Kazuyoshi Shimakage1, Katsuji Sakata1, Hiromichi Yamao1 and Susumu Morioka1
1Department of Metallurgy,Faculty of Engineering, Tohoku University, Sendai
Some experiments on the ammonia pressure leaching of nickelferrite have been performed to determine the relation between the reducing power of various reducing gases and the extraction percentage in subsequent leaching of nickel.
H2, H2-H2O, CO and CO-CO2 gases were used as the reducing gas, and ammonia solution containing ammonium sulphate, as the leaching solution for nickel reduced.
The results obtained were as follows:
(1) Nickelferrite did not dissolve in ammonia solution under the condition of pressure leaching.
(2) Reducing power of the gases used was in the order of H2>CO>CO-CO2(2:1)>H2-H2O(3:7)>CO-CO2(1:1)>CO-CO2(1:2) at the rate beyond the critical flow rate.
(3) The use of ammonium sulphate is required for efficient extraction of nickel by way of preventing hydrolysis, and it has the additional advantage that the leach solution can be efficiently kept without iron ion.
(4) Adequate and satisfactory reduction previous to leaching was attained by CO-CO2 gas, maintaining 100% extraction of nickel at 50% reduction of nickelferrite as expected theoretically.
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