Investigation of bubble-particle attachment in the context of flotation

Boris Albijanic (2012). Investigation of bubble-particle attachment in the context of flotation PhD Thesis, School of Chemical Engineering, The University of Queensland.

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Author Boris Albijanic
Thesis Title Investigation of bubble-particle attachment in the context of flotation
School, Centre or Institute School of Chemical Engineering
Institution The University of Queensland
Publication date 2012-01
Thesis type PhD Thesis
Supervisor Prof Anh V Nguyen
Prof Dee Bradshaw
Total pages 182
Total colour pages 5
Total black and white pages 177
Language eng
Subjects 091404 Mineral Processing/Beneficiation
Abstract/Summary Bubble-particle attachment is critical to separation of valuable minerals by flotation in aqueous solutions. The main focus in this work was to understand factors controlling bubble-particle attachment mechanism using measurements and first principle modelling. In order to investigate bubble-particle attachment mechanism, attachment time was determined. Attachment time represents a time needed for thinning and rupture of wetting thin films, and the expansion and relaxation of gas-liquid-solid contact lines. Apart from the attachment time measurements, several experimental techniques such as microflotation experiments, bubble-particle wetting film stability measurements, and colloid and surface characterization and analysis were used to provide further information on bubble-particle attachment mechanism, and to find a relationship between attachment time experiments and other experimental techniques. For this purpose, glass beads-dodecyl amine hydrochloride (DAH) system was studied in detail. The results from this study showed that the attachment time was inversely related to the flotation recovery and the minimum attachment time matched the maximum flotation recovery, which occurred around the isoelectric point (iep) for the glass particles and air bubbles. Moreover, it was found that the hydrophobic force was a driving force for the bubble-particle attachment. Additionally, the adsorption, contact angle and wetting film experiments helped to explain the glass-DAH system very well. All results obtained from these experiments indicated the important role of liquid films and colloidal forces affected by surfactant adsorption in bubble-particle attachment interactions. This PhD project also focuses on the prediction of attachment time from the first principles using the glass-DAH system. In these calculations, the overall disjoining pressure and the overall energy of bubble-particle interactions comprised a sum of DLVO and non-DLVO intermolecular forces. The overall energy of interactions was used to determine the critical film thickness. The overall disjoining pressure was employed to estimate the wetting film drainage time using the two models. The first model is the classical Stefan-Reynolds equation which describes the drainage of liquid film between two plane immobile surfaces. The second model was proposed by Tsekov et al (1998) who extended the Stefan-Reynolds equation by taking into account surface rheology of adsorbed surfactants. By applying the model proposed by Tsekov et al (1998), it was found that one film surface was fully mobile while another one was fully immobile. The wetting film drainage time versus DAH concentration curve, calculated using either model, followed the trend of experimental data. However, a better agreement between experimental and calculated data was achieved using the model proposed by Tsekov et al. (1998), demonstrating that the surface mobility of wetting film, caused by the Maragoni effect, plays an essential role in bubble-particle attachment. Although important mechanisms and phenomena have been established using the glass beads-DAH systems, the real value lies in ascertaining whether it is possible to use attachment time to understand the factors contributing to flotation of real ores. However, there is not much data for attachment time of real ore particles being governed particularly by the surface liberation of valuable minerals and solution chemistry. Therefore, this PhD project also discusses the contribution of surface liberation of valuable minerals and solution chemistry to attachment time. The attachment time measurements were performed using the (106 × 53 µm) fraction from concentrates obtained at different times and tails by flotation of copper-gold sulphide ore (Northparkes Mine, Australia) in a mechanically agitated batch flotation cell. All products and tails were analyzed using quantitative mineral liberation analysis. The results indicated that for particles with high Cu grade, a small increase of collector dosage resulted in a dramatic reduction of attachment time with no further decrease on subsequent addition of collector. However, for particles with moderate Cu grade, the effect of collector addition on attachment time was reduced to a much less extent because valuable minerals were mainly moderately and poorly liberated. For particles with low Cu grade, collector addition made no difference with attachment time remained long. These results confirmed that there is a highly non-linear correlation between surface liberation of valuable minerals, collector dosage and attachment time. This work showed that bubble-particle attachment time method can be used to better understand bubble-particle attachment mechanism for model and real systems. However, this method is still an off-line laboratory technique and needs further development for practical applications.
Keyword bubble-particle attachment
attachment time
zeta potential
wetting film
contact angle
first principle modelling
collector dosage
glass beads
copper sulphide ore
Additional Notes XX page, 5 page, 114 page, 116 page, 132 page

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Created: Thu, 21 Jun 2012, 15:52:59 EST by Boris Albijanic on behalf of Library - Information Access Service