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    An investigation of the effect of clay type on coal flotation along with DLVO theoretical analyses
    (Taylor & Francis Inc, 2020) Gungoren, Can; Guven, Onur; Cinar, Mustafa; Ozdemir, Orhan
    Coals generally exist with clay minerals, which are very fine-sized minerals, and adversely affect the flotation of coal. For instance, they make the coal surface hydrophilic by coating coal surfaces and therefore, they inhibit bubble-particle attachment. Clay minerals can also cause over-consumption of reagents due to their high surface area. Additionally, clay minerals can transfer into the concentrate during the flotation process by entrainment because of their low weight and small particle size, and thus, increase pulp viscosity and changing froth stability. In this study, the influence of various clay minerals (kaolinite, illite, and bentonite) on the flotation behavior of coal sample was studied in detail by conventional flotation tests. In addition, the values obtained from flotation tests were correlated with theoretical energy barrier values established with classical DLVO theory based on zeta potential values of coal and clay samples measured at different pH values. According to the results of this study, no significant effect of clay minerals was observed on coal flotation. This was probably because of the high floatability of the coal used for this study. Both the results obtained from the experiments and theoretical analysis, DLVO calculations, showed that the type of clay mineral is the main indicator parameter for coal flotation.
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    Effect of roughness and shape factor on flotation characteristics of glass beads
    (Elsevier, 2016) Hassas, Behzad Vaziri; Caliskan, Hidayet; Guven, Onur; Karakas, Firat; Cinar, Mustafa; Celik, Mehmet S.
    The effect of surface roughness and shape factor on behavior of particles in flotation has been investigated. Surface roughness of various degrees was applied on spherical glass beads of 150 + 106 mu m by means of acid etching. The same procedure was also performed on ground glass beads of the same size interval with different shape factors. The effect of these variations on surface morphology of particles was investigated in terms of flotation recovery, contact angle, and bubble-particle attachment. An Atomic Force Microscope (AFM) was used for surface roughness characterizations and a correction methodology on roughness measurements of spherical particles is proposed. A digital image analyzer was used for shape factor characterizations. It is shown that increase in surface roughness improves the flotation recovery, contact angle, and bubble attachment. Shape factor, however, was found to be more predominant in flotation and bubble attachment. This is attributed to the effect of sharp edges of ground particles which triggers the film rupture process and shortens the attachment time. (C) 2015 Elsevier B.V. All rights reserved.
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    Improved flotation of heat treated lignite with saline solutions containing mono and multivalent ions
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2018) Ozdemir, Orhan; Ersoy, Omer F.; Guven, Onur; Turgut, Hatice; Cinar, Mustafa; Celik, Mehmet S.
    Flotation of lignites is inherently difficult. However, pre-heat treatment of coal is also known to make coal surfaces more hydrophobic possibly through removal of water entrapped in the structure of coal. In this context, the objective of this study was, therefore, to determine changes in the hydrophobicity of some lignites under moderately controlled heat treatment, and correlate the flotation response of lignites in different salt solutions of NaCl, KCl, CaCl2, and MgCl2 without using any reagent. The results of flotation tests suggested that, under the present test conditions, it was possible to float thermally pre-treated lignite samples of partially hydrophobic character in salt solutions in the absence of collector and frother. In addition, the effect of heat treatment on hydrophobicity, and in turn flotation was explained by a theoretical model based on extended DLVO interactions to quantify the effects of both heat treatment and salt concentration on bubble-particle interactions. The results of theoretical modeling suggested that the removal of hydrogen containing groups from coal surfaces significantly contributed to the electrical double layer and hydrophobic forces that governed the magnitude of energetic barrier and also the extent of bubble-particle attachment.