Tiny Bubbles Could Help Clean Water, Process Food And Recover Metals More Efficiently

Industry faces growing pressure to reduce energy use and chemical consumption while improving efficiency. Researchers at Luleå University of Technology have shown how microscopic bubbles generated by ultrasound can be used to improve processes ranging from water treatment to food production and metal extraction.

“Cavitation has significant potential, but for the technology to work on an industrial scale we need to understand how to control it efficiently,” says Sara Maghami, PhD candidate in Engineering Acoustics at Luleå University of Technology.

Energy released when bubbles collapse
Cavitation refers to a phenomenon when tiny bubbles form, growth and collapse in a liquid. During the implosion, extremely high local temperatures and pressures are created, which can be used to influence chemical and biological processes.

In the thesis Toward Improved Process Intensification through Acoustic Cavitation, Sara Maghami investigates how ultrasound-based systems can be designed to generate cavitation more efficiently while reducing energy losses.

“The aim has been to develop systems that deliver as much of the supplied energy as possible to the regions where cavitation generates the desired effects,” she says.

Breaking down PFAS
One part of the research focuses on PFAS, a group of persistent chemicals found in products such as firefighting foams, textiles and industrial materials.

The implementation of multiple ultrasound frequencies within an integrated acoustic–hydrodynamic cavitation unit enabled energy-efficient PFAS degradation in water.

“The results show that it is possible to improve degradation while keeping energy demand under control,” she says.

Gentler food processing
The technology was also tested for the pasteurization of apple juice. Traditional pasteurization relies on heat, which can affect flavor and quality of juice.

By combining ultrasound with reduced processing temperatures, microorganisms could be inactivated while maintaining a gentler treatment process.

”Our findings show that acoustic and hydrodynamic cavitation can treat juice through localized behavior, thereby reducing the need for conventional high-temperature processing,” says Sara Maghami.

Improving gold extraction
The researchers also investigated how cavitation can be used in gold extraction. The results show that the process became faster when ultrasound was combined with leaching techniques.

At the same time, the study demonstrated that different applications require different levels of cavitation intensity. More is not always better.

“For some processes, successful application of cavitation does not depend on achieving the highest possible intensity, but rather on identifying the optimal cavitation level required for the specific process,” she says.

Bringing the technology closer to industry
The work shows how the same underlying technology can be applied across very different industries, while also highlighting the importance of adapting systems to specific applications.

By combining simulations, experiments and practical case studies, the research provides knowledge that can help move cavitation technologies beyond the laboratory.

“For the technology to become widely adopted, we need to understand both the underlying physics and how it performs in real industrial environments,” says Sara Maghami.