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