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Publications (5)5.21 Total impact

  • Yanmin Wang · Eric Forssberg · Robert J. Pugh · Sten Åke Elming
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    ABSTRACT: In the present paper, magnetic contributions on the aggregation of some magnetic mineral particle ultrafines were studied. There are two different magnetic properties that may enhance particle aggregation: a) field-induced magnetic moment; and b) magnetic moment due to the remanent magnetisation.The magnetic field-induced aggregation of the oxide mineral particle ultrafines (hematite and chromite) in aqueous suspension at moderate ionic strength was investigated using a laboratory scale electromagnetic solenoid. The experimental results relate the aggregation process (as determined by magneto-sedimentation analysis) to particle size and the external magnetic field in the natural pH value of the dispersions by using a modified form of the DLVO theory. In cases where the electrostatic repulsion was not suppressed, then the long range magnetic forces enabled aggregation to occur in the “secondary minimum” potential energy sink. This caused the formation of chains/rings, which appeared to be relatively stable at enhanced rates of settling.It is indicated in this paper 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. The formation of aggregates is attributed to the presence of the remanent magnetisation in these oxide iron minerals, mainly in the magnetite.
    Journal of Dispersion Science and Technology 03/1995; 16(2):137-154. DOI:10.1080/01932699508943665 · 0.71 Impact Factor
  • SEKHAR AYYALA · ROBERT J. PUGH · ERIC J. FORSSBERG
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    ABSTRACT: Physical characteristics of mineral aggregates (such as density, size, shape, structure and strength) formed by either electrolytic coagulation or polymeric flocculation, need to be critically controlled by optimum conditioning in mineral processing. The present paper discusses the various experimental techniques used to determine these properties. In addition, physical and chemical factors that determine the rates of floe growth and which subsequently influence the floe morphology are summarised. This review also elucidates the hydrodynamic aspects of creeping flow and summarises the various settling velocity equations pertaining to the calcuation of floe density.
    Mineral Processing and Extractive Metallurgy Review 01/1995; 12(2-4):165-184. DOI:10.1080/08827509508935257 · 0.69 Impact Factor
  • Yanmin Wang · Robert J. Pugh · Eric Forssberg
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    ABSTRACT: In this paper, it is shown that the coagulation of dispersions of weakly magnetic mineral ultrafines (such as hematite and chromite) in an external magnetic field can be described theoretically by invoking interparticle forces. Essentially, coagulation occurs when the short-range London—van der Waals interactions and the long-range magnetic forces outweigh the stabilizing electric double layer repulsion. From classical colloid chemistry theory, we have calculated the various components of the potential energy for different-sized particles at a series of ionic strengths and magnetic field intensifies. Principles governing the stability of the suspensions were derived and the computations lead to the establishment of criteria which can be used to predict the stability of the suspensions of weakly magnetic oxide mineral ultrafines in a “wet magnetic separation process”.Experimentally, the magnetic-field induced coagulation of ultrafines of natural hematite and chromite in aqueous suspensions at moderate ionic strength was investigated using a laboratory-scale electromagnetic solenoid. The experimental results relate the coagulation process (as determined by magnetosedimentation analysis) to particle size, slurry pH and the external magnetic field. In the magnetic fields, maximum coagulation occurred near the pH of the point of zero charge (pHPZC) of the minerals (where the electrostatic double layer repulsion was reduced to a minimum) enabling the particles to enter the “primary minimum” energy sink. In contrast, in cases where the electrostatic repulsion was not suppressed, the long-range magnetic forces enabled coagulation to occur in the “secondary minimum”. This caused the formation of chains which appeared to be relatively stable at enhanced rates of settling. The experimental results could be interpreted from a theoretical analysis of the interparticle forces controlling the process.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 10/1994; 90(2-3-90):117-133. DOI:10.1016/0927-7757(94)02908-3 · 2.35 Impact Factor
  • Yanmin Wang · Robert J. Pugh · Eric Forssberg
    Magnetic and Electrical Separation 01/1993; DOI:10.1155/1993/40239
  • Yanmin Wang · Eric Forssberg · R.J. Pugh
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    ABSTRACT: 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.
    International Journal of Mineral Processing 09/1992; 36(s 1–2):93–105. DOI:10.1016/0301-7516(92)90066-6 · 1.46 Impact Factor