ZIF-67/melamine derived hollow N-doped carbon/Co9S8 polyhedron to activate peroxymonosulfate for degradation of tetracycline

A N-doped carbon-wrapped Co9S8 catalyst (N-C/Co9S8) was prepared in this work by pyrolysis sulfurized-ZIF-67 and melamine mixture. The prepared catalyst was used to degrade tetracycline (TC) with peroxymonosulfate (PMS) as oxidant. The optimized catalyst could remove 96.8 % TC in 15 min with a rate constant of 0.196 min(-1). The degradation mechanism, intermediates, and possible pathway were discussed. It was found that pyridinic N, Co-N, Co species, S2-, C-S-C, and C-SOx were active sites to activate PMS. The N-doped carbon (N-C) could facilitate electron transfer. The surface-bound (OH)-O-center dot, SO4 center dot-, and O-center dot(2)- radicals, especially O-1(2) and electron transfer mechanism contributed to TC degradation. The effects of solution pH, inorganic ions and humic acid on TC degradation were discussed. This study might prompt the development of other ZIF-67-derived sulfides for environmental remediation.