(2021) Separation and Purification Technology_Catalytic reduction of bromate by Co-embedded N-doped carbon as a magnetic Non-Noble metal hydrogenation catalyst

Li B.-C., Yang H., Kwon E., Dinh Tuan D., Cong Khiem T., Lisak G., Xuan Thanh B., Ghanbari F., Lin K.-Y.A.

(Elsevier B.V.) Separation and Purification Technology ISSN: 13835866 Vol.277 Issue. Article No.119320 DOI: 10.1016/j.seppur.2021.119320

While catalytic hydrogenation of bromate represents a useful technique for eliminating carcinogenic bromate, expensive noble-metal catalysts and excessive H₂ gas are usually required, impeding large-scale implementation of this technique. As borohydride is an alternative source for releasing H₂ in a more controllable way and non-noble metal catalysts (e.g., Co) can catalyze hydrolysis of borohydride to generate H₂, it is promising to employ Co and borohydride for hydrogenation of bromate. Moreover, it is even more practical to develop heterogeneous catalysts with magnetism for easier handle and recovery of catalysts. Therefore, the aim of this study is to develop such a magnetic heterogeneous catalyst for bromate reduction by using borohydride. Herein, a special Co-based catalyst is fabricated by transforming Co-substituted prussian blue analogue into Co-embedded N-doped carbon (Co@NC) composite through carbonization. Co@NC also exhibits a higher catalytic activity for reducing bromate than the commercial Co₃O₄ as Co@NC could accelerate hydrolysis of NaBH₄ to generate H₂ gas much faster. The activation energy (Ea) of bromate reduction by Co@NC is also much lower than the reported Ea. Co@NC could still completely remove bromate and reduce it to bromide under alkaline conditions, and Co@NC also exhibit a very high selectivity towards bromate reduction in the presence of other anions. Moreover, Co@NC could be also reused for multiple-cycles to continuously reduce bromate to bromide. These features demonstrate that Co@NC is certainly an advantageous and convenient heterogeneous catalyst for reducing bromate in water. © 2021

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.