Other Frothers

Acetal frothers had been reported in foreign documents. Acetal frothers can be prepared from vinethenes and monohydric alcohol or polyalcohol. One example for synthetic reactions of acetal frothers is as follows  

It was reported that the frothing capabilities of the following acetal derivatives are comparatively good among the eighteen kinds of acetal derivatives [4]  

2-oxybutyl-2,3-dioxyethanol-6-acetal 2-oxybutyl-2-oxyethanol-6-acetal 2,9-diethyoxyl-2,4,6,8-tetraoxydecyl acetal 2,7-diethyoxyl-2,6-dioxyoctyl acetal 2,5-dioxybutyl-2,4-dioxyethanol acetal  

It was recendy reported that butyl and methyl butyl acetals also have good frothing capability in the flotation of copper ore. The molecular formulas of butyl and methyl butyl acetals are as follows  

Methyl butyl acetal CH3CH(OC4H9)(OCH3) 

---

Hercules cationic collectors include a rosin-derived primary amine and its acetic acid salt. Dehydroabietylamine is the primary amine, with the -NH, group being the polar group, and is positively charged in solution with acetic acid, the addition of which makes it water soluble. They are soluble in kerosene, fuel oil, and other frothers. 

Other firothers can also be synthesized by adopting epoxy alkyls as one of the raw materials. The synthetic reactions of other frothers can be found as follows ... 

In addition to the above frothers, some other frothers can also be used to flotate polyoxometallic acid [5]. One of these frothers is diethyoxyl ethyleneoxy ether glycerin. The stracture of diethyoxyl ethyleneoxy ether glycerin is as follows ... 

The frother should not in itself be a strong collector, especially of minerals meant for drowning. It should work in the presence of the other reagents necessary for flotation. The frothers must be soluble in water to some extent otherwise they would be distributed very unevenly in an aqueous solution, with the result that their surface activity would not be fully effective or exploited. There are three main groups of reagents employed by the mineral industry as frothers (Figure 2.24) these different groups include aliphatic alcohols (me-... 

When the sulfide ore carroUite, CuS C02S3, is the starting material, first sulfides are separated by flotation with frothers. Various flotation processes are applied. The products are then treated with dilute sulfuric acid producing a solution known as copper-cobalt concentrate. This solution is then electrolyzed to remove copper. After the removal of copper, the solution is treated with calcium hydroxide to precipitate cobalt as hydroxide. Cobalt hydroxide is filtered out and separated from other impurities. Pure cobalt hydroxide then is dissolved in sulfuric acid and the solution is again electrolyzed. Electrolysis deposits metallic cobalt on the cathode. 

Promoters or collectors give the mineral the water-repellent coating that will adhere to an air bubble. Frothers enhance the formation and stability of the air bubbles. Other additives are used to control the pFI, to prevent unwanted substances from floating, or to control formation of slimes that may interfere with selectivity. 

Hydrotalcite is often too fine grained to produce treatment columns with suitable permeability. As an alternative, the sorbent may be mixed with contaminated water in a tank (Lazaridis et al, 2002). The spent sorbent is then separated from the treated water by flocculation, flotation, or other separation methods (see Section 7.2.4). Lazaridis et al. (2002) investigated the use of surfactants with dispersed-air flotation to separate spent hydrotalcites from treated water. At ionic strengths of 0.1 M using KNO3, effective flotation and separation could be obtained by using a mixture of dodecylpyridinium chloride, sodium dodecylhydrogen sulfate, and a cetyltrimethyl ammonium bromide frother (Lazaridis et al., 2002,322,323). 

Froth flotation is an application of foams that is used to separate mineral components from each other based on their having different surface properties, typically their wettability and surface electrical charge. For example, froth flotation is the classic process used to separate copper from lead ore. The process involves having hydrophobic particles attach to gas bubbles which rise through a turbulent suspension to create a surface foam called a froth. Figure 10.2 shows an illustration of a mechanical flotation cell. This is the classic flotation device [53,91,625], First, the flotation feed particles are well dispersed into a particle suspension. Together with chemical flotation aids, such as collectors and frothers, this constitutes what is called the flotation pulp. In a mechanical flotation cell, air is fed in the form of fine bubbles and introduced near the impeller (see Figure 10.2). In addition to mechanical flotation cells, there are also pneumatic cells and cyclone flotation cells. Pneumatic... 

As discussed in Section 1.2.2 the bubble shapes in fairly dry foams and froths (4 gas > 0.83, approximately) are not spheres or distorted spheres, but polyhedrons. In practice there will be distributions of both gas-cell sizes and shapes. In addition to the gas bubbles, froth contains the floated particles, pulp liquor, and a fraction of (hydrophilic) particles that did not float due to bubble attachment, but which were mechanically entrained in the froth. The pulp liquor and these latter particles all have to be allowed to drain back out of the froth. The rate of this drainage will be greatest at the froth-pulp interface (i.e., the bottom of the froth layer) and slowest near the top of the froth layer. Froth drainage equations are discussed elsewhere [53]. The froth needs to be a stable enough foam that some time can be allowed for these drainage processes, and also so that the upper layer(s) of the froth can be swept out of the flotation cell. On the other hand, the froth should not be too stable as a foam so that it will break easily after collection. In addition to the role of the frother, froth stability is also promoted by increasing liquid viscosity. 

Frothing agents are intended to stabilize the particle (mineral)-air mixture (foam) at the surface of the flotation tank. Alkyl or amyl alcohols in the C5 to C12 range are typical frothers. They lower 7sv which is beneficial to the stability of the foam to some extent collectors and frothers may counteract each other in their effects so that compromise conditions must be selected. 

Oils,—These are of two kinds the collectors which have high affinities for sulphides and the frothers. Hard-wood creosote is the standard collective oil but owing to its expense other wood-, coal-, and oil-distillate products are substituted for it either entirely or in part, coal tar being a favorite. On silver minerals... 

Flotation is commonly employed for beneficiation of minerals. Frothers are added to the vigorously agitated mixture. Air bubbles attach to the collector-mineral particles, which then rise and are removed along with the froth or foam. The valuable components are separated from the waste or gangue by preferential floating of one of the components to the top while the other sinks to the bottom. 

Reagents used in flotation, collectors, frothers, depressants, flocculants and inorganic modifiers can interact with each other in the flotation pulp and at the mineral-solution interface. The chemical equilibria involved in these interactions and the nature of the products will have a significant effect on their adsorption and the resultant flotation processes. 

Criteria of frother performance and interactions between frothers and other flotation agents... 

Possible interactions of frothers on the collector and other dissolved species include ... 

Flotation has been used for more than 100 years to separate sulphides, oxides and other salts from ores, as well as to obtain phosphates, barite, chromite and other materials. Up to 90% of copper, lead, nickel, zinc are extracted using flotation in the USA [152 - 153]. In Russia, flotation is widely used to additionally obtain apatite, barite and phosphates. Flotation of iron oxides is not used in practise yet, but the number of experiments carried out in this direction is rather large. The main physicochemical principles of flotation have been discussed above [59 -74]. Here, only some practical problems will be discussed. In [153], requirements are pointed out which apply to three-phase flotation foams, and the main components of the process are defined, i.e. surfactant - collector surfactant - frother activator, depressants, colligend, gangue. The peculiarities of flotation and foam separation in batch and continuous modes are outlined as well as the structure and properties of the main types of flotation agents described. As surfaces of the majority of mineral particles are hydrophilic in nature, hydrophobisation of particles is necessary for a selective separation. 

Insolubility of the collector in coal flotation requires prior emulsification or long conditioning time. On the other hand, the time of contact with the frother should be as short as possible to avoid unnecessary adsorption of frother by highly porous solids, such as coal. 

In addition to collectors, a number of other chemical additives ate used in flotatioa to aid separation by this process. They include frothers, activators, depressants, deactivalots, flooculanis, and diqrersants. 

---