In contrast, the E–E and F–F association in saline water as a result
of the attractive van der Waals forces and the compression of electrical double layers [10] was stronger and went through the flotation process. These aggregates resulting from the interaction of
saline water and clay minerals not only increased the recovery of
clay minerals by entrainment, but also increased froth stability
and true flotation of coarse particles. However, when the pulp viscosity was sufficient high, the mobility of E–E and F–F aggregates
or dispersed particles was limited resulting in poor flotation as
observed in the flotation of HCC.
4. Conclusions
In coarse coal flotation, a synergistic interaction between clay
minerals and saline water occurred and affected the recovery by
entrainment and true flotation. At pH 9, saline water facilitated
the formation of clay aggregates which sustained in the dynamic
flotation process and resulted in the recovery of more clay minerals. This in turn increased froth stability and promoted higher
combustible recovery by true flotation. Flotation of the highclay-content coal was poor in terms of both entrainment and true
flotation as a result of high pulp viscosity limiting bubble and particle mobility.
Acknowledgements
The authors greatly appreciate financial support from the
Australian Coal Industry’s Research Program (ACARP), and New
Start-up Grant awarded to Dr. Yongjun Peng by the University of
Queensland as well as discussions and suggestion from Frank
Mercuri and John Gartlan at Xstrata Coal and Ian Brake, Ben Cronin
and Susan Watkins from BHP Billiton Mitsubishi Alliance (BMA).
Thanks also to the scientific and technical assistance of the
Australian Microscopy and Microanalysis Research Facility at the
University of Queensland on the coal surface analysis