Synergetic effect of photocatalysis and peroxymonosulfate activated by MFe2O4 (M = Co, Mn, or Zn) for enhanced photocatalytic activity under visible light irradiation

Nanosized MFe2O4 (M = Co, Mn, or Zn) photocatalysts were synthesized via a simple sol-gel method. MFe2O4 photocatalysts exhibited lower photocatalytic activity for the degradation of levofloxacin hydrochloride under visible light irradiation. For enhancement of photocatalytic activity, MFe2O4 was used to activate peroxymonosulfate and degrade levofloxacin hydrochloride under visible light irradiation. The influences of peroxymonosulfate dosage, levofloxacin hydrochloride concentration, pH value, and temperature on peroxymonosulfate activation to degrade levofloxacin hydrochloride were investigated in detail. The mechanism of activation of peroxymonosulfate by MFe2O4 was proposed and proved by radical quenching experiments, electron spin resonance analysis, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and transient photocurrent responses. The combined activation effects of photogenerated e-/h+ and transition metals on peroxymonosulfate to produce sulfate radical clearly enhanced the degradation efficiency.