Flotation behaviour of sulphide mineral size fractions with controlled contact angle

Abstract

The flotation response of chalcopyrite has been characterized as a function of particle size and advancing contact angle. The advancing contact angle of individual size fractions was manipulated to different values, measured using the Washburn technique. A flotation feed sample was constituted from the individual size fractions. Parameters such as frother concentration, impeller rotational speed, and superficial gas velocity were the same in each flotation test. The chalcopyrite sample, in the absence of any steps to intentionally manipulate the contact angle, displayed advancing contact angles which varied with particle size fraction. In the presence of a standard thiol collector, the advancing contact angle was also particle size dependent, with the -20 micron fraction displaying the lowest contact angle. Flotation tests showed that the chalcopyrite size fractions above 20 microns floated independently of each other, and that the flotation response was the same for the same particle contact angle and size fraction across different flotation tests. The flotation response was characterized by the maximum recovery at infinite flotation time and the distributed rate constant, assuming a single floatable fraction existed within each size fraction. When the distributed and undistributed rate constants were compared, the latter gave a greater dependency on contact angle as it took into account the non-floating fraction. The two rate constants converged at high advancing contact angles as the non-floating fraction approached zero. Further work on mineral floatability characterization will lead to the development of calibration curves of rate constant against particle size and contact angle, a tool that could be used to benchmark flotation response.