Modifying flotation

Although froth flotation is recognized as the best available fine coal cleaning technique, it becomes iueffective when the particle size is much smaller than 0.1 mm or when the feed contains a large amount of clay, resulting iu low coal recovery or poor selectivity. A solution to these problems is the use of modified flotation devices. 

Modifiers. Flotation modifiers include several classes of chemic s. 

Thind, B.B. 2000. Determination of low levels of mite and insect contaminants in food and feedstuffs by a modified flotation method. J. Assoc. Off. Anal. Chem. Int. 83, 113-119. 

Interaction of Solids With Flotation Reagents. For flotation to occur with the aid of reagents, such compounds must adsorb at the sohd—hquid interface unless the soHd to be floated is naturally hydrophobic. In this latter case only depression can be attempted by the use of additional ions or depressants that hinder bubble—particle adhesion. Frothers (typically long-chain alcohols) and/or modifying agents such as hydrocarbon oils can, however, be used to enhance the collection of naturally hydrophobic soflds such as M0S2, talc, or plastics. 

Froth flotation (qv) is a significant use of foam for physical separations. It is used to separate the more precious minerals from the waste rock extracted from mines. This method reHes on the different wetting properties typical for the different extracts. Usually, the waste rock is preferentially wet by water, whereas the more valuable minerals are typically hydrophobic. Thus the mixture of the two powders are immersed in water containing foam promoters. Also added are modifiers which help ensure that the surface of the waste rock is hydrophilic. Upon formation of a foam by bubbling air and by agitation, the waste rock remains in the water while the minerals go to the surface of the bubbles, and are entrapped in the foam. The foam rises, bringing... 

Flotation Reagents. Three types of chemical reagents are used during the froth flotation process collectors, frothers, and modifiers. 

On the basis of the function it performs, the flotation process can be divided into two categories (i) bulk and (ii) selective. The process is called bulk or collective flotation when it accomplishes the separation of several valuable components from the gangue minerals. In selective flotation, one valuable component is separated from several others. This selectivity could be accomplished by either using collectors selective with respect to a particular mineral or by differential flotation wherein two or more mineral concentrates are recovered consecutively from the same feed by using modifiers. 

Modified Reduction-Flotation Wastewater Treatment System. 247... 

MODIFIED REDUCTION-FLOTATION WASTEWATER TREATMENT SYSTEM... 

A modified reduction-flotation system (Figure 6.5) is very similar to the existing conventional reduction-precipitation system (Figure 6.4), except that a DAF clarifier [T-101F] is used for clarification15-57 instead of using a conventional sedimentation clarifier (Tank T-101, Figure 6.4). 

It should be noted that the chemical reactions of the conventional reduction-precipitation system (Figure 6.4) and the modified reduction-flotation system are identical. 

Comparatively, the modified reduction-flotation system will have lower annual total cost (amortized capital cost plus O M cost) and will require less space, because the flotation unit is very shallow in depth and thus can be elevated. It is expected, however, that the treatment efficiency of the modified system will be higher due to the fact that the DAF clarifier can separate not only the suspended solids but also organics such as oil and grease, detergent, and so on.57-58-61 Conventional sedimentation clarifiers can separate only insoluble suspended solids. 

The modified reduction-flotation wastewater treatment system (Figure 6.5) will be very attractive if all or most of an existing wastewater treatment facilities are to be reused. The high-rate DAF clarifier is a very low-cost clarification unit. 

Vilan A, Cahen D (2002) Soft contact deposition onto molecularly modified GaAs. Thin metal film flotation principles and electrical effects. Adv Funct Mater 12 795-807... 

In flotation of gold-containing base metal ores, a number of modifiers normally used for selective flotation of copper lead, lead zinc and copper lead zinc have a negative effect on the floatability of gold. Such modifiers include ZnS04-7H20, S02, Na2S205 and cyanide when added in excessive amounts. 

The adsorption of collector on gold and its floatability is considerably improved by the presence of oxygen. Figure 17.1 shows the relationship between collector adsorption, oxygen concentration in the pulp and conditioning time [4], The type of modifier and the pH are also important parameters in flotation of gold. 

Effect of amine-modified C11SO4 on gold-bearing sulphide flotation from carbonaceous refractory ore... 

The modifier used in the flotation of these ores included a mixture of sodium silicate and Calgon. Good selectivity was also achieved using boiled starch. 

Because of the complex nature of gold-containing Cu-Pb-Zn ores, the reagent schemes used are also complex. Reagent modifiers such as ZnS04, NaCN and lime have to be used, all of which have a negative effect on gold flotation. 

In recent years, a new class of collectors, consisting of xanthated fatty acids (TY collector), and monoester-modified xanthate (PM230) have found industrial applications with improved metallurgical results. From plant practice, treating oxide copper and copper cobalt ores, two basic flotation methods are practiced (a) sulphidization flotation method, and (b) anionic flotation method. 

Summary of modifiers and depressants used for oxidized zinc flotation... 

There are a fairly large number of modifiers and depressants that are used for flotation of oxidized zinc minerals. Table 20.12 lists some of the most commonly used depressants. 

The niobium circuit flowsheet (Figure 22.7) was modified to include (a) thickening of the deslimed calcite tailing before flotation, and (b) retreatment of the niobium cleaner tailing for extra niobium recovery. 

Floatability of bastnaesite found in barite-fluorite ores is extremely poor using either fatty acid flotation or sodium oleate. Research work conducted on an ore from Central Asia showed that the floatability of bastnaesite improved significantly after barite preflotation [5]. The flotation of bastnaesite from a carbonatite ore improved with the use of oleic acid modified with phosphate ester. The flotation of bastnaesite from deposits ofpegmatitic origin can be successfully accomplished with several types of collectors, including tall oil modified with secondary amine, and tall oil modified with petroleum sulphonate-encompassing group. 

During fluorite flotation, Quebracho and lignin sulphonate mixture (MESB) was used with collector composed of a mixture of oleic acid and phosphoric ester. Collectors used for bastnaesite flotation included tall oil fatty acid modified with three ethylene tetra... 

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