Direct flotation

Once a mixture of plastics is reduced to chips on the order of 0.6 cm in diameter, liquids with intermediate densities can be used to differentiate polymers, assuming that the polymers do not contain fillers that alter their density. A mixture of the six plastics listed in Table 15.6 can be separated into two groups using water. The polyolefins (numbers 2,4, and 5) will float and the others (numbers 1, 3, and 6) will sink. 

Further differentiation of the polyolefins requires liquids that are lighter than water and that do not swell the polymers. Aqueous solutions of methyl or ethyl alcohol are applicable. A solution of sodium chloride in water can be used to separate PS from the two denser polymers. However, separation of polyester (PET) from PVC is complicated by the fact that many variations in compounding PVC result in densities that can be greater or less than that of PET. 

There are other complications in using float-sink separations. The adhesion of a small bit of label made of a different material alters the apparent density of a chip. Fillers and dirt may increase the apparent density. The method is obviously of greatest use when the overall composition of the mixed plastic stream remains relatively uniform. 

---

To recover barite from drilling muds, a direct flotation without prior dewatering and washing of the drilling muds has been described [809]. An alkyl-phosphate is used as a collecting and frothing reagent. 

In the case of carbonatite ores, a beneficiation process involves preflotation followed by reactivation and flotation of pyrochlore. In the case of pegmatitic ores that contain silicates, biotite, albite and limonite, as the gangue minerals, direct flotation of pyrochlore can be achieved with a variety of different collectors. 

There are approximately 130 different minerals that contain tantalum and niobium, from which about 80 are Ta/Nb only. The other minerals contain tantalum and niobium in the form of impurities. There is very little information available on beneficiation of Ta/Nb-containing ores. In actual practice, there are three basic methods for production of Ta/Nb concentrate (a) physical preconcentration, (b) combination of physical preconcentration and flotation and (c) direct flotation. In most cases, Ta/Nb ores contain significant quantities of zircon and rare earth ores (REO). 

Direct flotation of Ta/Nb from mainly tantalum-containing ore is not practiced in operating plants. Only a few currently operating plants have tested the possibility of using flotation to recover tantalum from gravity tailings. 

Because this ore was high in barite and fluorite, direct flotation of bastnaesite from the ore was not possible. It should be pointed out that fluorite has similar flotation properties as bastnaesite and depression of fluorite during bastnaesite flotation is difficult. 

Froth Flotation. A variation of direct flotation is froth flotation. In froth flotation, a stirred tank is generally employed, with air sparged in from the bottom. The feed also enters from the bottom. (Mginally a tool of the mining industry, it operates on the principle of the affinity of different materials for air bubbles. Materials with loww wettabilities will cling to air bubbles and rise to the surface. Frothing agents provide a... 

The key stage of the entire process is a selective wetting of one of the components of the ore pulp with its subsequent concentration in the foam layer ( direct flotation) or in the chamber product ( inverse flotation). The physicochemical basis of flotation were formulated in the thirties-fifties of the last century [59—60] and further subjected to more specific investigations. Plenty of chemical and colloid-chemical processes take place simultaneously in the flotation pulp during a rather short period of time (usually several minutes), the main of which are ... 

The reverse flotation of halite is preferable when KCl is in the form of carnallite (KCl.MgCl.6H2O). Traditional direct flotation of sylvite (KCl) with fatty amines will not work with carnallite ores. From carnallite, it is possible to produce pure KCl and MgCl2 by using... 

Foot, D. G., C. E. Jordan, and J. L. Huiatt. 1980. Direct Flotation of Potash From Camallite, U.S. Bureau of Mines Report of Investigations 8678. 

Petroleum sulfonate was used to directly flotate the raw ore in laboratory. Meanwhile, fatty acid was used to reversely flotate quartz in the flotation of the raw ore. Comparison between direct and reverse flotation separations is given as follows ... 

Direct flotation with petroleum sulfonate Quartz reverse flotation with fatty acid ... 

---