Tane morfolojisinin flotasyona olan etkisi

Today, due to the finer liberation sizes of minerals, mineral processing methods utilizing the wettability differences of particles like flotation has become more preferable than other methods. Although many individual parameters in flotation process like pH, surfactant type have been explained in detail in many papers, the effect of morphology on flotation recoveries has not been dwelled much. Particularly, the mechanism responsible for the effect of shape and roughness on flotation grade and recoveries requires a thorough systematic studies in order to reveal the extent of bubble particle interactions upon changes in morphology. It is therefore the aim of this PhD thesis study, to investigate these still questionable and yet still misunderstood phenomenon of particle morphology on flotation recoveries from the persepective of both experimental and theoretical issues and extend the findings to practical industrial roadmaps. In the experimental part of the thesis, the surface roughness of the particles was monitored with different methods such as acid etching in the presence of HF, grinding in different media (ball and autogenously grinding with very fine sized abrasive) and sand blasting. Among them, sand blasting is probably the most unique. In the literature, sand blasting is generally used for surface etching by blasting of sand sized particles to the surfaces. However, in this study, the morphological changes of particles was investigated by changing the distance between plate–gun and the nozzle pressure. The size distributions of particles, shape factor and roughness of these particles was determined by image analysis method for each fraction upon grinding and sand-blasting processes. The roughness parameter was determined by different methods as B.E.T., optical profilometer, atomic force microscopy (A.F.M.) and scanning electron microscopy (SEM). After morphological characterization of particles, certain fractions (150-106 µm) was subjected to systematic micro-flotation tests. In addition, contact angle measurements were also performed for materials produced under different conditions. The results of these various tests showed that the selection of particle production method is most critical to assess the particle morphology in terms of roughness and shape factor. It is clearly shown that angular particles always float better than round particles using both flotation and bubble-particle attachment tests. On the other hand, comparison of smooth-spherical and rough-spherical particles identified that roughness is the major parameter determining the flotation rates. In this context, increasing the roughness degree resulted in higher flotation rates, which well correlated with the theoretical models. The results of flotation studies showed that the influence of morphology in terms of shape factor and roughness varied with the hydrophobicity of particles. In other words, at high reagent concentrations, while the shape factor became dominant, at lower hydrophobicities, particle roughness became the major driving force in the evaluation of flotation recoveries. From this point of view, it is proposes that tuning the particle morphology is of significant importance for industrial applications. In the theoretical part of the study, a derivative of DLVO theory was adapted from the literature and in order to explain the flotation results through the interactions between bubbles and particles with only roughness values taken into consideration. As a result, it was shown that the distance of separation increased with increasing the roughness which concamitantly increased the level of particle hydrophobicity