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    Adsorption Kinetics of Various Frothers on Rising Bubbles of Different Sizes under Flotation Conditions
    (Mdpi, 2021) Batjargal, Khandjamts; Guven, Onur; Ozdemir, Orhan; Karakashev, Stoyan, I; Grozev, Nikolay A.; Boylu, Feridun; Celik, Mehmet Sabri
    This paper studies the effect of the type and concentration of selected frothers, the gas flowrate, and the pore size of the porous frit on the bubble sizes (Sauter mean diameter, SMD) of bubbling flow produced in a micro-flotation cell, and the determination of bubble size distribution (BSD) in the presence of the frothers. The commercial frothers polypropylene glycols (PPG 200, 400, and 600), tri propylene glycol (BTPG), triethylene glycol (BTEG), dipropylene glycol (BDPG), and Methyl Isobutyl Carbinol (MIBC) were used in the present investigation. The frother concentration varied from 1 to 1000 ppm. The flow rate varied in the range of 25 to 100 cm(3)/min. The pore sizes of the frit were selected as 10-16 mu m, 16-40 mu m, and 40-100 mu m. Each frother exhibited its own unique ability in preventing coalescence of the bubbles in the order of BTEG < BDPG < PPG 200 < MIBC < BTPG < PPG 400 < PPG 600. The factorial experiments established that the type of the frother and its concentration have a major effect on the size of the bubbles. The bubbles decreased twice their size when the frother concentration was increased from 1 ppm to 1000 ppm. The pore size of the frit is a significant factor as well. The size of the bubbles can be reduced from about 10% to about 40% by decreasing the pores from 40-100 mu m to 10-16 mu m but the level of this decrease depends on the type of the frother. The increase of the flowrate from 25 cm(3)/min to 100 cm(3)/min produced bubbles smaller by 25% to 50% for the case of BTEG, BDPG, PPG 200, MIBC, BTPG, while a minimum of the bubble sizes was reached for the case of PPG 400 and PPG 600, beyond which the bubbles enlarged their size. The BSD in the presence of PPG 600 varied around 0.3 mm, whereas BTEG gave a wider BSD which indicated that the type of frother affected the bubble production. Our analysis shows that the first group of frothers adsorbs instantly on the bubbles, once they leave the porous frit, thus reaching equilibrium. PPG 400 and PPG 600 adsorb significantly slower on the bubbles, possibly not reaching equilibrium during their resident time.
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    Bubbling properties of frothers and collectors mix system
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2022) Batjargal, Khandjamts; Guven, Onur; Ozdemir, Orhan; Karakashev, Stoyan I.; Grozev, Nikolay A.; Boylu, Feridun; Celik, Mehmet Sabri
    This paper studies the effect of the type and concentration of selected frothers and collectors mix system on the bubble sizes (Sauter mean diameter, SMD) of bubbling flow produced in a micro flotation cell and the determination of bubble size distribution (BSD). The usage of dodecyl amine hydrochloride (DAH) collector on the critical coalescence concentration of commercial frothers PPG200, PPG400, and PPG600 was investigated in detail. The results of these studies showed that the usage of DAH decreased the CCC of these frothers. Each frother + collector mixing system exhibited its unique ability in preventing coalescence of the bubbles in the order of PPG200 < PPG400 < PPG600. The factorial experiments established that the type of the frother, collector, and their concentration had a major effect on the size of the bubbles. The BSD in the presence of PPG600 + DAH mix system resulted in a little bit wider BSD which indicated the effect of frother in mixed
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    Bubbling properties of frothers and collectors mix system
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2022) Batjargal, Khandjamts; Guven, Onur; Ozdemir, Orhan; Karakashev, Stoyan I.; Grozev, Nikolay A.; Boylu, Feridun; Celik, Mehmet Sabri
    This paper studies the effect of the type and concentration of selected frothers and collectors mix system on the bubble sizes (Sauter mean diameter, SMD) of bubbling flow produced in a micro flotation cell and the determination of bubble size distribution (BSD). The usage of dodecyl amine hydrochloride (DAH) collector on the critical coalescence concentration of commercial frothers PPG200, PPG400, and PPG600 was investigated in detail. The results of these studies showed that the usage of DAH decreased the CCC of these frothers. Each frother + collector mixing system exhibited its unique ability in preventing coalescence of the bubbles in the order of PPG200 < PPG400 < PPG600. The factorial experiments established that the type of the frother, collector, and their concentration had a major effect on the size of the bubbles. The BSD in the presence of PPG600 + DAH mix system resulted in a little bit wider BSD which indicated the effect of frother in mixed
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    Correlation of Flotation Recoveries and Bubble-Particle Attachment Time for Dodecyl Ammonium Hydrochloride/Frother/Quartz Flotation System
    (Mdpi, 2023) Batjargal, Khandjamts; Guven, Onur; Ozdemir, Orhan; Boylu, Feridun; Pural, Yusuf Enes; Celik, Mehmet Sabri
    Recent studies in the flotation of fine particles have necessitated new techniques and analyses for developing various strategies. Particularly, the improvements in flotation chemistry including the selection of the type of frother, collector, and other reagents have become very significant. In this study, the effect of different commercial polypropylene glycol frothers (PPG200, 400, and 600) in the presence of dodecylammonium hydrochloride (DAH) was investigated for their contribution to flotation recoveries and bubble-particle attachment time values of fine quartz minerals. Zeta potential measurements with DAH were also carried out as a function of pH and reagent concentration to justify the effect of collector usage alone on the charge of particles. A linear increase in flotation recoveries against collector concentration, e.g., 7.4% recovery at 1 x 10-5 mol/L DAH and 65.4% recovery at 1 x 10-3 mol/L DAH, was obtained. In this context, the contribution of frothers was particularly important in that a recovery of 15.91% in the absence of the frother and a modest increase to 19.70% was obtained upon the addition of PPG600 at its critical coalescence concentration (CCC) of 3 ppm. Finally, a strong correlation was found between the bubble-particle attachment time and flotation recovery as a function of collector concentration (lowest attachment time vs. highest flotation recovery). The latter correlation is very promising because bubble attachment time leads to various micro-mechanisms in flotation including bubble film thinning, bubble rupture, and induction time, and consequently, frother efficiency in the presence and absence of a collector. As a result, the experimental findings were gathered to achieve a consistent base for further fundamental studies on the application of the synergistic effect of frothers and collectors in the flotation of fine particles.
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    Correlations for Easy Calculation of the Critical Coalescence Concentration (CCC) of Simple Frothers
    (Mdpi, 2020) Karakashev, Stoyan I.; Grozev, Nikolay A.; Batjargal, Khandjamts; Guven, Onur; Ozdemir, Orhan; Boylu, Feridun; Celik, Mehmet Sabri
    Can the critical coalescence concentration (CCC) of the flotation frothers be predictable? What is the relation between their molecular structure and their CCC values? A literature survey found specific correlations between the hydrophilic-lipophilic balances (HLB) and HLB/Mw (where Mw stands for the molecular mass) of homologue series of frothers and their CCC values, but the results are invalid when the molecule's functional groups change. For this reason, 37 frothers with known values of CCC were analyzed. The CCC values of seven frothers were determined, and the rest were taken from the literature. The frothers were subdivided in homologue series with an increasing number of the carbon atoms with an account for the type and the location of the functional group, thus deriving three types of correlations lnCCC =f(HLB) applicable for: (i) alcohols; (ii) propylene glycols alkyl ethers and propylene glycols; (iii) ethylene glycols alkyl ethers. The average accuracy of these correlations between CCC and HLB is 93%.
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    Design and process optimisation of double emulsions loaded with casein hydrolysate
    (Elsevier Sci Ltd, 2024) Salum, Pelin; Ulubas, Cagla; Guven, Onur; Cam, Mustafa; Aydemir, Levent Yurdaer; Erbay, Zafer
    Water-in-oil-in-water (W1/O/W2) emulsions show promise for encapsulating hydrophilic active substances. However, the low stability of W1/O/W2 hinders its use for encapsulation purposes, and peptide encapsulation has challenges due to its surface-active properties. This study aimed to determine the appropriate formulation based on turbidity and encapsulation efficiency, as well as the optimal production parameters (ultrasound amplitude and time) for double emulsions containing casein hydrolysate, with a focus on the second homogenisation stage. Double emulsions were produced with three different emulsifiers (polysorbates 20, 60, or 80) at different concentrations (0.25%, 1%, or 1.75%) and dispersed phase ratios (10%, 20%, or 30%) using an ultrasound homogeniser. The results indicated that dispersed phase ratios and emulsifier concentrations had higher impact on emulsion properties than emulsifier types. A stable emulsion with high encapsulation efficiency was achieved with 1% polysorbate 20 and a 30% dispersed phase ratio, using sonication at 54% amplitude for 66 s. (c) 2024 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
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    Determining the effect of tung biodiesel on thermodynamic, thermoeconomic, and exergoeconomic analyses at high engine speeds
    (Frontiers Media Sa, 2024) Sanli, Bengi; Guven, Onur; Ozcanli, Mustafa; Uludamar, Erinc
    Tung biodiesel is a promising alternative fuel type produced from the tung tree. In the current study, the effect of the addition of 20%, by volume, of tung biodiesel to diesel fuel was evaluated in terms of energetic-exergetic analyses based on the first and second laws of thermodynamic at various high engine speeds (2,400, 2,600, and 2,800 rpm). Additionally, this study aimed to assess the thermoeconomic and exergoeconomic aspects of a diesel engine. The findings revealed that the amount of energy converted to useful work for the diesel fuel was higher than that of the DTB20 fuel, even though the fuel energy obtained from DTB20 fuel was higher than that of diesel fuel at all engine speeds. The highest energy and exergy efficiencies for the engine fueled with diesel fuel were obtained as 31.07% and 29.15% respectively, while the corresponding values for the engine fueled with DTB20 fuel were determined as 27.15% and 25.19% at the engine speed of 2,400 rpm, respectively. However, at 2,800 rpm, a significant decrease in both the energy and exergy efficiencies was observed for both diesel and tung biodiesel blended fuels due to the increased mechanical friction of the engine components. Furthermore, at the highest engine speed, entropy generation increased, owing to a higher exergy destruction rate. The entropy generation rate increased to 0.38 kW/K for diesel fuel and 0.46 kW/K for DTB20 fuel since the enhancement of the engine speed caused the ascent of the fuel consumption rate. Regarding thermoeconomic-exergoeconomic analyses, for both diesel and tung biodiesel blended fuels, there is no distinct difference in the thermoeconomic-exergoeconomic parameters at 2,400 and 2,600 rpm as the values of these parameters at the engine speed of 2,800 rpm increased significantly. In light of all the findings, it can be concluded that the engine speed of 2,800 rpm is not applicable to run the engine due to higher friction and corresponding energy destruction in the engine system.
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    Effect of different drying techniques on silaning efficiency
    (Elsevier Sci Ltd, 2023) Ozturk, Busra; Yavuz, Merve; Aydinoglu, Aysu; Guven, Onur; Hazar, Afife Binnaz Yoruc
    Colloidal drying is a method that is used in many areas but leads to particle agglomeration. In this study, the effects of drying methods on the agglomeration, dispersion, and silanization efficiency of silica nanoparticles (NSp) were investigated using vacuum oven dryer (VOD), rotary evaporator (RE), and freeze-dryer (FD) methods. In addition, dried silica nanoparticles were mechanically ground using a conventional ball mill system, and the relationship between grinding effect and agglomeration was investigated. The results of the SEM analysis showed that the surface energy, which increased with the reduction of the grain size as a result of the prolon-gation of the grinding time, caused the agglomeration of the grains. BET analysis, it was observed that the surface areas of silica nanoparticles vary depending on the drying method. Contact angle measurement was performed to investigate the silanization ability of silica nanoparticles and it was determined that silica nanoparticles with the low surface area had the lowest contact angle. Therefore, the silanization ability of silica nanoparticles was observed to increase with the reduction of agglomeration. As a result, the VOD technique, which allows the production of low surface area silica nanoparticles, was chosen as the best method for increasing the silanization efficiency.
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    Effect of particle shape properties on selective separation of chromite from serpentine by flotation
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2020) Guven, Onur; Serdengecti, M. Tayhan; Tunc, Berivan; Ozdemir, Orhan; Karaagaclioglu, Ibrahim E.; Celik, Mehmet S.
    Although many studies have been conducted on the morphological variations and its effects on flotation recoveries of a single mineral system, a systematic study for the flotation behavior of mixtures of minerals has not dwelled much. In this study, th flotation behavior of chromite and serpentine minerals was investigated to distinguish and isolate the contribution of morphology in single and binary systems. For this purpose, the shape analyses for the minerals ground as single and mixture were performed, and their flotation behaviors determined with the micro-flotation experiments. Additionally, the zeta potential measurements were carried out in the presence of sodium oleate as a collector. The shape analysis of the ground samples showed that while the roundness values of chromite and serpentine (gangue) minerals as single were quite different, the particle shape of chromite favored serpentine in the mixture system which in turn suggested that the mineral with the high hardness value dominates the shape characteristics in binary grinding conditions. Accordingly, while the flotation characteristics of chromite in the mixture followed the same trend with the flotation of a single chromite system as a function of particle shape, almost a reverse trend was obtained for the shape and flotation of serpentine in the mixture compared to a single serpentine system. Thus, at roundness values of chromite particles from 0.797 to 0.732, the flotation recoveries of chromite in the mixture increased from 51.0% to 75.4%. On the other hand, likewise chromite, the flotation recoveries of serpentine increased from 20.0% to 37.3% proportional to the roundness range of 0.757 and 0.709. These findings in turn showed that the grinding conditions dictate the soft component to be monitored by the harder and denser component which dominates the angularity and floatability of the mixture.
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    Effect of particle shape properties on selective separation of chromite from serpentine by flotation
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2020) Guven, Onur; Serdengecti, M. Tayhan; Tunc, Berivan; Ozdemir, Orhan; Karaagaclioglu, Ibrahim E.; Celik, Mehmet S.
    Although many studies have been conducted on the morphological variations and its effects on flotation recoveries of a single mineral system, a systematic study for the flotation behavior of mixtures of minerals has not dwelled much. In this study, th flotation behavior of chromite and serpentine minerals was investigated to distinguish and isolate the contribution of morphology in single and binary systems. For this purpose, the shape analyses for the minerals ground as single and mixture were performed, and their flotation behaviors determined with the micro-flotation experiments. Additionally, the zeta potential measurements were carried out in the presence of sodium oleate as a collector. The shape analysis of the ground samples showed that while the roundness values of chromite and serpentine (gangue) minerals as single were quite different, the particle shape of chromite favored serpentine in the mixture system which in turn suggested that the mineral with the high hardness value dominates the shape characteristics in binary grinding conditions. Accordingly, while the flotation characteristics of chromite in the mixture followed the same trend with the flotation of a single chromite system as a function of particle shape, almost a reverse trend was obtained for the shape and flotation of serpentine in the mixture compared to a single serpentine system. Thus, at roundness values of chromite particles from 0.797 to 0.732, the flotation recoveries of chromite in the mixture increased from 51.0% to 75.4%. On the other hand, likewise chromite, the flotation recoveries of serpentine increased from 20.0% to 37.3% proportional to the roundness range of 0.757 and 0.709. These findings in turn showed that the grinding conditions dictate the soft component to be monitored by the harder and denser component which dominates the angularity and floatability of the mixture.
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    Effect of surface roughness on particle-bubble interaction: A critical review
    (Elsevier Ltd, 2023) Sun, Yujin; Bu, Xiangning; Ulusoy, Ugur; Guven, Onur; Vaziri Hassas, Behzad; Dong, Xianshu
    Particle roughness affects flotation recovery in terms of wettability, kinetics, bubble-particle interactions, and even inter-particle aggregation. The influence of the surface roughness of particles on flotation recovery and their underlying mechanisms have been proven to be important. To achieve this goal, researchers have used a variety of industrial minerals or natural hydrophilic/hydrophobic materials to demonstrate the effect of morphological characteristics on particle-bubble adhesion, detachment processes, and flotation rates and recoveries. However, the current conclusions are not uniform and the findings vary with the materials used. Therefore, the preparation, as well as measurement methods used in the current studies on flat surfaces, and the effects of particle surface roughness, are summarized and discussed in this paper, respectively. The effects of roughness on the contact angle, induction time, particle-bubble interaction energy, and flotation effectiveness are reviewed. A systematic review of the relevant literature from recent decades is presented with the expectation of shedding light on the underlying mechanisms behind the inconsistent findings and providing instructive guidance for future studies focusing on the effect of surface roughness on particle-bubble interactions. © 2023 Elsevier Ltd
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    Experimental Procedure for the Determination of the Critical Coalescence Concentration (CCC) of Simple Frothers
    (Mdpi, 2020) Guven, Onur; Batjargal, Khandjamts; Ozdemir, Orhan; Karakashev, Stoyan, I; Grozev, Nikolay A.; Boylu, Feridun; Celik, Mehmet Sabri
    In this study, the critical coalescence concentrations (CCC) of selected commercial frother solutions, namely polypropylene glycols (PPG 200, 400, and 600), tri propylene glycol (BTPG), triethylene glycol (BTEG), dipropylene glycol (BDPG), and as a reference, methyl isobutyl carbinol (MIBC), were determined using a bubble column based on light absorption. The results for all seven frothers showed that BTEG has the worst bubble inhibiting performance, and PPG 600 has the best bubble inhibiting performance. While critical coalescence concentration (CCC) was found as 3 ppm for PPG 600, it increased to 25 ppm for BTEG. In the case of MIBC, which was the reference point, the CCC value was found as 10 ppm, which was consistent with the literature. The surface tension isotherms of the frothers were determined and analyzed with one of the latest adsorption models. The results indicated that the polypropylene glycol frothers showed more surface activity compared to alcohol or other frothers investigated. This is due to the additional reorganization of the PPG molecules on the air/water interface, thus boosting its surface activity.
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    Frothing Performance of Frother-Collector Mixtures as Determined by Dynamic Foam Analyzer and Its Implications in Flotation
    (Mdpi, 2023) Batjargal, Khandjamts; Guven, Onur; Ozdemir, Orhan; Karakashev, Stoyan I. I.; Grozev, Nikolay A. A.; Boylu, Feridun; Celik, Mehmet Sabri
    In recent years, most of the studies have been adapted to determine the optimum conditions for the flotation of very fine minerals. In this context, besides parameters such as particle size, morphology, and pH, the effects of frother type and its concentration present a very significant role in optimizing the flotation conditions. Therefore, the effects of froth stability during flotation can be considered one of the most important issues. Considering that knowledge in mind, in this study, the foamability and froth decay rate of six frothers (PPG200, PPG400, PPG600, BTEG, BTPG, and BDPG) having different molecular weights but similar polyglycol structures were investigated. In addition, methyl isobutyl carbinol (MIBC) which is a well-known frother type in the industry was also used as a reference. Additionally, a series of tests were also performed in the presence of collectors (Dodecylamine hydrochloride, DAH, and sodium oleate, NaOL) + frother mixtures to mimic the flotation conditions. The results of these tests indicated that the bubble size became finer at even low concentrations of PPG600 and PPG400 frothers. Following that, a significant decrease in bubble size was also found for the collector + frother mixtures system regardless of the concentration of the frothers.
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    Microscopy-Assisted Digital Image Analysis with Trainable Weka Segmentation (TWS) for Emulsion Droplet Size Determination
    (Mdpi, 2022) Salum, Pelin; Guven, Onur; Aydemir, Levent Yurdaer; Erbay, Zafer
    The size distribution of droplets in emulsions is very important for adjusting the effects of many indices on their quality. In addition to other methods for the determination of the size distribution of droplets, the usage of machine learning during microscopic analyses can enhance the reliability of the measurements and decrease the measurement cost at the same time. Considering its role in emulsion characteristics, in this study, the droplet size distributions of emulsions prepared with different oil/water phase ratios and homogenization times were measured with both a microscopy-assisted digital image analysis technique and a well-known laser diffraction method. The relationships between the droplet size and the physical properties of emulsions (turbidity and viscosity) were also investigated. The results showed that microscopic measurements yielded slightly higher values for the D(90), D[3,2], and D[4,3] of emulsions compared to the laser diffraction method for all oil/water phase ratios. When using this method, the droplet size had a meaningful correlation with the turbidity and viscosity values of emulsions at different oil/water phase ratios. From this point of view, the usage of the optical microscopy method with machine learning can be useful for the determination of the size distribution in emulsions.
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    Morphological changes of glass bead particles upon an abrasive blasting as characterized by settling and flotation experiments
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2021) Hassas, Behzad Vaziri; Guven, Onur; Basturkcu, Esra; Celik, Mehmet S.
    The recent developments in mineral processing led researchers to look for alternative methods and propose new mechanisms for enhancing the efficiency of relatively costly processes (e.g., flotation, aggregation), where especially dealing with fine particles. Finer the particles, the higher the role of their surface on their behavior and properties. The importance of particle morphology becomes even clearer when particle-particle and particle-bubble interactions are considered. In this study, the effect of particle shape roundness on the surface wettability and flotation response was investigated upon producing fine particles with the abrasion blasting method. In order to provide a fundamental perspective, adsorption measurements were also carried out along with the flotation experiments under the same conditions. In addition to these, zeta potential measurements were also carried out with both spherical and blasted particles as a function of collector concentration. The results suggested that the roundness of particles decreased up to a certain nozzle pressure value, which was followed by higher adsorption degrees and consequently higher flotation recoveries. Additionally, settling rate tests were also performed with very fine material to show the effect of particle morphology on particle-particle interactions. The results showed that while lower settling rate values were obtained for spherical ones, higher values were obtained in the case of the ground and blasted samples in the presence of DI water. It was concluded from this study that the Abrasive blasting method could be an effective alternative for tuning the surface morphology of particles and their wettability, which in turn can affect the particle-particle interactions in the system.
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    On the frother's strength and its performance
    (Pergamon-Elsevier Science Ltd, 2021) Karakashev, Stoyan, I; Grozev, Nikolay A.; Ozdemir, Orhan; Batjargal, Khandjamts; Guven, Onur; Ata, Seher; Bournival, Ghislain
    It is a common rule that the strength of the frother is assessed by either its dynamic foamability index (DFI) or its critical coalescence concentration (CCC). The smaller the value of CCC the stronger the frother is. This general rule (CCC rule) however is superficial although being well accepted. Yet, there are critical questions about the performance of the frothers on the bubbles: 1. Are the Gibbs elasticities stemming from the different frothers equally efficient in inhibiting the bubble coalescence? 2. How the Gibbs elasticity control the mean bubble diameter for every specific frother? 3. How the CCC value of the frothers and the mean bubble diameter are related? This work raises these questions and suggests a rule based on the Gibbs elasticity performance (Gibbs elasticity rule). The performances of seven frothers (PPG 200, PPG 400, PPG 600, BDPG, BTPG, BTEG, and MIBC), whose surface tension isotherms, CCC values, bubble fraction coalescence, and Sauter mean bubble diameter vs. frother concentration were previously studied, were analyzed According to the CCC rule, these frothers follow the order of increasing strength: MIBC approximate to BTEG < BDPG < PPG 200 < BTPG < PPG 400 < PPG 600. The Gibbs elasticity rule questions what will be the bubble fraction coalescence at a certain fixed value of the Gibbs elasticity of a frother? The above mentioned frothers according to this rule follow the series of PPG 400 < BTPG approximate to BDPG < MIBC approximate to BTEG < PPG 200. Surprisingly, it was established that PPG 600 exhibits abnormal behavior, thus significantly inhibiting the bubble coalescence in a different way, not related to the Gibbs elasticity. For this reason, PPG 600 in the above series was not included. Moreover, correlations between the mean bubble diameter, the Gibbs elasticity, and the CCC value were established. Additionally, a new dimensionless parameter was developed. It estimates the strength of a frother - zeta = ln(Ks.lCH2/alpha 0). A Surprising correlation between the CCC values of 21 frothers and their zeta values was developed. Moreover, it was established a correlation allowing us to calculate the bubble fraction coalescence vs. the frother concentration if the CCC value is known.
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    Physical restrictions of the flotation of fine particles and ways to overcome them
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2022) Karakashev, Stoyan, I; Grozev, Nikolay A.; Ozdemir, Orhan; Guven, Onur; Ata, Seher; Bournival, Ghislain; Batjargal, Khandjamts
    This work analyses the basic problems of the fine particles flotation and suggests new ways to overcome them. It is well accepted that the poor recovery of fine particles is due to the small collision rate between them and the bubbles due to the significant difference between their sizes. This common opinion is based on a theory, assuming in its first version a laminar regime, but later has been advanced to intermediate turbulence. It accepts that the particles are driven by the streamlines near the bubbles. In reality, the high turbulence in the flotation cells causes myriads of eddies with different sizes and speeds of the rotation driving both bubbles and particles. Yet, a theory accounting for high turbulence exists and states that the collision rate could be much higher. Therefore, we assumed that the problem consists of the low attachment efficiency of the fine particles. Basically, two problems could exist (i) to form a three-phase contact line (TPCL) the fine particle should achieve a certain minimal penetration into the bubble, requiring sufficient push force; (ii) a thin wetting film between the bubble and the particle forms, thus increasing the hydrodynamic resistance between them and making the induction time larger than the collision time. We assumed particles with contact angle theta = 80 degrees, and established a lower size flotation limit of the particles depending mostly on the size of the bubbles, with which they collide. It spans in the range of Rp = 0.16 mu m to Rp = 0.40 mu m corresponding to bubbles size range of Rb = 50 mu m to Rb = 1000 mu m. Hence, thermodynamically the particle size fraction in the range of Rp = 0.2 mu m to Rp = 2 mu m are permitted to float but with small flotation rate due to the small difference between the total push force and maximal resistance force for formation of TPCL. The larger particles approach slowly the bubbles, thus exceeding the collision time. Therefore, most possibly the cavitation of the dissolved gas is the reason for their attachment to the bubbles. To help fine particles float better, the electrostatic attraction between bubbles and particles occurred and achieved about 92% recovery of fine silica particles for about 100 sec. The procedure increased moderately their hydrophobicity from theta approximate to 27.4 degrees to theta approximate to 54.5 degrees. Electrostatic attraction between bubbles and particles with practically no increase of the hydrophobicity of the silica particles ended in 47% recovery. All this is an indication of the high collision rate of the fine particles with the bubbles. Consequently, both, an increase in the hydrophobicity and the electrostatic attraction between particles and bubbles are key for good fine particle flotation. In addition, it was shown experimentally that the capillary pressure during collision affected the attachment of the to the bubbles.
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    Physicochemical Characterization of Natural Wollastonite and Calcite
    (Mdpi, 2020) Kangal, Murat Olgac; Bulut, Gulay; Guven, Onur
    Wollastonite and calcite minerals are significant raw materials and are extensively used due to their unique properties. Wollastonite is used in plastics, paint, ceramics, paper, resins, and in construction as a substitution for asbestos due to its chemical stability, thermal resistivity, needle-like shape, and brightness. Calcite is one of the most used raw materials because of its low hardness, high alkalinity, sorptive properties, white and bright color. Wollastonite and calcite are two minerals found together in nature. The most common method used for separating these two minerals is flotation. In this study, the surface properties of pure mineral samples were investigated. The pH profiles of both minerals were obtained by measuring the surface charge of particles followed by the measurement of the zeta potential in different collector concentrations. The wettability of minerals was examined by measuring their contact angles.
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    The effect of NaCl concentration on the interaction energy between feldspar minerals
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2022) Guven, Onur; Can, Muhammed Fatih; Karaguzel, Cengiz
    The impact of the usage of monovalent ion concentration on the selective flotation of feldspar minerals has been receiving more attention in recent years. Although many experimental studies have been reported to justify its contribution to their flotation recovery, the effect of particle-particle interaction with theoretical calculations has rarely been studied. The objective of this study was, therefore, to explain the effect of monovalent ion concentration (in particular NaCl) on interactions between albite and microcline particles with a theoretical model based on the classical DLVO. The theoretical modeling results suggested that controlling the monovalent ion concentration not only adjusts the energy barrier between particles but also can be used to determine the critical salt concentration for further tests.
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    The effect of shape and roughness on flotation and aggregation of quartz particles
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2022) Guven, Onur
    A combination of grinding and abrasion processes was applied to control the shape and roughness of quartz particles to investigate their roles in flotation recoveries and aggregation rates at different collector concentrations. The results showed that while the roundness values (Ro) of quartz particles varied in the range of 0.56-0.58 (Ro) at 480 and 1920 sec grinding, the roughness values of particles varied between 3.12-4.02 ?m at 60 and 240 min abrasion. The flotation and aggregation tests showed while the flotation recovery increased from 31.3 % to 34.2 % in reverse proportion to their roundness values at 1x10-6 M DAH concentrations, a similar increasing trend from 34.1% to 38.1 % as a function of their roughness value from 3.12 ?m to 4.02 ?m. On the other hand, in the case of aggregation tests, while the turbidity values decreased from 40.6 NTU to 32.1 NTU at 1x10-6 M DAH concentrations for rounder particles, it was found as 36.2 NTU to 31.8 NTU for rougher ones. The overall results of this study indicated that tuning the morphology of quartz particles may be used to adjust both the flotation and aggregation rate of particles. © Wroclaw University of Science and Technology