Separation of nickel and cobalt using a chelating resin by the mixing of citric acid and ammonium chloride as the complexing agent in solution for resource recovery from used lithium batteries

• The separation of Ni and Co using iminodiacetic acid chelating resin was successful. • Citric acid and ammonium chloride was mixed as the complexing agent in solution. • Ni changed from a citric acid complex to an ammonia coordinated complex under basic. • The adsorbed metal ions were easily desorbed using 0.6 M hydrochloric acid solution. For resource recovery from used lithium batteries, the separation of nickel and cobalt using an iminodiacetic acid type chelating resin (MC-700) by the mixing of citric acid and ammonium chloride as the complexing agent in solution was successful under basic condition (pH: 10 or more). The separation mechanism was found that Ni changed from a citric acid complex to an ammonia coordinated complex under the basic conditions. On the other hand, Co in this solution mainly formed the citric acid complex even under the basic conditions. The separation occurred when the ammonia-coordinated Ni was transferred and adsorbed on the chelating ion exchange resin, while Co formed a stable citric acid complex. In addition, when the concentrations of the mixed citric acid and ammonium chloride as complexing agents were evaluated, the separation performance was improved by reducing the citric acid concentration. The adsorbed metal ions could be easily desorbed and recovered using a 5 % (0.6 M) hydrochloric acid solution. This new technique is expected to repeatedly and easily separate Ni and Co in a low cost hydrochloric acid dissolved solution of waste lithium batteries.