| 1. |
- Alexandrova, L, et al.
(författare)
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The influence of mixed cationic-anionic surfactants on the three-phase contact parameters in silica-solution systems
- 2011
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 373, s. 145-151
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Tidskriftsartikel (refereegranskat)abstract
- The formation of thin wetting films on silica surface from aqueous solution of (a) tetradecyltrimetilammonium bromide (C14TAB) and (b) surfactant mixture of the cationic C14TAB with the anionic sodium alkyl- (straight chain C12-, C14- and C16-) sulfonates, was studied using the microscopic thin wetting film method developed by Platikanov. Film lifetimes, three-phase contact (TPC) expansion rates, receding contact angles and surface tension were measured. It was found that the mixed surfactants caused lower contact angles, lower rates of the thin aqueous film rupture and longer film lifetimes, as compared to the pure C14TAB. This behavior was explained by the strong initial adsorption of interfacial complexes from the mixed surfactant system at the air/solution interface, followed by adsorption at the silica interface. The formation of the interfacial complexes at the air/solution interface was proved by means of the surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants controls the strength of the interfacial complex and causes synergistic lowering in the surface tension. The film rupture mechanism was explained by the heterocoagulation mechanism between the positively charged air/solution interface and the solution/silica interface, which remained negatively charged.
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| 2. |
- Kota, Hanumantha Rao, et al.
(författare)
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Atomistic simulations on the adsorption of water, methanoic acid and methylamine on pure and hydroxylated quartz
- 2006
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Ingår i: Proceedings of the XXIII International Mineral Processing Congress. - Istanbul : IMPC. ; , s. 1729-1735
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Konferensbidrag (refereegranskat)abstract
- The atomistic simulation code METADISE was used to construct and describe the predominant quartz surfaces at atomic level by static energy minimisation procedure. The surface energies were calculated and unsaturated surface sites are identified. Hydroxylation of quartz surfaces was performed in order to satisfy full coordination of surface sites. The surfaces became most stabilised when they adsorb water in dissociated form justifying hydroxylated quartz surface prevalence in nature. Water, methanoic acid, and methylamine adsorption calculations were carried out on both pure and hydroxylated quartz surfaces. Relative adsorption energies suggest that both methanoic acid and methylamine adsorb preferably than water on pure quartz surface. On hydroxylated quartz surfaces, methylamine adsorption is preferred than water and methanoic acid, which match quartz flotation practice with cationic amine collectors. These simulations have given an insight into interactions at the atomic level which indicate that modelling techniques should be capable of predicting adsorption behaviour and designing mineral specific collector molecules.
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| 3. |
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