Boris Albijanic

A review of induction and attachment times of wetting thin films between air bubbles and particles and its relevance in the separation of particles by flotation

Bubble-particle attachment in water is critical to the separation of particles by flotation which is widely used in the recovery of valuable minerals, the deinking of wastepaper, the water treatment and the oil recovery from tar sands. It involves the thinning and rupture of wetting thin films, and the expansion and relaxation of the gas-liquid-solid contact lines. The time scale of the first two processes is referred to as the induction time, whereas the time scale of the attachment involving all the processes is called the attachment time. This paper reviews the experimental studies into the induction and attachment times between minerals and air bubbles, and between oil droplets and air bubbles. It also focuses on the experimental investigations and mathematical modelling of elementary processes of the wetting film thinning and rupture, and the three-phase contact line expansion relevant to flotation. It was confirmed that the time parameters, obtained by various authors, are sensitive enough to show changes in both flotation surface chemistry and physical properties of solid surfaces of pure minerals. These findings should be extended to other systems. It is proposed that measurements of the bubble-particle attachment can be used to interpret changes in flotation behaviour or, in conjunction with other factors, such as particle size and gas dispersion, to predict flotation performance.

Evaluation of SDBS surfactant on coal wetting performance with static methods: Preliminary laboratory tests

ABSTRACT Coal dust contributes to lung diseases in coal miners. Spraying water mixed with surfactants is a method to suppress high concentration coal dust. This study presents the evaluation of the effect of SDBS surfactant on coals. Surfactant concentrations ranging from 0% to 1.0% were analyzed through the characterization of coal wettability and surfactant adsorption by using sink test, capillary penetration test, drop penetration test, surface tension test, and zeta potential test. Results show that SDBS surfactant greatly increased the coal wetting performance and the 0.02%-0.40% concentration was suggested as the optimum concentration range to improve coal wettability of coals.

Recovery of fine and ultrafine mineral particles by electroflotation – A review

ABSTRACT Fine and ultrafine particles are successfully recovered by flotation when fine bubbles are present. Electroflotation is a technique in which fine bubbles are generated by the electrolysis of water. This article reviews the experimental studies into mineral recovery by electroflotation and the potential application of electrolytic bubbles in the recovery of fine and ultrafine mineral particles. The literature reveals that electroflotation resulted in better recoveries of ultrafine particles (e.g. dolomite, magnesite, and pyrite) as compared with dispersed-air flotation because electrolytic bubbles are smaller in size and are more active than those generated during dispersed-air flotation.

Characterizing surface properties of oxidized coal using FTIR and contact angle measurements

ABSTRACT This paper compares FTIR (Fourier Transform Infrared Spectroscopy) and contact angle measurements to characterize surface properties of the oxidized coals with different ash contents. FTIR analysis was employed to investigate functional chemical groups of the oxidized coals. Contact angle measurements were utilized to characterize the hydrophilicity of the oxidized coal. The results showed that contact angle measurements were the same regarding of the type of the oxidized coal. However, FTIR results show that the coal samples with lower ash content had more hydrophobic groups and less hydrophilic groups than the coal samples with higher ash content. This paper demonstrated that FTIR technique is more sensitive than contact angle measurements in studying surface properties of oxidized coal samples.