Effects of Sparger pore Size and frother concentration on Bubble size and Stability

Ivy Rose D. Belaro

(MS Graduated: 2nd Sem 2009-2010)


The froth phase plays a significant role in the kinetics of flotation. Recovery and grade of minerals/metals greatly depends on the stability of froth produced thus controlling froth or bubble properties is an essential factor to be considered in a flotation system. Compared to water alone, the addition of frother produces finer bubbles with higher stability. This study aims to determine the effects of pore size and surfactant concentration on bubble size and stability Five (5) different frothers were used as surfactants, namely: Nasfroth301, Nasfroth240, Dowfroth250, Pine oil, and Ethanol, Surface tension of the liquid system was determined by Capillary-Rise method. Single bubble analysis was simulated by utilizing syringe needles with shaft hole diameters ranging from 0.40mm while bubble ‘cloud’ formation were investigated using ceramic porous materials with average mean pore sizes of 0.10, 0.50, and 0.90µm. All bubble size measurements and interactions were monitored by photographic and imaging analysis. It was found that increased addition of frother concentration resulted in the decrease I both surface tensions of the bulk medium and mean bubbles size produced. Nasfroth301 was confirmed to be the most effective frother with regards to the ability to reduce bubble size and Dowfroth250 was found to be the least effective. Furthermore, increasing the pore size also increased the mean bubble diameter generated. Images of bubbles as it detaches from the orifice implied that frother addition made the bubble shape more spherical compared to a more oblate shape when it was generated in a water medium. Instantaneous coalescence of bubbles was observed in an ordinary aqueous environment. In the presence of frother like pine oil, however, repulsive forces seem to exist between interacting bubbles that resulted in the retardation of bubble coalescence. Images of bubbles generated by the porous ceramic materials were also examined and no considerable change in bubble size was significantly observed even if pore size was decreased. The addition of only 0.010 ml of Nasfroth240, however, yielded finer and distinct bubble formation. Logarithmic curves of present results indicated adherence of actual data to the predicted values based on past studies. The resulting trend agrees with those in literatures.

Subject Index : Flotation Reagents