SEPARATION OF COBALT(II) AND NICKEL(II) IONS FROM ACID AQUEOUS SOLUTIONS BY Co IT ION-EXCHANGE INTO γ-TITANIUM PHOSPHATE

ABSTRACT

The Co²⁺-2H⁺, Ni²⁺-2H⁺, and Co²⁺-Ni²⁺-2H⁺ ion exchange processes into γ-Ti(H₂PO₄)(PO₄)2H₂O were studied. Exchange isothenns and titration curves were obtained. Monometallic half ion exchange phases were formed by using MC₂+HCl (M=Co,Ni) solutions. Equilibrium constants, free energy, enthalpy, and entropy of the Co²⁺-2H²⁺ ion exchange reaction were determined. In (Co,Ni)Cl₂ solutions, bimetallic a half ion exchange substitution solid solution is detected. Equilibrium constant of the Co²⁺-Ni²⁺ substitution process in the γ-Ti(Co_xNi_0.5−x.HPO₄)(PO₄)nH₂O phase at 85°C was determined. In (Co,Ni)Cl₂+HCl solutions, total separation of Co²⁺ and Ni²⁺ is obtained.