Intensification of sonochemical decolorization of anthraquinonic dye Acid Blue 25 using carbon tetrachloride

In this work, the influence of CCl4 on the sonochemical decolorization of anthraquinonic dye Acid Blue 25 (AB25) in aqueous medium was investigated using high frequency ultrasound (1700 kHz). This frequency, reputed ineffective, was tested in order to introduce the ultrasound waves with high frequency in the field of degradation or removal of dyes from wastewater, due to its limited use in this field, and to increase the application of high frequency ultrasound wave in the field of environmental protection. The effects of various parameters such as the concentration of CCl4, frequency (22.5 and 1700 kHz), solution pH, temperature and tert-butyl alcohol adding on the decolorization rate of AB25 was studied. The obtained results clearly demonstrated the significant intensification of AB25 decolorization in the presence of CCl4. The enhancement effect of CCl4 increased by decreasing temperature and by increasing the CCl4 concentration. The pH has a significant influence on the bleaching of dye both in the absence and presence of CCl4. The three investigated dosimeter methods (KI oxidation, Fricke reaction and H2O2 production) well corroborate the improvement of the sonochemical effects in the presence of CCl4. The best sonochemical decolorization rate of AB25 in aqueous solution both in the absence and presence of CCl4 is observed to occur at 1700 kHz compared to 22.5 kHz. The sonochemical oxidation of CCl4 generates oxidizing species in the liquid phase that are highly beneficial for oxidation of hydrophilic and non-volatile pollutant, such as dyes, because they are less susceptible to free radical attack due to lower stability of the generated free radicals.