Investigation of the Effect of Electrolytes on the Breakaway of Air Bubbles at an Underwater Capillary Using High-Speed Cinematography and Passive Acoustic Techniques
Saline water froth flotation has received increasing attention in recent years due to sustainability-related concerns. Although the presence of electrolytes in these flotation systems is known to produce the desired bubble swarms, i.e., a macroscopic observation, the fundamental mechanism through wh...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-07-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/12/8/972 |
| _version_ | 1797408732097806336 |
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| author | Pengbo Chu Ronghao Li Mark Lepage Kristian Waters |
| author_facet | Pengbo Chu Ronghao Li Mark Lepage Kristian Waters |
| author_sort | Pengbo Chu |
| collection | DOAJ |
| description | Saline water froth flotation has received increasing attention in recent years due to sustainability-related concerns. Although the presence of electrolytes in these flotation systems is known to produce the desired bubble swarms, i.e., a macroscopic observation, the fundamental mechanism through which the solutes produce such an effect at the microscopic level remains obscure. For example, there is no agreed mechanism (i.e., break-up or coalescence—two major bubble formation mechanisms) of how the effect is achieved. Not only is understanding the impact of electrolytes on the bubble formation mechanisms a fundamental question, but it can also provide insight into the design of more efficient air dispersing mechanisms for saline flotation systems. Previous studies have demonstrated that electrolytes can inhibit coalescence, but their potential impact on break-up remains vague, which is the focus of this study. It is hypothesized that electrolytes have an impact on break-up, and by isolating break-up from coalescence, the effects of electrolytes on break-up can be revealed. A break-up-only bubble formation system was built. Under this condition, any impact from the electrolytes on the produced bubble can be attributed to an impact on break-up. High-speed cinematography and a passive acoustic technique were employed to capture the bubble size, acoustic frequency, and damping ratio during the break-up process. Under the quasi-static condition, an increase in the electrolyte concentration increased the bubble size produced via break-up, contradicting the common observations made for bubble swarms. The break-up imparted an initial capillary wave to the bubble surface, which is correlated with the bending modulus of the air/water interface affected by the electrolytes. No direct correlation was observed between the acoustic damping ratio and that of the capillary wave, suggesting that the electrolytes affect the break-up via a different mechanism from that by surfactants. |
| first_indexed | 2024-03-09T04:03:51Z |
| format | Article |
| id | doaj.art-a92efef165ac42d292ee7a49f1ac05e1 |
| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-09T04:03:51Z |
| publishDate | 2022-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-a92efef165ac42d292ee7a49f1ac05e12023-12-03T14:10:10ZengMDPI AGMinerals2075-163X2022-07-0112897210.3390/min12080972Investigation of the Effect of Electrolytes on the Breakaway of Air Bubbles at an Underwater Capillary Using High-Speed Cinematography and Passive Acoustic TechniquesPengbo Chu0Ronghao Li1Mark Lepage2Kristian Waters3Department of Mining and Metallurgical Engineering, University of Nevada, Reno, 1664 North Virginia St., Reno, NV 89557, USADepartment of Mining and Materials Engineering, McGill University, 3610 Rue University, Montreal, QC H3A 0C5, CanadaDepartment of Mining and Materials Engineering, McGill University, 3610 Rue University, Montreal, QC H3A 0C5, CanadaDepartment of Mining and Materials Engineering, McGill University, 3610 Rue University, Montreal, QC H3A 0C5, CanadaSaline water froth flotation has received increasing attention in recent years due to sustainability-related concerns. Although the presence of electrolytes in these flotation systems is known to produce the desired bubble swarms, i.e., a macroscopic observation, the fundamental mechanism through which the solutes produce such an effect at the microscopic level remains obscure. For example, there is no agreed mechanism (i.e., break-up or coalescence—two major bubble formation mechanisms) of how the effect is achieved. Not only is understanding the impact of electrolytes on the bubble formation mechanisms a fundamental question, but it can also provide insight into the design of more efficient air dispersing mechanisms for saline flotation systems. Previous studies have demonstrated that electrolytes can inhibit coalescence, but their potential impact on break-up remains vague, which is the focus of this study. It is hypothesized that electrolytes have an impact on break-up, and by isolating break-up from coalescence, the effects of electrolytes on break-up can be revealed. A break-up-only bubble formation system was built. Under this condition, any impact from the electrolytes on the produced bubble can be attributed to an impact on break-up. High-speed cinematography and a passive acoustic technique were employed to capture the bubble size, acoustic frequency, and damping ratio during the break-up process. Under the quasi-static condition, an increase in the electrolyte concentration increased the bubble size produced via break-up, contradicting the common observations made for bubble swarms. The break-up imparted an initial capillary wave to the bubble surface, which is correlated with the bending modulus of the air/water interface affected by the electrolytes. No direct correlation was observed between the acoustic damping ratio and that of the capillary wave, suggesting that the electrolytes affect the break-up via a different mechanism from that by surfactants.https://www.mdpi.com/2075-163X/12/8/972froth flotation bubblesbreak-upelectrolytesacoustic frequencyacoustic damping ratiocapillary wave |
| spellingShingle | Pengbo Chu Ronghao Li Mark Lepage Kristian Waters Investigation of the Effect of Electrolytes on the Breakaway of Air Bubbles at an Underwater Capillary Using High-Speed Cinematography and Passive Acoustic Techniques Minerals froth flotation bubbles break-up electrolytes acoustic frequency acoustic damping ratio capillary wave |
| title | Investigation of the Effect of Electrolytes on the Breakaway of Air Bubbles at an Underwater Capillary Using High-Speed Cinematography and Passive Acoustic Techniques |
| title_full | Investigation of the Effect of Electrolytes on the Breakaway of Air Bubbles at an Underwater Capillary Using High-Speed Cinematography and Passive Acoustic Techniques |
| title_fullStr | Investigation of the Effect of Electrolytes on the Breakaway of Air Bubbles at an Underwater Capillary Using High-Speed Cinematography and Passive Acoustic Techniques |
| title_full_unstemmed | Investigation of the Effect of Electrolytes on the Breakaway of Air Bubbles at an Underwater Capillary Using High-Speed Cinematography and Passive Acoustic Techniques |
| title_short | Investigation of the Effect of Electrolytes on the Breakaway of Air Bubbles at an Underwater Capillary Using High-Speed Cinematography and Passive Acoustic Techniques |
| title_sort | investigation of the effect of electrolytes on the breakaway of air bubbles at an underwater capillary using high speed cinematography and passive acoustic techniques |
| topic | froth flotation bubbles break-up electrolytes acoustic frequency acoustic damping ratio capillary wave |
| url | https://www.mdpi.com/2075-163X/12/8/972 |
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