The phenomenon of cavitation is currently one of the most researched processes to support many classical approaches used in chemical and environmental engineering. The ability to concentrate high energy and pressure while significantly increasing mass transfer, mainly through the formation of microcirculations, has already been utilized for water and wastewater treatment in advanced oxidation processes (AOPs) based on cavitation. Currently most studies focus on typical Venturi tube or orifice cavitation systems. These systems, which mainly contain a constriction in the treatment line, force a high recirculation rate of the treated medium – 50 to even 200 cycles are required for an effective degradation of the pollutants. In contrast, the current project relates to unique studies of cavitation phenomena in micro-channels and micro-channel arrays that allow cavitation effects to be intensified by taming cavitation bubbles in a controlled environment in multiple parallel lines. To study such systems, a detailed research plan includes tasks related to the design and characterization of such cavitation zones; a detailed analysis of the fundamentals of cavitation occurring in micro-channels; the definition of optimal conditions and behavior of the liquid and gaseous phase; the study of the differences between micro- and macrocavitation in terms of phase behavior, oxidant’s activation, radical’s formation, and organic pollutant degradation mechanisms. Several important insights will be gained in this project that will have a strong impact on future studies in this area. These include the knowledge and visualization of cavitation generated in micro-channels and procedural approaches to describe and optimize the phenomenon, and the description of the mechanisms of oxidant’s activation, radical’s formation, and organic pollutant degradation. The results of this project should also be useful for further studies on the application character of Cav-Micro reactors. It is expected that at least 6 milestone papers will be published in high-ranking JCR journals. These papers will provide basic knowledge, rules, and methods for conducting further studies in this field. It is therefore expected that the published research papers will achieve high recognition in the field and a high citation rank.

WP1: Project management (M1-M36)  The purpose of this WP is to ensure that the project is running according to the established schedules. 

Task 1.1 Progress and cost reporting (M1-M36)

Task 1.2 Monitoring, control and quality management (M1-M36)

Project management is proceeding according to the planned trajectory. An initial kick-off meeting was held in the first month, where all project participants were introduced to the research plan. The entire project team meets regularly on a monthly basis, while the project leader also coordinates specific activities individually with researchers as needed. Project progress is monitored monthly. Effective management is reflected in the completed work, which aligns with the project’s defined objectives.

WP2: Studies on cavitation for downscale from macro- to micro-channels (M1-M12) WP2 includes studies on cavitation for downscale from macro to micro geometries for better control of cavitation effects.

Task 2.1 Design and manufacture of micro-channels (M1-M12) 

Task 2.2 Characterization of cavitation in micro-channels (M7-M12) 

Task 2.3 Comparison of chemical effects between macro- and micro-channels (M7-M12) 

Within WP2, our objective was to design, fabricate, and characterize a lab-scale microchannel. The microchannel was manufactured from a thin steel plate using laser processing and characterized through pressure pulsation measurements and high-speed imaging. Its chemical performance was also evaluated by monitoring hydroxyl radical formation and dye degradation. The microchannel proved to be highly efficient, showing higher radical generation compared to various macro-scale channels.

The results from WP2 are essential for the subsequent work packages, where a broader range of pollutants will be investigated in the developed microchannels, with or without the addition of external oxidants. Within this WP, the planned Results (R) and Milestone (M) were achieved, confirming Hypothesis (H1). The findings were published in two high-impact journals [1,2].

Preliminary results will be presented at the 19th Meeting of the European Society of Sonochemistry (25–29 May 2026, Chania, Crete, Greece), while the complete study is currently in preparation for submission to the Chemical Engineering Journal (IF: 13.4).

WP3: Studies on degradation of pollutants in macro- and micro-channels (M1-M22) The purpose of this WP is to firstly develop and optimize the analytical methods for determination of the selected pollutants and to investigate their degradation using existing macro- and newly developed micro-channels.

Task 3.1: Development and optimization of an analytical method (M10-M12) 

Task 3.2: Degradation of pollutants in macro- and micro-channels (M13-M22)

Task 3.3: Characterization of cavitation in macro- and micro-channels with pollutants (M11-M17)

Work within WP3 started in the 10th month, as planned, and is scheduled to continue until month 22; therefore, the first phase of WP3 is assessed as 100% completed. Within WP3, in collaboration with a colleague from Poland and partners from the Faculty of Pharmacy (UL FFA), we developed and optimized a method for the degradation of various micropollutants, with a focus on pharmaceuticals. We also initiated the characterization of cavitation processes occurring in synergy with different oxidants.

WP4: Studies on activation of external oxidants in macro- and micro-channels (M13-M24)  The purpose of this WP is to firstly optimize macro- and micro-channels for the administration of external oxidants and characterization of the developed cavitation.

Task 4.1: Evaluation of degradation effectiveness and mechanisms in presence of external oxidants (M13-M24) 

Task 4.2: Characterisation of cavitation in macro- and micro-channels with external oxidants (M17-M24) 

WP5: Micro-channel array development (M25-M36) 

Task 5.1 Development and design of micro-channel array (M25-M33)

Task 5.2 Evaluation of the degradation of pollutants by micro-channel arrays (M31-M33)

Task 5.3 Comparison of micro-channel array with a single macro-channel (M31-M36)

WP6: Holistic analysis of project results (M30-M36) [led by both PIs]. The aim of this WP is to find general conclusions of the project and perform overall analysis of the data.

 Tasks will be focused on:

• selection of optimal conditions and processes for degradation of individual groups of chemical compounds under cavitation in micro-channels;
• description of reaction mechanisms and its kinetics, comparison of reaction pathways between micro- and macro-channels;
• defining similarities and differences between micro- and macro-channels.

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[1] ZUPANC, Andraž, ORTAR, Jernej, PAHOVNIK, David, ZABUKOVEC LOGAR, Nataša, STRES, Blaž, ŠMID, Alenka, ZUPANC, Mojca, PETKOVŠEK, Martin, ŽAGAR, Ema. Preparation of low molecular weight chitosan through hydroxyl radicals generated via hydrodynamic cavitation. Ultrasonics Sonochemistry. 2025, vol. 123, 107688, str. 10. [COBISS.SI-ID 258816515]

[2] GOSTIŠA, Jurij, DULAR, Matevž, RIHAR, Andraž, ŠIROK, Brane, VONČINA, Danijel, ZUPANC, Mojca, LAVRIČ, Henrik. Design and development of a novel magnetic generator of hydrodynamic cavitation. Results in engineering. 2026, vol. 29, 109903, str. 1-9. [COBISS.SI-ID 270892291]