Synthesis of core-heteroshell structure for ZIF-67/VTM and its efficient activation of peroxymonosulfate in treatment of levofloxacin from an aqueous solution

A core-heteroshell structural magnetic composite of ZIF-67/Vanadium-titanium magnetite (VTM) was successfully synthesized through a feasible solvothermal method and efficiently used in activation of peroxymonosulfate (PMS) for the treatment of levofloxacin (LVF) in an aqueous solution. The catalytic activity of the ZIF-67/VTM composite in LVF degradation was thoroughly evaluated, demonstrating the LVF removal rate could reach up to 93.3% within 60 min at ZIF-67/VTM composite dosage of 100 mg/L, PMS concertation of 75 mg/L, and the natural pH of 6.4. It is quite interesting that the carbon organic skeleton (in the ZIF-67 shell) have accelerated the internal electron transformation rate of the ZIF-67/VTM composite, thus efficiently promoting the O–O band (in PMS) breakage and the redox cycle of cobalt, further favoring the free radicals generation. The quenching experiments and EPR analysis results demonstrated that ·SO4− would play a crucial role in the LVF degradation process. Surprisingly, we have found that the introduction of Cl− (at some certain dosage) would not always decrease the LVF degradation ratio, for a new reactive oxygen species (singlet oxygen) was emerged in this system. What's more, the ZIF-67 (as the wrapping structure) could stabilize the VTM (the inner structure) in changing reaction conditions, prompting a good adaptability at a wider pH range (3–10) for inhibiting the leaching of various metal ions into the aqueous solution. This novel ZIF-67/VTM composite could provide new ideas and routes for the removal of emerging pollutants from an aqueous solution.