Enhanced reduction of bromate in water by 2-dimensional porous Co3O4 via catalytic hydrogenation

Abstract

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.