Zeta Potential Of Bubbles Research Articles

Generation of a positively charged bubble and its possible mechanism of formation

Research Article| November 01 2006 Generation of a positively charged bubble and its possible mechanism of formation M. Y. Han; M. Y. Han 1The School of Civil, Urban & Geosystems Engineering, Seoul National University, Seoul, 151-742, Korea E-mail: myhan@snu.ac.kr; bmw337@waterfirst.snu.ac.kr E-mail: myhan@snu.ac.kr Search for other works by this author on: This Site PubMed Google Scholar M. K. Kim; M. K. Kim 1The School of Civil, Urban & Geosystems Engineering, Seoul National University, Seoul, 151-742, Korea E-mail: myhan@snu.ac.kr; bmw337@waterfirst.snu.ac.kr Search for other works by this author on: This Site PubMed Google Scholar M. S. Shin M. S. Shin 2Eco-Frontier, 207-43, KAIST, Cheongryangri-dong, Dongdaemoon-guSeoul, 130-722, Korea E-mail: msshin@ecofrontier.co.kr Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2006) 55 (7-8): 471–478. https://doi.org/10.2166/aqua.2006.055 Article history Received: March 15 2006 Accepted: July 21 2006 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation M. Y. Han, M. K. Kim, M. S. Shin; Generation of a positively charged bubble and its possible mechanism of formation. Journal of Water Supply: Research and Technology-Aqua 1 November 2006; 55 (7-8): 471–478. doi: https://doi.org/10.2166/aqua.2006.055 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex The zeta potential of bubbles was measured in various solutions containing the metal ions Na+, K+, Ca2 + , Mg2 + and Al3 + . We discovered the main factors that can affect a bubble's zeta potential, resulting in a foundation for tailoring the zeta potential of bubbles during flotation processes. Bubbles were negatively charged in solutions of metal ions such as Na+, K+ and Ca2 + at every concentration and pH range studied. However, the magnitude of the zeta potential decreased with an increase in concentration and a decrease in pH value. Positively charged bubbles were observed in a solution of 0.01M MgCl2 and an alkaline pH range, and below pH 8.2 with AlCl3 in the concentration range of 10−5 to 10−2 M. Metal hydroxide precipitates affected the generation of positively charged bubbles, and minor hydroxylated species also contributed to increase the zeta potential of bubbles. Generation of positively charged bubbles could be the result of a combined mechanism, with both specific adsorption of hydroxylated species and precipitation of metal hydroxides on the bubble surface. bubble charge, flotation, microbubbles, metal hydrolysis, metal precipitation, zeta potential This content is only available as a PDF. © IWA Publishing 2006 You do not currently have access to this content.

Effects of Al3 + and hydraulic characteristics on the removal and behaviour of particles in dissolved air flotation

The removal efficiency of the dissolved air flotation (DAF) process to separate particles from water and wastewater depends on the size and zeta potential of bubbles and particles, the solution and operating conditions, hydraulic characteristics, etc. The effects of aluminium ions and turbulent flow-produced when air-saturated water was spouted into the reactor in the DAF process, on removal and, particle behaviour were on investigated. When bubble size was similar to particle size (10–50 μm), the maximum removal efficiency was 92% in a Kaolin solution of 10−3 M Al3 + without pre-treatment for flocculation process, and, as time passed, the floc size was observed to increase at a pH of 8, which was the condition of high removal efficiency as seen through image analysis. When the air-saturated water was spouted into the reactor, the size of particle at p.z.c. (point of zero charge) seemed to increase to form a floc due to collision effects caused by turbulent flow. Consequently, floc formation by turbulent flow in the reactor seemed to positively affect removal efficiency.

Effects of surface charge, micro-bubble size and particle size on removal efficiency of electro-flotation

Flotation is a water treatment alternative to sedimentation, and uses small bubbles to remove low-density particles from potable water and wastewater. The effect of zeta potential, bubble size and particle size on removal efficiency of the electro-flotation process was investigated because previous model-simulations indicated that these attributes are critical for high collision efficiency between micro-bubbles and particles. Solutions containing Al3+ as the metal ion were subjected to various conditions. The zeta potentials of bubbles and particles were similar under identical conditions, and their charges were influenced by metal ion concentration and pH. Maximum removal efficiency was 98 and 12% in the presence and absence of flocculation, respectively. Removal efficiency was higher when particle size was similar to bubble size. These results agree with modelling simulations and indicate that collision efficiency is greater when the zeta potential of one is negative and that of the other is positive and when their sizes are similar.

The effect of divalent metal ions on the zeta potential of bubbles

Micro-bubbles are used in electro-flotation (EF) and dissolved air flotation (DAF) for particle separation. The efficiency of these flotation processes depends on the collision of bubble and particle and the collision efficiency is affected by certain parameters with respect to the size and zeta potential of bubble and particle. Therefore, it is necessary to monitor not only the zeta potential of the particle, but also that of the bubble. Gas bubbles are reported to be generally negatively charged in water. In this paper, we report a study performed to measure the zeta potential of bubbles in solutions containing divalent metals and find factors which can produce positively charged bubbles. Calcium and magnesium ions were selected as divalent metal ions because natural water normally contains an appreciable quantity of them. It was found that bubbles are negatively charged in CaCl2 solutions whereas, under certain conditions, they become positively charged in MgCl2. Charge reversal of bubbles was observed above 10(-2) M Mg, especially above pH 9. A probable principle that explained the charge reversal could be a combined mechanism with both specific adsorption of hydroxylated species and formation of hydroxide precipitates. Creating solution conditions that can produce positively charged bubbles in flotation methods might make it possible to remove particles using lesser amounts of coagulant or even none at all.

Zeta Potential of Nanobubbles Generated by Ultrasonication in Aqueous Alkyl Polyglycoside Solutions

A simple and convenient method to measure microelectrophoretic mobilities was proposed to determine the zeta potential of nanobubbles generated by ultrasonication. Bubbles in pure water solutions and in aqueous solutions of alkyl polyglycoside (AG) with different alkyl chain lengths and degrees of polymerization in the head group were sonicated with a palladium-coated electrode designed specially by the manufacturer. The zeta potentials of bubbles with ordinary cationic and ionic surfactants are consistent with others' previous results. The average size of the bubbles generated by sonication is in the range of 300 to 500 nm. The zeta potentials of bubbles in both pure water and AG solutions at all pH values are negative. As the chain length of AG increases, zeta potentials significantly decrease at high pH. For nonionic AG, a possible charging mechanism based on known mechanisms is suggested to explain the negative charge, known to be unusual. Even with a very high concentration of H+ ions in solution the bubbles are charged negatively because the interface is covered with slightly acidic alcohol groups of AGs. At high pH, the less polar the surfactant, the more negative the charge, since nonpolar surfactant molecules induce the adsorption of OH− ions, rather than H+ ions that prefer hydration by water molecules.

Zeta potential measurements of bubbles in aqueous surfactant solutions

The Dorn effect, or the sedimentation potential created when finely divided argon gas bubbles are allowed to rise through an aqueous solution, was measured under various conditions. The sedimentation potential was found to be proportional to the volume fraction of gas bubbles depending upon the surfactant involved and the specific conductances of the solutions. The zeta potentials of bubbles in aqueous solutions of sodium hexadecyl sulfate (SHS) and hexadecyltrimethylammonium bromide (HTAB) are given as a function of surfactant concentrations ranging from 10 −7 to 10 −5 M. Zeta potentials of bubbles in solutions of nonionic surfactants, such as polyoxyethylene dodecyl ether or 1-butanol, and in a mixture of these with SHS and HTAB, respectively, are also given. Electrokinetic adsorption densities of SHS or HTAB at moving bubble surfaces were calculated from zeta potentials using the Gouy—Chapman theory and were compared with data available in the literature that were obtained under equilibrium conditions. The former are always smaller than the latter over the concentration range tested.