Sonocatalytic degradation of fluoroquinolone compounds of levofloxacin using titanium and zirconium oxides nanostructures supported on paper sludge/wheat husk-derived biochar

Abstract

The present study aimed at treating a water medium containing pharmaceutical compounds such as levofloxacin (LEV). For this purpose, ultrasound (US)-based degradation of LEV was catalyzed by TiO2 and ZrO2 nano-catalysts supported on biochar (BC). BC was obtained from a precursor composite of paper sludge and wheat husk. The application of BC-ZrO2 led to a degradation efficiency of 54.65% within 60 min. When BC-TiO2 was used, a lower degradation efficiency of 49.62% was obtained at the same reaction time. However, increasing the time to 120 min improved the sonocatalytic degradation of LEV by BC-TiO2 (72.88%) compared to that of BC-ZrO2 (66.42%). In the presence of H2O2 and S2O82−, the LEV degradation efficiency of US/BC-TiO2 increased from 72.88% to 87.98% and 94.03%, respectively, and for the US/BC-ZrO2 process, it increased from 66.42% to 76.79% and 90.14%, respectively. The addition of isopropanol caused the most suppressive effect on the sonocatalytic degradation of LEV for both US/BC-TiO2 (decreasing from 72.88% to 13.99%) and US/BC-ZrO2 (decreasing from 66.42% to 16.43%) processes. The reusability test results showed an approximately 20% reduction in the sono-reactor performance within three consecutive experimental runs with no substantial change in the functional groups of the as-prepared sonocatalyst. Intermediates of LEV decomposed by the two sonocatalytic processes were also identified.