It is worth pointing out that the classification of flotation reagents is conditional. Certain agents belong to this category under certain conditions and may belong to another category under another condition. For example, sodium sulfide (Na 2 S) in the flotation of non-ferrous metal sulfide ore which is an inhibitor, while the flotation of non-ferrous metal oxide ore is an activator, when it is the amount of excess inhibitor; Furthermore, one The medicament can also play several roles simultaneously in the same flotation process. The lime slurry can adjust the pH, and the like can be suppressed pyrite.
Collector
Collectors are the most important and most important class of agents that change the floatability of minerals. It can form a hydrophobic film on the surface of useful minerals, improve the hydrophobicity of minerals, and facilitate the collection of mineral particles and bubbles. The collector is an isopolar substance having a polar group at one end and a non-polar group at the other end. When the agent interacts with the surface of the ore, the polar group adsorbs on the surface of the mineral, and the non-polar group faces outward, thereby weakening the affinity of the water molecule to the mineral surface and improving the hydrophobicity of the mineral surface. For example, the collector xanthate is in the pulp. When the yellow medicinal agent is attached to the surface of the granule and then in contact with the bubble, the non-polarity of the xanthate is inserted into the bubble, and the granule floats up to the surface of the slurry with the bubble (see Fig. 1).
Depending on the polar group acting on the surface of the mineral, the collector can be divided into: anionic (thio compounds, hydrocarbyl acids), cationic (amines), amphoteric, nonionic (lipids, polysulfide). ()), non-polar collector (oil). [next]
The thio compound collector mainly includes xanthate, black drug, mercaptan, etc., and is commonly used for flotation of natural metals, non-ferrous metal sulfides and sulfided oxidized ores. The hydrocarbon acid collectors are oleic acid, oxidized paraffin soap, etc., and are commonly used in flotation oxidized ore, alkaline earth metal ore, silicate ore, and the like. Amine collector is mainly used in the flotation of quartz and adaptation aluminosilicate minerals, coal oil collector comprises oils, transformer oils, suntan lotion, the flotation hydrophobic natural minerals such as molybdenite, Graphite , natural sulfur, etc., can also be used as an auxiliary collector to float natural gold. The collectors commonly used in gold selection plants include xanthate, black medicine, and amine black medicine.
1) Xanthate Xanthate is the most commonly used collector for flotation of gold-containing sulfides. Its chemical composition is hydrocarbyl dithiocarbonate (ROCSS Me), where R is C n H2 n+1 , hydrocarbyl group, Me is Metal sodium or potassium. It is a light yellow powder with a pungent odor, has a certain toxicity, is soluble in water, and is easily oxidized. When using the xanthate collector, the pH of the slurry must be adjusted to be 7 or higher, that is, used in alkaline pulp. If used in acidic pulp, the amount must be increased appropriately. Flotation practice also proves that the high-chain hydrocarbon high-yield yellow drug has a higher ability to capture than the lower-level xanthate.
Generally, when processing gold-bearing sulfide ore, the amount of yellow medicine is 10-15 g/t. The specific amount depends on the nature of floating mineral stone, pulp density and the like. The amount of the metal increases with the increase of the metal grade; it increases with the degree of oxidation of the ore. Increasing the concentration of the pulp can reduce the amount of yellow medicine.
2) Black Black drug medicine chemical name dithiophosphoric phosphate. The general formula is (RO) 2 PSSH. The hydrocarbon groups of commonly used black medicines are cresol, xylenol and various alcohols.
The cresol black drug is formed by reacting cresol and phosphorus pentasulfide under heating, and is a dark brown oily liquid. The density is 1.19~1.21g/cm 3 , which has a pungent odor.
In addition to its collecting performance, black medicine also has foaming ability. The more free cresol is contained, the stronger the foaming ability. Butylamine black is an anionic collector that is a white solid with no odor and foaming. The effect on the gold-bearing quartz vein ore is very good. Because it has both capture and blister properties, it can be used in some gold exchanges instead of 2# oil and xanthate.
Further, the collector may be hydrocarbyl acids used for sorting copper, gold oxide ores; non-polar hydrocarbon oils such as kerosene, transformer oil, sun oil, when gold is selected as an auxiliary collector may be used.
2. Foaming agent
The foam at the time of flotation is a collection of many bubbles after the air is dispersed in the liquid. Flotation foam has certain requirements on the number, size and strength of bubbles. First, it must have a certain strength, can maintain stability during the flotation process, and second, the bubble size is appropriate. Generally, the size of the bubble is preferably 0.2 to 1 mm. Foam is the medium for the floating of the ore during the flotation process. The bubble is too large, the gas-liquid interface area is reduced, the attached ore particles are reduced, and the flotation effect is low. If the bubble is too small, the floating speed of the ore is slow due to the small buoyancy, and the flotation effect is not good. [next]
The role of the foaming agent is to disperse air into tiny bubbles in the slurry and form a relatively stable foam. The principle of action of the foaming agent is that it reduces the surface energy at the interface between water and air. The foamer molecules are adsorbed in the slurry at a gas-liquid interface in a certain direction. Since the foaming agent is aligned on the surface of the bubble, a layer of hydrated film is formed to prevent the bubble from being merged. On the other hand, since the foaming agent molecules have an directional adsorption effect, the surface energy of the gas-liquid interface is lowered, the water layer between the bubble walls is not easily thinned, the bubbles are not easily broken, and the foam stability is enhanced.
The foaming agents commonly used in gold selection plants are 2# oil, pine oil, eucalyptus oil, heavy pyridine, cresol acid and the like.
No. 2 oil is the most commonly used flotation foaming agent, and has good foaming performance and flotation effect. No. 2 oil is a light yellow oily liquid, which is irritating and has strong foaming properties. When selecting gold ore, the amount is generally 20~100g/t.
Emu oil can be used instead of turpentine. It has good performance and is used to obtain high quality concentrate and priority flotation.
Both cresol and heavy pyridine are by-products of the coking industry. They are commonly used foaming agents and are also used for gold selection.
Practice has shown that the amount of foaming agent should not be large. The relationship between the concentration of the foaming agent and the surface tension of the solution and its foaming ability is shown in Fig. 2. Beginning to increase the concentration of the foaming agent, the surface tension of the solution is reduced more obviously, and the foaming ability is significantly increased. When the foaming ability reaches a peak, the foaming agent concentration is increased, the surface tension changes little, and the foaming ability decreases. It can be seen that the foaming ability of the solution is not entirely due to a decrease in surface tension. The foaming agent concentration reached saturation (point B) and pure water (point A) did not produce a stable foam layer.
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3. Conditioner adjuster is an important type of flotation agent in the flotation process. In the flotation, after adding the collector and the foaming agent, the minerals with similar properties are usually floated at the same time. However, the flotation process requires the separation of two or more products, such that one or a group of useful minerals are enriched in such products. However, it is difficult to achieve this purpose with collectors and foaming agents alone, and some agents that adjust the properties of mineral floatability and slurry are needed to selectively adjust the flotation process.
The regulators can be classified into activators, inhibitors, medium pH adjusters, and dispersion and flocculants according to their roles in the flotation process. Which specific regulators belong to them is often closely related to the specific conditions of the action. The same agent belongs to the activator under this condition and is an inhibitor under another condition. It has been previously mentioned that the same agent can function two or more under certain conditions. Therefore, which kind of medicament belongs to which one should be specifically analyzed.
1) Inhibitors It is possible to remove active ions from the mineral surface or solution, adsorb a hydrophilic film on the surface of the mineral or form a hydrophilic colloid on the surface of the mineral to produce an inhibitory effect. Several ways to inhibit minerals are as follows:
1 Eliminate the activated ions in the solution and inhibit the minerals. For example, quartz can be floated by fatty acids under the activation of Ca 2+ and Mg 2+ . If soda is added before flotation, Ca 2+ and Mg 2+ are precipitated by insoluble salts, which eliminates the activation of Ca 2+ and Mg 2+ and makes the quartz lose its floatability.
2 Eliminate the activated film on the mineral surface. Flash with cyanide solution to the copper sulfide surface film of zinc ore, sphalerite lost floatability purpose is suppressed.
3 The hydrophilic surface of the mineral surface is formed to enhance the hydrophilicity of the mineral surface and weaken its adsorption activity on the collector. Inhibiting hydrophilic film forming several situations: a) forming a hydrophilic ion adsorption membranes, such as in the presence of pulp HS - and S 2 - ions, the hydrophilic surface of the mineral can HS - or S 2 - Adsorption membrane; b) forming a hydrophilic colloid film after the silicate mineral surface adsorption silicic acid colloid, colloid-forming hydrophilic film to achieve inhibition; compound film c) forming a hydrophilic, galena hydrophilic surface PbCrO 4 film, is suppressed so that the galena heavy chromate.
Commonly used inhibitors in gold selection plants are: lime, cyanide, sodium sulfide, dichromate. Inhibitors for gangue are: water glass, starch, and the like.
Lime has a strong inhibitory effect on pyrite. Cyanide is a common inhibitor of pyrite, copper sulfide, sphalerite, etc., and also inhibits gold. But silver cyanide dissolves gold and other precious metals, gold and silver so mineral flotation is generally not used as inhibitors cyanide, to avoid loss of gold.
The above effects are not isolated, and some agents are often used in combination to effectively achieve inhibition. [next]
2) Activator It can change the chemical composition of the mineral surface, form a film that can promote the adhesion of the collector, and improve the floating ability of the mineral. At the same time, the activator can also remove the inhibitory film on the mineral surface and restore the original floating vitality of the mineral. Activators generally activate minerals in several ways:
1 A poorly soluble activated film is formed on the surface of the mineral. For example, white lead ore is difficult to be floated by xanthate. After activation by sodium sulfide, an activated film of lead sulfide is formed on the surface of the white lead ore, which makes it easy to float with xanthate.
2 The adsorption of activated ions on the mineral surface. For example, pure quartz cannot be floated by fatty acid type collector, and the adsorption of Ca 2+ and Mg 2+ ions on the fatty acid by quartz adsorbs Ca 2+ and Mg 2+ ions, so that the quartz can be floated.
3 Wash away the hydrophilic film on the mineral surface. For example, in a strongly alkaline medium, a hydrophilic Fe(OH) 3 film is formed on the surface of pyrite and cannot be floated. Flotation is obtained after removing the hydrophilic film on the surface of the pyrite with sulfuric acid.
4 Eliminate the effects of harmful ions in the slurry. When sulfide ore is flotation, if S 2 - or HS - ions are present in the slurry, the sulfide ore is often not floated by the yellow drug, and only when the ions in the slurry disappear and free oxygen is present can be floated.
In practice, activators are available: colored heavy metal soluble salts such as copper sulfate; alkaline earth metals and partial heavy metal cations; sodium sulfide and soluble sulfides. The activators commonly used in gold selection plants are sodium sulfide, aluminum nitrate, copper sulfate and the like. Some activators also have inhibitory properties. For example, sodium sulfide can activate gold-containing oxidized ore and also inhibit gold and sulfide minerals. Therefore, in the flotation process, the activator should be properly selected and added.
3) Medium pH adjuster It is mainly used to adjust the pH of the slurry and adjust the activity of other chemicals, eliminate the influence of harmful ions, and adjust the dispersion and agglomeration of the slurry. Medium (pulp) pH is an important process parameter for flotation, and minerals are usually in a certain pH range to get good flotation. Adjusting the pH of the medium generally plays the role of:
1 Adjust the concentration of heavy metal cations. Heavy metal cations can generally form hydroxide [Me(OH) m ] precipitates. Its solubility product is LMe(OH) m = [Me m+ ]·[OH - ] m = constant. Increasing the pH of the medium can significantly reduce the concentration of metal cations. If Me m+ is a harmful ion, increasing the pH can reduce its deleterious effects.
2 Adjust the collector ion concentration. The state in which the collector is present as molecules or ions in water is closely related to the pH of the medium. When a weak acid or base salt is added to the slurry as a collector, the collector is hydrolyzed to different components with the pH of the solution.
The effect of 3pH on the electrical properties of mineral surfaces. Various minerals have their own zero point (or isoelectric point) in aqueous solution. For various oxidized minerals, H + and OH - ions are their localized ions. When the pH is higher than the zero point, the mineral surface is negatively charged; Below the zero point, the surface is positively charged. [next]
The effect of 4pH on the collector and minerals. The effect between the collector ion and the mineral surface is closely related to the pH of the slurry. There is a competition between the collector anion and OH - on the mineral surface. The higher the pH, OH - ion concentration is greater, the more energy collector repulsion anion, under certain mineral collector concentration starts to be OH - pH at pH suppressing called critical minerals. The critical pH of different minerals is different. For example, in a solution of ethylxanthate at a concentration of 25 mg/L, the critical pH of several sulfides at room temperature is: pyrrhotite 6.0, arsenopyrite 8.4, galena 10.4, pyrite 10.5, white Iron ore 11.0, chalcopyrite 11.8, copper blue 13.2, activated sphalerite 13.3, copper ore 13.8, chalcopyrite 14.0. When flotation of actual ore, the critical pH is a range, because there are often some differences in the floatability of the same mineral in the same ore.
In view of the fact that lime flotation plants generally use lime as a pH adjuster, there is less research and introduction on the situation of lime suppression gold. Jin Jingtan, Liu Binyi, etc. (1994) used the bubble contact method in the laboratory to determine the critical pH curve of gold (as shown in Figure 3). It can be seen that: a) alkali has an inhibitory effect on gold, and the order in which several minerals are inhibited by alkali is pyrite > galena > chalcopyrite > gold, which is in the order of increasing buoyancy of the four minerals. Consistently, the gold and thio-type collectors have strong ability to act, are not easily inhibited, and are easy to float; b) the inhibition of gold by alkali is caused by OH-, regardless of the type of alkali, no lime is found compared with sodium hydroxide. It has a stronger inhibitory effect (curve 4 and curve 5 are basically coincident), therefore, no so-called "lime strongly inhibits gold" phenomenon; c) the result of the assay provides a critical pH range for xanthate float: pH for xanthate <11, the pH of the diced yellow drug is <12. This is basically in line with the practice of gold flotation production.
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5pH affects the dispersion and cohesion of the slime. The pH adjuster used in production is also a dispersion or coagulant for the slime.
6 pH affects the concentration of the inhibitor. Some inhibitors are composed of a strong base and a weak acid, which can be hydrolyzed in water, so the pH of the medium will directly affect its degree of hydrolysis.
4) Dispersion and flocculating agent In order to keep the slurry in a dispersed state, a dispersing agent must be added. The common feature of the dispersant is to enhance the negative charge of the surface of the ore particles, increase the repulsive force between the ore particles, and make the surface of the ore particles strong hydrophilic. It is necessary to strongly disperse the slime before adding the dispersant. The caustic soda is first added to raise the pH of the slurry, and the slime has high dispersibility in the strong alkaline medium.
The most widely used dispersant in production is water glass. Because of its low cost and good dispersion effect, water glass produces H 2 SiO 3 molecules, SiO 3 2- and HSiO 3 - ions and water glass micelles in water, which adsorbs on the surface of the ore particles and greatly enhances the ore particles. The hydrophilicity of the surface, so water glass is a good dispersant.
Soda is a base that regulates the pH of the slurry and has a dispersing effect. Soda is an effective agent when it is required that the pH of the slurry is not very high and it is desirable to disperse the slurry. Sometimes a small amount of water glass can be used in order to enhance the dispersion of soda.
Various polyphosphates have a dispersion, and commonly used are tripolyphosphate (Na 5 P 3 O 10 ) and hexametaphosphate (NaPO 3 ) 6 .
Lignosulfonates, tannins, etc. also have a dispersion effect, but are specifically used as dispersants, and are rarely used in production.
There are three kinds of substances that can make the fine particles in the slurry agglomerate: 1 inorganic electrolyte, the most common are lime, alum (aluminum sulfate), iron sulfate and ferrous sulfate; 2 organic collector; 3 organic polymer Flocculant. Organic polymer flocculants are divided into natural and synthetic products by their origin: starch, dextrin, spindle methyl cellulose, etc., which are natural and synthetic, and have polyacrylamide and various types. Water soluble high molecular polymer.
Because the synthetic polymer flocculant has the advantages of strong flocculation ability, low dosage and low price, it has been widely used in the selection of gold mines, as a clarification of circulating water, purification of tailings water and the like.
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