Sonochemical degradation of ciprofloxacin by hydrogen peroxide and persulfate activated by ultrasound and ferrous ions

This paper evaluates the use of various oxidation methods such as ultrasonic/persulfate (US/PS), ultrasonic/ hydrogen peroxide (US/H2O2), US/H2O2/Fe2+, US/PS/Fe2+, and the US/PS/H2O2/Fe2+ process and compares their potential in removal of ciprofloxacin (CIP). The results showed that US/PS/H2O2/Fe2+, was the most efficient among the studied processes. In US/PS/H2O2/Fe2+, 100% removal of CIP was achieved at pH 3 and 50 min of treatment when the initial concentration of CIP, H2O2, PS and Fe2+ were 25 mg/L, 4 mM, 6 mM and 1 mM, respectively. The results showed that with increasing ultrasonic power and increasing concentrations of H2O2, PS, and Fe2+, the removal percentage increases. Toxicity of CIP solution was scrutinized by Daphnia magna, and the US/PS/H2O2/Fe2+ process was able to provide toxicity elimination of 100% for the solution. Also, the equilibrium data for all processes followed first-order kinetics with a regression coefficient above 0.9, and the reaction rate constant for the US/PS/H2O2/Fe2+ process was higher than other systems. At 60 min of sonochemical time, the energy consumptions by US/PS, US/H2O2, US/H2O2/Fe2+, US/PS/Fe2+, and US/PS/H2O2/ Fe2+ were 105.5, 87.5, 64.7, 41.4 and 16.2 kWh/m(3), respectively, suggesting the last one as the most economical. Additionally, for the processes combined with the iron, biochemical oxygen demand/chemical oxygen demand (BOD5/COD) in the CIP solution was above 0.4, which indicated the conversion of non biodegradable wastewater to biodegradable form. The total organic carbon (TOC) test was performed, and the mineralization percentage by the US/PS/H2O2/Fe2+ process was 82%. Studies conducted for evaluating the effect of scavengers also showed that both sulfate (SO4 center dot-) and hydroxyl ((OH)-O-center dot) radicals play an important role in the studied process.