In this study the fundamental science underpinning the interaction of saline water and clay minerals was
studied under flotation contexts to address important problems confronting the coal industry. For the
first time, the beneficial effect of clay minerals in some flotation scenarios was revealed after testing a
typical coal sample having a low content of clay minerals and its mixture with another coal sample having
a high content of clay minerals in de-ionised water and saline water with medium conductivity.
Equipped with a range of techniques including froth stability measurements, modelling true flotation,
settling tests and Cryo-SEM analyses, it was found that froth stability was higher in the flotation with
a higher concentration of clay minerals in both de-ionised water and saline water, corresponding to
increased combustible matter recovery and ash recovery. A synergistic interaction was evident between
saline water and clay minerals in stabilising the froth and recovering combustible matter by true flotation.
This is because saline water promoted the formation of association of clay platelets that sustained
in the dynamic flotation condition, entered the flotation concentrate and altered the froth property and
coarse coal flotation behaviour.