalytic hydrogenation

Tuan D.D., Yang H., Huy N.N., Kwon E., Khiem T.C., You S., Lee J., Lin K.-Y.A.

(Elsevier Ltd) Journal of Environmental Chemical Engineering ISSN: 22133437 Vol.9 Issue.5 Article No.105809 DOI: 10.1016/j.jece.2021.105809

As catalytic hydrogenation is validated as one of the most useful approach to reduce a potential carcinogenic bromate in water, the usage of continuous purge H₂ gas and precious metal catalysts are typically required, making it less feasible for practical implementation. Since sodium borohydride (NaBH₄) represents a potential alternative source for releasing H₂ and non-precious metal catalysts (cobalt (Co)) are usually required to accelerate the hydrolysis of NaBH4 for faster H₂ production, the combination between Co-based catalysts and NaBH₄ could be favorable for bromate hydrogenation. Especially, it is even more advantageous to fabricate a porous heterogeneous catalyst with high surface area. Thus, this study aims to construct such a novel porous heterogeneous catalyst for reducing bromate using sodium borohydride. Herein, a Co-coordinated framework with TMC ligand (CoTMC) is employed as precursor, which is then transformed into hexagonal porous Co₃O₄ (HPCO) via one-step calcination. The resultant HPCO possesses remarkable surficial oxygen vacancies as well as textural properties in comparison with Co₃O₄ NP. Importantly, HPCO could completely reduce bromate to bromide within 20 min. The calculated bromate removal capacity using HPCO and NaBH4 is achieved as 781.25 μmol/g, and the activation energy (Ea) is also calculated as 28.5 kJ/mol. Besides, HPCO also exhibits high catalytic activities for bromate reduction in the presence of various anions. Moreover, HPCO could be also reusable for reducing bromate to bromide over multiple-cycles without any remarkable change of catalytic activities. These features indicate that HPCO is a robust and effective heterogeneous catalyst for bromate reduction in water. © 2021 Elsevier Ltd

This work is supported by the Ministry of Science and Technology (MOST) (110-2636-E-005-003-), Taiwan, and financially supported by the “Innovation and Development Center of Sustainable Agriculture” from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE), Taiwan. The authors gratefully acknowledge the use of SQUID000200 of MOST110-2731-M-006-001 belonging to the Core Facility Center of National Cheng Kung University.