| Copper, cobalt and nickel are in adjacent position in the periodic table, so the chemical properties of nickel-copper-cobalt are very similar. Copper, cobalt and nickel are often in associated relations, and they are mainly from low-grade sulfide ore, oxide ore, sea manganese nodules and other secondary materials. These resources are generally processed by ammonia system or acid system to leach. Since ammonia leaching process has the advantages of good selectivity, fewer impurities in leaching solution, non-corrosive to the equipment, and it is superior to the conventional acid leaching process, thus it is favored. By ammonia/ammonium salt leaching, copper, cobalt and nickel metals enter the leaching solution in the form of ammonia complex ions. However, due to similar chemical properties of the ammonia complex ions of nickel-copper-cobal, so separation of copper, cobalt and nickel has become a recognized problem in hydro-metallurgy.Solvent extraction method is an industrially widely used metal ion extraction and separation technology, which has many advantages, including flexible operation, wide range of treatment, controllable selectivity and low energy consumption. Hydroxamic extractants are widely-used as copper extraction agents, but because chemical properties of copper, cobalt, nickel the ammonia system are very similar, this kind of extractants can not process separation of copper, cobalt and nickel. Our results show that add a certain amount of phosphonate modifier into hydroxamic extractants, since such a kind of modifier contains P=O double bond, has the electron donating properties, and it can form hydrogen bonds with -OH in the hydroxamic extractants, so that reducing the activity of hydroxamic extractant to some extent, and it has a certain degree of antagonistic effect on extraction of copper, cobalt and nickel, but the strength of this effect have significant differences on copper-cobalt-nickel extraction, which can achieve the efficient separation of copper, cobalt and nickel in ammonia system.Using N902 and M5640 as extractants, selecting TRPO, TBP, BESO as antagonists, and made a study on the separation of copper, cobalt and nickel in ammonia solution:1. In ammonia/ammonium chloride system, first, using N902 as extractant, kerosene as diluent, research the separation and extraction of copper, and make the further study of the extraction and separation of copper and nickel, the results show that,N902 has excellent performance on the extraction of copper and nickel, the extraction rate of copper and nickel is up to 100% and 88.1% respectively, but it is less than separation. When add an amount of TRPO, TBP or BESO into the N902 extractant, extraction efficiency of extractant on nickel extraction decreases significantly, while the effect of the copper extraction efficiency does not change significantly, so that it can achieve the separation of copper and nickel. Put emphasis on the study of the effect of oscillation time, N902 concentration, antagonist concentration, total ammonia concentration, phase ratio and the extraction capacity on the extraction of copper and nickel separation, and results showed that:when using 10 vol% N902 and 1 vol% TRPO as the extractant, kerosene as diluent, phase ratio as 1:1, the total ammonia concentration as 4.0 mol/L, then the experiment is under optimal conditions, the extraction rate of copper is up to more than 99.96%, and nickel extraction rate is less than 22.8%. Comparing the efficiency of antagonist TRPO, TBP and BESO on copper and nickel separation, TRPO> TBP> BESO.2. In the ammonia-ammonium chloride system, using M5640 which was dissolved in kerosene and antagonists (TRPO, TBP or BESO) and the extraction and separation of copper and nickel are studied. The effects of contact time, M5640 concentration, modifier concentration, total ammonia concentration, and phase ratio on the extraction and separation of both metals were determined.The results show that:the addition of modifiers into M5640 exerts significant antagonistic effects on copper and nickel extraction. The antagonistic effect of the extractant mixture was significantly weaker on the extraction of nickel than on that of copper. More than 99.96% of copper and less than 6.6% of nickel are extracted using a mixture of 10 vol.% M5640 and 2 vol.% TRPO in kerosene from an ammonia solution totally containing 4.0g/L, each of copper and nickel under optimal extraction conditions, then the separation factor of copper over nickel reaches 35,250. Comparing the efficiency of modifier TRPO, TBP, BESO on separation of copper and nickel, TRPO is the best, followed by TBP, and it is consistent with the N902 system. Meanwhile, the paper also make researches on the extraction mechanism of M5640 on copper and antagonistic effect mechanism of TRPO on hydroxamic extractants, studies have shown that the form of extraction complexes is R2Cu, the antagonists have a weak hydrogen bonding with the-OH in the hydroxamic extractants.3. In the ammonia-ammonium chloride system, adding a certain amount of antagonist (TRPO, TBP and BESO) in the N902 or M5640 extractants and make studies on the separation of copper, cobalt and nickel. The study found Co (II) ions can easily be oxidized into Co (III) ions by O2 in the air in ammonia systems, and Co (III) ions can not be extracted by hydroxamic extractants. The effects of time, extractant concentration, antagonist concentration, pH and the phase ratio on the separation efficiency have been considered, and the results show that, first make the efficient separation of copper from cobalt and nickel by using the modified hydroxamic extractants, then cobalt and nickel in the raffinate can use unmodified Acorga M5460 to separate and extract, and nickel ions are extracted, but the Co (III) ions are left in the raffinate, so the separation of cobalt and nickel can be achieved. After the two extraction steps above, the efficient separation of copper, cobalt and nickel can be achieved. |
PDF Full Text Request