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

Abstract

• 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 H 2 O 2 , 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 H 2 O 2 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.