- dCcu 2 + =KCcu 2 + F fe - K 1 Cfe 3 ++ Fcu (6) d Ï„ Figure 1 Schematic diagram of the adsorption process Nylon Metallic Lace,Metallic Flower Lace,Nylon Metallic Fabric,Nylon Metallic Flower Lace Fabric SHAOXING LANGDENG IMP&EXP CO.,LTD , https://www.ldfabric.com
Wet copper smelting - recovery of copper from copper-depleted solution
In the regeneration non-ferrous metallurgy, the application of hydrometallurgical method increasingly widespread, fairly efficient. Compared with pyrometallurgy, its main advantages are:
(1) The recovery rate of major metals and associated metals is higher;
(2) The process is more flexible;
(3) The energy consumption is relatively small;
(4) It is easier to solve environmental protection problems;
(5) Metallurgical processes are easy to mechanize and automate.
Hydrometallurgical treatment of recycled materials has its outstanding characteristics. These characteristics are first manifested in the ingredient stage. Metal scrap has various oily grease deposits, various emulsions, dirt agglomerates, and the like on its surface. The large size of the scrap is very detrimental to hydrometallurgy. Fine-grained residues, salt, silicon carbide and other materials contain many non-metallic inclusions, making it difficult to handle these materials.
In order to obtain high technical indicators of the hydrometallurgical treatment process, raw materials must be prepared.
Recover copper from copper- depleted solution
In some companies, mainly in the electrical engineering and radio electronics industries and other sectors of the national economy, a large amount of copper-depleted solution is produced. This solution is obtained by pickling a copper oxide mold on the surface of a commercial copper or the like. The copper content of this solution is low - from 0.5 g / decimeter 3 and the sulfuric acid content is high (up to 200 g / decimeter 3 ).
Years of practice in primary non-ferrous metallurgical companies have determined the copper content of the solution. Copper is reasonably separated from the solution by electro-extraction (1 ton of copper per precipitate deposits approximately 3,500 kWh of electricity on the cathode). This copper content is 10 to 12 g/dm 3 (lower limit). Only in a few cases, when the amount of solution is small, the lower limit of copper content can be reduced to 5 g / decimeter 3 .
Separation of copper from a copper-depleted solution can be accomplished by one of four methods: precipitation, displacement, adsorption, and extraction in the form of a poorly soluble salt (carbonate, hydroxide, sulfate).
The first method should be considered the easiest. A soda solution or a lime slurry is usually used as a precipitating agent. The following reactions occur in this way:
2CuSO 4 +2Na 2 CO 3 +2H 2 Oâ†â†’ Cu(OH) 2 ·CuCO 3 +
↓
+2NuSO 4 +H 2 CO 3 (H 2 O+CO 2 ) (1)
CuSO 4 +Ca(OH) 2 â†â†’Cu(OH) 2 +CaSO 4 (2)
In order to precipitate copper from the solution, it is necessary to neutralize the solution to pH = 5.2 to 5.5 in advance. Neutralize with the same precipitant:
H 2 SO 4 +Na 2 CO 3 =Na 2 SO 4 +H 2 CO 3 (H 2 O+CO 2 ) (3)
H 2 SO 4 +Ca(OH) 2 =CaSO 4 +2H 2 O (4)
When the sulfuric acid is particularly excessive, the consumption of the neutralizing agent is considerable. This is one of the shortcomings of this process. The second drawback is that it is a loss for companies that need copper because the company processes the deposit in the same way that ordinary copper concentrates process copper.
The precipitation was carried out in a mechanical stirrer. This method can be recommended to companies with a small amount of solution. Copper's main carbonate, Cu(OH) 2 ·CuCO 3 , can be used to produce copper chloride.
The displacement method for separating copper from a solution is quite extensive. In order to replace copper, iron scrap is usually used. The rate of copper exchange from the solution increases as the copper content increases. At high copper contents (above 20 g/dm 3 ), a dense displacement precipitate is obtained. When the copper content is low, a loose precipitate which is easily separated from the iron is obtained.
The displacement process can be carried out in a solution having a large acidity range. However, it is desirable to carry out the substitution at the most H + content, because the acidity is insufficient, and the hydrolysis of iron may occur, making it difficult for Cu 2 + to reach the surface of the precipitant. At a high acid concentration, H + begins to penetrate into the reaction zone. The dissolution of iron increases and the consumption of iron also increases. [next]
In order to obtain a large particle, the pH of the precipitate must be 1.5 to 2.0. It is not desirable to generate Fe 3 + because it causes the reverse dissolution of copper:
2Fe 3 + +Cuâ†â†’Cu 2 +2Fe 2 + (5)
The negative effect of Fe 3 + is particularly manifested after a large amount of copper precipitation.
Considering the reverse dissolution, the kinetics of copper precipitation is expressed by the following formula:
The presence of Cl - ion is best because it speeds up the displacement and promotes more dispersed precipitates.
It can be seen that the disadvantage of displacement precipitation is the precipitation of copper in the form of a salt - the solution must be neutralized beforehand (at this time the pH is adjusted to 1.5 to 2.0). The rate of displacement increases in proportion to the surface area of ​​the precipitant. The amount of precipitant depends on the block size and geometry of the particles. It is undesirable to have oil, lacquer or rust on the surface of the precipitant.
The replacement copper is carried out under the diffusion system. Therefore, it is best to continuously stir the solution. This not only increases mass transfer, but also eliminates concentration polarization and updates the surface of the precipitant. The displacement speed increases slightly with increasing temperature. The displacement is usually carried out at room temperature. The precipitated copper contains 75 to 95% of copper, and the rest is iron that does not react. The precipitated copper is sent to the copper smelter. The displacement reaction is carried out in a displacement sedimentation tank, a drum-shaped displacement depositor, a vertical column, a pulsation tower, a mechanical agitating tank, and a vibrating precipitator depending on the volume of the solution.
The most widely used is the drum displacement precipitator. It has a diameter of 1 to 3 meters and a length of 5 to 9 meters. At the time of displacement precipitation, the rotational speed of the drum-shaped displacement depositor is 2 to 8 rpm. Iron filings (or other scrap iron) come into contact with the solution that constantly enters the drum. The time the solution stays in the drum is controlled by the amount of iron filings at the inlet and outlet. The optimal displacement precipitation regime depends on the solution supply rate and the drum speed.
The precipitated copper is trapped from the solution continuously flowing from the drum, and the precipitated copper is separated from the solution in the sedimentation tank. The copper edge is separated from the solution from the sedimentation tank. The copper edge gathers and is discharged from the sedimentation tank. The solution after separating the copper is used as a return liquid or discharged. Depending on the degree of dissolution of the iron, a new batch of iron is loaded into the drum. Â Â Â
The adsorption method and the extraction method for separating copper from a solution are intermediate steps. The copper-rich solution is produced by preheating adsorption or extraction from a poor liquid by these two methods. The schematic diagram of the adsorption process is shown in Figure 1.
The adsorption and extraction processes are similar. For enterprises that produce copper solutions as by-products, the adsorption process is appropriate rather than the extraction process because the adsorption process equipment is simple and the production cost is low. Good results in the adsorption of copper ions from a sulfuric acid solution can be obtained using an AHK ф-10 Б ion exchanger or its equivalent (AHK ф-80, AHK ф-20). The ion exchanger or its equivalent active group N≡,≡N,-PO(OH) 2 ; the unit volume is 2.9 ml/g in H + and SO 4 ; the mechanical strength is greater than 97%; the permeation stability is 92%.
The purification process is carried out in three stages in the countercurrent process. In the case where the original copper content in the solution is from 0.1 to 0.5 g/dm 3 , the copper content in the final solution is only 0.0 n g/dm 3 .
From the ion exchanger, copper is rinsed with 0.5 to 1 equivalent of sulfuric acid. The desorption process is carried out in two stages in the countercurrent. The eluent contains 25-30 g/L of copper. The eluent can be used to produce cathode copper or copper sulfate.
The adsorption process can facilitate the adsorption of metal from an excess of sulfuric acid solution, ie without neutralization, and is used in the enterprise to separate the sulfuric acid solution. According to the study, in order to separate the sulfuric acid from the solution, it should be used AHKф-3г phosphoric acid type ion exchanger. Such amphoteric resin capacity when the concentration of sulfuric acid in the solution was 400 g / dm3, 20.0 mmol / g. AHKф-3г and AB-17×8 amphoteric resins can be applied. In this case, desorption is carried out with water.
After removal of excess sulfuric acid, copper can be separated from the solution by displacement precipitation process adsorption.