(1) Discussion on the selectivity of combining copper oxide
The concept of combining copper oxide was originally proposed by two scholars, the Soviet Union Raleigh-Dobrowski and Klimenko. From the perspective of beneficiation, copper oxide ore can be divided into two types, namely free copper oxide and combined copper oxide. The so-called free copper oxide is present in the presence of copper as an oxide, which occurs in the state of oxidizing minerals alone. In most cases, it is mainly carbonate. The so-called combined copper oxide means that some of the oxides of copper are in a certain form and vein. The stone phase combines or mechanically becomes an inclusion of a very finely dispersed copper mineral, or chemically becomes a homogeneous or adsorbed impurity. For the combination of copper oxide, whether by mechanical means, grinding the ore to the finest fineness of fineness that can be achieved technically does not separate this part of the copper. Binding copper oxide of silicon and aluminum shale three forms of osteoporosis, Ca, Mg, Fe, Mn, or other oxide combined.
The above concept of combining copper oxide has clearly shown that it refers to the state of the copper oxide mineral in the ore, rather than the various types of minerals.
However, at present, many units at home and abroad use the cyanide leaching method as the standard when combining the content of copper oxide in the right side of the mine. In the potassium cyanide analysis method, the portion of the copper oxide mineral that can be dissolved in cyanide is called free copper oxide, and the one that cannot be dissolved is called combined copper oxide.
In the books and literature on mineral processing published at home and abroad, when describing the flotation problem of copper oxide ore, it has been repeatedly pointed out that the combination of copper oxide is not optional. Such as: Mitrovofov pointed out: the part of the copper oxide dissolved in the cyanide solution, it is easier to recover by flotation, the part of the copper oxide not dissolved in the cyanide solution is called copper, using flotation The law cannot be recycled.
Comrade Chen Anda, the scientific research department of Jiangxi Copper Company, believes that the arguments in the literature and literature at home and abroad have repeatedly pointed out that the combination of copper is not optional. This argument may be unsuitable for the adsorption-type combination of copper oxide and for mechanically dispersed copper oxide. Its one-sidedness is that it does not consider the following factors:
(1) The argument that is not optional does not consider the development of flotation technology, the effect of flotation conditions on the surface morphology and floatability of combined copper oxide.
(2) The concept of artificially combining copper does not clearly explain the degree of integration with the gangue. That is to say, there is no provision for the range of grades of copper, so it is obvious that the combination of high and low differences in the copper grade of the ore particles is large, so the selectivity is also very different.
(3) The argument that is not optional does not consider the difference between the artificial concept of combining copper oxide and the chemical analysis.
The author has discussed the combination of calcium-magnesium-type refractory copper oxide ore flotation experiments to discuss the combination of copper oxide has certain selectivity. Its selectivity is related to the occurrence pattern and increases as the flotation conditions improve. The test results are only an indication of the selectivity of this type of copper oxide. For other types of ores, the combination of copper oxide options, such as: silicon-aluminum type, iron-manganese type, has not been studied.
The refractory copper oxide ore in this area is deeply oxidized, severely weathered, and contains a large amount of mud, which is a carbonate type. The ore grade is 0.6%, the oxidation rate is 80%, and the combined copper oxide occupancy rate is 36.44%. The copper oxide ore is composed of Suihua Baiyun rock with dense structure and fine particles. Common are malachite, chrysocolla, azurite.
Most of the copper oxide minerals are highly disseminated in the gangue to form "dyed bodies", and some of them exist in an invisible state and can only be analyzed by chemical analysis. These "color dyes" are legally combined with copper oxide according to chemical analysis of potassium cyanide. It forms a microscopic network vein and a supermicroscopic network vein structure which are difficult to dissociate from dolomite, and belongs to the mechanically dispersed type of combined copper oxide.
For the mechanically dispersed type combined with copper oxide, it is different from the gangue after all. The nature of the copper-coated gangue: "color dye" and pure gangue is obviously different, and the difference is related to the increase of copper in the gangue. Increase. This part of the copper is optional when the flotation conditions are appropriate. The following phenomena can be seen in the test tube test:
(1) Take dark "color dye" and pure dolomite ore to 90%-200 mesh to add to flotation tube. Under suitable flotation conditions, dark "color dye" can be seen floating. The stone stays at the bottom of the tube. [next]
(2) The light color "dye body" and pure dolomite ore particles are tested under the above conditions, and the "color dye body" or the gangue are not floated, and the purpose of sorting is not achieved. However, when the appropriate modifiers, inhibitors, and collectors are selected, a light-colored "dye" can be seen to float, while the gangue remains in the bottom of the tube for sorting purposes.
(3) Take the dark "dye body" and the light color "dye body": The mineral grain is ground to 90%-200 mesh and added to the test tube. When suitable, the dark "color dye" can be seen to float and the light color "dye" remains at the bottom of the test tube.
It can be seen that the combined copper oxide ore particles are optional when the flotation conditions are suitable.
In order to prove whether the "dye body" belongs to the combined copper, whether the pure silicon malachite contains bound copper, some typical ore blocks are taken for phase analysis. Analysis of the enchantment proves that the "dye body" is basically combined with copper, and the same pair further proves that the cyanite is selected and selected. In order to investigate the copper-containing grade of copper oxide, five mineral samples were selected for chemical analysis. The results show that the grade difference of copper is very large. It is obvious that the high floatability and the low floatability are absolutely different. . The higher the grade, the more optional it is, and it is confirmed by microscopic observation from the concentrate products of various sorting conditions.
The following experimental studies have been carried out on the selectivity of the above-mentioned calcium-magnesium type combined with copper oxide (mechanically dispersed) ore: "Experimental research of conventional chemicals, research on new type of agent flotation test, application of energy field test, test of chemical treatment of ore surface the study.
Conventional agents refer to several agents commonly used in vulcanization flotation. Such as: sodium sulfide, xanthate, black powder, ammonium phosphate, sodium hexametaphosphate and the like, and pine oil. The test results show that the recovery rate of combined copper oxide is very low, and this part of copper is basically not recovered.
The flotation test study of the new medicament is based on the addition of a conventional agent to a regulator, 150 g/ton of ethylenediamine phosphate. The process is the same as conventional drugs. The results show that the combined copper recovery rate can be greatly improved. Mainly ethylenediamine phosphate can significantly increase the adsorption rate and adsorption capacity of minerals on sodium sulfide and xanthate, and it has selective dissolution on the mineral surface, thus eliminating the influence of slime and improving flotation conditions. The difference between the floatability of the combined copper oxide ore and the flotation of the gangue is increased to achieve the purpose of sorting.
The test method for the enhanced energy field to enhance the flotation process: the ore is ground to the selected particle size and sent to the magnetic field treatment. The magnetic field strength H = 4000 Oersted. Then pour the slurry into the float for 10 to 12 minutes. The power supply is an alternating current, the voltage is 20 volts, and the copper wire is used as a two-pole insertion into the slurry for energization. The medicament is formulated into a solution, and the magnetic line is vertically cut in a magnetic field having a magnetic field strength of 2000 Oersted, and then added to a flotation machine for flotation. The process is the same as above. The results of the experimental research have greatly improved the selection indicators.
The above test results are shown in the table below.
test results |
Test plan | Original ore grade % | Concentrate grade % | Total copper recovery rate% | Combined copper recovery rate% | Free copper oxide recovery% | Copper sulfide recovery rate% |
Conventional medicament | 0.619 | 9.68 | 61.98 | 29.12 | 82.22 | 80 |
New agent | 0.618 | 10 | 69.31 | 40.96 | 88.92 | 86.46 |
Energy field | 　 | 　 | 75.48 | 52.11 | 93.74 | 86 |
The method of chemical treatment on the surface of the ore is to grind the ore to 70%-200 mesh, clean the surface of the mineral with a saturated aqueous solution of sulfur dioxide for 20 minutes, then filter it, and then filter the residue to 95%-200 mesh for flotation machine flotation. The test results are shown in the table below.
Experimental study results |
Program | Original ore grade % | Concentrate grade % | Tailings grade % | Copper recovery rate% | Combined copper oxide recovery rate% | Free copper oxide recovery% | Copper sulfide recovery rate% |
Ore surface chemical treatment | 0.215 | 18.35 | 0.032 | 85.38 | 74.92 | 89.42 | 87.53 |
[next] The test results show that after cleaning the mineral surface with a saturated aqueous solution of sulfur dioxide, the floatability of the combined copper oxide is greatly improved, and the combined copper recovery rate is as high as 74.92%. Thus, under such flotation conditions, the combination of copper oxide is essentially optional.
The results of the above experimental studies have fully proved that the argument that combined copper is not optional is one-sided. The difference in selectivity between different flotation conditions and copper is very large. It is worth pointing out that the development and use of new agents, energy field flotation and chemical treatment of ore surface are effective ways to improve the selectivity of copper oxide.
(2) Discussion on the mechanism of LPCF method
At present, most of the oxidized ore treatment in China adopts the flotation flotation method. The process flow and the pharmaceutical system are complicated, the ore dressing index is low, and the cost is high. It is difficult to obtain satisfactory technical and economic indicators by sulfide flotation method with a large amount of ore combined with copper oxide. However, the leaching-precipitation-support flotation method provides a great possibility for treating such deep oxidation, having a large amount of mud, and having a fine mineral inclusion size, and containing ore having a high combined copper oxide.
Kunming Institute of Metallurgy Cheng comrades of the text on the leach - precipitation - vector float (referred LPCF Act) and its mechanism were discussed.
The main process of LPCF treatment of copper oxide ore is to first dissolve the refractory ore or medium ore with sulfuric acid, and convert various copper oxides into copper ions into the liquid phase as much as possible, while the pickling effect of sulfuric acid can cause pollution. The surface of the copper sulfide recovers the activity and is buoyant. Adding a certain amount of vulcanizing agent to the slurry after leaching, neutralizing the free acid and making the copper ion into a colloidal copper sulfide precipitate, and finally using colloidal vulcanization with high-grade copper concentrate as a carrier (trying to use self-produced concentrate) Copper has the property of adsorbing to the solid surface of the same-named ion, achieving a higher floatation rate and a better flotation index. The principle flow of the LPCF law is shown in Figure 1 below.
figure 1
[next]
1. Mechanism of the leaching process The leaching process of the LPCF method is a heterogeneous reaction process between a solid phase and a liquid phase. The main chemical reactions in the leaching process of copper oxide minerals are as follows:
CuCO 3 •Cu(OH) 2 +2H 2 SO 4 â†â†’2CuSO 4 +CO 2 +H 2 O
CuSiO 3 •nH 2 O+H 2 SO 4 â†â†’ CuSO 4 +H 2 SiO 3 +nH 2 O
When the copper-containing particles are in a solvent, the entire leaching process includes the following five steps:
(1) migration and diffusion of solvent molecules to the surface of the ore;
(2) solvent molecules are adsorbed on the surface of solid ore particles;
(3) a solvent molecule chemically reacts with a soluble solid compound;
(4) the resulting soluble compound is desorbed on the solid surface;
(5) The dissolved compound diffuses into the solution.
The reaction of copper oxide ore with sulfuric acid is a proton reaction, which is a general comprehensive reaction, and the comprehensive reaction is much faster than other chemical reactions. Therefore, for copper oxide ore, the diffusion rate becomes the main link affecting the leaching speed. The leaching speed is affected by the particle size, solvent concentration, leaching temperature, slurry agitation strength, slurry solid ratio and viscosity of the impregnated material.
2. Factors affecting the leaching rate The leaching rate is an important technical indicator of the leaching operation. It indicates whether the copper mineral in the copper oxide ore can be dissolved to the maximum extent and transferred to the liquid phase. The leaching rate directly affects the flotation index. In general, the leaching rate is affected by the following factors.
Combined with the combination of copper oxide Mineral composition and content have a great impact on the leaching rate. Taking the # 4 and # 5 mineral materials stored in the open-air deposit of Tonglu Mountain in Hubei Province as an example, the problem can be explained.
From the table below, we can see # 4, # 5, although the oxidation rates of copper are similar, 95.7% and 97.94%, respectively, but the # 4 material contains 7 times of calcium in # 6, combined with copper oxide content of up to 59.97%, and most of them. It is similar to iron minerals. Therefore, the leaching rate will vary greatly. # 4, # 5 The raw ore leaching rate is shown in the following table.
Copper phase analysis results |
Sample | Copper sulphide | Free copper oxide | Combined copper oxide | all bronze |
# 4 Â content(%) | 0.05 | 0.45 | 0.662 | 1.162 |
Occupancy rate (%) | 4.3 | 38.73 | 56.97 | 100 |
# 5 Â content(%) | 0.04 | 1.45 | 0.54 | 2.03 |
Occupancy rate (%) | 2.06 | 71.21 | 26.73 | 100 |
# 4, # 5 material leaching test results |
Sample | Sulfuric acid dosage (kg/ton) | Leaching particle size - 200 mesh content (%) | Leaching time | Leachate solid ratio | Leach rate |
# 4 Â Â | 80 | 70 | 30 | 1:01 | 49.8 |
# 5 | 80 | 70 | 30 | 1:01 | 83.74 |
[next] The effect of ore particle size and structure The smaller the particle size is than the surface, the larger the effective contact surface between the ore particles and the solvent, the higher the chance of chemical reaction, and the more thorough the copper ore leaching. Conversely, ore with a large block size is difficult to leach. Similarly, loose or porous ores are easily leached, while dense ores are difficult to leach. However, the leaching particle size is not as fine as possible. The fine particle size will increase the viscosity of the slurry, affect the diffusion of the dissolved copper sulfate, and also bring difficulties to the next step.
Effect of slurry viscosity When the viscosity of the slurry is high, the internal resistance of the liquid increases, hindering the diffusion of molecules, and slowing down the immersion speed. The increase in viscosity is mainly due to fine, highly dispersed particles, especially particles close to the colloid (-10 -4 mm). Therefore, when leaching coarse ore particles, a smaller liquid-solid ratio can be used in order to obtain a leachate having a high copper concentration. Conversely, when handling fine-grained minerals, it is advisable to take a larger liquid-solid ratio to facilitate leaching.
In order to reduce the influence of slurry size on the leaching speed and process, the liquid-solid ratio should be selected reasonably. The liquid-solid ratio is too small to increase the viscosity of the slurry and affect the leaching rate. However, the liquid-solid ratio is too large and the concentration of copper ions in the diluted solution will be affected. Precipitation process.
The effect of leaching temperature is similar to that of other minerals. The leaching rate of copper oxide ore is very low at normal temperature and normal pressure. Increasing the temperature of the pulp can reduce the viscosity of the slurry, reduce the diffusion layer and accelerate the chemical reaction, thereby increasing The dissolution rate of the copper oxide mineral greatly improves the leaching rate. However, the increase in temperature is often limited by factors such as economic costs, process conditions, and labor protection.
Effect of Stirring Strength Stirring makes the ore particles that are easy to sink at the bottom of the tank suspend in the slurry, so that the ore particles can be in good contact with the solvent, and the diffusion layer around the surface of the ore particles can be thinned. Undoubtedly, the thinning of the diffusion layer will contribute to the migration of the solvent and the diffusion of copper sulfate into the solution. However, even with very vigorous agitation, the entire diffusion layer cannot be completely eliminated, but it can only be reduced to a certain extent. Therefore, after the stirring strength reaches a certain value, it is further increased, and there is no effect on increasing the leaching rate.
3. Mechanism of action of the precipitation process
The precipitation process is the addition of an alkali metal or alkaline earth metal sulfide to the slurry to cause copper ions in the copper sulfate solution to form a colloidal copper sulfide precipitate. The precipitant is generally sodium sulfide or calcium sulfide, and it is also necessary to add appropriate sodium hydroxide to adjust the pH of the slurry.
The main reaction formula during the precipitation process is as follows:
CuSO 4 +Na 2 S → CuS↓+Na 2 SO 4
CuSO 4 +CaS → CuS↓+CaSO 4
The precipitation is formed because the product of the ion concentration in the solution is greater than the solubility product (Ksp) of the substance, and precipitation of such a substance occurs. According to the ionization equilibrium theory, it can be seen from the above reaction formula that the essence of the precipitate is an ion exchange reaction, which is a combination of Cu 2+ and S 2- to form a poorly soluble CuS molecule.
Sodium sulfide is a strong base weak acid salt that will hydrolyze in water. The hydrolyzate is further dissociated into OH - , S 2 - , and SH - plasmas; the dissociation constants of SH - and H 2 S are small, and the dissociation constant of NaOH is large, so the sodium sulfide solution is always strong. Alkaline.
The composition of several ions of OH - , SH - , S 2 and H2S molecules in the slurry changes with the pH value of the solution. According to the relevant determination and calculation results, the composition of the solution ions at various pH values ​​in the sodium sulfide solution is as shown in Fig. 2 below. The figure shows a Ha 2 S•9H 2 O concentration of 1 mg/l. [next]
figure 2
The figure shows that the concentration of sulphur ions reaches a maximum at pH=9.75. The concentration of sulphur ions decreases with increasing pH or lower than 9.75. As the pH increases, the concentration of S 2- increases continuously. The concentration of OH - in the slurry is also increasing. Then, Cu 2+ in the leached CuSO 4 solution is mainly converted into CuS colloidal particles during the precipitation process.
First, we know that the formation of the precipitate depends on the concentration product Ksp of the product. Under the condition of lower pH, the adsorption capacity of OH - is weaker, and the concentration of S 2- increases after the pH increases, S 2- When the product of the concentration of Cu 2+ is larger than the Ksp of CuS, CuS precipitation is formed. Since the Ksp of CuS is much smaller than the Ksp of Cu(OH) 2 , CuS precipitates.
It can also be explained from the viewpoint of ion exchange adsorption. S 2- and SO 4 2- are equal in radius, and it is entirely possible that S 2- is substituted for SO 4 2- and Cu 2+ to form CuS, while the radii of OH - , HS - and the radius of SO 4 2- are quite different. Moreover, the outer structure of Cu 2+ is 8-18 electron type, and the polarization ability is strong; the outer structure of S 2- is 8 electron type and has a large radius and large deformation, and when CuS is generated, due to polarization The role of the bond is not an ionic bond but a covalent bond component. The affinity of S 2- for Cu 2+ is much greater than that of SO 4 2- for Cu 2+ . Therefore, S 2- is more likely to replace SO 4 2- to form CuS, while OH - and HS - may not easily replace SO 4 2- ions and Cu 2+ to form copper compounds.
4. Influencing factors of precipitation process Effect of precipitant dosage: According to the principle of precipitation formation, the higher the initial concentration of S 2- , the more colloidal copper sulfide formed in the slurry. If the amount of precipitant is not enough, the ion concentration of S 2- and Cu 2+ is not greater than the Ksp of CuS. Colloidal copper sulfide is not formed, but if the amount of precipitant is too large, excess HS - and S 2- will be inevitable. The adsorption of the collector causes a repulsion and inhibits the floating of the copper sulfide.
Effect of Precipitant Type: The type of precipitant has a direct effect on carrier flotation. Sodium sulfide solubility, faster dissolution rate, the hydrolysis of S 2- and Cu 2+ fast gum formation CuS, but the HS - has a higher ratio of S 2- sulfide activity, it will also cause other easily HS- The activation of vulcanized minerals makes it difficult to sort. [next]
Small solubility of calcium sulfide, slower dissolution rate, HS generated in the pulp - and S 2- less, and therefore not to produce gum copper sulfide and sodium sulfide in speed and quantity. However, the flotation test index using calcium sulfide as a precipitant is far superior to sodium sulfide. This can be considered as the adsorption force of the unhydrolyzed calcium sulfide surface due to the chemical bond force causes the Cu 2+ in the slurry to combine with the solid surface of the calcium sulfide to make it a solid component, and the solid surface is positively charged. This is extremely easy and the collector xanthate produces copper xanthate (ROCSSCu) and is floated. At the same time, the partially hydrolyzed Ca 2+ of calcium sulfide can inhibit the floating of Fe 2+ and some minerals, thereby improving the concentrate grade.
5. Mechanism of carrier flotation process High-quality copper concentrate is added as a carrier in the leaching-precipitated slurry, so that the fine-grained copper sulfide or colloidal copper sulfide in the slurry forms a cap layer on the carrier material, and then passes through The mediation of the agent is floated.
The mechanism of carrier flotation is relatively complex, including the agglomeration of colloidal copper sulfide and carrier particles and the interaction of the envelope or the carrier carrying the colloidal copper sulfide with the bubbles. The tendency of copper sulphide micelles to form a cover onto the surface of the carrier is due to the electrostatic forces of the colloidal particles and the solid surface of the carrier as well as the chemical bonding forces within their respective interiors.
Colloid adsorption: There is a certain interface between the colloidal particles and the dispersant, and it is a highly dispersed system. The total surface area of ​​the particles is very large, so it can exhibit a high adsorption capacity. When the carrier is added to the slurry, if the charge on the surface of the carrier is different from the colloidal particles, the electrostatic attraction force causes the colloidal particle to adsorb to the surface of the carrier. If the surface of the carrier and the colloidal particles have the same charge, since the electric double layer around the colloidal particles is very thin, when they are in contact with each other or close to each other, the chemical bond between Cu 2+ and the sulfide may also overcome the weak static electricity. Repulsive force produces adsorption.
Adsorption of solid (carrier) surface: Adsorption of the surface of the support in the slurry is localized ion adsorption. The surface of the solid due to the breaking of chemical bonds causes residual energy on the surface, which creates an adsorption force on the surface of the solid material, adsorbing some ions or molecules in the surrounding medium on its surface. The high-quality copper sulfide concentrate is used as a carrier to adsorb the colloidal copper sulfide in the slurry to the surface of the carrier, so that the carrier and the surface of the colloidal copper sulfide which is carried by the collector are hydrophobic, and then float with the bubbles, thereby Complete carrier flotation.
6. Influencing factors of carrier flotation process
Carrier quality The quality of the carrier has a great influence on the flotation of the carrier. Since the colloidal copper sulfide adsorbs a large amount of collector, the floatability, particle size, grade and adsorption amount of the carrier will affect the consumption of the carrier flotation, flotation recovery rate and grade. . It is preferred that the carrier has a higher optional material and a coarse-grained copper sulfide ore having better buoyancy.
The number of carriers It is the key to economically and rationally grasp the carrier flotation by experimenting with the appropriate amount of carrier. When the amount of addition is too small, the colloidal copper sulfide cannot be sufficiently adsorbed and consumes a large amount of chemicals, and even cannot float, causing the tailings to run high. If too much is added, the carrier surface is adsorbed with a large amount of slime, thereby reducing the floatability of the carrier, causing the carrier to be depleted, forming unnecessary carrier dissimilation, and reducing the quality and recovery of the concentrate.
The LPCF method makes the mineralization and metallurgy interpenetrate into an edge process sea, land and air, representing a possible direction of refractory copper oxide ore processing. The research work on the LPCF method has just begun, and the mechanism and process essence are still not well understood. Many theories still have to be worked hard to find out.
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