Lead Zinc is one of the older metal human extracted from the lead-zinc ore. Lead and zinc are widely used in the electrical industry, machinery industry, military industry, metallurgical industry, chemical industry, light industry and pharmaceutical industry. In addition, lead metal has many uses in the nuclear industry, petroleum industry and other sectors. There are 11 kinds of lead industrial minerals in lead-zinc ore and 6 kinds of zinc industrial minerals, with galena and sphalerite being the most important.
The chemical formula of galena is PbS, the crystal structure is equiaxed, the sulfur ions form the closest packing, and the lead ions are filled in all the octahedral spaces. The surface of the fresh galena is hydrophobic, and the unoxidized galena is easily floated, and the surface is oxidized and floatable. Xanthate or black medicine is a typical collector of galena. The yellow medicine is chemically adsorbed on the surface of galena. Baiyao and ethyl sulphide are also commonly used collectors. Take effect.
Heavy chromate are potent inhibitors of galena, but activated by Cu2 + galena, the inhibitory effects decrease. Galena, which has been inhibited by dichromate, is difficult to activate and can be activated by treatment with hydrochloric acid or in an acidic medium with sodium chloride. Cyanide can not inhibit its flotation, sodium sulfide is very sensitive to the floatability of the lead ore. Excessive sulfur ions can inhibit the flotation of galena; sulfur dioxide, sulfurous acid and its salts, lime, zinc sulfate or Other agents can inhibit the flotation of galena.
The chemical formula of sphalerite is ZnS, the crystal structure is equiaxed, and the Zn ions are distributed at the top of the corner of the unit cell and at the center of all faces. S is located at the center of four small cubes among the eight small cubes into which the unit cell is divided. Potassium permanganate concentration of 4 ~ 6 × 10-5 mol / have a stronger inhibitory effect on the activation of sphalerite when liter, high concentration of suspended Shique so good. The mechanism of action is as follows: when the concentration of potassium permanganate is low, the metal hydroxy compound formed by the reaction between the surface of the zinc blende surface activation surface and the surface lattice ions acts to inhibit the depletion of the xanthate, and when the concentration is high, the redox occurs on the surface of the mineral. The reaction produces a large amount of elemental sulfur.
Cyanide can strongly inhibit sphalerite, and zinc sulfate, thiosulfate and the like can inhibit the flotation of sphalerite.
Pyrite sulfides crust is the most widely distributed, is formed in a variety of different geological conditions, symbiotic with other minerals. Pyrite can exist in a variety of stable fields because of the electronic configuration of Fe2+, which allows it to enter the octahedral field composed of sulfur ions to obtain larger crystal field stabilization energy and additional adsorption energy. Therefore, pyrite can be formed and stabilized under a variety of different geological conditions.
In addition to the influence of the crystal structure, chemical composition and surface structure of pyrite on its floatability, many studies have also shown that the ore-forming conditions of the pyrite deposit, the formation characteristics of the ore, the structure and structure of the ore, etc. It also has an impact. Shi Tongyuan's chemical analysis of pyrite from 13 different deposits in Japan indicated that the S/Fe ratio of each sample fluctuated within the range of 1.93 to 2.06. The closer the S/Fe ratio is to the theoretical value of 2, the yellow iron The better the floatability of the mine.
The paper studies the floatability of pyrite in eight different producing areas. It is considered that the use of sulfur-iron ratio to judge its floatability has certain limitations. The floatability of pyrite is also related to its semiconducting properties. Related to chemical composition. The relationship between the two is: the pyrite with high S/Fe ratio is an N-type semiconductor, the temperature difference electromotive force is negative, the floatability is poor, and it is easily suppressed by Na2S and Ca2+ plasma; the S/Fe ratio is close to the theoretical value 2 It is a P-type or an N-type semiconductor. It has good buoyancy in an acidic medium and a poor floatability in an alkaline medium. Pyrite with a low S/Fe ratio is a P-type semiconductor, and the thermoelectric potential is large. It has good buoyancy and is difficult to be inhibited by Na2S, Ca2+, etc., but it is poor in buoyancy in acidic media.
Short-chain xanthate is a traditional collector of pyrite, and its hydrophobic product is dihuang. Under the action of xanthate, pyrite is easy to float in an acidic medium with a pH of less than 6, but different studies have shown that the floatability is worse or better floated at a pH of 6-7. Ling Jinghong and other studies have shown that this phenomenon is related to the treatment of mineral samples. Under alkaline conditions, the floatability of pyrite decreases with increasing pH.
The activator of pyrite is generally sulfuric acid, and may also be activated by Na2CO3 or CO2. The mechanism of action is as follows: one is to lower the pH value of the solution, so that the Ca2+, Fe2+, Fe3+ plasma forming complex or insoluble salt on the pyrite surface is desorbed from the pyrite surface and enters the solution to restore the fresh surface of the pyrite; The second is that the surface of the pyrite is difficult to be oxidized due to the presence of the activator, so that the inhibited pyrite is activated and floated. When the surface of the pyrite is oxidized deep, it can be activated by Cu2+. The mechanism may be substituted for the lattice Cu2 + Fe2 + in the surface of the copper sulfide-containing film is generated thereby enhancing the adsorption of xanthate pyrite; but when pyrite collector adsorption or by lime inhibition deeper, the need It can be activated by CuSO4 in acidic medium or after acid cleaning. Lime is often used to increase the pH of the pulp and inhibit the iron sulfide minerals.
Lead and zinc flotation
Common collectors for lead-zinc mines are:
1, xanthate such agents include xanthate, xanthate ester and so on.
2, sulfur and nitrogen, such as ethyl sulfide, its ability to capture is stronger than yellow medicine. Its lead ore and chalcopyrite have strong ability to capture, have weaker ability to collect pyrite, have good selectivity, and have a faster flotation speed and less use than xanthate. It has a stronger recovery effect on the coarse-grained continuous body of sulfide ore. It can obtain a better sorting effect than the xanthate when it is used for the separation of copper-lead sulfide ore.
3, black medicine
Black drug is effective sulphide ore collector, which collector capacity than xanthate weak solubility dihydrocarbyl dithiophosphate metal ion salt of the same volume than those corresponding xanthate salt large ions. Black medicine has foaming properties.
Commonly used black medicines in the industry are: No. 25 black medicine, butyl ammonium black medicine, amine black medicine, and naphthol black medicine. Among them, butyl ammonium black drug (ammonium dibutyl dithiophosphate) is a white powder, soluble in water, blackened after deliquescence, and has certain foaming properties, suitable for flotation of copper, lead, zinc, nickel and other sulfide ore. . The weak alkaline pulp has weaker ability to capture pyrite and pyrrhotite, and the lead in the other is more capable of collecting.
4, lead and zinc flotation regulator
The regulators can be classified into inhibitors, activators, medium pH adjusters, slime dispersants, coagulants and flocculants according to their roles in the flotation process.
The regulator includes various inorganic compounds such as salts, bases and acids, and organic compounds. The same agent often plays different roles under different flotation conditions.
Inhibitor
(1) Lime (CaO) has strong water absorption and acts with water to form hydrated lime Ca(OH)2. It is insoluble in water, a strong base, the reaction floating mineral slurry was added as follows:
CaO+H2O=Ca(OH)2
Ca(OH)2=CaOH++OH-
CaOH+=Ca2++OH-
Lime is often used to increase the pH of the slurry and inhibit iron sulfide minerals. In copper sulfide, lead, zinc ore, often associated with iron sulfide ore (pyrite, pyrrhotite and pyrite, sulfur- arsenic ore (such as arsenopyrite), in order to better handle flotation copper, lead, Zinc minerals, often with lime to inhibit iron sulfide minerals.
Lime lead ore, especially galena with slightly oxidized surface, has an inhibitory effect. Therefore, when flotation of galena from polymetallic sulfide ore, sodium carbonate is often used to adjust the pH of the slurry. If the pH of the slurry must be adjusted with lime due to the high pyrite content, care should be taken to control the amount of lime.
Lime has an effect on the foaming ability of the foaming agent. For example, the foaming ability of the foaming agent is increased with the increase of PH, and the foaming ability of the phenolic foaming agent increases with the pH. And lower.
Lime itself is a coagulant that condenses fine particles in the ore. Therefore, when the lime is most suitable, the flotation foam can maintain a certain viscosity; when the amount is too large, the fine ore particles will be condensed, and the foam will be bonded and expanded, which affects the normal progress of the flotation process.
(2) Cyanide (NaCN, KCN) cyanide is a effective inhibitor in the separation of lead and zinc. Cyanide is mainly sodium cyanide and potassium cyanide, and it is also useful for calcium cyanide.
Cyanide is a salt formed by a strong base weak acid, which hydrolyzes in the slurry to form HCN and CN-
KCN=K++CN-
CN+H2O=HCN++OH-
It can be seen from the above equilibrium formula that the CN-concentration is increased in the alkaline slurry, which is favorable for inhibition. When the pH is lowered, the formation of HCN (hydrocyanic acid) lowers the inhibition. Therefore, the use of cyanide must maintain the alkalinity of the slurry.
Cyanide is a highly toxic agent and has been conducting research on cyanide-free or less-cyanide inhibitors for many years.
(three) zinc sulfate
Zinc sulfate is pure white crystal, soluble in water, and is an inhibitor of sphalerite. It usually has an inhibitory effect in alkaline pulp. The higher the pH of the pulp, the more obvious its inhibition effect. Zinc sulfate produces the following reactions in water:
ZnSO4=Zn2++SO42-
Zn2++2H2O=Zn(OH)2+2H+
Zn(OH)2 is an amphoteric compound soluble in acid-forming salts
Zn(OH)2+H2SO4=ZnSO4+2H2O
In an alkaline medium, HZnO2- and ZnO22- are obtained. Their adsorption to minerals enhances the hydrophilicity of the mineral surface.
Zn(OH)2+NaOH=NaHZnO2+H2O
Zn(OH)2+2NaOH=Na2ZnO2+2H2O
When zinc sulphate is used alone, the co-inhibition effect is poor, and it is usually used in combination with cyanide, sodium sulfide, sulfite or thiosulfate, sodium carbonate and the like.
The combination of zinc sulphate and cyanide enhances the inhibition of sphalerite. Generally used ratios are: cyanide: zinc sulfate = 1: 2 ~ 5. At this time, CN- and Zn2+ form a colloidal Zn(CN)2 precipitate.
(4) Sulfuric acid, sulfite, SO2 gas, etc.
Agents such as sulfurous acid, sulfite, and sulfur dioxide gas include sulfur dioxide (SO2), sulfurous acid (H2SO3), sodium sulfite, and sodium thiosulfate.
Sulfur dioxide is dissolved in water to form sulfurous acid:
SO2+H2O=H2SO3
The solubility of sulfur dioxide in water decreases with increasing temperature. At 18 ° C, it is absorbed by water, wherein the concentration of sulfurous acid is 1.2%; when the temperature is raised to 30 ° C, the concentration of sulfurous acid is 0.6%. Sulfuric acid and its salts are strongly reducible and therefore unstable. Sulfurous acid can form an acid salt, a hydrogensulfite or a normal salt (sulfite) with many metal ions. Except for the alkali metal sulfite normal salt, which is easily soluble in water, the positive salts of other metals are slightly soluble in water. Sulfuric acid is dissociated in two steps in water, and the concentration of H2SO3, HSO3- and SO32- in the solution depends on the pH of the solution.
When using sulfite flotation, the pulp pH is often controlled in the range of 5-7. At this time, the main inhibitory effect is HSO3-. Sulfur dioxide and sulfurous acid (salt) are mainly used to inhibit pyrite and sphalerite. A weakly acidic ore (pH=5-7) caused by lime dissolved in sulfur dioxide, or a combined inhibitor of sulfur dioxide and zinc sulfate, ferrous sulfate, iron sulfate, or the like. At this time, the galena, pyrite, and sphalerite are inhibited, and the suppressed sphalerite can be activated with a small amount of copper sulfate. It is also possible to use sodium thiosulfate or sodium metabisulfite instead of sulfite to inhibit sphalerite and pyrite.
For sphalerite which is strongly activated by copper ions, the inhibition effect is only poor with sulfite. At this time, if zinc sulfate, sodium sulfide or cyanide is added at the same time, the inhibitory effect can be enhanced. Sulfite is prone to oxidative failure in the slurry and, therefore, its inhibition is temporal. In order to stabilize the process, a method of segmentation is usually adopted.
(5) Foaming agent
The foaming agent should be a heteropolar organic substance, the polar group is hydrophilic, and the non-polar group is aerated, so that the foaming agent molecules are oriented at the interface between air and water, and most of the foaming agent is a surface active substance. , can strongly reduce the surface tension of water. The top surfactant activity of the same series of organic surfactants is increased by the law of "one third", which is called "special fangba rule".
The foaming agent should have a suitable solubility. The solubility of the foaming agent has a great influence on the foaming performance and the characteristics of bubble formation. For example, if the solubility is high, the consumption is large, or a large amount of foam rapidly occurs, but it cannot be durable, and when the solubility is too low, the ice is too late to dissolve. With the loss of foam, or the slow rate of foaming, the duration of the principal is difficult to control.
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