The precipitation of Ni3S2 from sulfate solutions |
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Authors: | Akitsugu Okuwaki Osamu Kanome Taijiro Okabe |
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Affiliation: | (1) Department of Applied Chemistry, Faculty of Engineering, Tohoku University, 980 Sendai, Japan |
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Abstract: | The formation conditions for the recovery of nickel from sulfate solutions as Ni3S2 have been investigated; this sulfide is
more reactive than NiS in subsequent leaching operations. Hydrogen sulfide gas at atmospheric pressure is introduced into
a NiSO4-Na2SO4-MgSO4-Al2(SO4)3 solution in the presence of reduced iron powder. Although the formation of Ni3S2 is compctitive
with that of NiS, the nickel precipitation efficiency and the ratio of nickel as Ni3S2 to the total nickel precipitated reached
99.5 to 99.9 and 90 to 95 pct, respectively, under the following conditions: 363 K, Ph2s 31 kPa, Ni2+ 4.0 g · dm-3, 3Feo]/Ni2+] 1.25 to 1.5, H2S flow rate 70 to 100 cm3 · min-1, and 45 to 60 minutes retention time. Selective formation of Ni3S2 is achieved within 10 minutes, and a reaction on the surface
of the iron is rate-determining during the early stages of precipitation. Since the iron is almost totally consumed after
1 to 2 hours of reaction, the precipitated Ni3S2 is gradually converted to NiS. Calculations considering the buffer action of sulfate ion and sulfate complex formation with
polyvalent metal cations as well as with nickel ions confirmed that significant nickel precipitation as Ni3S2 should occur under the test conditions. |
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