Flotation is arguably the most important mineral separation technique. It has been demonstrated that hydrophobic nanoparticles adsorbed onto hydrophilic mineral surfaces can facilitate mineral particles attachment to air bubbles in flotation process. This thesis explores the effects of nanoparticle adhesiveness, size and shape on the performance of nanoparticle flotation collectors. For this, a series of rigid polystyrene, soft shelled polystyrene-poly (n-butyl methacrylate) (PS-PB) and soft lobed polystyrene/poly (n-butyl methacrylate) (PS/PB) Janus nanoparticles were prepared and characterized. Flotation experiments with glass beads, a model for mineral particles, revealed that soft-shelled particles were more effective collectors than were hard polystyrene particles. The small (92 nm) Janus particles were particularly good flotation collectors for glass beads. The pull-off forces required to remove nanoparticles from glass were measured by AFM and the results were compared to the abilities of the nanoparticles to induce the flotation of hydrophilic glass beads. Soft PS-PB particles were strongly adhering and were very effective nanoparticle flotation collectors. By contrast, hard PS particles were weakly adhering and were poor flotation collectors. These observations led to the hypothesis that weakly adhering nanoparticles were dislodged from the glass bead surfaces during flotation. Experimental support for this hypothesis included: (1) the coverage of nanoparticle on glass bead surfaces decreased with increased conditioning time; (2) large nanoparticles aggregates were detected in flotation pulp as well as on bead surfaces; and, (3) dislodged soft-shelled PS-PB particles left polymeric patches, we call footprints, on the glass bead surfaces. Indeed, the presence of the footprints, suggests that a nano-scale stamping process can be used to cover surfaces with hydrophobic polymer footprints. Arguments are made that hydrodynamic forces alone were insufficient to detach the small nanoparticles from the glass bead surfaces in our experiments. Instead, it is proposed that bead-bead collisions during conditioning and flotation caused weakly adhering particles to detach; a process is termed as “nano-scale ball milling”. Furthermore, geometric arguments show that during a bead-bead encounter, larger nanoparticles are more susceptible to removal than small particles which is consistent with the experimental data. Although all experiments were performed with model glass beads and rather simple nanoparticles, this work has for the first time explained why larger polystyrene nanoparticles are ineffective flotation collectors. The work highlights the need to consider nanoparticle/mineral adhesion when designing collectors for real mineral systems. / Dissertation / Doctor of Philosophy (PhD)

No description available.

A dissertation submitted to the faculty of Engineering and the Built Environment, University of Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering November 2018 / The aim of this study is to improve the flotation of non-sulphide PGM ores from the Mimosa Mine in the Great Dyke of Zimbabwe by evaluating a variety of collector reagents that have not been tested on such material before and applying a full factorial experimental design to investigate the effects of the main primary collector, co-collector and depressant on PGM recovery and grade. The mineralogical studies by XRD revealed that the non-sulphide PGM ore had substantial amounts of gangue material, comprising of 45% quartz, 21% chabazite and 33% of magnetite. The ICP-OES analysis showed that this particular non-sulphide PGM ore is a low-grade ore with an average 4E head assays of 2.37ppm. In the preliminary flotation stage, three reagent suites made up of (i) a collector, (ii) a co-collector and (iii) a depressant i.e. (SIBX, DTP, M98B); (SIBX, C7133, M98B) and (SIBX, AM810, M98B) respectively were tested. It was observed that (SIBX, AM810, M98B) reagent suite gave the best performance with respect to both recovery and grade of the PGM concentrate from the ore. Attempts were made to optimize the dosage levels of the 3 reagents. The optimization studies revealed that 78.5% Pt and 69.3% Pd can be recovered at grades of 17.90g/t Pt and 9.44g/t Pd respectively. This represents a significant upgrade for the roughing stage from the 1.42g/t Pt and 0.85g/t Pd in the feed. These results were obtained at optimized dosages of 86g/t SIBX and 80g/t AM810, with depressant M98B at 50g/t. The observations from the experiments indicated that recovery of PGEs was on the upward trend as the dosage of hydroxamate was increasing hence the effect of the hydroxamate co-collector was further tested at higher dosages while fixing SIBX at 100g/t. The experiments were carried out using 50g/t, 60g/t, 70g/t and 80g/t hydroxamate (AM810) with the depressant M98B at 50g/t. It was observed that the Pt recovery only increased slightly with increasing hydroxamate (AM810) dosage. / E.R. 2019

No description available.

The relationship between operating parameters, cell hydrodynamics, flotation response and scale-up of flotation rates has been explored using three geometrically similar Rushton turbine flotation cells with volumes of 2.25, 10 and 50dm³. Mean energy dissipation values measured using Laser Doppler Velocimetry (LDV) and a torque turntable method were in good agreement. As the cell volume was increased, the mean energy dissipation was proportional to N³D, rather than N³D² as may be expected based on dimensional analysis. Possible reasons for this difference are discussed. Aeration resulted in a slight increase in mean energy dissipation. Bubble diameters were measured using a University of Cape Town bubble size analyser to determine the frother concentration at which a constant bubble diameter was achieved for all operating conditions and cell volumes. The critical frother concentration required to achieve this was 20 ppm MIBC.

Thesis (M.Eng.)(Metallurgical)--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016. / Nickel, a valuable base metal, is the predominant product from the Nkomati mine in South Africa. High-grade nickel mineral ores (2%) from the Massive Sulphide Body have been depleted leaving those of low grade (0.3%). The beneficiation of this ore presents a challenge to the minerals processing industry. In response, batch froth flotation tests were used to explore the effects of mixtures of potassium amyl xanthate (PAX) and IPETC (Isopropyl ethyl thionocarbamate) on the grades and recoveries of nickel. In the mixtures, the xanthate accounted for 95.5, 90, 85 and 80 mole% respectively. Generally an increase in the nickel grade and recovery was observed with the mixtures relative to PAX. IPETC gave a significant increase in the cumulative water recovery with a significant decrease in cumulative nickel grade relative to PAX. PAX gave the highest cumulative nickel grade for the singular collector tests (1.9%), while obtaining the lowest cumulative recovery (77%). Out of the collector mixtures, mixtures 85% PAX: 15% IPETC and 90% PAX: 10% IPETC produced the joint highest cumulative grades (1.8%). These mixtures both gave recoveries of 82%. Collector mixture 95.5% PAX: 4.5% IPETC gave the second highest grade (1.7%) and the highest nickel recovery (85%). Although there were differences in the cumulative nickel grades and recoveries there were statistically no significant improvements observed with the use of the mixtures of PAX and IPETC in comparison to the industry mixture (95.5% SIBX: 4.5% IPETC). Tests were performed using the three best performing collector mixtures at molar dosages of 1.3, 0.65 and 0.325mmol/t. The highest cumulative nickel grades were obtained at the lowest collector dosages (at a molar dosage of 0.325mmol/t of 95.5% SIBX: 4.5% IPETC) with collector mixture 95.5% PAX: 4.5% IPETC being the most selective with a nickel grade of 2%. It was also observed that an increase in collector dosage, generally increased the cumulative nickel recovery with collector mixture 95.5% PAX: 4.5% IPETC at a molar dosage of 1.3mmol/t gave the highest cumulative recovery out of the tested mixtures (85%). The study also indicated that an increase in selectivity (i.e. cumulative grade) was at the expense of cumulative recovery. With a decrease in dosage, there was no significant improvement in the cumulative nickel grade and recovery for the tested mixtures compared to the industry mixture. There was however a significant decrease in the water recoveries achieved with PAX and collector mixtures 95.5% PAX: 4.5% IPETC at a molar dosage of 1.3mmolg/t of as well as mixture 90% PAX: 10% IPETC at a molar dosage of 0.65mmol/t.

Column flotation cells have become increasingly popular in the coal industry due to their ability to improve flotation selectivity. The improvement can be largely attributed to the use of froth washing, which minimizes the nonselective entrainment of ultrafine minerals matter into the froth product. Unfortunately, the practice of adding wash water in conventional flotation machines has been largely unsuccessful in industrial trials. In order to better understand the causes of these failures, a detailed in-plant test program was undertaken to evaluate the use of froth washing at an operating coal preparation plant. The tests included detailed circuit audits (solid and liquid mass balances), salt tracer studies, and release analyses. The data collected from these tests have been used to develop criteria that describe when and how froth washing may be successfully applied in industrial flotation circuits. A second series of tests was developed to look at other alternatives to froth washing and their effectiveness. This involved two-staged flotation circuitry. A two-staged approach was developed because the existing flotation cells did not have enough residence time to support froth washing. The process owner wanted to evaluate possible alternatives to column cell flotation. The testing included release analysis testing as well as a detailed series of tests with percent solids control to the secondary flotation unit. / Master of Science

Column flotation is commonly employed in the processing and recovery of fine mineral particles due to an increase in flotation selectivity unattainable using conventional flotation methods. Such an increase in selectivity is due to the employment of wash water, minimizing hydraulic entrainment of fine gangue particles, and the presence of quiescent operating conditions assisted by the use of various air sparging technologies. High performance air spargers increase the probability of collision and attachment between air bubbles and particles, thereby improving recovery of fine and coarse mineral particles otherwise misplaced to the tailings fraction in conventional flotation cells. Although many high-pressure spargers, including the static mixer and cavitation tube, are currently employed for the aeration of column cells, a low pressure sparger capable of providing equivalent performance while resisting a reduction in aeration efficiency does not exist. In light of escalated energy requirements for operation of air compressors necessary to provide high pressure air to existing external and internal spargers, a low-pressure and porous sparger capable of resisting plugging and scaling was developed. Following the design, construction, and optimization of such a prototype, air holdup and flotation performance testing was completed to verify the viability of the sparger as a replacement to existing aerators. Performance evaluations suggest that the sparger is capable of providing similar functionality to currently employed sparging technologies, but further work is required with regards to manipulation of the porous medium to prevent sparger fouling and sustain high aeration efficiencies. / Master of Science

The potential for improved selectivity has made column flotation cells a popular choice for upgrading fine coal. Unfortunately, recent production data from full-scale column plants indicate that many industrial installations have failed to meet original expectations in terms of clean coal recovery. Theoretical studies performed using a simple dispersion model showed that this inherent shortcoming could be largely minimized by reconfiguring the columns to operate in series as a cell-to-cell circuit. Follow-up field data showed that this low-cost modification increased flotation recovery as predicted by the dispersion model. This study presents the key findings obtained from the field investigation and provides generic guidelines for designing multi-stage column circuits. / Master of Science