Correlation of sonochemical activities measured via dosimetry and an area-selective analysis of sono(chemi)luminescence†

Abstract

Ultrasonic industrial applications require theoretical support and practical guidance from a comprehensive understanding of sonochemical reaction dynamics. The influence of acoustic factors (frequency and pressure amplitude) and external parameters (liquid height) on sonochemical activity were researched. The phenomenon of sonoluminescence (SL), sonochemiluminescence (SCL) and potassium iodide (KI) dosimetry were investigated at 114 different settings. The settings included electrical loading-power of 10, 20, 30, and 40 W, 10 frequencies ranging from 22 to 2000 kHz, and reactor volumes of 200, 300, and 400 ml. A new area selection image processing technique was used to conduct a systematically quantitative analysis of SL and SCL across a broader frequency range. The sonochemical activity could be categorised into three zones based on the ultrasonic frequency (22 to 2000 kHz): f < 200 kHz, 200 kHz ≤ f ≤ 1000, and 1000 kHz ≤ f ≤ 2000 kHz. The Pearson and Spearman correlation coefficients were used to discuss the correlation between SL, SCL, reactive oxidant species (ROS) and hydrogen peroxide yields. The findings indicate that the influence of liquid height on cavitation activity within the reactor is mostly manifested in the power density. The ultrasonic oxidation capacity (as indicated by the yield of ROS) exhibits a strong positive relationship with SL intensity. A divergence of correlation between SL and I₃⁻ yield was observed. There was a lack of correlation between sonochemical activities (e.g. SCL and ROS yield). The poor correlation highlighted the importance of considering chemical mechanisms and reaction locations concerning the collapsing bubble.