## 3 Results
### The Use of Ultrasound for Dye Removal  
The process using acoustic waves resulted in low efficiency in removing the analyzed dyes (Figures 4 and 5). Using an acoustic wave intensity of 3.02 W/cm\({}^{2}\), after 30 min, the removal of Indigo Carmine was 9.5%, Tartrazine was 9.1%, and Allura Red AC was 3.5%. Figure 3: The effect of catalyst dose on the removal of Indigo Carmine. Figure 2: The effect of UV on the removal of selected dyes. Increasing the acoustic wave intensity to 5.16 W/cm\({}^{2}\) led to an increase in the removal efficiency of Indigo Carmine to 15%, while the efficiency for the other two dyes decreased to 5.4% and 2% for Tartrazine and Allura Red AC, respectively. No statistically significant difference was observed at different time points. [PERSON] et al. (2016) [PERSON] et al. (2016), using ultrasound with a vibration amplitude of 100% and a frequency of 26 kHz, at 200 watts power, achieved a removal of Indigo Carmine of 39.4% after 4 h from an initial concentration of 50 ppm. The removal efficiency using ultrasound typically increases when combined with advanced oxidation processes. However, the introduction of H\({}_{2}\)O\({}_{2}\) into the system generally resulted in a decrease in the dye removal efficiency of aqueous solutions. The removal of Allura Red AC using acoustic waves at 3.02 W/cm\({}^{2}\), after the introduction of hydrogen peroxide, increased by just over 5%. At higher concentrations, hydrogen peroxide can lead to an increase in the viscosity of the solution due to its chemical properties, such as  
Figure 4: The effect of ultrasound (A = 20%) on the removal of selected dyes. Figure 5: The effect of ultrasound (A = 50%) on the removal of selected dyes. the formation of hydrogen bonds between hydrogen peroxide molecules. In the case of lower, working concentrations, the change in viscosity is typically minimal. However, in more complex processes like cavitation, this can influence the dynamics of the process. The increase in viscosity may reduce the effectiveness of acoustic cavitation because it slows down the fluid flow and decreases the ability to form intense cavitation bubbles, which are crucial for the efficiency of this process. Additionally, the reduced intensity of cavitation may lead to a decrease in the local temperature and a reduction in the number of thermally generated radicals, which impacts the overall efficiency of the process. The decomposition under the influence of ultrasound mainly occurs due to acoustic cavitation effects. Intense ultrasonic waves cause the formation and collapse of bubbles in the liquid, generating locally extreme conditions (high pressure and temperature). The achievement and exceeding of a certain threshold of ultrasonic intensity (the cavitation threshold) are prerequisites for the occurrence of cavitation in a solution. The development of cavitation in a liquid medium is associated with a minimum intensity threshold in the range of 1.0-2.0 W/cm\({}^{2}\). The presence of solid, liquid, or gaseous impurities causes a reduction in the value required to induce cavitation. In completely degassed liquids, free from solid impurities, cavitation virtually does not occur [4; 5; 8]. In the case of ultrasound application, the molecular form of a substance plays a significant role, as pollutants in this form have a greater chance of undergoing thermal degradation under these conditions, unlike ions, which may be more chemically stable in such extremes. Ions in solution are surrounded by a hydration layer, which acts as a protective barrier, preventing the direct interaction between -OH radicals and the dye molecule. Additionally, ultrasonic cavitation generates extreme local conditions, where the molecular form absorbs energy more effectively than the ionic form, facilitating the breakdown of chemical bonds [4; 5; 8; 14]. Indigo Carmine, Tartrazine, and Allura Red AC are anionic dyes that exist in ionic form at neutral pH (5.5).