Agitation-intensified sonochemistry for water disinfection

Abstract

Sonochemistry has been widely investigated in sterilization, while the high energy input hinders the translation from a lab-scale study into practical applications. In this work, a low-power and low-frequency ultrasonic cleaner was coupled with mechanical agitation to reduce the energy barriers for the evolution of cavitation bubbles. Then, hydroxyl radicals (^•OH) was generated at the interface upon the collapse of cavitation bubbles. We discovered that a rise of agitation speed will accelerate the production of ^•OH, leading to remarkably improved Escherichia coli (E. coli) inactivation efficiency. During E. coli treatment, cell envelopes were initially attacked by ^•OH. Then, cytoplasm was released into the solution, remaining the empty E. coli cells. Radical oxidation and thermal decomposition by interior hotspot region synergistically remove the carbon organic matter of the liquid. In addition, the side byproduct of H₂O₂ generated via the self-quenching of two hydroxyl radicals will be removed by MnO₂ catalysts in the treated effluent, proposing a continuous series design combined purification of carbon organic matter with H₂O₂ removal. This study presents a simple strategy to promote the low-energy sonochemistry-based antibacterial applications.