Non-target analysis of radicals in sonochemical and advanced oxidation processes (AOPs)

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Several chemical and biological processes involve short-lived radicals that are either generated by a reaction or the interaction of a source of energy with the matter. To date, most mechanisms of the radical formation and their fate are still elusive to understand due to their short lifetime. This is the case for several research projects in the teams of Prof. Boffito and Yargeau, which involve radicals generated either sonochemically or by advanced oxidation redox processes (AOPs). In sonochemical processes, the energy transmitted by ultrasound (20 kHz - 1 MHz) produces acoustic cavitation, i.e. the formation, growth, and collapse of rarefied gas micro-bubbles. Their collapse results in micro hot spots (up to 5000 K and 1000 atm), and high speed jets (100 m s-1). In these conditions, radicals form. Their type and concentration depends on several factors, such as the characteristics of the ultrasound equipment and the physico-chemical identity of the reaction medium. The radicals thus generated can be leveraged to intensify several chemical and physical processes, including AOPs. AOPs describe a broad family of oxidation processes to unselectively degrade organic pollutants by radicals generated in different ways. These include ozonation, plasma, electrochemical oxidation, chemical oxidation, photocatalysis, sonochemistry, and combined AOPs. We request a portable electron spin resonance (ESR) spectrophotometer for the detection of free radicals. ESR is key to identify and quantify the radicals involved in sonochemical processes not only to establish the mechanisms of sonochemistry, which are still largely ignored, but also to design efficient sonochemical reactors to maximize yield and selectivity while minimizing energy requirements. Similarly, quantifying reactive oxidation species and intermediates in AOPs is crucial to design more efficient AOP systems and to identify the degradation mechanisms of contaminants of emerging concern (CECs). This allows to design methods to completely mineralize pollutants leading to no residual ecotoxicity. There are no portable ESR apparatuses in Canada. Non-portable ESR are available in 5 Canadian institutions but require re-locating reactors. We anticipate that many different research groups will request access to the ESR both from academia and industry. ESR finds application to investigate the activity of enzymes, and tissue damage by free radicals, in geological studies for absolute dating and in industrial applications for quality control of product stability and shelf-life. It will also help developing new collaboration with both academic and industrial partners. The acquisition will greatly enhance the quality of the research of at least 20 HQP and provide them with marketable skills to work not only in scientific research but also in commercial sectors such as pharmaceuticals and personal care sectors, water remediation, plastics, fibers, and food products.