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Revisiting flotation mechanisms of the selective separation of alkali feldspars in the presence of NaCl

Karagüzel Cengiz, Çelik Mehmet Sabri

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 5

art. no. 149928

EN

Selective separation of Na-feldspar (NaAl3SiO8) from K-feldspar (KAl3SiO8) by flotation appears to be the only alternative in commonly found mixed-type ore formations. For this purpose, various mechanisms in various studies have been proposed by which selective separation can be achieved in the presence of salt ions. These mechanisms under different flotation conditions are systematically discussed in this study. Literature review reveals that two adsorption mechanisms are operating in the presence of Na+ ions and natural pH: Ion exchange and ion adsorption. In mixed feldspar systems, the mineral surface properties change due to ion exchange of counter ions on K-feldspar surface and become suitable for amine adsorption, while Na-feldspar surface is suppressed due to co-ion adsorption leading to limited amine adsorption. Similar mechanisms occur in acidic conditions with fluorine ions which increases the dispersion of particles and provides selectivity for K-feldspar by forming AlSiF-amine complexes. K-feldspar at alkaline pH with NaOH is activated with fluorine ions at the previous flotation stages and then floated with amine releasing K ions into the solution. The ion exchange/ion adsorption mechanism seems effective in alkaline as well as in natural and acidic conditions.

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Physical restrictions of the flotation of fine particles and ways to overcome them

Karakashev Stoyan I., Grozev Nikolay A, Ozdemir Orhan, Guven Onur, Ata Seher, Bournival Ghislain, Batjargal Khandjamts, Boylu Feridun, Hristova Svetlana, Çelik Mehmet Sabri

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 5

art. no. 153944

EN

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 θ = 80°, 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 um to Rp = 0.40 um corresponding to bubbles size range of Rb = 50 um to Rb = 1000 um. Hence, thermodynamically the particle size fraction in the range of Rp = 0.2 um to Rp = 2 um 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 θ ≈ 27.4° to θ ≈ 54.5°. 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 significantly the attachment efficiency of the particles to the bubbles.

3

Bubbling properties of frothers and collectors mix system

Batjargal Khandjamts, Guven Onur, Ozdemir Orhan, Karakashev Stoyan I., Grozev Nikolay A., Boylu Feridun, Çelik Mehmet Sabri

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 5

art. no. 152890

EN

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 type in mixed systems.

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Analysis of flotation and aggregation characteristics of muscovite particles through the extended DLVO theory

Tunç Berivan, Guven Onur, Ozdemir Orhan, Çelik Mehmet Sabri

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 5

art. no. 151789

EN

In this study, the flotation and aggregation characteristics of muscovite mineral particles were determined as a function of dodecyl amine hydrochloride (DAH) concentration and correlated with the theoretically calculated “particle-particle” and “particle-bubble” interactions using extended DLVO theory. In this series of tests, the flotation and aggregation characteristics of the muscovite mineral were determined with micro-flotation and turbidity measurements, respectively. In addition to these analyses, surface tension measurements were carried out as a function of pH. Also, the zeta potential and contact angle measurements were also performed as a function of DAH concentration prior to the flotation and aggregation tests. The experimental studies showed that while almost minimum and maximum points of flotation and turbidity values were obtained up to a critical concentration of DAH as 6.10-6 mol/dm3, a significant increment was obtained following that concentration. Accordingly, while repulsive forces dominated the interactions up to that concentration, the attractive forces became more effective at further concentrations such as 2.10-5, 4.10-5, 8.10-5, and 1.10-4 mol/dm3 DAH concentrations for both “particle-particle” and ”particle-bubble” interactions. This in turn suggested that the determination of energy barrier heights between ”particle-particle” and ”particle bubble” may provide important insights into both flotation and aggregation characteristics of particles.