Improved PMS activation by natural sepiolite/Fe3O4 composite for effective tetracycline degradation: Performance, mechanism and degradation pathway

In this study, Fe3O4/sepiolite composites as peroxymonosulfate (PMS) catalysts were successfully synthesized via a simple water bath method for tetracycline (TC) degradation. The results indicated that the composite with 70% Fe3O4 loading amount exhibited the highest TC degradation efficiency (90.12%), and its reaction rate constant (0.02193 min−1) was around 2.07 times higher than that of pure Fe3O4. The enhanced catalytic activity was mainly attributed to the uniform deposition of Fe3O4 nanoparticles with smaller grain size (17.24 nm) on sepiolite, leading to the larger specific surface area (120.61 m2/g) and more exposed reaction active sites. The electron paramagnetic resonance (EPR) and quenching experiments displayed that 1O2 species played the predominant roles in TC degradation process. Besides, potential catalytic mechanisms and degradation pathways of TC were proposed. The toxicity of TC was reduced during the degradation process. Overall, this work can provide a new strategy for the rational design of promising mineral-based PMS catalyst for the wastewater treatment.