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  • 1.
    Alexandrova, L.
    et al.
    Institute of Physical Chemistry, Bulgarian Academy of Sciences.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Grigorov, L.
    Department of Inorganic Chemistry, University of Sofia.
    Pugh, R.J.
    Institute for Surface Chemistry, Box 5607, SE-11486 Stockholm.
    The influence of mixed cationic-anionic surfactants on the three-phase contact parameters in silica-solution systems2011In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 373, no 1-3, p. 145-151Article in journal (Refereed)
    Abstract [en]

    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.

  • 2.
    Alexandrova, L.
    et al.
    Institute of Physical Chemistry, Bulgarian Academy of Sciences.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Grigorov, L.
    Department of Inorganic Chemistry, University of Sofia.
    Pugh, R.J.
    Three-phase-contact parameters measurements for silica-mixed cationic-anionic surfactant systems2009In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 348, no 1-3, p. 228-233Article in journal (Refereed)
    Abstract [en]

    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 [Platikanov D., 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 hetero-coagulation 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.

  • 3.
    Alexandrova, L.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forssberg, Eric
    Pugh, R.J.
    Grigorov, L.
    University of Sofia.
    Thin film studies in mixed cationic-anionic surfactant system2003In: Proceedings of the XXII International Mineral Processing Congress / [ed] Leon Lorenzen, Marshalltown, South Africa: South African Institute of Mining and Metallurgy, 2003, p. 838-846Conference paper (Refereed)
  • 4.
    Ayyala, Sekhar
    et al.
    Luleå University of Technology.
    Pugh, R.J.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Aggregate characteristics in coagulation and flocculation1995In: Mineral Processing and Extractive Metallurgy Review, ISSN 0882-7508, E-ISSN 1547-7401, Vol. 12, no 2-4, p. 165-165Article in journal (Refereed)
  • 5.
    Ayyala, Sekhar
    et al.
    Luleå University of Technology.
    Subrahmanyam, T.V.
    Departmento de Geologia, CCE/UFRN, Campus Universitario, Natal.
    Pugh, R.J.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effect of corrosion inhibitors on grinding and flotation of a lead-zinc ore1993In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 6, no 8, p. 929-935Article in journal (Refereed)
    Abstract [en]

    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.

  • 6.
    Forssberg, Eric
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pugh, Robert
    Shen, Huiting
    Changsha Research Institute of Mining and Metallurgy.
    Review of plastics waste recycling and the flotation of plastics1999In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 25, no 2, p. 85-109Article in journal (Refereed)
    Abstract [en]

    This paper summarizes 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 plastics 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.

  • 7.
    Lu, Shouci
    et al.
    Resources Engineering School, University of Science and Technology Beijing, Beijing.
    Pugh, Robert
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interfacial separation of particles2005Book (Other academic)
    Abstract [en]

    Interfacial Separation of Particles is concerned with the processing and separation of fine solid particles in liquid solutions using interfacial technology. Interfacial separation has been finding wide application in many industrial fields, such as pigment and filler production, mineral processing, environmental protection, hydrometallurgy, bioengineering, food and beverage industry and chemical industry. This book describes all interfacial separation techniques and discusses the general and specific fundamentals of the techniques. The book intends to promote theoretical understanding and the more promising developments of interfacial separation technology whilst broadening the reader's background knowledge of industrial suspensions

  • 8. Pugh, R.J.
    Experimental techniques for studying the structure of foams and froths2005In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 114-115, p. 239-251Article in journal (Refereed)
    Abstract [en]

    Several techniques are described in this review to study the structure and the stability of froths and foams. Image analysis proved useful for detecting structure changes in 2-D foams and has enabled the drainage process and the gradients in bubble size distribution to be determined. However, studies on 3-D foams require more complex techniques such as Mutiple-Light Scattering Methods, Microphones and Optical Tomography. Under dynamic foaming conditions, the Foam Scan Column enables the water content of foams to be determined by conductivity analysis. It is clear that the same factors, which play a role in foam stability (film thickness, elasticity, etc.) also have a decisive influence on the stability of isolated froth or foam films. Therefore, the experimental thin film balance (developed by the Bulgarian Researchers) to study thinning of microfilms formed by a concave liquid drop suspended in a short vertical capillary tube has proved useful. Direct measurement of the thickness of the aqueous microfilm is determined by a micro-reflectance method and can give fundamental information on drainage and thin film stability. It is also important to consider the influence of the mineral particles on the stability of the froth and it have been shown that particles of well defined size and hydrophobicity can be introduced into the thin film enabling stabilization/destabilization mechanisms to be proposed. It has also been shown that the dynamic and static stability can be increased by a reduction in particle size and an increase in particle concentration

  • 9. Pugh, R.J.
    et al.
    Wang, Yanmin
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of magnetic and surface forces on the coagulation of hematite and chromite1994In: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 11, no 3, p. 133-140Article in journal (Refereed)
    Abstract [en]

    The coagulation of dispersed ultrafine weakly magnetic oxide mineral particles (e.g., natural hematite and chromite) in an external magnetic field can be described by interparticle forces. Essentially, coagulation occurs when the short-range London-van der Waals interactions and the long-range magnetic forces outweigh the stabilizing electrical double-layer repulsion. Using the classical colloid chemistry theory, the various components of the potential energy for different-sized particles at a series of ionic strengths and magnetic field intensities were calculated.

  • 10. Shen, Huiting
    et al.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pugh, R.J.
    Institute for Surface Chemistry, Box 5607, SE-11486 Stockholm.
    Selective flotation separation of plastics by chemical conditioning with methyl cellulose2002In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 35, no 4, p. 229-241Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Shen, Huiting
    et al.
    Luleå tekniska universitet.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pugh, R.J.
    Institute for Surface Chemistry, Box 5607, SE-11486 Stockholm.
    Selective flotation separation of plastics by particle control2001In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 33, no 1, p. 37-50Article in journal (Refereed)
    Abstract [en]

    A study on the control of particle size distribution (PSD) of the ground carbonate product in stirred media mills (wet Drais stirred bead mill and dry Sala Agitated Mill) is presented in this paper. The results indicated that the slope of product size distribution can be controlled by altering some operating parameters, such as size of grinding media and tip or peripheral speed. The profile of product size distribution from the stirred media mills was found to follow most closely the Rosin-Rammler-Bennett (RRB) model.

  • 12.
    Shen, Huiting
    et al.
    Luleå University of Technology.
    Pugh, Robert
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Floatability, selectivity and flotation separation of plastics by using a surfactant2002In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 196, no 1, p. 63-70Article in journal (Other academic)
    Abstract [en]

    In this paper, the floatability of seven plastics (POM. PVC, PET. PMMA, PC., PS and ABS) in the presence of alkyl ethoxylated nonionic surfactant (15-S-7) was investigated. It was found that the floatability of all the plastics decreases with the addition of the surfactant; but they are different in floatability and follow the order POM < PVC < PMMA < PET < PC < ABS < PS. From the separation test results of several plastic mixtures, it was shown that Gamma flotation method not only can be used to separate plastics mixture with different density, such as separation of POM and PVC from PC, POM and PVC from PS and ABS, PET and PMMA from PS and ABS, but also can be used to separate plastics mixture with similar density, such as separation of PMMA from PC. Products with grade higher than 99%. and recovery higher than 97% can be obtained for the separation of some plastic mixtures. Finally, 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 surfactant 15-S-7 on the plastics is mainly due to the reduced liquid surface tension, and flotation selectivity for the plastics with identical particle size is dominated by contact angle, particle density and shape. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 13.
    Tan, Su Nee
    et al.
    Ian Wark Research Institute, University of South Australia.
    Pugh, R.J.
    Fornasiero, D.
    Ian Wark Research Institute, University of South Australia.
    Sedev, R.
    Ian Wark Research Institute, University of South Australia.
    Ralston, J.
    Ian Wark Research Institute, University of South Australia.
    Foaming of polypropylene glycols and glycol/MIBC mixture2005In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 18, no 2, p. 179-188Article in journal (Refereed)
    Abstract [en]

    The surface tension and foamability of a series of polypropylene glycols (PPG) with average molecular weights (MW) ranging from 200 to 2000 g mol-1 and hydrophilic-lipophilic balance (HLB) values ranging from 10.4 to 5.8 were compared to methyl isobutyl carbinol (MIBC), 4-methyl-2-pentanol (MW102 g mol-1 and HLB 6.1). Experiments were carried out using a modified Bikermann column in which the foam heights were determined at a range of gas flow rates and retention times were calculated at different foamer concentrations. These studies show the six-carbon polypropylene glycol (PPG400) with HLB value of 9.7 is an unusually strong frother. Since many industrial foamers/frothers commonly contain a mixture of chemical types, we have also studied the foaming behaviour of mixed systems of PPGs and MIBC at a range of concentrations. The foaming data indicated that a synergistic effect occurred for several of the mixed systems with differences in HLB values, which resulted in an increase in foam height compared to the performance of the individual systems. Dynamic surface tension measurements, determined in the short time span range of 0.1-10 s, correlated with the synergistic effect and it was found that the blended systems gave a higher dynamic surface tension gradient compared to the individual PPGs. It could be suggested that the mixed foamer (containing high HLB and low HLB value components) produce closed packed, molecular cohesive films at the air/solution interface giving greater surface elasticity, which appeared to increase foamability

  • 14. Wang, Yanmin
    et al.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pugh, R.J.
    Influence of pH on the high gradient magnetic separation of1992In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 36, no 1, p. 93-105Article in journal (Refereed)
    Abstract [en]

    This paper presents the influence of surface interaction on wet high gradient magnetic separation (WHGMS) for hematite and quartz particles (<10 μm), by controlling the pH value of the slurry flow. This influence is discussed by computing the net interaction energies for the particle-particle and particle-matrix element systems at various pH values. Such an approach leads to an improvement in the efficiency of separating the mineral ultrafines by WHGMS.

  • 15. Wang, Yanmin
    et al.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pugh, Robert
    Hydrophobic magnetite seeding of hematite ultrafines in high gradient magnetic separation1993In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 6, no 5, p. 537-546Article in journal (Refereed)
    Abstract [en]

    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.

  • 16. Wang, Yanmin
    et al.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pugh, Robert
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Magnetic aggregation in dispersions of mineral ultrafines1995In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 16, no 2, p. 137-154Article in journal (Refereed)
    Abstract [en]

    Particle aggregation can be enhanced in two ways; (a) field-induced magnetic moment and (b) magnetic moment due to the remanent magnetisation. Investigation of the magnetic field-induced aggregation of hematite and chromite in aqueous suspension with the use of a laboratory scale electromagnetic solenoid related the aggregation process to particle size and external magnetic field in the natural pH value of the dispersions. This study have shown that hematite ultrafines in a well-dispersed slurry are selectively aggregated with sized magnetite in the absence of aggregating reagents, high shear rates or an external magnetic field.

  • 17. Wang, Yanmin
    et al.
    Pugh, R.J.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Carrier coagulation of chromite fines in wet magnetic separation1993In: Magnetic and Electrical Separation, ISSN 1055-6915, E-ISSN 1029-0303, Vol. 5, no 1, p. 33-52Article in journal (Refereed)
    Abstract [en]

    A 'carrier' or 'piggy-back' coagulation process was applied to improve the separation efficiency of chromite slimes in wet high-gradient magnetic separation. This was achieved by the addition of a coarse chromite fraction to the slime fraction (< 10 mm). Three coarse chromite fractions were investigated in the present study with size ranges <106>75, <75>53 and <53>38 μm. The results suggested that the <53>38 μm coarse fraction was the most effective in improving the process efficiency. Superior performance was also found to occur between pH 5 and 6. The results were discussed by computing the various components for potential energy of interaction between the slime particles and the 'carrier' or 'piggy-back' particles at a range of surface potentials in the absence or presence of the magnetic field.

  • 18. Wang, Yanmin
    et al.
    Pugh, R.J.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of interparticle surface forces on the coagulation of weakly magnetic mineral ultrafines in a magnetic field1994In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 90, no 2, p. 117-133Article in journal (Refereed)
    Abstract [en]

    The paper demonstrates that the coagulation of dispersions of weakly magnetic mineral ultrafines in an external magnetic field can be described theoretically by invoking interparticle forces. This was done with the use of experimental results that relate the coagulation process to particle size, slurry pH and the external magnetic field. Coagulation were seen to occur either on the primary minimum or secondary minimum depending on the exerted magnetic force.

1 - 18 of 18
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