Introduction of ZIF-67 shell in NiCo2O4 nanocage to enhance peroxymonosulfate activation based on nonradical pathway for effective removal of organic contaminant

It is of great significance to rationally regulate the activation mechanism of peroxymonosulfate for wastewater treatment. Herein, for the first time, a newly-constructed NiCo2O4@ZIF-67 core–shell nanocage was employed as a mediator for effective removal of tetracycline (TC). As-prepared NiCo2O4@ZIF-67 displayed reduced charge transfer resistance and enhanced electron transfer rate. Importantly, more than 99.58% of TC can be degraded within 30 min by developed NiCo2O4@ZIF-67/PMS system, and the removal efficiency of TOC was as high as 72.81%. Moreover, antimicrobial tests revealed the low toxicity or non-toxic of degradation products. More interestingly, after coating ZIF-67 film on the surface of NiCo2O4, the electron transfer process among PMS, contaminant and catalyst was enhanced. The radical and nonradical pathways worked in coordination each other and achieved the rapid removal of various organic pollutants. The ZIF-67-derived NiCo2O4 core dominated the generation of reactive oxygen species, while the coated ZIF-67 shell induced the electron transfer from TC to PMS. Besides, the introduction of ZIF-67 not only improved the anti-interference for inorganic anions, but also boosted the water stability, thereby resulting in that NiCo2O4@ZIF-67 still remained great catalytic performance after repeated use for several times. In short, current work shared a promising approach for wastewater treatment.