Intensified degradation of Acid Violet 7 dye using ultrasound combined with hydrogen peroxide, Fenton, and persulfate

•First detailed study into ultrasound induced decolorization of acid violet 7 containing effluent.•Establishing the optimum operating parameters for both individual and combined approaches.•Ultrasound + Fenton is the best treatment approach resulting in complete removal.•Hydroxyl radicals are more effective as compared to the sulphate radicals for acid violet 7 removal.•Kinetic analysis and quantifying the mineralization of the effluent. In the present work, the sonochemical degradation of an acid dye, acid Violet-7, has been investigated using an ultrasonic bath at an working volume as 1 L. Effect of ultrasonic power, treatment time, temperature, pH, ultrasonic frequency, initial concentration, and combination with oxidants such as H2O2, Fenton’s reagent and persulfate on the decolorization has been studied. The results showed that lower dye concentration, acidic conditions and lower temperature (20 ˚C) favored the decolorization for the only ultrasound approach. The maximum extent of decolorization for only ultrasound based process was 76.3% under conditions of 20 ppm dye concentration, 100 W power, pH 3 and 40 kHz frequency. For the combination approaches, maximum effect was seen for Fenton reagent where the combination of US + Fenton resulted in almost 100% decolorization and extent of COD reduction as 80.9%. Combinations of ultrasound and H2O2 or ultrasound and KPS demonstrated comparatively lower efficacy compared to US + Fenton. Kinetic studies were also performed for various treatment approaches. It has been clearly elucidated that ultrasound in combination with optimized loading of Fenton reagent are effective in treating Acid Violet-7 dye containing effluents.