| 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. |
- Alexandrova, L, et al.
(författare)
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Three-phase contact parameters measurements for silica-mixed cationic-anionic surfactant systems
- 2009
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 348:1-3, s. 228-233
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Tidskriftsartikel (refereegranskat)abstract
- The stability and interactions in thin wetting films between the silica surface and air bubble containing (a) straight chain C10 amine and (b) cationic/anionic surfactant mixture of a straight chain C10 amine with sodium C8, C10 and (straight chain) C12 sulfonates, were studied using the microscopic thin wetting film method developed by Platikanov [D. Platikanov, J. Phys. Chem. 68 (1964) 3619]. Film lifetimes, three-phase contact (TPC) expansion rate, receding contact angles and surface tension were measured. The presence of the mixed cationic/anionic surfactants was found to lessen contact angles and suppresses the thin aqueous film rupture, thus inducing longer film lifetime, as compared to the pure amine system. In the case of mixed surfactants heterocoagulation could arise through the formation of positively charged interfacial complexes. Mixed solution of cationic and anionic surfactants shows synergistic lowering in surface tension. The formation of the interfacial complex at the air/solution interface was confirmed by surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants system controls the strength of the interfacial complex. The observed phenomena were discussed in terms of the electrostatic heterocoagulation theory, where the interactions can be attractive or repulsive depending on the different surface activity and charge of the respective surfactants at the two interfaces.
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| 3. |
- Ayyala, S, et al.
(författare)
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Effect of corrosion inhibitors on grinding and flotation of a lead-zinc ore
- 1993
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Ingår i: Minerals Engineering. - 0892-6875 .- 1872-9444. ; 6, s. 929-935
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Tidskriftsartikel (refereegranskat)abstract
- Grinding and flotation experiments on a Pb-Zn ore were carried out to evaluate : 1) wear of the grinding media both in the presence and absence of an inhibitor and 2) effect of the inhibitor on the flotation of Pb-Zn minerals. The percentage reduction in the wear of the grinding media was observed to be between 25-36%, depending on the type of the inhibitor and its critical concentration. The inhibitors used in the investigation were sodium sulphite, sodium nitrite, sodium chromate and sodium silicate. The results indicate that a specific corrosion inhibitor, for example sodium sulphite, may give better recoveries and grades in flotation but is not as efficient as sodium chromate in inhibiting the wear of the grinding media. Pulp solutions (after grinding) analysed for metal ion concentrations showed low Fe. Iron released into the solution as a result of corrosion reactions subsequently forms insoluble hydroxy complexes and may coat the mineral surfaces. Such hydrophilic coatings may adversely affect the floatabilities of minerals. The particle size analysis of the ground product has been carried out and the results are discussed.
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| 4. |
- Shen, H, et al.
(författare)
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A review of plastics waste recycling and the flotation of plastics
- 1999
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Ingår i: Resources, Conservation and Recycling. - 0921-3449 .- 1879-0658. ; 25, s. 85-109
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Tidskriftsartikel (refereegranskat)abstract
- This paper summerizes the importance of plastic waste recycling and plastic waste separation. Based on an analysis of the physical and chemical characteristics of plastics and plastic waste, the potentials and limitations of several technological processes are discussed. In addition, a review of the surface chemical aspects of plastic flotation is presented. It can be concluded that the flotation of plasics is a fairly flexible technique and could prove to be a useful process for the separation of mixtures of several different types of plastics. however, more research and development effort is required before this technology can be introduced to industry.
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| 5. |
- Shen, H, et al.
(författare)
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Selective flotation separation of plastics by chemical conditioning with methyl cellulose
- 2002
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Ingår i: Resources, Conservation and Recycling. - 0921-3449 .- 1879-0658. ; 35, s. 229-241
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Tidskriftsartikel (refereegranskat)abstract
- The floatability of seven plastics (POM, PVC, PET, PMMA, PC, PS and ABS) in the presence of methyl cellulose (MC) and separation of plastics mixtures were investigated in this paper. It was found that the seven plastics can be separated into three groups by using the wetting agent MC. Group one includes POM and PVC. They are depressed at very low MC concentrations. Group two, including PET, PMMA and PC, has an intermediate floatability. Group three (ABS and PS) has a high floatability. They are almost not depressed within the given MC concentration range. In order to understand the mechanism of selective flotation of plastics and the chemical conditioning process, surface chemical factors, such as wettability of plastics and surface tension of flotation medium, and gravity factors, such as particle density and shape, were studied. It was found that the depressing effect of MC on plastics is ascribed mainly to its adsorption on the plastics surfaces. The MC molecules absorbed on plastics expose some of their polar groups oriented towards the aqueous phase, hence making the plastics surfaces hydrophilic. In addition, flotation selectivity for the plastics is dominated not only by wettability of plastics, but also by particle size, density and shape
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| 6. |
- Wang, Yanmin, et al.
(författare)
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Hydrophobic magnetite seeding of hematite ultrafines in high gradient magnetic separation
- 1993
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Ingår i: Minerals Engineering. - 0892-6875 .- 1872-9444. ; 6, s. 537-546
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Tidskriftsartikel (refereegranskat)abstract
- The application of hydrophobic magnetite seeding to concentrate hematite ultrafines (<10 µm) in slimes using a high gradient magnetic separator (HGMS) with coarse expanded metal matrices was investigated. It was shown that the selective aggregation at high shear rate of the seeded hematite particles (produced by surface treatment with sodium oleate and colloidal magnetite) could significantly enhance the HGMS capture of hematite ultrafines. The mechanism of selective aggregation was discussed in terms of the combination of hydrophobic and magnetic interactions.
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