3.2. Foam/froth structure formed by single reagents and reagent blends
During the foam height measurements it was noticed that the
structure of the foam formed by the frother alone and the two frother/
depressant blends had a very distinct structure. Therefore, the foam/
froth structure formed with the different reagents was studied in a
laboratory batch flotation cell. The foam/froth formed on the top of the
cell was photographed. This approach gave two-dimensional information
on the structure of the foam/froth. Due to lack of suitable
experimental setup precise data on the 3D structure of the foams/froths
could not be obtained (the cylindrical glass column is not suitable for
imaging due to distortions and reflections).
The images of the foam and froth surfaces produced by the different
reagents are presented on Fig. 7. The Dowfroth 200 foam (Fig. 7a)
consisted mainly of fine bubbles with few larger bubbles present,
suggesting that coalescence was not a main contributor to the froth
breakdown. The structure of the foam formed by the DF200-Depramin
267 frother–depressant blend (Fig. 7c) strongly resembled the froth
formed by the frother alone, however, medium size bubbles were more
abundant than in the previous case. The most striking difference in the froth structure was noticed with the DF200-Stypress 504 blend (Fig. 7b).
The froth seemed more fragile, dryer, consisting of large and medium
size bubbles, probably Polyederschaum, suggesting that enhanced
coalescence and fast drainage takes place in the foam phase. This result
was in good agreement with the observations done in the dynamic
frothing studies on the structure of the foam phase