1. Background Introduction
Flotation is essentially a separation process induced by the motion differences based on the physical and chemical property differences of particles under the action of a multiphase flow field. As an efficient interface sorting technology, it has been widely used in industrial processes such as mineral processing, wastewater treatment, paper deinking, tar sand extraction, plastic recycling, etc. During the flotation process, dispersed bubbles and particles collide with each other under hydrodynamic action. When the liquid film between the bubble and the particle thins and bursts, the two adhere to form a particle-bubble aggregate, which floats up to the foam layer to become a concentrate product under the action of buoyancy, or the particle-bubble interface is unstable and desorption occurs. Theoretically, the probability of particles being captured mainly depends on the collision probability, adhesion probability, and detachment probability between particles and bubbles. Therefore, studying the interaction between bubbles and particles is crucial for enhancing the flotation process.
Image 1--Flotation Principle
2. Research Content
The research team of Professor Jiang from the School of Chemical Engineering of China University of Mining and Technology used a Revealer high-speed camera to track the spreading process of bubbles on homogeneous and heterogeneous solid surfaces. Scanning Electron Microscopy (SEM), Infrared Spectrometer, and Contact Angle Meter were utilized to analyze the physical and chemical structural characteristics of the solid surface. Furthermore, MATLAB software was employed to explore the three-phase line spreading mechanism and the evolution pattern of the gas-liquid interface morphology on both homogeneous and heterogeneous solid surfaces.
To accurately observe the dynamic spreading process of a single bubble on a solid surface, an experimental system as shown in Image 2 was constructed. The image acquisition part consists of a Revealer high-speed camera (5F01, 1280X1024@2000fps) connected to a computer. A precision XYZ positioning adjuster ensures that the observation area is within the shooting range of the Revealer high-speed camera, guaranteeing the stability and reliability of the experiment.
Image 2-- Schematic diagram of experimental system
After ensuring the airtightness of the experimental testing device, deionized water is added to the observation tank. The light source and high-speed camera are adjusted so that the bubble is located directly below the solid surface and is clearly displayed in the computer acquisition window. By controlling the distance between the needle tip and the solid surface, efforts are made to keep the initial shape and size of the bubble spreading consistent. The entire process of bubble spreading is recorded by the Revealer high-speed camera, with a capture speed of 9200fps and an exposure rate of 100μs. Each set of experiments is repeated at least three times.
3. Research Conclusion
The results of the bubble spreading experiment revealed that the three-phase wetting perimeter primarily undergoes two stages: rapid spreading and slow spreading. During the rapid spreading stage, the spatiotemporal evolution of the three-phase line exhibits universal self-similar behavior characteristics. In contrast, the motion characteristics of the three-phase line during the slow spreading stage are closely related to the properties of the solid interface.
Image 3-- The dynamic spreading process of bubbles on different solid surfaces.
Based on the analysis of the physicochemical structure of solid surfaces, it is concluded that the better the hydrophobicity of homogeneous/heterogeneous solid surfaces, the greater their attraction to bubbles, and the longer the three-phase line spreads; the more irregular the solid surface, and the more pores/grooves it has, the greater its impact on the length of the three-phase line during the spreading process, the maximum width of the bubble, and their corresponding positions; in summary, the spreading behavior of the three-phase line during the particle-bubble adhesion process is closely related to the physical and chemical structure of the solid surface and its uniformity.
4. Summary of Industrial Applications
High-speed cameras have always been a powerful tool in the study of bubbles. The X series and M series high-speed cameras from Revealer have extensive case experience in research on cavitation bubbles, bubble dynamics, fluid machinery bubbles, multiphase flow bubbles, and the mechanisms of bubble generation and collapse. They can provide you with professional solutions. Consultations are welcome! (Excerpted from the article "Research on the Dynamic Behavior of Bubble Spreading Process Based on High-Speed Dynamics" by Jiang Xiaofeng etc., published in the Journal of Coal Science and Chemical Engineering Science).
