The application of contact angle measurement as a method for flotation collector evaluation

S.G.E. De Jager1, J.H.P. Van Heerden1 and F.W. Petersen2,*

1ASTECH, P.O. Box 1, Sasolburg, 1947, South Africa
2Intek, Private Bag X3015, Randburg, 2125, South Africa

Received 30 January 2003; accepted 20 July 2004


Contact angle measurement of flotation reagents (called collectors) on coal is used for screening suitable collectors that will enhance flotation performance of coal. The application of this method is associated with uncertainties due to the hysteresis that is associated with contact angle measurements.

Three coal samples namely Waterberg, Witbank seam 2, and Witbank seam 4 coal were evaluated for flotation purposes. A range of characterisation techniques, were used and included contact angle measurements. Contact angle measurements are used, as a screening tool to predict which reagent would be suitable for froth flotation.

Two methods of contact angle measurements were evaluated. The first method included contact angle measurement on acid treated or demineralised (mixture of hydrochloric acid and hydrofluoric acid) coal. In the second method the selectivity of the reagent on the coal was tested during contact angle determinations on density separated coal. During the selectivity contact angle determinations the coal was separated into coal-rich (density < 1.6g/cm3) and mineral-rich fractions (density >1.6g/cm3).

The contact angle results showed that there is an increase in flotation yield percentage as well as ash content with increasing contact angles. The reagent resulting in optimum flotation was a substituted alcohol, and was suitable as reagent for all three South African coals used in this study.

Keywords: Contact angles, South African coal, demineralised, density separation, hysteresis

* Corresponding author
   E-mail : francisp@mintek.co.za