A Review on Sonochemistry and Its Environmental Applications

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.

Sonoproduction of nanobiomaterials – A critical review

“…US-synthesised nanobiomaterials have the advantages of controlled structure and dimension by changing the synthesis parameters. Compared to conventional synthesis methods, US-synthesis is more environmentally friendly and consumes only a fraction of the energy [12] , [13] . US-assisted synthesis improves the quality and yield of graphene layers [14] .…”

Greener organic synthetic methods: Sonochemistry and heterogeneous catalysis promoted multicomponent reactions

“…Ultrasound is characterized as any sound wave in frequencies above the normal hearing range of the human ear (i.e., above 16 kHz) [14] and the field of application of ultrasonic waves is surprisingly vast, such as in the pharmaceutical and food industries [15] , [16] , [17] , [18] , [19] , [20] , extraction processes [16] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , waste treatment [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] , [43] , [44] , [45] , [46] , materials chemistry [47] , [48] , [49] , analytical chemistry [50] , [51] , [52] , [53] , and nanoparticle synthesis [24] , [41] , [54] , [55] , [56] , [57] , [58] , [59] . All these examples, addressing the application of ultrasound for different purposes, serve as consolidating pillars for the importance of this tool for the progress of science and technology.…”

“…The third moment occurs when the cavity has grown to a certain limit, and can no longer absorb energy, it is when a violent implosion occurs. At this point, the extremes of temperature and pressure provide an unusual environment or high energy microreactors that allow molecular fragmentation of the gases trapped in the collapsing cavities [14] . However, some chemical transformations have been observed that cannot be explained by the effect of cavitation [65] , [66] ; in these cases, the need for a broader investigation of the aspects that make possible the occurrence of chemical reactions by irradiation of ultrasonic waves is implicit .…”

“…In most cases, with increasing potency, the reaction rate also increases. When high ultrasonic power is applied, a great number of cavitation bubbles are generated in the solution [14] . The applied power density must be sufficient to provide the necessary pressure for cavitation, but not so drastic as to interrupt the growth dynamics of the cavitation bubbles, which can result in deficient cavitation and material growth [68] .…”

Effects of gas-liquid phase transitions on soundwave propagation: A molecular dynamics study

“…For example, metal processing uses the energy of ultrasound, and sonar uses its propagation properties to detect objects. In energy applications, ultrasonic cavitation is used in chemical reactions, wastewater treatment, medical treatment, food processing, and casting among others [1][2][3][4][5][6][7][8][9][10][11] . Ultrasonic cavitation is induced by irradiating a liquid with powerful ultrasonic waves for bubble generation.…”