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. China's cobalt resources are poor, the cobalt grade is only 0.02% on average, and the individual high is 0.05% to 0. Congo (Gold) and Zambia's copper- cobalt ore, cobalt grade is 0.1% to 0.5%, high is 2% to 3%. . Due to the low grade of cobalt ore and complex ore composition, the recycling 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.
1. Method for extracting cobalt from cobalt-containing scrap and copper-cobalt alloy
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, zinc , manganese , 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 quenching, including Cu, Co, Fe, Mn, Si and the like (currently Copper and cobalt alloys as cobalt raw materials are imported from Congo (Golden), Zambia, and Zaire, and copper-rich products are smelted cobalt oxide ore and 8% cobalt concentrate. 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.
(1) 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 Al>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 Â° C, and then leached with a sulfuric acid solution at a constant temperature of 90 Â° C for 5 h, the cobalt leaching rate was 95%; When the amount of CaCO 3 is reduced by half, 5% Na 2 SO 3 is added, and after slag roasting at the same temperature, it is leached with concentrated sulfuric acid, and the cobalt leaching rate can be increased to 97%. The fire process is rather cumbersome.
(2) Wet process
For cobalt-rich alloys, acid leaching, chlorine oxidative 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:
When aerobic is present, metallic copper and other reactive metals react with the acid to form metal ions that enter the solution:
When the initial concentration of sulfuric acid is 6 mol/L, the leaching temperature is 100 Â°C, the leaching time is 6 h, and the liquid solid mass ratio is 5:1, the leaching rates of cobalt and nickel are 95.37% and 96.73%, respectively.
(2) Chlorine gas leaching. When leaching with dilute sulfuric acid, the introduction of chlorine into the solution enhances the leaching process. Increasing the metal leaching rate, but the chlorine gas is easy to overflow, causing environmental pollution, and it is necessary to recover 3 to 5 g/L of cobalt in the chlorinated leachate of various materials.
(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:
(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. The ore with the main mineral being hydrocobalt manganese ore (cobalt mass fraction 0.0054%) was leached with Thiobacillus ferrooxidans at pH=2.5, total iron mass concentration 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 Â°C. According to the characteristics of high manganese content in 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 , NaClO 3 and HNO 3 to oxidize low-cost ions such as iron and manganese into high-valent ions to form a precipitate. The chemical reaction is:
(2) Yellow sodium iron sputum method. The yellow sodium iron sputum method is to form a precipitate of ferric iron from a sulphate solution containing K + , Na + , NH 4 + ions as a pale yellow crystalline compound, namely M 2 Fe 6 (SO 4 ) 4 (OH) 12 . (M represents K + , Na + , NH 4 + , Pb (I), Ag + , H 2 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 whose composition is Î±-FeOOH, which is an orthorhombic system and has a low solubility. And without crystal water, the filtration performance is good.
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 superior to P507 in removing impurities such as calcium, iron and copper from nickel sulfate, so the two can be used together. The former is used for impurity removal and the latter is used. Nickel and cobalt are separated and the effect is very good. P204 and P507 common lack 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 synthesized by the Beijing Institute of Chemical Metallurgy, Nuclear Industry. Its performance is similar to that of P507, but its ability to adapt to calcium is better than P507, and it has a certain ability to extract lead , the price is lower than P507. It is an excellent extractant.
In the hydrochloric acid medium, FeCl 3 can be extracted by N235, extracted and removed by P204, and cobalt and nickel can be separated by P507 extraction to obtain nickel or cobalt solution, which can produce corresponding salt or compound, and can also produce electro-nickel and electro-cobalt.
In synergistic extraction studies. Pyridine carboxylates and alkylpyridines are the most promising extractants for the extraction of cobalt. Tests have shown that Versatiel0+10% isopropanol + C1 2 + fat is used as an extractant, and the extraction selectivity of nickel and cobalt can be significantly improved in a mixed system of nickel, cobalt and other metals.
(2) Liquid film method. The literature describes a Span-80 surfactant film with P507 as a fluid. In the range of pH 4.2 to 5.3, cobalt and nickel can be extracted and separated from industrial wastewater containing cobalt and nickel. The separation effect is better. Described in the literature, with EDTA, NH 4 F and the like DMSA mask interfering ions, to HDTHP, L113B, liquid paraffin, sulfonated coal oil phase and the liquid film 2.5mol / L HCl aqueous solution and the like separation of pyrite, The cobalt extraction rate of soot, slag and cobalt-containing spent catalyst is above 9l%.
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.
Second, wet method for cobalt extraction
Jinchuan Nonferrous Metals Co., Ltd. extracts cobalt from cobalt slag. The process is as follows: acid leaching, yellow, sodium iron, iron removal, iron removal, P204 extraction, depletion, P507 extraction, separation of cobalt, nickel-oxalic acid, precipitation of cobalt, production of cobalt oxide powder.
The process adopted by the Chengdu Electric Metallurgical Plant uses N235 to extract cobalt from the nickel slag leaching solution, remove impurities by ion exchange, and recover metal cobalt by electrowinning. When Sumitomo Corporation of Japan recovers cobalt from the cobalt-nickel ore leaching solution, it uses a neutralization precipitation method to remove iron and manganese, and hydrogen sulfide removes copper and zinc. The tertiary carbon monocarboxylic acid separates nickel and cobalt and converts them into chloride.
The process described in the literature is: neutralization, iron removal, ammonia leaching, separation of manganese, distillation, separation of cobalt and nickel, nickel precipitation in the form of basic nickel carbonate, filtration, washing, drying, calcination to nickel oxide, and finally reduction to metal by hydrogen. Nickel; cobalt is precipitated and recovered as cobalt hydroxide. Nickel and cobalt recovery rates can reach 95% to 96%.
For the refractory cobalt-containing waste containing copper, zinc, manganese, nickel and other elements, the principle of "reduction leaching - chemical impurity removal - P204 deep impurity removal - P507 extraction separation of nickel, cobalt" principle production of cobalt oxalate, cobalt recovery rate It is 95.61%.
The literature introduces a new process for extracting cobalt oxide from nickel electrolysis anolyte purification and cobalt removal. After addition of cobalt sulfate reducing residue dissolved sodium jarosite process iron, P204 and extracted impurity extraction separation of cobalt, nickel, magnesium, calcium ammonium fluoride addition. The precipitate cobalt oxalate, calcination step, is not less than the total recovery of cobalt 92%, the total nickel recovery rate is not less than 95%.
The literature describes the process of extracting cobalt oxide from Co. Mn spent catalyst waste with a cobalt mass fraction of 9.44%. Dissolve the waste with acid. Excess ammonia water was added to cause Mn 2 + to form MnO(OH) 2 precipitate under the action of 10% hydrogen peroxide at pH=10, while Co 2 + produced Co(NH 3 ) 4 2 + complex ions. To further remove traces of Mn from the solution, CoS was precipitated in a buffer system of pH = 3 with Na 2 S as a precipitant, and MnS hardly precipitated under these conditions. In the final CoS precipitation, the mass fraction of Mn is less than 0.6%, the mass fraction of other impurities is less than 0.5%, and the recovery rate of cobalt is above 92%. CoS was dissolved in nitric acid at 70-80 Â° C under reflux, filtered, and the filtrate was precipitated with oxalic acid at 80 Â° C to form cobalt oxide.
According to the properties of lithium- ion secondary battery cathode material- aluminum- cobalt membrane raw material, LiCoO 2 was decomposed in sulfuric acid and hydrogen peroxide system. The reaction was as follows:
The process for recovering cobalt is as follows: alkali pickling and acid solution purification of cobalt. Cobalt is recovered in the form of cobalt oxalate, and the direct recovery of cobalt is 95.7%.
The niobium and sulfuric acid were used to dissolve the valuable metals such as Cu, Ni and Co in the waste residue. The leaching rate of Cu and Ni was 99% c, and the Co leaching rate was 87%. The leachate was separated by iron powder replacement method, the iron was removed by the method of iron powder, the calcium removal by the NaF method, the deep removal of P204, and the separation of nickel and cobalt by P507. The recovery rates of Cu, Ni and Co were over 94%.
Uganda's first biological oxidation extraction plant, Kasese, was commissioned in 1999 to process concentrates containing 80% pyrite. After the first stage oxidation, the second stage oxidation was carried out with a medium iron-oxidizing strain, and the cobalt recovery rate was 92%.
The metallurgical laboratory of Beijing Research Institute of Mining and Metallurgy studied chlorine and cobalt leaching of copper-cobalt alloy, electrolysis copper removal, and TBP extraction and iron removal. The results show that copper recovery rate is high and cobalt loss is small.
Liao Chunfa of the Southern Institute of Metallurgy studied the process of extracting cobalt oxide from copper-iron-cobalt alloy slag, and determined the process conditions of alloy smelting, silicon removal, electrolytic refining, removal of impurities such as iron and copper, and alloy smelting can effectively remove the alloy. Silicon; electrolytic refining not only achieves the purpose of dissolving the alloy, but also has the effect of purifying and removing copper. The copper can be recovered in the form of sponge copper with a purity of 92.5% and a yield of over 99%.
For the leaching of cobalt from copper-cobalt alloy, at present, a sulfuric acid pressure leaching process or an electrolysis process is often used abroad. Finland's OMG is the world's first cobalt production company to process copper-cobalt alloys. The specific processing technology is unknown. Another company dealing with copper-cobalt alloys is the Chambishi cobalt smelter in Zambia, which uses a sulfuric acid pressure leaching process to produce CuSO 4 , CoSO 4 solution. Due to the small production volume and the demanding equipment, there are fewer manufacturers.
Third, the outlook
The conventional fire process obtains a nickel anode, and the nickel anode is electrolyzed to obtain a cathode nickel, and the cobalt is separated by nickel and cobalt in the anolyte to obtain a cobalt chloride salt. When electrolysis, copper ions preferentially obtain electrons than nickel ions, so this method cannot handle materials with high copper content; when used in the usual acid process, the cobalt leaching rate is not high; using the liquid membrane method, the extraction rate of cobalt is only 91%; The leaching rate is slower when the cobalt-containing waste is leached by the microbial leaching method, and the cobalt leaching rate can only reach 96%. If leaching with an oxidizing agent and a low acid (acid concentration of less than 2 mol/L) is used, the leaching speed can be greatly improved and the leaching rate is also ensured.
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