Sonochemistry: from Basic Principles to Innovative Applications
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The term “sonochemistry” is used to describe the chemical and physical processes occurring in solution through energy provided by ultrasound (in the range from 20 kHz to 2 MHz). The effects of ultrasound are the consequence of the cavitation phenomenon, namely the formation, growth, and collapse of gaseous microbubbles in liquid phase. The intense local effects (mechanical, thermal, and chemical) due to the sudden collapse of these micrometric bubbles lie at the origin of all applications of sonochemistry. Use of ultrasound in chemical processes increased between 1980 and 2000, and the corresponding literature has increased enormously in volume from 2000 onwards, reporting many applications in several areas including but not limited to sonocatalysis, organic chemistry, materials preparation, polymer chemistry, biomass conversion, extraction, electrochemistry, enzymatic catalysis, and environmental remediation.
The potential of sonochemistry is often directly connected to the choice of the sonochemical parameters and experimental conditions. The first contribution to this topical collection, provided by Prof. Ashokkumar’s research group, provides theoretical considerations regarding the use of ultrasound in the laboratory, to better understand the mechanisms involved and determine which parameters can affect the observed results. Specifically, a detailed discussion on single-bubble sonochemistry is provided in this contribution.
Further contributions highlight how sonochemistry represents a key area for research and innovation in chemistry. Indeed, the conditions obtained in a medium submitted to ultrasound can account for a large number of physicochemical effects, such as enhanced kinetics of chemical reactions, changes in reaction mechanisms, emulsification effects, erosion, crystallization, and precipitation, among others. Sonochemistry is multidisciplinary, and recent advances highlighting this are reported in this topical collection, in particular applications such as organic chemistry (Prof. Draye’s group), synthesis of nanostructured materials (Prof. Suslick), synthesis of photoactive materials (Prof. Colmenares’ group), advanced oxidation processes (Prof. Neppolian’s group), and treatment of sewage sludge (Prof. Zielewicz). Results in these areas show that the improvements achieved require use of recently developed sonochemical processes.
The combination of sonochemistry with other innovative technologies is also highlighted, using microwave irradiation (Prof. Cravotto’s group), ionic liquids as solvent or catalyst (Dr. Chatel), and coupling with microfluidics (Prof. Rivas’ group). In all these cases, synergistic effects are observed, representing a new source of innovation for further research.
The final contribution, provided by Prof. Gogate’s group, covers laboratory equipment and the opportunity to scale up the technology for maximum process intensification benefits. We conclude by stating that scientific rigor is essential in the sonochemistry area to understand the associated mechanisms and benefit from the full potential offered by ultrasound.
The editors kindly acknowledge the Topics in Current Chemistry editorial office (Springer) for inviting us to compile this comprehensive topical collection on sonochemistry. We would also like to extend our most sincere gratitude to international experts for their time and consideration regarding this project, as well as for their general contributions to sonochemistry science; It was pleasing and instructive to work with them on this topical collection. Last but not least, we sincerely thank our publishing editor, Elizabeth Hawkins, and assistant editor, Na Xu, who patiently and kindly took us through the development of this topical collection over the past few months to achieve this impressive final result, which would not have been possible without such support.
We sincerely hope that this topical collection will be useful both to (bio)chemistry, chemical engineering, and materials science students, as well as to graduates interested in green chemical technologies, and wish you an enjoyable and satisfactory read.