The formation of hydroxyl radicals during hydrodynamic cavitation in microfluidic reactors using salicylic acid dosimetry

Maleki, Mohammadamin (author), Talabazar, Farzad Rokhsar (author), Davoudian, Salar Heyat (author), Dular, Matevž (author), Koşar, Ali (author), Petkovšek, Martin (author), Šmid, Alenka (author), Zupanc, Mojca (author), Ghorbani, Morteza (author)

Cavitation is a phase change phenomenon that generates highly energized bubbles due to low local pressures. The collapse of these bubbles releases this energy to the surrounding area in different forms upon the pressure recovery. Free radical production, which is considered as chemical effect of the bubble collapse, plays a major role in many applications, from wastewater treatment to material exfoliation. Although some studies underscore the importance of chemical effects for acoustic cavitation (AC), their investigations in hydrodynamic cavitation (HC) are challenging due to the difficulty in controlling cavitating flows. One of the approaches that could shed light on this challenging aspect is to shrink the reactor scale to micro-scale size (“HC on a chip”). In this regard, we investigated the chemical effects of HC using Salicylic Acid (SA) dosimetry in three different micro-scale designs (long diaphragm, micro-orifice, and micro-venturi configurations) and compared the results to those of a macro-scale HC reactor. High-speed visualization revealed important links between flow patterns and the formation of hydroxyl radicals (•OH), which contributed to the SA products. This study thus focused on comparing the effectiveness of the three micro-scale reactors in terms of •OH formation. According to the results, the “HC on a chip” concept demonstrated significantly higher efficiency in generating SA products compared to the macro-scale HC reactor. For instance, the micro-scale HC reactors achieved an SA concentration of approximately 0.6 μg/mL in just 5 cycles, while the macro-scale HC reactor required 164 cycles to reach a similar concentration (0.45 μg/mL). This substantial reduction in the number of cycles highlights the potential of micro-scale HC reactors for efficient and rapid generation of SA products.

• Language: English
• Keywords: hydrodynamic cavitation, microfluidic reactors, chemical effects, hydroxyl radical, salicylic acid
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering; FFA - Faculty of Pharmacy
• Publication status: Published
• Publication version: Author Accepted Manuscript
• Year: 2025
• Number of pages: 12 str.
• Numbering: Vol. 511, art. 161976
• PID: 20.500.12556/RUL-168390
• UDC: 532.528:66
• ISSN on article: 1873-3212
• DOI: 10.1016/j.cej.2025.161976
• COBISS.SI-ID: 230634243
• Publication date in RUL: 11.04.2025

Record is a part of a journal

• Title: Chemical engineering journal
• Publisher: Elsevier
• ISSN: 1873-3212
• COBISS.SI-ID: 23123973

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: hidrodinamska kavitacija, mikrofluidika, kemijski učinki, salicilna kislina, hidroksilni radikal