EARTH

[3913-23-01] Solvent extraction equilibria of nickel(II) and ammonia with LIX84I

Shubin Wang^1,2, Jie Li², Hirokazu Narita¹, ○Mikiya Tanaka¹ (1. National Institute of Advanced Industrial Science and Technology (AIST), 2. Central South University)

Chairman: Atsushi Shibayama （Akita University）, Mikiya Tanaka (AIST)

Keywords:solvent extraction, nickel(II), ammonia, LIX84I, co-extraction

Nickel is often recovered via ammoniacal alkaline solution by solvent extraction using a chelating reagent. In this process, a certain amount of ammonia is known to be co-extracted with nickel which is removed by dilute acid scrubbing before stripping of nickel with sulfuric acid. In order to effectively design and control the process, it is important to establish a thermodynamic model of the system. In this study, therefore, equilibrium solvent extraction of nickel and ammonia from ammoniacal alkaline solutions with LIX84I, a typical chelating reagent, of which active component is 2-hydroxy-5-nonylacetophenone oxime (HR), is targeted at 298K. The equilibrium distribution ratios of nickel and ammonia are measured at various total ammonium concentrations, pHs, kinds of counter anions, and phase ratios. The masking effect for nickel extraction is found at 8 < pH < 10 due to preferential formation of nickel-ammine complexes, while ammonia co-extraction is obvious. Ammonia in the organic phase is minimized at the saturation of nickel; however, a small amount of ammonia still remains. The system involves the equilibria of ammonium dissociation, nickel-ammine complexes formation, nickel-anion complex formation, hydroxyoxime aggregation, nickel extraction, nickel-hydroxyoxime complex (NiR₂) distribution, and ammonia extraction. We will determine the equilibrium constants of these equilibria and compare the distribution ratios of nickel and ammonia between experiment and calculation.