As part of its research programs, the U.S. Bureau of Mines is investigating the partitioning of complex sulfide minerals to simpler sulfide phases by sulfidation reactions. Partitioning in this manner can afford opportunity to improve selective extraction of mineral constituents of value. This report describes research involving the sulfidation partitioning of the mineral pentlandite, which is an important source of ni in primary production. For the laboratory studies, the pentlandite was synthesized in nominally equiatomic proportions of ni and fe. Elemental ni, fe, and s powders were blended, compacted, and sealed under reduced he pressure in vitreous silica tubes. The tubes were heated under controlled conditions at 500 deg c for 24 h. The product was verified by x-ray diffraction and chemical analysis to consist essentially of (ni,fe)9s8. Small samples of the (ni,fe)9s8 were encapsulated with sulfur in silica tubes at reduced he pressures and heated for 1 to 24 h at specific temperatures between 400 and 600 deg c, both below and above the boiling point of sulfur ( 445 deg c). Reaction rate increased with temperature. Within this temperature range, partitioning to individual ni and fe disulfides proceeded to essential completion according to the reaction 2(fe,ni)9s8 + 20s0(l,g) -> 9fes2 + 9nis2. The substitutional solubility of fe in the nis2 phase and ni in the fes2 increases with temperature.
Miner., Met., and Mater. Soc., 1988, PP. 309-322