Frother persistence: A measure using gas holdup

Persistence here refers to the how long a frother remains effective in producing small bubbles, one of its prime functions in flotation. One way to evaluate is to track gas holdup over time while air is sparged into a column: if frother is depleted bubble size will start to increase consequently increasing bubble rise velocity and hence decreasing gas holdup. Persistence of nine frothers was evaluated in this manner. Polyglycol frothers exhibited high persistence with gas holdup virtually constant over 50 h compared with alcohol frothers. The alcohols divided into two groups, one showing steady decline in gas holdup, e.g., 1-hexanol, and a second group exhibiting a sharp decline at a given time, e.g., MIBC. Tests on MIBC showed increasing concentration extended persistence while increasing gas velocity and increasing bubble size decreased persistence. The decrease in gas holdup was related directly to measured decrease in frother concentration. It appears that the transport of frother to and through the froth and from froth to atmosphere needs to be considered.