Mineral carrier flotation

Very finely divided minerals may be difficult to purify by flotation since the particles may a ere to larger, undesired minerals—or vice versa, the fines may be an impurity to be removed. The latter is the case with Ii02 (anatase) impurity in kaolin clay [87]. In carrier flotation, a coarser, separable mineral is added that will selectively pick up the fines [88,89]. The added mineral may be in the form of a floe (ferric hydroxide), and the process is called adsorbing colloid flotation [90]. The fines may be aggregated to reduce their loss, as in the addition of oil to agglomerate coal fines [91]. 

In carrier flotation, small-sized (several pm diameter) particles become attached to the surfaces of larger particles (perhaps 50 pm diameter, the carrier particles) [630]. The carrier particles attach to the air bubbles and the combined aggregates of small desired particles, carrier particles, and air bubbles float to form the froth. An example is the use of limestone particles as carriers in the flotation removal of fine iron and titanium oxide mineral impurities from kaolinite clays [630]. The use of a fatty acid collector makes the impurity oxide particles hydrophobic these then aggregate on the carrier particles. In a sense, the opposite of carrier flotation is slime coating, in which the flotation of coarse particles is decreased or prevented by coating their surfaces with fine hydrophilic particles (slimes). An example is the slime coating of fine fluorite particles onto galena particles [630],... 

Emulsion flotation is analogous to carrier flotation. Here, small-sized particles become attached to the surfaces of oil droplets (the carrier droplets). The carrier droplets attach to the air bubbles and the combined aggregates of small desired particles, carrier droplets, and air bubbles float to form the froth. An example is the emulsion flotation of submicrometre-sized diamond particles with isooctane. Emulsion flotation has also been applied to the flotation of minerals that are not readily wetted by water, such as graphite, sulfur, molybdenite, and coal [623]. Some oils used in emulsion flotation include mixed cresols (cresylic acid), pine oil, aliphatic alcohols, kerosene, fuel oil, and gas oil [623], A related use of a second, immiscible liquid to aid in particle separation is in agglomeration flocculation (see Section 5.6.4). 

Each of the sulphide minerals, which are PGM carriers (i.e. pyrrhotite, pyrite, pentlan-dite, etc.) have different flotation properties under some flotation conditions. The selectivity between sulphide minerals and gangue minerals is relatively poor in principle, and in the majority of cases, a hydrophobic gangue depressant has to be used. 

The major carriers of PGM are a variety of minerals and alloys, where the flotation properties of the PGM minerals and alloys are not well defined. These ores have very little to no sulphides present that are PGM carriers. 

The PGM carriers in this ore include a variety of PGM minerals (sperrilite) and its alloys. The main problems identified associated with processing this ore type were (a) poor concentrate grade, (b) low rate of PGM flotation, (c) excessive chromium reporting to the PGM concentrate and (d) high collector consumption. 

Rubio, J. and H. Hoberg (1993). Process of separation of fine mineral particles by flotation with hydrophobic polymeric carrier. Int. J. Mineral Process. 37, 1-2, 109-122. Sincero, A. P. and G. A. Sincere (1996). Environmental Engineering A Design Approach. Prentice Hall, Upper Saddle River, NJ. 

In this technique, known also as piggyback flotation, a carrier material is used for floating the fine particles. For example, anatase is removed on a commercial scale from clay for use in the paper industry by using calcile as the carrier. While anatase does not float by itself, it is cofloated with a coarse auxiliary mineral such as cakhe. 

Flocculated slurries are encountered in flotation cells circuits, thickeners, and various processes in mineral extraction plants. With the formation of floes, the slurry may develop an internal structure. This structure may develop properties leading to a non Newtonian flow, shear thinning behavior (pseudoplastic), and sometimes thixotropic time dependent behavior. When shear stresses are applied to the slurry, the floe sizes may shrirrk and be come less capable of entrapping the carrier slurry. At higher shear stresses, the floes may shrink to the size of particles, and the flow may lose its non Newtonian behavior. 

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