1. Separation of cobalt and nickel from acidic sulphate solutions using mixture of di(2-ethylhexyl)phosphoric acid (DP-8R) and hydroxyoxime (Acorga M5640);Cerpa;Journal of Chemical Technology and Biotechnology,2004
2. Cheng, C.Y. and Urbani, M.D., 2006. Synergistic solvent extraction process. WO Patent publication No. 2006032097.
3. Separation of copper, iron and zinc from cobalt and nickel in Minara process liquor by synergistic solvent extraction: pilot plant operation;Cheng,2007
4. Duyvesteyn, W. P. C., Neudorf, D. A. and Weenink, E. M., 2002. Resin-in-pulp method for recovery of nickel and cobalt. US Patent 6, 350, 420 B1.
5. Selective absorption of copper, nickel, cobalt and other transition metal ions from sulphuric acid solutions with the chelating ion exchange resin XFS 4195;Grinstead;Hydrometallurgy,1984