Natural floatability

Surfaces that do not have strong surface chemical bonds that were broken tend to be nonpolar and are not readily wetted. Substances such as graphite and talc are examples that can be broken along weakly bonded layer planes without rupturing strong chemical bonds. These solids are naturally floatable. Also, polymeric particles possess... 

Some porphyry copper ores contain naturally floatable gangue minerals, such as chlorites and aluminosilicates, as well as preactivated quartz. Sodium silicate, carboxy methyl-cellulose and dextrins are common depressants used to control gangue flotation. 

Fuerstenau (1980) found that sulphide minerals are naturally floatable in the absence of oxygen. Yoon (1981) ever attributed the natural floatability of some sulphide minerals to their very low solubility. Finkelstein et al. (1975) considered that the natural floatability of sulphide minerals are due to the formation of elemental sulphur and related to the thickness of formation of elemental sulphur at the surface. Some authors reported that the hydrophobic entity in collectorless flotation of sulphide minerals were the metal-deficient poly sulphide (Buckley et al., 1985). No matter whichever mechanism, investigators increasingly concluded that most sulphide minerals are not naturally floatable and floated only under some suitable redox environment. Some authors considered that the natural floatability of sulphide minerals was restricted to some special sulphide minerals such as molybdenite, stibnite, orpiment etc. owing to the effects of crystal structure and the collectorless floatability of most sulphide minerals could be classified into self-induced and sulphur-induced floatability (Trahar, 1984 Heyes and Trahar, 1984 Hayes et al., 1987 Wang et al., 1991b, c Hu et al, 2000). 

Natural Floatability and Collectorless Flotation of Sulphide Minerals... 

The most controversial and contradicting problem is, perhaps, the natural and collectorless floatability of sulphide minerals. Gaudin (1957) classified the natural hydrophobicity of different minerals according to their crystal structure and showed that most sulphide minerals were naturally hydrophobic to some extent, which had been fiirther proved based on van der Waals theory by Chander (1988, 1999). Lepetic (1974) revealed the natural floatability of chalcopyrite in dry grinding. Finklestein (1975, 1977) demonstrated that orpiment, realgar and molybdenite were naturally floatable, and that pyrite and chalcopyrite had natural floatability at certain conditions due to the formation of surface elemental sulphur. Buckley and Woods (1990,1996) attributed the natural floatability of chalcopyrite... 

Heyes and Trahar (1984) leached pyrite with cyclohexane and compared the extract with a sulphur-containing solution of cyclohexane in a UV spectra photometer as shown in Fig. 1.4, indicating that sulphur was present at the mineral surface. Therefore, the inherent hydrophobicity and natural floatability once thought to be typical of sulphides is now thought to be restricted to sulphides such as molybdenite and other minerals or compound with special structural features. The collectorless floatability that most sulphide minerals showed came from the self-induced or sulphur-induced flotation at certain pulp potential range and certain conditions. 

Chapter 2 Natural Floatability and Collectorless Flotation of Sulphide Minerals -AG =244.891(kJ/mol)... 

Miner. Process Extra. Metall. Rev., 2 203 - 234 Hayes, R. A. and Ralston, J., 1988. The collectorless flotation and separation of sulphide minerals by control. Inter. J. Miner. Process, 23 55 - 84 Hepel, T. and Pomianowski, A., 1977. Diagrams of electrochemical equilibria of the system copper-potassium ethyl xanthate-water at 25°C. Int. J. Miner. Process, 4 345 - 361 Heyes, G. W. and Trahar, W. J., 1977. The natural floatability of chalcopyrite. Int. J. Miner. Process, 4 317-344... 

Hodgson, M. and Agar, G. E., 1984. An electrochemical investigation into the natural floatability of pyrrhotite. In P. E. Richardson, S. Srinivasan, R. Woods (eds.). Electrochemistry in Mineral and Metal Processing. The Electrochemistry Society Inc., 84 - 10 185-201 Hoey, G. R., Dingley, W., Freeman, C., 1977. Corrosion behaviour of various steels in ore grinding. CM Bull., 2 105... 

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