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Effect of surface roughness on interaction of particles in flotation

Karakas F., Hassas B. V.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 1

18--34

EN

In this study, the effect of roughness of particles on flotation efficiency along with surface forces among interacting particles was investigated. Glass beads representing smooth spherical particles with a size fraction of -150+90 μm were used. The etching technique was used to produce roughness of different degrees. Microflotation of round+smooth, and its corresponding etched samples were used to evaluate the efficiency of flotation in the case of smooth and rough systems. Atomic Force Microscope (AFM) was used to reveal the interaction forces between the smooth and rough surfaces. According to the results, roughness of particles increased the flotation efficiency. Although the roughness of particles increased with the etching, excess etching time caused a decrease on the roughness and in turn in the flotation recoveries. The interaction forces between the glass beads changed from repulsion to attraction with the increasing hexadecyltrimethylammonium bromide (HTAB) concentration. Further, the increase in HTAB concentration caused a change in the reversal of interaction forces from attraction to repulsion for both smooth and rough surfaces. This change started at low HTAB concentrations for rough surfaces compared to smooth ones though the magnitude of interacting forces decreased for the rough surfaces. The extent and kinetics of HTAB adsorption was dramatically influenced by the roughness of particles that affected the interaction forces as revealed by AFM measurements, and governs the flotation efficiency of particles. These results showed that roughness of particles causes significant improvement in flotation recoveries.

2

Optimum separation route for semi bituminous coal using semi-pilot scale pneumatic stratification jig

Boylu F., Cetinel T., Guven O., Karakas F., Cinku K., Karaagaclioglu I. E., Celik M. S.

Physicochemical Problems of Mineral Processing

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2015

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Vol. 51, iss. 2

559--573

EN

Nowadays, dry beneficiation technologies with an air dense medium fluidized bed come into prominence in the field of coal preparation. In this study, the optimum conditions for different operational parameters such as discharge stargate rate, pulsation frequency, and superficial air velocity were investigated on separation of semi bituminous coal from Soma (Imbat) region using a semi pilot scale Allair jig unit. The experimental studies were carried out with two coal size fractions of -15+4 and -4+1 mm by applying rougher and scavenging stages. After the optimization of each parameter, the results for the rougher stages indicated that clean coal products could be obtained with 11.80% and 16.74% ash contents for -15+4 mm and -4+1 mm size ranges, respectively. In addition, discardable tailings with 65.44% and 60.95 % ash contents could be obtained as the result for the scavenging stages. Finally, the combination of these results for -15+1 mm size exhibited that 59.80% of the feed material with 37.70% ash content can be upgraded to clean coal products with low ash content as 19.80% while the remaining part was discarded as tailings with 68.60% ash content. These values suggested that optimizing the operational parameters of unit brings better results which are applicable in industrial application of dry processes compared to wet processes.

3

Effect of calcinated magnesite on rheology of bentonite suspensions. Magnesia-bentonite interaction

Cinku K., Karakas F., Boylu F.

Physicochemical Problems of Mineral Processing

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2014

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Vol. 50, iss. 2

453--466

EN

In this study, the effect of calcination temperature and time on the structure of calcinated magnesite was investigated. In addition, the effect of calcinated magnesite on rheology when added into bentonite suspension was also examined. Electrokinetic, rheological and stabilization studies including coagulation and gelation tests were performed to explain the mechanism of viscosity increase in bentonite suspension upon addition of the calcinated products. FTIR, SEM, BET analyses and rheological data were used to determine the transition degree of MgCO3 to MgO, and evaluate the structure of MgO and bentonite suspensions. The results from this study showed that specific surface area (SSA) and mean pore radius (MPR) values for the calcinated products were directly affected by the calcination temperature and time. According to the ignition loss and transition ratio from MgCO3 to MgO of the calcinated samples, it was found that the calcination was completed above 800 oC. In order to obtain a bentonite suspension with higher viscosity, interaction of the sufficient amount of MgO particles with bentonite particles were necessary. Based on these results, the formation of gelation and heterocoagulation between MgO and bentonite particles were found to be responsible for these effects.