Effect of Particle Size on Reverse Flotation of Quartz from Hematite using Dodecylamine in Acidic Media

Cationic flotation of quartz and hematite was investigated by varying pH and collector (dodecyl ammonium acetate, DAA) concentration with the intention of elucidating the effect of particle size on the reverse flotation of quartz from hematite. Flotation tests were carried out on quartz and hematite, alone and in artificial mixtures (1: 1 by weight), of three different sizes, i. e. coarse particles (149 -210 μm), intermediate particles (44 -53 μm), and fine particles (-10 μm).Results obtained in acidic media (pH 5), where quartz aquires negative charge, while hematite does positive charge, are summarised as follows.1) In the case of coarse particles system complete reverse flotation of quartz was possible as expected from single flotation results.2) Fairly good separation was obtained in the case of intermediate particles system.3) Complete separation was also possible for the system consisting of fine quartz and coarse hematite.4) No reverse flotation of quartz was achieved for fine particles system (fine quartz -fine hematite) and for the system consisting of coarse quartz and fine hematite. One of the reasons of this difficulty is due to the heterocoagulation between quartz and hematite or slime coating of hematite fines onto quartz surfaces. Scanning electron micrographs taken at pH 5 indicated that a critical size below which hematite fines attach onto quartz surfaces was estimated to be about 0.3 μm.