CYANEX® 301 binary extractant systems in cobalt/nickel recovery from acidic chloride solutions

Abstract

The extraction and stripping characteristics of CYANEX 301 binary extractant systems were investigated for the recovery of cobalt and nickel from chloride solutions. The selectivity of these systems against calcium, manganese and magnesium was also studied. These binary extractant systems consisted of mixtures of CYANEX 301 with basic extractants (Primene® JMT, Amberlite® LA-2, Alamine® 336 and Aliquat® 336). Based on criteria such as extraction and stripping characteristics (efficiency and rates) and selectivity against calcium, manganese and magnesium, screening experiments were performed to select the most appropriate binary extractant systems. From this screening work, the CYANEX 301–amine systems all demonstrated that cobalt and nickel could be selectively extracted from calcium, manganese and magnesium. A large synergistic effect on the stripping kinetics and efficiencies of cobalt and nickel was also observed when either amine was added to CYANEX 301. Depending on the amine concentration, near complete stripping of cobalt could be achieved with all systems, while the stripping of nickel still remained very low with the amines Primene JMT, Amberlite LA-2 and Alamine 336. Among the amine extractant systems, CYANEX 301–Aliquat 336 was shown to be the most promising binary extractant system. McCabe–Thiele extraction and stripping isotherms with this system were then constructed to determine the number of stages required. Complete extraction of cobalt and nickel could be achieved in 2–3 stages while still maintaining a high selectivity against calcium, manganese and magnesium. A decrease in cobalt stripping was observed when the hydrochloric acid concentration was increased from 2 to 4 M. The hydrochloric acid concentration had a reverse effect on nickel where nickel stripping was shown to increase with increase in acid concentration from 2 to 4 M.