Enhanced degradation of bisphenol A by mixed ZIF derived CoZn oxide encapsulated N-doped carbon via peroxymonosulfate activation: The importance of N doping amount.

In this study, mixed metal cobalt zinc oxide embedded nitrogen enriched porous carbon composites (CoZnO-PC) were prepared via pyrolyzing polyvinylpyrrolidone (PVP) encapsulated Co, Zn-bimetal centered zeolitic imidazolate frameworks (ZIF). The prepared composites were then used to activate peroxymonosulfate (PMS) for bisphenol A (BPA) removal in water. When mole ratio of Co/Zn was 2/1, the resulted CoZnO-PC possessed spinel structure with prominent degradation capability, in which the introduction of Zn accelerated the PMS activation performance of Co through establishing bimetal synergistic interactions. Both radical and non-radical activation pathways were existed in the CoZnO-PC/PMS system, in which CoZnO dominated the radical pathway whereas PC dominated the non-radical way. Since PVP contained abundant nitrogen atoms and could form strong coordination interactions with the ZIF precursor, the introduction of PVP in the ZIF precursor prevented pore collapsing during pyrolysis process, as well as enhancing the nitrogen content in the pyrolzed composites, which significantly promoted the generation of singlet oxygen. With combined pathways, the CoZnO-PC/PMS system showed a wide pH application range with promising mineralization rate. Meanwhile, the spinel-structured CoZnO-PC was magnetically separable with desirable recyclability. This study presents a novel composite with remarkable performance for the removal of refractory organic pollutants in municipal wastewater.