Design of a novel magnetic composite catalyst with highly efficient cobalt circulation for activating peroxymonosulfate to degrade tetracycline

Abstract

In this study, a magnetic CoFe2O4/Co2O3/Na-X Zeolite (CFCOZ) composite catalyst was prepared via a co-precipitation hydrothermal method. Comprehensive characterizations suggest that the porous shell layer composed of CoFe2O4 and Co2O3 nanoparticles is evenly supported on Na-X zeolite. The specific surface area of CFCOZ is 266.93 m2/g. CFCOZ was exploited to catalyze peroxymonosulfate (PMS) to degrade tetracycline (TC). Catalytic degradation experiments indicated that the TC removal rate in the PMS/CFCOZ system was higher than that in the CoFe2O4/zeolite/PMS oxidation system. The highest degradation rate reached 96.6 % ([PMS] = 1 mM, 0.2-g/L CFCOZ, [TC] = 20 mg/L, initial pH = 7, room temperature). Several influence factors were investigated, including initial solution pH, PMS concentration, and CFCOZ dosage, etc. on the TC degradation. Electron paramagnetic resonance spectroscopy and reactive species scavenging experiments showed that 1O2, SO4−, and O2− played the predominant role in the TC removal. The possible catalytic degradation mechanism was proposed. It is found that CoFe2O4 and Co2O3 could synergistically activate PMS, and enhance the circulation efficiency between Co2+ and Co3+ to promote the generation of ROS. The cyclic experiments and characterization results between the fresh and the used CFCOZ showed its continuous catalytic activity and good structural stability.