Dispersion selectivity and heterocoagulation in apatite-hematite-phlogopite fine particle suspensions II. Dispersion selectivities of the mineral mixtures

Abstract

Selective coagulation/dispersion of the apatite-hematite and apatite-phlogopite binary mineral mixtures has been studied. The selectivities observed from the mixed suspensions were much smaller than those obtained from single mineral tests. The largest selectivity observed was from an apatite-hematite 2:1 mixture with the apatite grade increasing to 82% from 67% and an apatite recovery of 60%. Selectivity obtained from the apatite-phlogopite mixture was smaller than that from the apatite-hematite mixture, contrary to the larger stability difference existing between apatite and phlogopite than that between apatite and hematite in single mineral tests. Selective dispersion between the minerals seems difficult and needs a very careful selection of dispersant concentration. Electrophoretic study of the mineral mixtures showed the evidence of heterocoagulation. The loss of the dispersion selectivities was studied on the basis of colloid stability theories. It shows that in a polydisperse binary system, if one of the particle species is undergoing the rapid Brownian coagulation, the heterointeraction stability of the ultrafine fractions may be very low, even if the stabilities of the second species is very high, which can significantly decrease the stability of the more stable species and also increase the stability of the less stable species via heterocoagulation and slime coating.