Yazar "Guven, O." seçeneğine göre listele
Listeleniyor 1 - 3 / 3
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Contribution of particle morphology on flotation and aggregation of sphalerite particles(Pergamon-Elsevier Science Ltd, 2021) Uysal, T.; Guven, O.; Ozdemir, O.; Karaagaclioglu, I. E.; Tunc, B.; Celik, M. S.Physical properties such as particle morphology (shape and roughness) play an important role in the flotation process to understand the bubble-particle and particle?particle interactions. In this study, a new approach was suggested for the first time to correlate the aggregation and flotation of sphalerite mineral along with the contribution of morphological variations. Towards this aim, fine particles of -74 + 38 ?m were produced with a ball mill while the effect of grinding time was investigated on morphology. In addition to the grinding, the roughness of particles was tuned through an abrasion treatment with silicon carbide. The shape factor of particles determined by image analysis and the roughness of particles measured with profilometer were also correlated with the micro-flotation experiments and aggregation analyses. The bubble-particle attachment time and fastcam recordings were used to shed light on the possible mechanisms, i.e. roughness played a major role in its contribution of morphology on both flotation and aggregation of particles which were supported by fast-cam recordings as the larger bundle of particles and lower attachment time on bubble-particle attachment timer. In sum, adjusting the morphology of sulfide particles enhanced particle?particle interactions (aggregation) and led to improved bubble-particle interactions and in turn to flotation.Öğe Does hemimicelle concentration (HMC) coincide with critical aggregation concentration (CAC) in flotation?(Pergamon-Elsevier Science Ltd, 2024) Celik, M. S.; Guven, O.; Karaagaclioglu, I. E.; Ozdemir, O.Flotation recoveries of oxide, silicate, and salt-type minerals when plotted against collector concentration exhibit a break point followed by a sharp increase. This threshold point called hemimicelle concentration (HMC) has been traditionally characterized by the formation of two-dimensional surfactant patches on the solid surface. The condensed phases have been identified by a variety of techniques since their inception in the early 1960s. Conversely, in another hypothesis, this breakthrough point was ascribed to surface precipitation of collector species on the mineral surface. Despite these controversies, a clear understanding of this issue has not been agreed upon. In fact, both occurrences are thermodynamically indistinguishable as they represent a similar property of surfactant deposition on the surface. In this context, the same researchers have stated that surface precipitation occurs way below the appearance of bulk precipitates. This issue of threshold point is a logical phenomenon and well documented in flotation literature. However, the alternatives discussed above have been usually taken for granted due to a lack of sufficient evidence. The objective of this paper is to present an alternative vision to the flotation literature. In this paper, we are proposing a third mechanism in which the threshold point is shown to correspond to the critical aggregation concentration (CAC) of particles in the bulk. Micro-flotation, zeta potential, and aggregation studies along with Fast-Cam recordings illustrate that aggregation of particles from this critical breakthrough point onward accelerates due to the formation of both hemimicelles and surface precipitates and particles undergo more intensive assemblage leading to higher flotation kinetics. The XDLVO calculations also confirm these findings.Öğe Effects of grinding time on morphology and collectorless flotation of coal particles(Elsevier, 2022) Guven, O.; Kaymakoglu, B.; Ehsani, A.; Hassanzadeh, A.; Sivrikaya, O.The impact of particle shape and surface properties has been mainly overlooked in the literature for different mineral systems. In this study, to investigate the effects of morphological variations, samples of clean coal parti-cles (-0.212 + 0.075 mm) were used and the flotation experimental in a batch condition (2 L Denver cell) were conducted in the absence of collectors by keeping the particle size constant. Binocular microscopic images were used to determine the shape factors of coal particles. A dry ball milling process was carried out as a function of grinding time (60-960 s) and representative samples were taken for determining both shape and floatability of particles. Further, particle-bubble attachment, zeta potential, roundness, surface roughness values and flotation kinetics were measured. It was indicated that by increasing milling duration from 60 s to 960 s, the round-ness and roughness increased from 0.792 to 0.809 and 23 nm to 57 nm, respectively. This led to increasing flotation rate constant from 0.4482 +/- 0.02 to 0.4856 +/-& nbsp;& nbsp;0.03 1/min. In addition, the theoretical calculations for energy barrier showed that upon increasing the roughness degree from 0 to 57 nm, the energy barrier signifi-cantly decreased from 2.79E-16 to 6.51E-17 J/m(2), which also proved our findings from a theoretical point of view. Thus, it was finally concluded that the more the roughness, the higher the flotation kinetics and the lower the energy barrier.(c) 2021 Elsevier B.V. All rights reserved.
