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    Coagulation and flocculation characteristics of celestite with different inorganic salts and polymers
    (ELSEVIER SCIENCE SA, 2004) Ozkan, A; Yekeler, M
    Coagulation and flocculation characteristics of celestite were investigated using CaCl2, MgCl2 and AlCl3 and anionic (A-150), cationic (C-573) and non-ionic (N-100) flocculants, respectively. Isoelectric point of celestite sample studied was found to be located at a pH of 2.6 using hindered settling technique. It was determined that the magnesium ion was more effective on the celestite suspension than calcium and aluminum ions and its effect significantly varied depending on concentration and pH of the suspension. The coagulation power values for magnesium ion increased rapidly towards the 5 x 10(-5) M concentration and reached a maximum value (similar to90%) at a pH of 11. While calcium and magnesium ions were not effective below neutral pH, aluminum ion caused the stabilization of the celestite suspension below pH 8.5. A-150 and N-100 polymers strongly flocculated the celestite suspension than C-573 polymer. While the celestite suspension with A-150 polymer was flocculated well at neutral and alkaline pH range, N-100 polymer was not much affected by the pH changes of the suspension. For the flocculation experiments with A-150 polymer at pH 11 with pre-addition of particular concentrations of calcium and magnesium ions into the suspension, i.e. destabilization process prior to the flocculation, the flocculation of the celestite suspension was enhanced by the coagulation process. (C) 2003 Elsevier B.V. All rights reserved.
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    Critical solution surface tension for oil agglomeration
    (ELSEVIER SCIENCE BV, 2005) Ozkan, A; Aydogan, S; Yekeler, M
    This paper presents the effect of surface tension of solution used as medium for the oil agglomeration of minerals. Naturally occurring hydrophobic and hydrophilic minerals are used in this study. It was determined that the oil agglomeration recoveries of these minerals decreased with decreasing solution surface tension and the oil agglomeration process of the mineral did not occur below a particular value of solution surface tension. The solution surface tension value at which oil agglomeration does not take place was defined as 'the critical solution surface tension for oil agglomeration, gamma (c-a)'. These critical solution surface tension values obtained for those hydrophobic minerals were close to their critical surface tension of wetting (gamma(c)) values. On the other hand, the gamma(c-a) values obtained for the hydrophilic minerals treated with surfactants were slightly higher than their gamma(c) values. For a successful oil agglomeration of a mineral, the solution surface tension value must be higher than the critical surface tension of oil agglomeration (gamma(c-a)). (c) 2004 Elsevier B.V. All rights reserved.
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    Shear flocculation of celestite with sodium oleate and tallow amine acetate: effects of cations
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2004) Ozkan, A; Yekeler, M
    Sodium oleate and tallow amine acetate (TAA) were used as surfactants for the shear flocculation of celestite. The shear-flocculation power values obtained with sodium oleate were higher than those obtained with TAA in terms of the concentrations used in the shear-flocculation experiments. In addition, sodium oleate and TAA were more effective on the celestite suspension in the pH ranges of 7-11 and 6-10, respectively. For the shear-flocculation experiments with sodium oleate at pH 11, with preaddition of calcium or magnesium ions at 5 x 10(-5) M and lower concentrations into the suspension, the shear-flocculation of the celestite suspension was promoted by the coagulation process due to the calcium and magnesium cations added. However, the shear-flocculation power values decreased due to the interaction between surfactant and cations at concentration values higher than 5 x 10-5 M for magnesium ions and 10(-3) M for calcium ion. Particularly, magnesium ions significantly reduced the shear-flocculation power values by slime coating of Mg(OH)(2) precipitates. (C) 2004 Elsevier Inc. All rights reserved.