Enhancement of levofloxacin degradation in US/H2O2 system by addition of fly ash

The intensification of levofloxacin degradation in ultrasonic/H2O2/fly ash combined system was studied. The experimental parameters such as fly ash adding amount, H2O2 concentration, pH value and levofloxacin initial concentration on degradation efficiency were evaluated. The results indicated that when compared with single sonolysis, H2O2 oxidation, ultrasonic/H2O2 and fly ash/H2O2 binary systems, levofloxacin degradation was markedly promoted in ultrasonic/H2O2/fly ash ternary system. Levofloxacin degradation in ultrasonic/H2O2/fly ash system followed apparent first-order kinetics. The removal efficiency for 20 mg/L levofloxacin under fly ash adding amount of 1.5 g/L, H2O2 concentration of 15.0 mmol/L, pH 7.16, and ultrasonic power of 325 W could achieve 99.12% within 160 min treatment, whereas TOC removal only attained 17.37%. Fluorescence probe analysis indicated that the combination of ultrasonic/H2O2/fly ash enhanced the heterogeneous Fenton-like reaction on fly ash surface. HPLC/MS/MS analysis revealed that three intermediates were generated, which derived from demethylation of the piperazinyl ring, the transformation of the quinolone moiety through the loss of C2 and attack of quinolone moiety by ·OH.