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Öğe Correlation of shear flocculation of some salt-type minerals with their wettability parameter(ELSEVIER SCIENCE SA, 2007) Ozkan, A.; Uslu, Z.; Duzyol, S.; Ucbeyiay, H.This paper considers the importance of surface hydrophobicity in the shear flocculation process and presents a correlation between the shear flocculation and the wettability parameter for barite, celestite and calcite as salt-type minerals. The critical surface tension of wetting (gamma(c)) as a wettability parameter describes wetting characteristics of any mineral. The variation of the shear flocculation behaviours of barite, celestite and calcite with sodium oleate concentration in various methanol solutions was investigated. The shear flocculation of these minerals in the methanol solutions increased rapidly towards the optimum surfactant concentration, and thereafter remained relatively constant or increased slightly. On the other hand, the shear flocculation of the minerals decreased with increasing methanol concentration, depends on decreasing surface tension. The gamma(c) values of these minerals as a function of surfactant concentration were determined using a shear flocculation approach. It was found that the gamma(c) values did not change much at surfactant concentrations above the optimum. This result provides a reason for the observed lack of significant increase in the shear flocculation of the mineral suspensions when surfactant concentrations higher than the optimum are used. Furthermore, a strong correlation between the effective shear flocculation and the critical surface tension of wetting (gamma(c)) value was established. As the effective shear flocculation of these salt-type minerals increased sharply below a particular gamma(c) value, it was not much improved after reaching the gamma(c) value obtained at the optimum concentration of sodium oleate. (c) 2006 Elsevier B.V. All rights reserved.Öğe Hydrophobic flocculation and Box-Wilson experimental design for beneficiating fine coal(ELSEVIER SCIENCE BV, 2013) Ucbeyiay, H.The purpose of this study is twofold: first, to determine the appropriate bridging liquid, pH, stirring speed and dispersant for hydrophobic flocculation of coal. Kerosene, n-heptane, benzole and n-hexane were used as bridging liquids. The coal suspension could be flocculated better by kerosene compared to the other bridging liquids at natural pH value of coal. From the experiments carried out to determine the effect of stirring speed on the hydrophobic flocculation of coal suspension, it was found that a stirring speed of 750 rpm was required to achieve the maximum combustible recovery and minimum ash content values of flocculated coal particles. The effects of sodium silicate, sodium hexametaphosphate, sodium phosphate and sodium pyrophosphate used as inorganic dispersants on the hydrophobic flocculation of coal were also studied. Sodium silicate was more effective than the other dispersants in the presence of kerosene. The best results were obtained with a concentration of 1 g/dm(3) sodium silicate and 4 g/dm(3) concentration of kerosene. It was determined that a clean coal having an ash content of 1033% with a combustible recovery of 89.54%. The second fold of study is the Box Wilson experimental design method and it was employed to evaluate the effects of important variables such as bridging liquid concentration (kerosene), dispersant (sodium silicate) concentration and stirring speed on the hydrophobic flocculation of coal. Response function coefficients were determined by the regression analysis of experimental data and the predictions were found to be in good agreement with the experimental results. Similar to the results of the first fold of experimental studies, the optimum kerosene concentration, sodium silicate concentration and stirring speed were determined as 4 g/dm(3), 1 g/dm(3) and 750 rpm, respectively, when considering combustible recovery and ash content. (c) 2012 Elsevier B.V. All rights reserved.Öğe Hydrophobic flocculation characteristics of calcite and effects of some inorganic dispersants(NATL INST SCIENCE COMMUNICATION, 2006) Ucbeyiay, H.; Ozkan, A.Hydrophobic flocculation characteristics of calcite mineral were investigated using sodium dodecyl sulphate (SDS) and Acro 845. Calcite suspensions could be flocculated by these anionic surfactants in the pH range of 9.3-11.5. Especially SDS was more effective on the calcite suspensions at pH values lower than 10.5. The flocculation of calcite with SDS and Aero 845 increased rapidly with increasing surfactant concentration. However, it started to decrease at concentrations higher than 30 mg/L for Aero 845 and 50 mg/L for SDS. It was found that the maximum aggregation degree of calcite particles could be achieved with a stirring speed of 500 rpm and a flocculation time of 3 min. The effects of sodium silicate, sodium polyphosphate and sodium phosphate, used as inorganic dispersants, on the flocculation of calcite were also studied. In the presence of sodium silicate and sodium polyphosphate, the flocculation power values obtained with both surfactants decreased with increasing dispersant concentration till approximately 0.5 and 1 g/L concentrations, respectively. Also, the flocculation of calcite with Aero 845 and SDS decreased towards 0.5 and 1 g/L concentrations of sodium phosphate, respectively. At higher dispersant concentrations, these power values remained relatively constant for sodium silicate, and different effects were also observed for other dispersants depending on surfactant type used in the experiments. In addition, it was found that sodium silicate was more effective to disperse the calcite suspensions with SDS and Aero 845.Öğe Investigation of coagulation and electrokinetic behaviors of clinoptilolite suspension with multivalent cations(TAYLOR & FRANCIS INC, 2018) Ozkan, A.; Sener, A. G.; Ucbeyiay, H.This paper presents the results of investigations concerning the influence of magnesium, copper, aluminum and ferric cations on the coagulation and electrokinetic behaviors of clinoptilolite suspension. While clinoptilolite exhibited a negative surface charge over a broad pH range and had no isoelectric point (iep), especially the trivalent ions strongly changed the sign and magnitude of the zeta potential of the mineral depending on pH and cation concentration. The coagulation of clinoptilolite particles with these metal cations also showed sharp dependences on pH and cation concentration. That is, the coagulation process significantly took place in the pH and concentration ranges in which metal hydroxides existed in the suspension. Moreover, the coagulation behavior of clinoptilolite at pH values below the iep of metal hydroxides was usually consistent with its zeta potential variation, indicating a coagulation process by the charge neutralization mechanism. However, at pH values larger than the iep of these hydroxides, sweep coagulation of clinoptilolite suspension occurred and a clear correlation between surface charge and the onset of coagulation was not determined.Öğe Two-stage shear flocculation for enrichment of fine boron ore containing colemanite(ELSEVIER SCIENCE BV, 2014) Ucbeyiay, H.; Ozkan, A.The enrichment of fine boron ore containing colemanite mineral was investigated using shear flocculation, two-stage shear flocculation, column flotation and floc flotation techniques. In these fine particle processing methods, sodium dodecyl sulfate (SDS) and Aero 801 were used as surfactant for colemanite. Also, sodium pyrophosphate and sodium hexametaphosphate were employed to improve the selectivity of the processes. The highest grade of the colemanite concentrate was obtained with two-stage shear flocculation method using Aero 801 and sodium hexametaphosphate. Under the optimum conditions, a concentrate of 38.65% B2O3 could be recovered by two-stage shear flocculation from the ore containing 26.98% B2O3. (C) 2014 Elsevier B.V. All rights reserved.
