Dissolution Amplification by Resonance and Cavitational Stimulation at Ultrasonic and Megasonic Frequencies

Abstract

Acoustic stimulation offers a green pathway for the extraction of valuable elements such as Si, Ca, and Mg via solubilization of minerals and industrial waste materials. Prior studies have focused on the use of ultrasonic frequencies (20–40 kHz) to stimulate dissolution, but megasonic frequencies (≥1 MHz) offer benefits such as matching of the resonance frequencies of solute particles and an increased frequency of cavitation events. Here, based on dissolution tests of a series of minerals, it is found that dissolution under resonance conditions produced dissolution enhancements between 4×-to-6× in Si-rich materials (obsidian, albite, and quartz). Cavitational collapse induced by ultrasonic stimulation was more effective for Ca- and Mg-rich carbonate precursors (calcite and dolomite), exhibiting a significant increase in the dissolution rate as the particle size was reduced (i.e. available surface area was increased), resulting in up to a 70× increase in the dissolution rate of calcite when compared to unstimulated dissolution for particles with d 50 < 100 μm. Cavitational collapse induced by megasonic stimulation caused a greater dissolution enhancement than ultrasonic stimulation (1.5× vs 1.3×) for amorphous class F fly ash, despite its higher Si content because the hollow particle structure was susceptible to breakage by the rapid and high number of lower-energy megasonic cavitation events. These results are consistent with the cavitational collapse energy following a normal distribution of energy release, with more cavitation events possessing sufficient energy to break Ca–O and Mg–O bonds than Si–O bonds, the latter of which has a bond energy approximately double the others. The effectiveness of ultrasonic dissolution enhancement increased exponentially with decreasing stacking fault energy (i.e., resistance to the creation of surface faults such as pits and dislocations), while, in turn, the effectiveness of megasonic dissolution increased linearly with the stacking fault energy. These results give new insights into the use of acoustic frequency selections for accelerating elemental release from solutes by the use of acoustic perturbation.

The effects of ultrasonic cavitation on the dissolution of lithium disilicate glass

“…Dissolution results combined with the microscopy analysis indicates that erosion affects the kinetics of glass dissolution. Changes in morphology have been associated with enhanced sonochemistry for other material systems 6,[10][11][12] . Erosion roughens the glass surface and releases particulates into solution causing the SA/V ratio of the reaction system to increase due to an increase in surface area.…”

“…Power and frequency were noted to be interconnected and possibly have optimal settings under which corrosion would peak. Papers by Wei et al 10 , Tang et al 11 , and Arnold et al 12 examined the dissolution of minerals such as calcite and quartz under sonication. These authors showed an inverse relationship between the hardness/ bond energy of a material and the dissolution enhancement that material saw from sonication.…”

Scale-up disaggregation of palygorskite crystal bundles via ultrasonic process for using as potential drilling fluid

“…S1 , there is no obvious differences in the dispersion of rod crystal in PPAL-50-5 and PPAL-70-5 compared with PPAL-30-5. In fact, the enhanced disintegration can be achieved by the high temperature (up to 5000 K) and high pressure (up to 1000 bar) caused by the ultrasonic energy concentrated on the particle surface [40] . In contrast, the heating is unfavorable for ultrasonic disaggregation of PAL crystal bundles due to the lower cavitational intensity at higher temperature [41] .…”

Detergent Dissolution Intensification via Energy-Efficient Hydrodynamic Cavitation Reactors

“…Under these circumstances, bubbles experience a rapid contraction–expansion cycle leading to an increase in overall bubble size. When the bubble size reaches a critical value, a sudden collapse of the bubble results in localized hotspots of energy . This approach is useful due to the controllable nature of a single bubble cavitation .…”

“…When the bubble size reaches a critical value, a sudden collapse of the bubble results in localized hotspots of energy. 14 This approach is useful due to the controllable nature of a single bubble cavitation. 15 However, its application on the industrial scale is difficult because of scale up and energy efficiency issues.…”