Cooperation of multi-walled carbon nanotubes and cobalt doped TiO₂ to activate peroxymonosulfate for antipyrine photocatalytic degradation

A hybrid catalyst system consisted of MWCNT and Co-TiO₂ through simple physical mixing was applied for peroxymonosulfate activation for antipyrine degradation. With 2 mM peroxymonosulfate, the removal rate of antipyrine is significantly increased from 53.24% and 86.23% to 100% in the presence of same weight of 0.2 g/L MWCNTs, Co-TiO₂, and MWCNTs/Co-TiO₂ (half/half) mixture, respectively in 12 min. The influence of various parameters, including the ratio of Co-TiO₂/MWCNT, catalyst dose, peroxymonosulfate dose, antipyrine concentration, and initial pH, were further investigated in detail. The underlying catalytic mechanism of the synergistic effect was unraveled by quenching tests and EPR analysis. It was attributed to the electrons tranferration between Co-TiO₂ and MWCNT, and the acceleration of Co³⁺/Co²⁺ by generated superoxide. This work not only provides a novel and efficient method of pharmaceutical wastewater treatment, but also reveals a new perspective to use the catalyst more efficiently.