Method for extracting cobalt from cobalt-containing scrap and copper-cobalt alloy

The world's cobalt resources are relatively abundant. In 2005, the world's cobalt reserves were 7 million tons, and the reserves were based on 13 million tons. The world's cobalt reserves are concentrated in the Congo ( DRC ), Australia, Cuba, Zambia, New Caledonia, Russia and Canada, and the total reserves account for more than 95% of the world's total reserves. Of cobalt resource-poor, cobalt ore grade average of only 0.02%, individual high 0.05% to 0.08%, while the Congo (DRC) and Zambia copper and cobalt, cobalt grade of 0.1% to 0.5%, high up to 2% 3%. Due to the low grade of cobalt ore and complex ore composition, the recovery process is complicated, the production cost is high, and the cobalt recovery rate is low. In recent years, the consumption of nickel , copper and cobalt in China has increased sharply. However, due to the constraints of mineral resources, the production of copper and cobalt ore in China has grown slowly. The import volume of copper and cobalt mineral products has gradually increased, and the contradiction between supply and demand has become increasingly prominent.

Copper-cobalt alloy is one of the main forms of Congo (gold) cobalt-copper ore deep processing products. It is also one of the main cobalt raw materials imported from Africa in the future. Therefore, it is studied to recover cobalt and copper from copper-cobalt alloy or cobalt-containing scrap. It is of great significance.

There are many types of cobalt waste, mainly waste superalloys, waste hard alloys, waste magnetic alloys, waste kovar alloys, spent catalysts and waste secondary battery materials. The composition of cobalt waste is relatively complex, and generally contains valuable metals such as copper, new, fierce, nickel, and cadmium .

There are two kinds of copper-cobalt alloys, one is an alloy obtained by converter slag obtained by converter blowing in copper smelting process and then refined by electric furnace reduction smelting water, which contains elements such as Cu, Co, Fe, Mn, Si (currently Copper-cobalt alloys, which are cobalt raw materials, are imported in large quantities from Congo (Gold), Zambia, and Zaire, and copper-rich products that smelt cobalt oxide ore and cobalt concentrates. In the electric furnace, the cobalt oxide ore is reduced by coke to produce two kinds of alloys. The higher density is red alloy (copper mass fraction is about 89%, cobalt mass fraction is 4% to 15%), and lighter is copper-cobalt alloy (copper). The mass fraction is about 15%, the cobalt mass fraction is about 42%, and the iron mass fraction is about 34%). The content of other elements in the two copper-cobalt alloys is low.

    First, the fire process

According to the affinity of each element in the cobalt-containing raw material with oxygen, the relevant elements can be separated by a fire method. The order of the relative oxygen affinity of the elements is A1>Si>V>Mo>Cr>C>P>Fe>Co>Ni>Cu. Therefore, the material with low cobalt content is melted at high temperature in the electric arc furnace, and then blown by the wind. The slag is refining, and impurities having a larger affinity for oxygen than Co are oxidized to different degrees to enter the slag, and a nickel anode containing Ni and Co is obtained. The nickel anode is electrolyzed by a diaphragm to obtain nickel, and cobalt enters the anolyte. This method is suitable for treating alloy scrap containing nickel and cobalt.

Peng Zhongdong, et al. used a slag-melting-leaching process to treat Cu-Co-Fe alloy, and added 10% CaCO ₃ slag to roast at 1300 ° C, and then leached with a sulfuric acid solution at a constant temperature of 90 ° C for 5 h, the cobalt leaching rate was 95%; Reduce the amount of CaCO _{3 by} half, while adding 5% Na ₂ SO ₃ , slag roasting at the same temperature, and then leaching with concentrated sulfuric acid, the cobalt leaching rate can be increased to 97%. The fire process is rather cumbersome.

    Second, the wet process

(a) leaching

For the cobalt-rich alloy, acid leaching, chlorine gas leaching, electrochemical dissolution and microbial leaching can be used.

1. Acid leaching. The metal in the cobalt alloy can be transferred into the solution by using sulfuric acid, nitric acid or hydrochloric acid, and the chemical reaction is:

2H ⁺ +Me=Me ^{2 +} +H ₂ ↑

(Me means a metal such as Co or Fe).

When aerobic is present, metallic copper and other reactive metals react with the acid to form metal ions that enter the solution:

2H ⁺ +Me+O ₂ =Me ^{2 +} +H ₂ O

(Me means a metal such as Cu).

When the initial concentration of sulfuric acid is 6mol/L, the leaching temperature is 100°C, the leaching time is 6h, and the liquid solid mass ratio is 5:1, the leaching rates of cobalt and nickel are 95.37% and 96.73%, respectively.

2. Oxidation and leaching of chlorine gas. When leaching with dilute sulfuric acid, the chlorine gas can be added to the solution to enhance the leaching process and increase the metal leaching rate, but the chlorine gas easily overflows, causing environmental pollution, and contains 3 to 5 g/L of cobalt in the chlorinated leachate of various materials. Need to recycle.

3. Electrochemical dissolution method. The sulfuric acid medium is used as the electrolyte, the alloy is used as the anode and the copper plate is used as the cathode. When the current is passed, the metal and the metal sulfide in the anode react as follows, and the cobalt is transferred into the solution:

Me(Co,Fe,Cu)-2e=Me ^{2 +} (Co,Fe,Cu)

CoS-2e = CO ^{2 +} +S.

4. Microbial leaching method. Microbial leaching is the use of certain microorganisms or their metabolites to oxidize, reduce, dissolve, adsorb, etc. certain minerals, and transfer cobalt into solution. The microbial leaching method is suitable for treating lean ore, tailings, slag, etc., with low investment, high metal extraction rate and no pollution. Using Thiobacillus main mineral ore leaching manganese ore aqueous cobalt (Co 0.0054% mass fraction) in pH = 2.5, total iron concentration of ^{3g / L, m (Fe 3+} ) / m (Fe 2+) The leaching rates of cobalt and manganese were 88.6% and 67.2%, respectively, at a mass ratio of liquid solid product of 4:1 and a temperature of 26 °C. In view of the high manganese content of the bacterial leachate, the pH is adjusted to about 4 precipitated iron with Na ₂ CO ₃ , and the cobalt and manganese are separated by sodium sulfide precipitation, and finally the cobalt sulfate solution is obtained.

(2) Removal of iron (manganese) from cobalt-containing solution

The cobalt leaching solution contains metal ions such as iron and manganese, and is generally removed by an oxidation neutralization method, a yellow sodium iron sputum method, a goethite method, or the like.

1. Oxidation neutralization method. Adjust the pH of the solution and add strong oxidants such as C1 ₂ , NaC1O ₃ and HNO _{3 to} oxidize low-valent ions such as iron and manganese into high-valent ions to form a precipitate. The chemical reaction is:

2Fe ^{2 +} +Cl ₂ +6H ₂ O=2Fe(OH) ₃ ↓+6H ⁺ +2C1 ^-

3Mn ^{2 +} + Cl ₂ + 4H ₂ O = Mn ₃ O ₄ ↓ + 8H ⁺ + 2C1 ^- .

2, yellow sodium iron sputum method. The yellow sodium iron sputum method is to precipitate ferric iron from a sulphate solution containing K ⁺ , Na ⁺ , NH ₄ ⁺ ions as a pale yellow crystalline compound, ie, M ₂ Fe ₆ (SO ₄ ) ₄ (OH) ₁₂ . (M represents K ⁺ , Na ⁺ , NH ₄ ⁺ , Pb (I), Ag ⁺ , H ₃ O ^{+ ,} etc.). This method is suitable for purifying iron from a solution containing sulfate ions.

3. Goethite method. Adjust the pH of the solution to about 2.0, reduce the Fe ^{3 +} to Fe ^{2 + by} adding a reducing agent, then slowly add the oxidant to maintain a certain pH, and slowly oxidize Fe ^{2 +} to Fe ^{3 +} to form goethite precipitate. . The goethite formed is a brown needle-like crystal, and its composition is α-FeOOH, which is an orthorhombic system, has a low solubility, and does not have crystal water, and has good filtration performance.

(3) Purification of solution and separation of nickel and cobalt

1. Extraction method. The solvent extraction method has become the main method for extracting cobalt because of its high selectivity, high straight yield, simple process, continuous operation and easy automation. There are many kinds of extracting agents. In the early days, the extractant for nickel and cobalt separation in China was P204, and later changed to P507. However, P204 is better than P507 in removing impurities such as calcium, iron and copper from nickel sulfate solution. Therefore, the two can be used together. The former is used for impurity removal, and the latter is used for separation of nickel and cobalt. P204 and P507 common drawback is more difficult back-extraction of trivalent iron, Canadian Falconbridge and Le Havre, France plant are TBP (tributyl phosphate) iron extraction process. 5709 is a phosphine extractant researched and synthesized by the Beijing Institute of Chemical Metallurgy, Nuclear Industry. Its performance is similar to that of P507, but its adaptability to calcium is better than that of P507, and it has a certain ability to extract lead . The price is lower than P507. An excellent extractant.

In hydrochloric acid medium, can be extracted N235 FeC1 _3, P507 P204 extracted impurity was extracted and then separated from cobalt, nickel, obtained nickel, cobalt solution may be produced the corresponding salts or compounds, can also produce an electroless nickel and cobalt electricity.

In synergistic extraction studies, pyridine carboxylates and alkylpyridines are the most promising extractants for cobalt extraction. Tests have shown that Versaticl0+10% isopropanol + Cl ₂ + aliphatic diluent is used as the extractant, and the extraction selectivity of nickel and cobalt can be significantly improved in the mixed system of nickel, cobalt and other metals.

2, liquid film method. Literature [1] introduced that Span-80 surfactant film with P507 as the flow carrier can extract and separate cobalt and nickel from industrial wastewater containing cobalt and nickel in the range of pH 4.2-5.3. [2] introduced, with EDTA, NH ₄ F and the like DMSA mask interfering ions, to HDTHP, L113B, liquid paraffin, sulfonated coal oil phase and the aqueous 2.5 mol / L HCl yellow liquid membrane separation, etc. The extraction rate of cobalt in iron ore, soot, slag and cobalt-containing spent catalyst is above 91%.

(4) Desiliconization

Since the alloy contains a large amount of silicon, when oxidized and leached under acidic conditions, a large amount of silicon will enter the solution to form silicic acid. When the silicic acid content reaches a certain level, silica gel is formed. Once formed, silica gel has a serious impact on production, making the solution unfilterable and even causing the entire production to stop.

At present, the conventional practice is to transfer valuable metals such as cobalt and copper into a solution, and to leave impurities such as silicon in the leaching slag; another method is to use a hydroxide such as cobalt, copper or nickel in a strong alkaline solution. The form is completely precipitated, and silicon enters the solution in the form of sodium silicate to separate the metal from the silicon. When the separated metal hydroxide is dissolved with an acid, the solution contains almost no silicon. The disadvantage of this method is that it is costly and is not recommended for direct use.

Note:

[1] Li Yuping, Wang Xianke. Extraction of cobalt chloride by liquid membrane method [J]. China Molybdenum Industry, 2002, 26 (2): 28-30.

[2] Bao Fuyi. The progress of solvent extraction in nickel-cobalt hydrometallurgy [J]. Non-ferrous metals: Smelting, 1995 (2): 12-6.