CuFe3O4@ZIF-2 with oxygen vacancies and multiple reactive sites to efficiently activate peroxymonosulfate for levofloxacin degradation
Yan Zhao, Fenglin Tang, Caixia Deng, Kashif Nawaz Khattak, Lianfang Chen, Xiupei Yang
Abstract
In this work, CuFe 3 O 4 @ZIF-X (X = 1,2,3,4 and 5) composite catalysts with oxygen vacancies and multiple reactive sites were synthesized for the first time by Cu-doped Fe 3 O 4 -supported ZIF-X and used to efficiently activate PMS for levofloxacin (LEV) degradation. Influencing factors on LEV degradation were investigated, including the amount of CuFe 3 O 4 , pH, catalyst dosage, PMS concentration, coexisting inorganic anions and natural organic matter . In the presence of 1 mM PMS and 40 mg/L CuFe 3 O 4 @ZIF-2, 98% removal of LEV (10 mg/L) and 47% mineralization could be achieved within 10 min. The rate constants of CuFe 3 O 4 @ZIF-2/PMS were 2.9 times and 4.3 times those of ZIF and Fe 3 O 4 @ZIF, respectively. Further investigation found that the introduction of Cu-doped Fe 3 O 4 onto ZIF significantly ameliorates the problem of the reduced catalytic performance of magnetic MOFs due to the high saturation magnetization intensity and severe hindrance of the active sites. Then, the mechanism of LEV degradation, including radical and nonradical pathways, was expounded. Furthermore, the intermediates of LEV degradation were identified, and five possible degradation pathways were proposed. CuFe 3 O 4 @ZIF-2 demonstrated a decent catalytic performance even after five consecutive recycles and low metal ion leaching after LEV degradation, greatly improving the problem of secondary contamination.