Measuring the Floatability of Sulphide Minerals and Ores: The Captive Bubble Attachment Times of Galena, Sphalerite and Cannington Lead-Zinc Ore Particles Floating at Different Rates

Maung Aung Min (2010). Measuring the Floatability of Sulphide Minerals and Ores: The Captive Bubble Attachment Times of Galena, Sphalerite and Cannington Lead-Zinc Ore Particles Floating at Different Rates PhD Thesis, Julius Kruttschnitt Mineral Research Centre, The University of Queensland.

       
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Author Maung Aung Min
Thesis Title Measuring the Floatability of Sulphide Minerals and Ores: The Captive Bubble Attachment Times of Galena, Sphalerite and Cannington Lead-Zinc Ore Particles Floating at Different Rates
School, Centre or Institute Julius Kruttschnitt Mineral Research Centre
Institution The University of Queensland
Publication date 2010-10
Thesis type PhD Thesis
Supervisor Prof. Anh Nguyen
Prof. Dee Bradshaw
Dr. Rob Morrison
Total pages 248
Total colour pages 87
Total black and white pages 161
Subjects 04 Earth Sciences
Abstract/Summary The attributes or properties of particles displaying different flotation rates under the same operating conditions are a topic of continuing research interest, both fundamental and practical. The main research question investigated in this thesis was whether particles that had displayed different collection zone flotation rates in a micro-flotation cell under constant operating conditions (air flow rate and agitation) also exhibited different captive bubble attachment time distributions in a quiescent environment. The other research questions investigated were whether the captive bubble attachment time method was applicable to heterogeneous mineral ores and whether the captive bubble attachment time was sensitive to changes in the grade and liberation of mineral ore particles. Based on our new findings, the question of whether captive bubble attachment times of particles predicted or correlated with their flotation rate was also revisited and evaluated. The main feed materials used in this thesis were three different particle size fractions (-75 +38 µm, -150 +75 µm and -212 +150 µm) of galena (PbS), sphalerite (ZnS) and Cannington lead-zinc ore. The investigation was achieved by measuring the captive bubble attachment times of micro-flotation concentrates (1, 2, 4, 8 and 16 minute concentrates) and tail of these feed particles, immediately after each micro-flotation test without a froth phase. The micro-flotation tests without a froth phase were carried out using a University of Cape Town (UCT) micro-flotation cell. The captive bubble attachment time measurements were carried out using the most modern captive bubble attachment time apparatus available at the time, developed at University of Alberta. Our approach allowed us to examine the captive bubble attachment times of not only particles with different flotation rates from different feeds, but also particles with different flotation rates from the same feed. The rates of recovery of galena, sphalerite and Cannington lead-zinc ore feed particles were varied by altering their surface chemistry, achieved by conditioning the feed particles prior to micro-flotation with depressant (potassium chromate), activator (copper (II) sulphate) and collector (Aero3418A) respectively, while keeping the micro-flotation cell operating conditions (air flow rate and agitation) constant. Back calculation of induction times of galena and sphalerite in the micro-flotation cell using a potential flow model confirmed that in this rate altering approach only the induction times and attachment efficiencies of the particles in the flotation cell were changed. If particles with different micro-flotation rates also had different captive bubble attachment time distributions in a quiescent environment, they should yield different percent attachment vs. contact time curves. Four different types of percent attachment vs. contact time curves were observed from the captive bubble attachment time measurements of micro-flotation concentrates and tails. They were designated accordingly as Types I, II, III and IV. They represented increasingly wider captive bubble attachment time distributions with longer attachment times. All micro-flotation concentrates displayed a Type I percent attachment vs. contact time curve, irrespective of their flotation rate, particle size and surface chemistry. Micro-flotation tails in contrast varied in their percent attachment vs. contact time curves, ranging from Type I to IV, depending on particle size and surface chemistry. A Type I percent attachment vs. contact time curve was a straight line with 100% attachment at every nominal contact time starting from the lowest nominal contact time used (10 milliseconds). It signified that particles had short captive bubble attachment times that were less than 10 milliseconds and narrowly distributed. The lack of easy differentiation between concentrate particles in terms of their percent attachment vs. contact time curve revealed that galena, sphalerite and Cannington ore particles with different micro-flotation rates did not have largely different captive bubble attachment time distributions in a quiescent environment. The less than 10 millisecond attachment times of concentrates were consistent with and corroborated by the captive bubble attachment times for completely floating feed particles in the literature, despite the differences in methodology. They were also in agreement with and explained by our postulation that the form of the relationship between micro-flotation rate and captive bubble attachment time was an exponential decay. Such a relationship was analogous to the relationship between micro-flotation rate and back-calculated induction time in the flotation cell for a potential flow model of liquid flow around a mobile bubble surface. In the potential flow model, the induction times of all three sizes of galena and sphalerite particles with non-zero flotation rate constant were all less than 10 milliseconds. The flotation rate was highly sensitive to induction time; a large change in flotation rate was affected by only a small change in induction time. A near tripling of induction time from 1.29 ms to 3.67 ms resulted in an order of magnitude decrease in micro-flotation rate constant from 0.88 min-1 to 0.08 min-1. Cannington lead-zinc ore concentrate and tail particles were found to have similar percent attachment vs. contact time curves to those for galena and sphalerite. The interpretation of percent attachment vs. contact time curves for mineral ores containing composites was not different from that for pure minerals. The applicability of the captive bubble attachment time method to heterogeneous mineral ores was therefore established. The thesis demonstrated that the captive bubble attachment time method simply measured the cumulative captive bubble attachment time distribution or attachment efficiency of particles for a quiescent environment and was oblivious to whether particles were single minerals or mineral ores. The captive bubble attachment time was in general not sensitive to changes in grade and mineral liberation of Cannington lead-zinc ore particles, as it was not possible to readily and easily differentiate between concentrates at a nominal contact time of 10 milliseconds. But the different percent attachment vs. contact time curves displayed by Cannington lead- zinc ore concentrate particles and barren tail particles provided experimental evidence that particles with a higher degree of liberation had shorter captive bubble attachment time distributions than un-liberated gangue particles. The experimental evidence was consistent with the prevailing school of thought that the flotation rate and attachment efficiency of particles in the flotation cell decreased with a decrease in their liberation.
Keyword attachment time method, captive bubble attachment time, flotation rate, induction time, micro-flotation, percent attachment vs. contact time curve, galena, sphalerite, Cannington ore, mineral liberation.
Additional Notes Pages in Colour 3 12, 16, 17, 19 21, 28 38, 39 48, 49 51, 55-60 62, 64-66 70-73, 77-80 83-86, 89 91-97 100-105, 109, 110 113-116, 119-121 124-127, 129-132 135, 137 143-147, 149 150-159 163, 167-169

 
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Created: Thu, 07 Apr 2011, 15:51:09 EST by Mr Maung Aung Min on behalf of Library - Information Access Service