Experimental Study of Dye Degradation in a Single-Jet Cavitation System

Fluid mechanical conditions are crucial for cavitation formation, and significantly influence chemical reactivity. This study investigates process conditions such as pressure, degassing, cavitation and reaction volume, and the sound emission of oxidative dye degradation by cavitation. For ensuring comparability and scalability, dimensionless similarity numbers aligned to the process were introduced. A further focus of the paper is reproducibility with corresponding guidelines. Measurements of dye degradation were carried out without additional chemicals. The oxidation process was assessed by the chemiluminescence of luminol. For this purpose, configurations with three nozzle sizes at different pressure differences were investigated. The generated cavitating jet was captured by imaging techniques and correlated to degradation. The most energy-efficient configuration was obtained by the smallest nozzle diameter of 0.6 mm at a pressure difference of 40 bar. Significant degassing occurred during cavitation. It was more pronounced with smaller nozzle diameters, correlating with higher degradation. Furthermore, discontinuous treatment methods can improve efficiency. Scaling to higher flow rates through multiple reactors in parallel proved more effective, compared to increasing the nozzle diameter or the pressure difference. For the same treated volume, two parallel reactors increased degradation by a factor of 1.35. The insights provide perspectives for optimizing jet cavitation reactors for water treatment.