correlating mineral surface energy and flotation response
TRANSCRIPT
Correlating Mineral Surface Energy and Flotation Response Department of Mining & Materials Engineering, McGill University
Presented by: Syed Saad Ali Supervisor: Prof. Kristian Waters
Introduction • Flotation is a physico-chemical separation
technique that utilizes the differences in wettability of different materials
• Used in the mining industry to separates valuable minerals in ores from gangue (waste material)
• An estimated 450 million tons/yr of minerals are processed using froth flotation1
• However, the principles of flotation are poorly understood
• There is room for process optimization and improved separation, yielding significant economic benefits
Objective • To optimize the procedure for surface energy
measurement using inverse gas chromatography • To determine the correlation between the measured
surface energy and the flotation response of an ore
Froth Flotation • Air is bubbled through a mineral ore/water
suspension in an agitated flotation cell • Hydrophobic (non-wettable) particles attach to air
bubbles and are collected in the froth at the top of the cell
• Hydrophilic (wettable) particles remain in the suspension and are removed as tailings
• Various surfactants are used to alter surface properties and control separation
Wettability and Surface Energy • Wettability: measure of solid-liquid intermolecular
interaction; characterized by Work of Adhesion (Wadh) • Surface energy: dependent on the types of interactions
occurring, and the chemical groups present, at the surface
• 2 components of surface energy: dispersive/non-polar (γd) and specific/polar (γ+ & γ-)
• The higher the solid surface energy, the higher the Wadh and the wettability (more hydrophilic)
Wadh = 2[(γsd*γL
d)1/2 + (γS+γL
-)1/2 + (γS-γL
+)1/2] Where γS = solid surface energy
γL = liquid surface tension4
Equipment
Results • Figure 2 shows the Flotation Recovery Percentage against the Wadh at a surface
coverage of 0.15 for galena, quartz and galena conditioned in KAX
Conclusions • Accurate mineral surface energy measurements may be obtained using the SEA • There is evidence of a direct positive correlation between the Work of Adhesion
with water of a mineral and its flotation response
Future Work • Repeat the experiment with other sulphide and oxide minerals • Investigate the effect of mineral oxidization
Acknowledgements • The McGill Summer Undergraduate Research in Engineering Program • Mr. Ray Langlois, Ms. Monique Rindeau & Dr. Mitra Mirnezami for their
assistance with the experimental setup
References 1- American Chemical Society. ‘New Technology for Recovering Valuable Minerals from Waste Rock’. ACS News Service Weekly PressPac (2011) 2- Encyclopedia Britannica. ‘Flotation’. Retrieved on 7th August from <http://www.britannica.com/EBchecked/topic/210944/flotation> 3- Coleman, R. ‘Flotation cells: Selecting the correct concentrate launder design’. Filtration and Separation, Vol. 46 Issue 6 (2009) 36-67 4- Khoo, J. ‘iGC SEA Basic Principles and Applications’. Seminar - Surface Measurement Systems (2011) 6- Rehman, M. et al. ‘Optimization of powders for pulmonary delivery using supercritical fluid technology’. Eur. Jrn. of Pharm Sci, Vol. 22 Issue 1 (2004) 1-17
Figure 1: Schema/c of a Flota/on Cell2
Figure 2: Top View of an Industrial Flota/on Cell3
Figure 3: Surface Energy Analyzer Schema/c6
Figure 4: Microflota/on Cell
• The Surface Energy Analyzer (SEA) is an inverse gas chromatography
• It analytically determines surface energy using retention time data of various vapour probes as they pass through a column containing the solid particles
• The microflotation cell is then used to determine flotation response via small-scale flotation
Experimental Methods • A hydrophobic ore (galena) and a hydrophilic one
(quartz) are tested • Ore samples were crushed to -75 µm • 2-3g of sample is used to make an SEA column for
surface energy analysis, giving a total particle surface area of ~0.5 m2 in the column
• 1 g of the sample was placed in the microflotation cell for 1 minute and the recovery percentage calculated
25.00
30.00
35.00
40.00
45.00
50.00
55.00
60.00
65.00
0 0.1 0.2 0.3 0.4
Surface En
ergy (m
J/m
2 )
Frac4onal Surface Coverage
Galena yt
Quartz yt
Condi/oned Galena yt
82 84 86 88 90 92 94 96 98
100 102
0 20 40 60
Wad
h (m
J/m
2 )
Flota4on Recovery (%)
Galena
Quartz
Condi/oned galena (KAX)
Figure 5: Plot of Surface energy vs. Frac. Surf. Coverage for galena and quartz
Figure 6: Plot of Wadh vs. Flota/on Recovery for galena, quartz and condi/oned galena