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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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    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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    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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    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.