Abstract
Sonochemistry is a significant contributor to green science as it includes: (i) the use of less toxic compounds and environmentally safe solvents, (ii) improvement of reaction conditions and selectivity, (iii) no toxic sludge generation, (iv) reduction in the energy use for chemical transformations, (v) reusability of materials. In water and wastewater treatment, ultrasound is used as an advanced oxidation process to eliminate refractory pollutants. Ultrasound is also used as a very effective sludge pretreatment technology in wastewater treatment plants to facilitate biogas production. Moreover, sonochemical synthesis of nanoparticles has recently attracted great attention as a greener protocol. This paper presents the main applications of ultrasound in environmental remediation and protection. The study also introduces mechanism for the degradation of pollutants from water via sonication in aqueous media and the principle factors affecting the cavitational effect.
Highlights
Introduction to SonochemistrySonochemistry is a field that studies the enhancement of chemical reaction and mass transfer rates under various ultrasonic conditions
In the last two decades, considerable interest has been shown in the application of ultrasound as an advanced oxidation process (AOP) for water decontamination
Due to stringent sludge disposal regulations worldwide, the processing and ultimate disposal of excess biomass known as waste activated sludge (WAS) is one of the major problems in biochemical wastewater treatment, because it accounts for approximately 35–60% of the whole operation cost [39]
Summary
Sonochemistry is a field that studies the enhancement of chemical reaction and mass transfer rates under various ultrasonic conditions. The third stage is when the cavity is so overgrown that it can no longer absorb energy to sustain itself, and the surrounding liquid rushes in to lead to a violent implosion as a catastrophic collapse [1,2,3,4]. Understanding the effect of solid particles on sonolysis is important as their presence may exhibit different influences on degradation kinetics Another consequence of acoustic cavitation in a liquid is the emission of light from the collapsing bubbles. The wavelengths shorter than 375 nm can excite the surface of TiO2 just like in photocatalytic processes [15] The explanation for this phenomenon is the hot spot theory, which basically states that when a bubble collapses sufficiently fast, its contents are strongly compressed to lead to an adiabatic temperature rise for light emission in the form of short flashes [16]. The flash duration (and intensity) depends on several details of bubble collapse (such as frequency, sound pressure amplitude, type of liquid and the gas inside the bubble) [17]
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