Confirmation of the Heterocoagulation Theory of Flotation

Abstract

To model the flotation process, we have used the microscopic method developed by Scheludko et al., to study the stability of an aqueous thin film containing tetradecyltrimethylammonium bromide (C14TAB) between an air bubble and a silica substrate. The experiments were performed at a range of C14TAB concentrations and pH values. Spontaneous rupture of the thin aqueous film was interpreted in terms of the earlier proposed heterocoagulation mechanism and resulted from the preferential adsorption of relatively low surfactant concentrations at the vapor/solution interface causing a net positive charge while the solution/silica interface remained negatively charged. This attractive electrostatic interaction was sufficient to overcome the van der Waals repulsion. At higher amine concentrations, the negative charge at the solution/silica interface was reversed. Finally, on approaching the critical micelle concentration (cmc), both interfaces were sufficiently positively charged to cause the restabilization of the film by electrostatic repulsion. In addition, in dilute solution, during the three-phase-contact (TPC) expansion or dewetting step following film rupture, it was suggested that the movement of TPC across the silica substrate leads to transfer of amine from the vapor/solution interface to the vapor/silica. This process resembles a Langmuir−Blodgett deposition process and emphasizes the importance of the solution/vapor interface in the dewetting process.

Polyoxyalkylated diethylenetriamine polymeric surfactants: molecular structure effect on thin wetting films

“…Increasing C s renders a decrease in the contact angle which indicates the formation of a bilayer of polymeric surfactant molecules. Similar θ(C s ) curves with a maximum have been obtained for the cationic surfactant cetyl trimethyl ammonium bromide as well [16,17]. Receding contact angle measurements determined on smooth glass spheres describes the surface hydrophobic/ hydrophilic transition with the change in surface coverage of amine.…”

“…3 Dependence of the receding contact angle θ r on polymeric A, B, C, and D surfactant concentration C s for hydrophilic SiO 2 glass surface the vapor/solution interface leading to heterocoagulation. At higher concentrations (>10 −3 M) approaching CMC, adsorption at the solution/silica interface begins to play an important role leading to patch or aggregate formation, or partial bilayer formation occurs as a result of which the hydrophobic layer becomes more hydrophilic (before the completion of the monolayer) [17]. Generally, the contact angle reflects a three-phase contact interaction.…”

“…In the presence of surfactants A, B, C, and D, there should be an electrostatic interaction between the residual negative charges on the glass surface (a negative potential of −20 to −40 mV at the aqueous solution/SiO 2 glass interface has been reported [17,24]; the nonionic polymeric surfactant adsorbed would hardly modify this charge) and any induced charge at the air/aqueous solution interface. In the later case, there should be some specific adsorption of OH − ions on the PPO and PPO/PEO tails at both interfaces pointing towards the aqueous solution.…”

The Impact of Ionic Liquid and Nanoparticles on Stabilizing Foam for Enhanced Oil Recovery

“…It is worth noting that the observation in this study is in agreement with some previous reports on foam created by hydrophilic silica particle and cationic surfactant. It was found that negatively charged nanoparticle acts in synergy with cationic surfactant such as CTAB to stabilize bubbles in the field of flotation, etc ,. Our previous studies have also shown hydrophobic silica nanoparticle can improve EOR in presence of anionic surfactant SDS, etc.…”

Treating chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation process with surfactant

“…Surfactants have been used to reduce bubble size and increase collective efficiency in the dispersed air flotation (DiAF) and dissolved air flotation (DAF) processes for a long time [12][13][14][15]. According to the hetero-coagulation theory, a small amount of surfactant (10 −7 -10 −6 M) in the solution can increase the contact angle, rupture the thin film and expand the three-phase-contact (TPC) between the gas and solid interface [16]. The expansion of the TPC perimeter produces a large contact area and a strong attachment force between the bubble and particle.…”