Wustite as a catalyst source for water remediation: Differentiated antimicrobial activity of by-products, action routes of the process, and transformation of fluoroquinolones

Wustite under simulated solar irradiation with addition of H2O2 was used to treat enrofloxacin and levofloxacin in water. Wustite was characterized, showing 2.1 eV of bandgap and species of Fe3+ on the surface that favor its catalytic ability. The effect of light intensity, wustite dose, concentration of H2O2, and pH on the removal of antimicrobial activity (AA, against S. aureus and E. coli), was tested, finding as suitable conditions: [intensity]: 500 W m(-2), [wustite]: 10 mg L-1, [H2O2]: 1.0 mmol L-1, and pH 6.5. Under such conditions, up to 100% of AA elimination occurred at 180 min of treatment. The Light-Wustite-H2O2 system involved, the action of light, O-2(& BULL;-), O-1(2), and HO & BULL;, where wustite acted as a semiconductor and a catalyst for heterogeneous photo-Fenton. Furthermore, this system mineralized 21% of ENR, and the wustite catalyst promoted 100% of AA removal up to the fourth reuse cycle. Interestingly, the application of Light-Wustite-H2O2 to an actual effluent led to complete AA removal after 180 min treatment. The process action on ENR generated six stable products, exhibiting the loss of the fluorine atom (induced by light directly) and modifications on the ethyl-piperazyl group (reactive region according to calculations of atomic charge) by radical attacks. The relationship between the AA and structural transformations showed that those products that retained quinolone and piperazyl moieties had AA.