The degradation of Direct Blue 71 by sono, photo and sonophotocatalytic oxidation in the presence of ZnO nanocatalyst

•The removal of DB71 dye was studied in association with color.•The yield decreased at the value of pH>2.5 in US oxidation.•DB71 removal efficiency increased with the increase of ZnO concentration in US oxidation.•The yield decreased as the dye concentration increased.•The amount of removed dye increased with the addition of H2O2 on US.•The yield increased with US/UV/ZnO and UV/ZnO processes. The sono, photo and sonophotacatalytic degradation of Direct Blue 71 (DB71) accompanied by heterogeneous ZnO catalysts were studied by using the ultrasonic power of 95W at 20kHz and aqueous temperature of 20°C within 20min. The effects of various experimental parameters such as the dye concentration, pH and amount of catalyst on the sonochemical degradation were also investigated. Sonochemical degradation of DB71 was strongly affected by initial substrate concentration, amount of catalyst and pH. Acidic pH was favored for the sonocatalytic degradation of DB71 using catalyst. The ultrasonic degradation of dye was enhanced by the addition of catalyst. In addition, the effects of H2O2 on sonolysis and sonocatalytic oxidation were studied, and it was found that H2O2 enhanced the degradation of dye. Then, the effect of ZnO on photo and sonophotocatalytic oxidation was also investigated, and it was found that UV/ZnO combination was a more effective treatment on DB71 dyestuff. The structure and morphology of the catalyst were investigated using scanning election microscopy (SEM) and XRD pattern.