SUMMARY extracted copper ore copper leach solution contains iron and other impurities, in order to improve the quality of copper, iron and copper need to be separated. Furthermore, the concentration of copper in the oxidized ore leaching solution is very low, and copper needs to be enriched before electrowinning. The extraction of copper serves these two tasks and plays a role in the process, as shown in Figure 1.
figure 1 
During the extraction, the protons of the organic phase exchange copper with the aqueous phase, so that the copper is extracted into the organic phase, and the protons enter the aqueous phase to supplement the acid consumed by the leaching, as shown in the following reaction formula:
The raffinate is returned to the leaching. The stripping is the reverse reaction of the extraction, the copper returns to the aqueous phase, the extractant obtains protons from the aqueous phase, restores the acid structure, and returns to the extraction. The concentration of copper in the electrolytic residue for stripping is increased, and the acidity is lowered to become an electrolyte rich, and the electrowinning is returned. The entire process is essentially maintained in acid consumption and balance.
Type copper industry oxime extractant is a high price is not a metal, manufacturing costs must be low extraction process, is likely to be employed. The oxonium extractant extracts copper in an acidic solution without the need for neutralization with a base, operating at a lower cost than other processes, and is superior to any other process.
Hydroxamidine extractants have produced three types in the development process. R 2 is a phenyl group called 2-hydroxybenzophenone oxime is the first generation product, and R 2 is a methyl group called 2-hydroxyacetophenone oxime. It is a type of filtration, and R 2 is H. 2-hydroxybenzaldehyde oxime is a second-generation oxindole extractant. R1 has a fluorenyl group and some are dodecyl groups.
The extraction capacity of different types of industrial oxonium extractants differs greatly. Figure 2 is the extraction equilibrium line of three types of extractants. The isothermal equilibrium of 2-hydroxybenzaldehyde oxime is better than 2-hydroxybenzophenone oxime and 2 - Hydroxy acetophenone oxime is much steeper. This means that its extraction capacity is much better than the latter two, so it can be extracted from a solution with a lower pH, and the load of the organic phase of the same concentration is much higher. The commercial 2-hydroxybenzaldehyde oxime extractant includes Acorga P50 and LIX860 and Acorga P series, M series and LIX800, 900 series which are mainly composed thereof. The commercial product of 2-hydroxyacetophenone oxime is Henkel LIX84-1 (formerly Shell Chemical SME529). Dihydroxybenzophenone oxime is the main component of early Henkel LIX64N and is rarely used alone. [next]
figure 2
Efficiency of transporting copper In most cases, the extraction process is used to extract copper from the leachate of low-grade ore. Although the leachate changes due to the grade of the ore and the leachability, most of them contain 1~3g/L of copper. The pH is 1~2. The stripping solution must be a lean electrolyte after electrowinning, generally containing 150~180g/L of sulfuric acid and 20~40g/L of Cu. In the modern extraction-electrochemical plant, secondary extraction is often used. At this time, the copper in the leachate should be extracted into the organic phase to reach the loading concentration Cu 1 , while the loaded organic phase is only subjected to one-stage stripping, and the loaded copper is Can not be completely stripped, but only dropped to a balanced concentration of Cu S .
Cu l - Cu s =Cu t Cu t
The transport capacity, referred to as the extractant, is the amount of copper that is actually transferred from the feed liquid to the electrowinning rich liquid per unit volume of the extractant during the extraction-back stripping process. The larger the amount, the higher the efficiency of the extractant. Therefore, the extraction and stripping should be taken into consideration when selecting the extractant. Adding a modifier to the highly extractable aldehyde extractant is to adjust its extraction and stripping ability to achieve maximum transfer capacity.
Figure 3 compares the loading and transport capacity of several LIX extractants [1] , all of which are 10% (v/v). LIX84 is a much weaker extracting agent based on ketone fat than LIX984 and 973. Under the same extraction conditions, LIX84 can only reach 65%~70% of the maximum load, but it is easy to strip back, so the net transmission capacity is even higher than the two strong extractants. (LIX84 is 3.00g/L, while the other two are 2.70g/L)[next]
image 3
The choice of copper oxonium extractant has a particularly good selectivity for copper, which can preferentially extract copper from a variety of elements. In particular, it exhibits extremely high selectivity to Cu 2+ at low pH. Since the Cu 2+ in the actual leachate coexists with Fe 2+ and Fe 3+ , the Cu/Fe separation coefficient is a very important parameter to measure the copper extractant. The table below lists the Cu/Fe selectivity of the main industrial extractants.
Extracting agent | Cu/Fe selectivity | Extracting agent | Cu/Fe selectivity |
Acorga P5050 Acorga P5100 Acorga M5397 Acorga M5640 | 2000 500 1000 2000 | LIX973N LIX984 LIX860 LIX622 LIX84N | 300 2000 2500 2500 2000 |
The concentration of copper in the extracted copper concentrate leaching solution of concentrated copper solution is between 50 and 90 g/L. To extract copper of this concentration, one is to increase the O/A ratio, and the other is to increase the concentration of the extractant. The performance of high copper concentration solution for the extraction of various extractants was compared. Several extractants such as LIX984N, LIX664N, Acorga M5640 and Acorga M5774 were selected. The first one is a mixture of aldoxime and ketone oxime. The latter three Both are aldoximes. The experimental organic phase extractant was 32% by volume, and the diluent was Shellso 12325 containing 25% aromatics. The copper concentration of the feed liquid is 60, 70, 80 g / L and 6 g / L of sulfuric acid, respectively. All four extractants can achieve the above objectives, and their extraction isotherms are very close. The relationship between the concentration of the extractant and the copper load is shown in Fig. 4. The load copper can reach 25g/L at a volume concentration of 48%. Even with such a high load, the operation of the extraction tank at normal temperature is still smooth, and no problem occurs.
Figure 4
Since these extractants have a strong extraction ability for copper, even if such a high load is reached, as long as there is sufficient copper concentration in the equilibrium aqueous phase, there is a reaction driving force, and it is not necessary to add an alkali to neutralize the acid produced by the extraction. The raffinate with increased acidity after extraction is returned to the leaching.
references:
1. Minerals Industry Divisiln, Henkel Corp. Technical Bulletin, Tucson, USA, June 31, 1996
2. Zenexa Specialties, Acorga Mining Chemicals, Manchester, UK
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