The structural and electronic properties of Cu 1.96 S and Ni 3 S 2 present in nickel–copper converter matte and sulfides such as CuS, Ni 7 S 6 , NiS, Ni 3 S 4 , and NiS 2 , likely existing as intermediates in the oxidative leaching of the matte, were investigated using first-principles calculations. Analyses of the total and partial density of states (DOS), with electron density and differential charge density, show that Cu–S and Ni–S bonds are of covalent character, and as the ratio of Ni/Cu to S decreases for the sulfides, Cu/Ni-3d orbital energies shift downward, while S-3p orbital energies shift upward. According to the values of their Cu/Ni-3d band centers, the oxidation activity decreases in the order Cu 1.96 S > Ni 3 S 2 > Ni 7 S 6 > NiS > Ni 3 S 4 > NiS 2 > CuS. This oxidation sequence leads to thermodynamically favorable substitution reactions between the nickel sulfides and Cu 2+ for obtaining more stable CuS, which is the theoretical basis of Sherritt Gordon’s selective leaching process.

No abstract

No abstract

The anodic dissolution of hypoeutectic cast iron consisting of pearlite and ledeburite was studied in a sulfuric acid solution by electrochemical methods. The oxidation activities of ferrite and cementite, which are two phases in cast iron, are evaluated by their structural and electronic properties according to the first-principles calculations. The results show that the anodic dissolution of ferrite occurs at the more negative potential compared with cementite. With comparison of ledeburite, the microstructure of pearlite is more easily crumbled during anodic dissolution because more of the ferrite dissolves from the framework of pearlite. The first principle calculations demonstrate that the Fe 3d-band center of iron is closer to Fermi level than that of cementite, indicating that Fe atoms in ferrite are more active and prone to suffering electrophilic attack. This is the intrinsic reason that cementite is more stable than ferrite under anodic polarization in the sulfuric acid solution.

No abstract