Evaluation of flotation reagents by normalization procedures

Froth flotation is a dynamic multiphase process in which particulate matter is separated with the help of chemical reagents by gas bubbles immersed in water. The original flotation results are usually presented in the form of kinetic curves relating recovered particulate matter mass (yield ) or mass of a selected component (recovery ), both shortly denoted as y, versus process time t at different concentrations c (g/dm3) of the applied reagents. The kinetic curves can be modified into three: incentive (maximum yield or recovery ymax vs c), limits (ymax vs kinetic constant k or specific rate) and half-life of flotation (t1/2 vs c) curves. The original and modified curves can be normalized by taking into account either an external parameter such as molecular mass (MW), critical coalesce concentration (CCC), critical concentration at the minimum bubble velocity (CMV), dynamic foaming index (DFI), and many other parameters or an internal parameter such as time, concentration needed to achieve certain yield, recovery (y) or kinetic constant. Normalization leads to new flotation curves and provides additional useful information about flotation performance. Normalization can be fully effective, partial or ineffective. Normalization of the original flotation kinetic curves usually is ineffective. Also, normalization of the incentive curve with external parameters such as frother molecular mass, which changes reagent concentration from c (g/dm3) to C (mol/dm3), is also ineffective. Partially effective are normalizations with other external parameters such as CCC and CMV, usually within the same class of regents, for instance alcohols. Only DFI seems to be a universal external normalization parameter for flotation results because it provides fully effective normalization and thus predicts the flotation results. Limited data on DFI restrict a full verification of this hypothesis. Normalization of the modified flotation curves with internal parameters such as k50 (value of 1st order kinetic constant when recovery or yield is 50% after a given flotation time), Ct1/2 (frother concentration in mol/dm3 at which the flotation half-life has an arbitrarily chosen value) and cy75 (frother concentration in g/dm3 at which recovery or yield is 75% after a given flotation time) is a good base for practical classification of flotation reagents.