At otherwise constant conditions, the prediction of R and K trends with increasing frother concentration is difficult and not uniform in nature. This is due, in part, to the observation that the pure concentration effect of a given frother on R and K is often dominated by interactions with particle size, collector type, pH, degree of agitation, and air flow. Thus increasing the concentration of a given frother in the laboratory can exhibit maxima or minima in the R-K curves for a given ore (e.g. Table III shows an increasing R curve and decreasing K curve with increasing frother concentrations, the data of Table IV shows a minimum in R and a maximum in K, and Figure X of reference (1) shows a maximum in R and a minimum in K). It does appear in many cases, that if a change in frother concentration causes an increase in R, a decrease in K will automatically be experienced (and vice versa).
With regard to differing frother chemical structures, it appears that there is a strong correlation between frother type and the rate of mass removal, K, when frothers are compared at similar dosages. Frothers such as the higher molecular weight members of the Dowfroth family clearly demonstrate superior over-all rate characteristics over frothers such as MIBC, pine oil, and cresylic acid.
Several other interesting rate phenomena with frothers can be demonstrated using the Dowfroth family. For example, Table VI demonstrates, using MIBC frother as a base, that increasing the molecular weight of the Dowfroth family decreases the value of R but increases the associated K values. Thus the Dowfroth family offers a wide spectrum of frother capability ranging from DF-200 giving a high R value and low K to DF—1012 giving a high K value with a potentially lower R value. The particular R and K value needed in a given application depends on the nature of the engineering layout and operation along with the ore type, etc. Reference gives a detailed discussion of how to determine whether a flotation process is in rate or equilibrium control.
Another interesting rate phenomena involving frothers is the observation that blending high rate frothers like the Dowfroth frothers with certain normally low rate frothers can synergistically produce a blend possessing the rate capability of the pure high rate frother alone. Tables VII and VIII demonstrate this concept quite well for MIBC, pine oil, cresylic acid, and DF-1012 and various blends of these three at approximately constant frother dosage. Such a concept has important implications in that the use of Dowfroth frothers, for example, in blends can upgrade normally very slow (and usually cheap) frother materials. Table IX demonstrates this blending carried out at extreme starvation dosages so that the effect of reagents is reflected in the observed recovery at longer times.