| 摘要 |
Impure NiCO3 is purified by dissolving it in aq ammoniacal (NH4)2CO3 soln. containing a soluble sulphide, separating the insoluble sulphides formed, and heating the soln. to precipitate purified NiCO3. The soluble sulphide may be Na2S, NaHS or H2S, and may be added as not more than 3% of the Ni content of the soln. The dissolving soln. may contain 50-150 g/l. NH3 and 25-75 g/l. CO2. The purified NiCO3 soln. may be heated to 170-250 DEG F. to ppt. 70-99% of Ni as NiCO3 at a rate of 0.2-2 g/l. of Ni per minute. The crude NiCO3 may be obtained from an optionally pre-heated nickel-containing ammoniacal (NH4)2CO3 leach soln. by adding a sulphide to ppt. the bulk of the insoluble sulphides which are then separated, and ppting. crude NiCO3 by heating the soln. The purified NiCO3 may be further purified by redissolving it in ammoniacal (NH4)2CO3 sulphide-containing soln. and reprecipitating by heating. The NiCO3 may be calcined to give nickel oxide. Na2S may be added to the NiCO3 before such calcination and the NiO formed on calcination then washed with H2O to remove all remaining sulphur as soluble Na-salts. |
