Activation of peroxydisulfate by magnetic MoS2/CoFe2O4 composite catalyst for efficient degradation of tetracycline in water

Persulfate-based advanced oxidation process (PS-AOPs) is a promising technique for removing antibiotic contaminants from water. Magnetic MoS2/CoFe2O4 nanocomposites were synthesized by a hydrothermal method and first used to activate peroxydisulfate (PDS) to degrade tetracycline (TC). The optimal MoS2/CoFe2O4-20 catalyst achieved 96.2% degradation efficiency of TC (20 mg L-1) in the presence of PDS (1.5 g L-1) after 80 min, which was significantly higher than that of pure MoS2 and CoFe2O4. Moreover, MoS2/CoFe2O4 catalysts exhibited a better catalytic activity for TC removal by activating PDS than that of recently reported ferrite-based catalysts. The influence of initial pH, PDS dosage and inorganic anions on the removal of TC in MoS2/CoFe2O4-20/PDS oxidation system was studied. The quenching experiments and electron paramagnetic resonance (EPR) experiments show that the free radical (O-2(center dot-), SO4 center dot- and center dot OH) and non-radical (O-1(2)) oxidation pathways collectively led to TC degradation in MoS2/CoFe2O4/PDS system. The exposed Mo(IV) sites on the surface of MoS2 can accelerate the cycle equivalent to X(III)/ equivalent to X(II) (X = Co or Fe) and the decomposition of PDS to generate the reactive species, thus enhancing the removal efficiency of TC. Cycling test confirms that as-synthesized MoS2/CoFe2O4 can be easily recovered and effectively reused. Besides, the removal of TC from various water matrices was also studied.