Non-radical-dominated catalytic degradation of bisphenol A by ZIF-67 derived nitrogen-doped carbon nanotubes frameworks in the presence of peroxymonosulfate

Abstract

Nitrogen-doped carbon materials have been one of the most remarkable families of materials with promising applications in many fields. In this study, a series of nitrogen-doped carbon nanotubes frameworks (NCNTFs) with distinguishable nitrogen content and graphitization degree have been successfully prepared through in situ transformation of ZIF-67 under N2/H2 atmosphere at different pyrolysis temperature. Compared with conventional nitrogen-doped carbon materials derived from metal-organic frameworks, the formation of intertwined carbon nanotubes harvests desirable mesoporous structure that is favorable for the mass transfer and diffusion of reaction substances. When they are applied for catalytic degradation of Bisphenol A (BPA) in the presence of peroxymonosulfate (PMS), NCNTFs-800 (pyrolyzed at 800 °C) promises higher BPA removal efficiency than its counterparts from other pyrolysis temperature, as well as porous carbon derived from ZIF-8. Radical-quenching tests and electron paramagnetic resonance measurements verify that non-radical process (1O2) dominates BPA degradation over NCNTFs-800, and some common radicals (such as OH, SO4− and O2−) only play auxiliary roles. It is believed that the good balance between surface graphitic nitrogen sites and graphitization degree is responsible for the enhanced catalytic performance, and facilitates electron transfer from BPA to PMS to induce the non-radical pathways. Besides, some potential influential factors, including catalyst/Oxone dosage and reaction temperature are investigated, and the effects of anions, humic acid, and actual wastewater on BPA degradation are also elucidated in detail. Finally, several intermediates are identified by GC–MS analysis and the possible degradation pathways are deduced tentatively.