Copper extraction - electrowinning operation process and precautions

First, the copper extraction process

The extraction equipment generally uses a multi-stage countercurrent mixing clarifier. Extraction parameters, such as the number of extraction stages, the concentration of the extractant in the organic phase, the contact time of the two phases in the mixing chamber, the phase separation time in the clarification chamber, the comparison of the two phases, etc., are selected by the test. The extraction efficiency is determined by the nature of the extraction system and the stage efficiency of the designed mixing clarifier. When the extraction system is certain, it mainly depends on the design level of the equipment and the quality of the processing.

The flow and process of the two phases during copper extraction can be illustrated by Figure 1.

Figure 1 Schematic diagram of the copper extraction process

As can be seen from Figure 1, the copper leachate and the organic phase move in opposite directions in the mixing clarifier. The copper leachate enters from the bottom of the mixing chamber of the first stage, and is mixed with the organic phase overflowed from the second stage clarification chamber to realize the extraction; the stirring not only makes the two phases are uniformly mixed, but also discharges the mixed liquid to the clarification chamber to let the two phases Let stand layering. The copper leaching solution is mixed and extracted by the first stage, mixed with the organic phase, and then discharged to the first-stage clarification chamber for stratification, and then enters the second-stage mixing chamber from the bottom of the first-stage clarification chamber, so gradually, until the clarification chamber of the fourth-stage The bottom is discharged to become a raffinate aqueous phase and returned to the leach solution. The lean (new) organic phase enters from the mixing chamber of the 4th stage, and is mixed with the copper leaching solution after several stages of extraction, and then discharged to the 4th stage clarification chamber for stratification, and then overflows into the 3rd stage mixing chamber, so progressive Until the first stage clarification chamber is discharged as a saturated organic phase, the copper is back extracted after washing.

The reverse extraction operation is like extraction; the difference is that in the extraction, the copper leaching solution is used as the continuous phase, and the organic phase is used as the dispersed phase. In the back extraction, the organic phase is used as the continuous phase, and the aqueous phase (back extraction solution) is used as the dispersed phase. .

The following should be noted in the extraction and stripping operations of copper:

(1) Maintain the stability of the interface. The deterioration of the extraction process is usually reflected in the abnormality of the interface. If the interface is found to be unstable during operation, it is necessary to find out the cause, adjust the extraction parameters, and strive to maintain the stability of the interface.

(2) In order to prevent the formation of the third phase, the solid content in the copper leaching solution should be less than 2 × 10 ^{- 5} , and should generally be checked and filtered.

(3) Corresponding to the regular purification treatment of lean and organic, timely removing impurities such as Si, Ca, Mg accumulated in the lean organic phase.

Second, the copper electrowinning process

The copper electrowinning process is very mature, and the tank voltage, current density, copper concentration in the electrowinning tail liquid, and sulfuric acidity can be selected according to the nature of the back extraction liquid (ie, the electrowinning stock solution) and the existing equipment and technical conditions of the factory. Parameters, procedures. The operation process is relatively simple. According to the preset solution flow rate, the electrowinning solution enters the electric storage tank for electrowinning, and the Cu ^{2 +} in the solution is gradually deposited on the initial electrode (cathode). In order to ensure the quality of the cathode copper, the following matters should be noted:

(1) Before the electrowinning stock solution enters the electric accumulator, a coarse granulation device for removing the residual organic phase is added to avoid black copper.

(2) The concentration of Cu ^{2 +} in the electrodeposited tail liquid is not less than 10g∕L, because when the concentration of Cu ^{2 +} is lower than 10g∕L, the electrode potential decreases, and H, As, Sb, Bi, etc. may be combined with Cu. ^The precipitation of ^{2 +} together on the cathode will seriously affect the quality of the cathode copper.

(3) The concentration of iron ions in the electrowinning solution is not higher than 5g∕L, because Fe ^{3 +} can promote the dissolution of copper deposited on the cathode under electrowinning conditions, reducing current efficiency.

(4) The current density should not be too high, generally controlled below 200A/m ² . Although the current density is increased, the production amount is increased, but the deposition rate of Cu ^{2 +} on the cathode is too fast, so that the cathode copper is rough and even a powdery structure appears.

(5) It is advisable to add a small amount of additives such as casein, thiourea, animal glue, etc. during the electrowinning process. The addition of a small amount of additives can make the copper deposition more uniform, the crystal is dense, and the surface is smooth. They are generally added in an amount less than 50 g ∕tCu.

The following table shows the technical indicators of copper electrowinning production of several enterprises at home and abroad.

Table Copper and copper production technical indicators of several domestic and foreign enterprises

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