Spent lithium ion batteries contain valuable critical metals such as cobalt, copper, lithium and nickel. In order to develop a process for the separation of the divalent metal ions from spent lithium ion batteries, solvent extraction experiments were performed by employing synthetic hydrochloric acid leaching solution. The synthetic solution contained Cu(II), Co(II), Mn(II) and Ni(II) and its acidity was 3 M HCl. Extraction with Aliquat 336 led to selective extraction of Cu(II) with a small amount of Co(II). After adding NaCl to the Cu(II) free raffinate to enhance the complex formation of Co(II), Co(II) was selectively extracted into Aliquat 336 together with Mn(II). The small amount of Mn(II) in the loaded Aliquat 336 was scrubbed by pure Co(II) solution. After adjusting the pH of the raffinate to 3, 91,3% of Mn(II) was selectively extracted over Ni(II) by the mixture of D2EHPA and Alamine 336. In this extraction, the mole fraction of D2EHPA in the mixture affected the extraction of Mn(II). McCabe-Thiele diagrams for the extraction of Cu(II) and Co(II) were constructed. Batch simulation experiments for the three stage counter-current extraction verified the selective extraction of the target metal ions in each extraction step. Namely, the total extraction percentage of Cu(II) and Co(II) was 71.6% and 98.8% respectively. Most metals in the loaded organic phase were stripped completely with the appropriate agents (1.0 M H2SO4 for Cu(II), 0.1 M H2SO4 for Co(II) and 0.3 M HCl for Mn(II) stripping). A process was proposed to separate the metal ions by solvent extraction.

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Spent electroplating solutions contain small amounts of Pd(II). Cementation of Pd(II) with zinc metal powder is practiced to concentrate the Pd. Dissolution of the cemented Pd metal is necessary to recover pure Pd metal or compounds. In this work, the leaching behavior of Pd metal in inorganic acid solutions (hydrochloric and sulfuric acid) in the presence of an oxidizing agent such as H2O2, NaClO3, or NaClO was investigated. To determine the optimum conditions for Pd leaching, experiments were conducted by adjusting the concentration of the acids and oxidizing agents, reaction temperature and time, and pulp density. Complete leaching of Pd was possible using a hydrochloric acid solution with 3 kinds of oxidizing agents, whereas only NaClO was effective in the leaching with sulfuric acid solution. The chloride ions of HCl and NaClO3/NaClO play an important role in enhancing the leaching of Pd, due to the formation of Pd chlorocomplexes and by decreasing the reduction potential of Pd(II). Compared to H2O2, NaClO3 and NaClO showed some merits as oxidizing agents in terms of reaction time, temperature and low acid concentration. Based on the optimum leaching conditions of single Pd metal, the conditions for the complete leaching of Pd and Zn from the metallic mixtures were obtained.

BACKGROUND Cobalt, nickel and lithium are crucial in the manufacture of batteries. Therefore, the recovery of these metals from spent lithium ion batteries (LIBs) has attracted much attention because of their benefits in terms of economics and the environment. RESULTS In the present work, the recovery of metals such as cobalt, nickel, manganese and lithium from synthetic sulfuric acid leaching solutions of spent LIBs was performed by solvent extraction using synthetic ionic liquids (ILs) and a mixture of Cyanex 301 and Alamine 336. First, cobalt was selectively extracted over other metal ions by extraction with IL(ALi‐SCN). The role of SCN− during the extraction was also investigated, and the extraction reactions of cobalt by both ALi‐SCN and Aliquat 336 were verified. The cobalt in the loaded ALi‐SCN was stripped by ammonia solution. After adjusting the raffinate pH, extraction with the mixture of Cyanex 301 and Alamine 336 selectively extracted nickel over manganese and lithium. The extracted nickel was completely stripped by 75% aqua regia. Manganese was selectively extracted by IL(ALi‐CY) after adjusting the pH of the raffinate. The manganese in the loaded ALi‐CY was stripped by HCl solutions. Therefore, three‐step solvent extraction resulted in a raffinate containing only lithium. CONCLUSIONS A process was proposed to separate Co(II), Ni(II) and Mn(II) from the sulfuric acid solutions of spent LIBs. The mass balance of continuous experiments indicated that the purity of the stripping solution of Co(II) and Mn(II) was higher than 99.9%. © 2020 Society of Chemical Industry

Cyanex extractants, such as Cyanex 272, Cyanex 301, and Cyanex 302 have been commercialized and widely used in the extraction and separation of metal ions in hydrometallurgy. Since Cyanex 301 and Cyanex 302 are the derivatives of Cyanex 272, these extractants have similar functional groups. In order to understand the different extraction behaviors of these extractants, an understanding of the relationship between their structure and reactivity is important. We reviewed the physicochemical properties of these extractants, such as their solubility in water, polymerization degree, acidity strength, extraction performance of metal ions, and the interaction with diluent and other extractants on the basis of their chemical structure. Synthetic methods for these extractants were also introduced. This information is of great value in the synthesis of new kinds of extractants for the extraction of metals from a diverse medium. From the literature, the extraction and stripping characteristics of metals by Cyanex 272 and its derivatives from inorganic acids such as HCl, H2SO4, and HNO3 were also reviewed. The replacement of oxygen with sulfur in the functional groups (P = O to P = S group) has two opposing effects. One is to enhance their acidity and extractability due to an increase in the stability of metal complexes, and the other is to make the stripping of metals from the loaded Cyanex 301 difficult.