Technology of Ultrasonic Extraction

Ultrasound extraction, also known as ultrasonic assisted extraction, ultrasonic extraction. It is a multi-stage effect such as strong cavitation effect, disturbance effect, high acceleration, crushing and stirring effect generated by ultrasonic radiation pressure, which increases the frequency and speed of molecular motion and increases the solvent penetration force, thereby accelerating the entry of target components into the solvent. Promote the progress of extraction.

Ultrasonic waves are elastic mechanical vibration waves that are essentially different from electromagnetic waves. Because electromagnetic waves can propagate in a vacuum, ultrasonic waves must propagate through the media, and as they pass through the media, they form the entire process including expansion and compression.

In the liquid, the expansion process creates a negative pressure. If the ultrasonic energy is strong enough, the expansion process creates bubbles in the liquid or tears the liquid into small holes. These holes are closed instantaneously, and an instantaneous pressure of up to 3000 MPa is generated when closed, which is called cavitation, and the whole process is completed in 400 μs.

This cavitation can refine various substances and make emulsions, accelerate the entry of target components into the solvent, and greatly increase the extraction rate. In addition to cavitation, many secondary effects of ultrasound are also beneficial for the transfer and extraction of target components.

The significance of the phenomenon of cavitation is what happens when the bubble bursts. At some point, the bubble no longer effectively absorbs the ultrasonic energy, thus creating an implosion. The rapid adiabatic compression of gases and vapors in bubbles or cavities produces extremely high temperatures and pressures. Since the bubble volume is extremely small relative to the total volume of the liquid, the generated heat is instantaneously lost, and does not significantly affect the environmental conditions. The cooling rate after the cavity bubble is broken is estimated to be about 1010 ° C / s.

In a pure liquid, when a hole ruptures, it always remains spherical due to the same conditions around it; however, at the solid boundary, the rupture of the hole is non-uniform, thereby generating a high-speed liquid jet, which converts the potential energy of the expanded bubble into The kinetic energy of the liquid jet moves in the bubble and penetrates the bubble wall.

The impact of the jet on the solid surface is very strong and can cause significant damage to the impact zone, resulting in a highly active fresh surface. The impact of the rupture bubble deformation on the surface is several times greater than the impact force generated by the bubble resonance.

Using the above effects of ultrasonic waves, it is very effective to extract various target components from different types of samples. Applying ultrasonic waves, high temperature (increasing solubility and diffusion coefficient) generated at the contact surface of the organic solvent (or water) and the solid substrate, increasing the permeability and transmission rate, and oxidizing energy of the radical generated by ultrasonic decomposition, etc. Provides high extraction energy.

Ultrasound itself has been widely used in the field of chemistry, and its application to various separations has also shown many advantages. Ultrasonic action on liquid-liquid, liquid-solid two-phase, multiphase systems, surface systems and membrane interface systems will produce a series of physicochemical effects and produce various additional effects such as turbulence effects and perturbation effects in the microenvironment. , interface effects and energy-concentration effects, etc., causing unique changes in the propagation medium.

These actions provide more active centers and also promote two-phase mass transfer to maintain concentration gradients and promote reactions. These characteristics are not easily obtained by some conventional means, and ultrasonic extraction utilizes these characteristics.