Currently, copper extractants which have been widely used in the industry are chelating oxindole compounds. During the reaction, a Cu 2 + with two molecules of chelator molecules bound to a chelate. This type of extraction is considered to be a cation exchange process in which one Cu 2 + in the leachate is exchanged with H + of two chelating agent molecules, and thus the acidity in the raffinate is increased. Theoretically, the sulfuric acid consumed by copper leaching during heap leaching will return to the raffinate in the extraction process due to the extraction of Cu 2 + and return to the leaching agent for heap leaching. Therefore, if only the ore is present in the ore Containing copper, heap leaching should not consume sulfuric acid. The corresponding response is as follows: Copper leaching CuSiO 3 ·2H 2 O+H 2 SO 4 Copper extraction CuSO 4 +2HR The sulfuric acid consumed during the copper heap leaching process is mainly caused by impurities such as iron , aluminum , calcium, magnesium and carbonate contained in the ore. Fe 2 O 3 +3H 2 SO 4 CaCO 3 +H 2 SO 4 The acid given by the extractant during the extraction process is essentially from the stripping-electrowinning process, that is, the electrolysis process of copper, the water is generated by electrolysis. Copper electrowinning CuSO 4 +H 2 O Copper stripping H 2 SO 4 +R 2 Cu First, copper extraction As can be seen from the above discussion, sulfuric acid is produced during copper extraction, so the extraction should be carried out in a low acid medium; and the back extraction is carried out in a high acid medium, which is a reversible process. Cu 2 + (aqueous phase) + 2HR (organic phase) Copper extraction distribution coefficient D = partial When the extraction system is constant and the temperature is constant, the partition coefficient can be extracted by the isothermal curve, which is generally called the extraction equilibrium curve, and the back extraction is also the same. As shown in Figure 1. Figure 1 LiX64N copper extraction and back extraction isotherms It can be seen from Fig. 1 that when the concentration of Cu 2 + in the heap leach liquor is 2g∕L, pH=2, if the concentration of Cu 2 + in the raffinate is required to be 0.2g∕L, after multi-stage extraction, after reaching equilibrium, The concentration of Cu 2 + in the saturated organic phase can reach 2.6g ∕L. At this time, the extraction rate of copper is 90%, and the partition coefficient of copper is 13.0. With 180g ∕L sulfuric acid, the concentration of Cu 2 + in the electrowinning solution is required. 45g / L, the lean organic phase Cu 2 + concentration was 0.17g / L. Copper was enriched 22.5 times by the extraction-back extraction process. Second, copper electrowinning The electrolytic cell of copper sulfate solution subjected to direct current, so that Cu 2 + copper deposition process of metal on the cathode, is called electrowinning copper; an anode in this process lead to insoluble silver (antimony) Alloy plate. If the anode is soluble blister copper, the process is referred to as electrolytic refining of copper. During the copper electrowinning process, the following reactions occur at the two poles. Cathode Cu 2 + +2e Anode H 2 O-2e The electrode potential during electrowinning is E=E Φ - Since copper electrowinning is carried out in high acid, Current efficiency during electrowinning is one of the main technical and economic indicators. It means the ratio of the amount of metal actually deposited on the cathode to the amount of theoretical deposited metal calculated according to Faraday's law. Taking copper as an example, the theoretical deposition amount (Q) according to Faraday's law is proportional to current density, plate area, and electrowinning time, ie Q=1.186DkSt×10 - 3 kg Where Dk-current density, A/m 2 ; S-cathode plate area, m 2 ; 1.186-the electrochemical equivalent of copper, kg∕A·h; T-electrowinning time, h. In actual production, the amount of metal deposited on the cathode is lower than the theoretical value. Hand Grade Stretch Film Machine Stretch film machine,Manual stretch film making machine ,Machine for manual stretch film ,China stretch film machine CHANGLONGXING SCIENCE & TECHNOLOGY (SHENZHEN) CO.,LTD , https://www.clxmachinery.com
CuSO 4 + SiO 2 + 3H 2 O R 2 Cu+H 2 SO 4 Fe 2 (SO 4 ) 3 +3H 2 O CaSO 4 +H 2 O+CO 2 Cu+ O 2 +2H + +SO 4 2 - CuSO 4 +2HR R 2 Cu (organic phase) + 2H + (aqueous phase) Cu O 2 +2H + =-0.89+0.0318lg ≈l, the copper ion is about 45g∕L, ≈0.l, can be calculated from the above formula, the theoretical decomposition voltage of copper electrowinning is -0.92V, the overvoltage of oxygen on the anode is about 0.5V, plus the voltage drop of electrolyte and conductive parts, so in practice, The cell voltage of the copper electrode is 1.8 to 2.5 V, which is about 10 times higher than the cell voltage of the copper electrolytic refining. The copper electrode has a high tank voltage and a low current efficiency, generally 72% to 92%. Therefore, the power consumption of copper electrowinning is as high as 1700-2500 kWh ∕tCu, which is about 10 times that of copper electrolysis, and becomes the largest copper product. weakness.