Osamu Itabashi

Hydrometallurgical process for recovery of metal values from spent lithium-ion secondary batteries

We report studies on the separation and recovery of metal values such as cobalt and lithium from spent lithium-ion secondary batteries. Effects of leachant concentration, temperature, reaction time and solid-to-liquid ratio on leaching of cobalt and lithium contained in the anode material of the batteries were examined using several reagents such as sulfurous acid, hydroxylamine hydrochloride and hydrochloric acid as leachants. Hydrochloric acid was found to be the most suitable leachant among the three reagents. A leaching efficiency of more than 99% of cobalt and lithium could be achieved when 4 M HCl solution was used at a temperature of 80°C and a reaction time of 1 h. The pH of the final pregnant liquor obtained was around 0.6 and the concentrations of cobalt and lithium were approximately 17 and 1.7 (g l−1), respectively. The cobalt in the leach liquor was extracted selectively and nearly completely with 0.90 M PC-88A in kerosene at equilibrium pH ≈ 6.7 in a single stage at an O:A ratio of 0.85:1. Then the cobalt in the loaded organic phase was recovered as cobalt sulfate with high purity (LiCo < 5 × 10−5) after lithium scrubbing with a dilute hydrochloric acid solution containing 30 g l−1 of cobalt at an O:A phase ratio of 10:1. This was followed by stripping with a 2 M H2SO4 solution at an O:A ratio of 5:1. The raffinate was concentrated and the lithium remaining in the aqueous solution was readily recovered as lithium carbonate precipitate by the addition of a saturated sodium carbonate solution at close to 100°C. The content of cobalt in the lithium precipitate was found to be less than 0.07%. Lithium recovery approached 80%. A flowsheet of the hydrometallurgical process for the recovery of cobalt and lithium from the spent lithium-ion secondary batteries has been established based on the experimental results.

Hydrometallurgical process for recovery of metal values from spent nickel-metal hydride secondary batteries

Abstract A completely hydrometallurgical process has been developed for the recovery of metal values such as cobalt, nickel and rare earths from spent nickel-metal hydride (Ni-MH) secondary batteries. Effects of hydrochloric acid concentration, temperature, reaction time and solid-to-liquid ratio on leaching of metals contained in the electrode materials of the batteries were studied. The optimal operating conditions were found to be 3 M HCl at a temperature of 95°C and a 3-h leach time, and it was possible to treat up to 5.5 g of scrap in 50 ml of acid solution where the recoveries 100% of cobalt, over 96% of nickel and 99% of rare earths were achieved. A typical chemical composition of the resulting leach liquor was approximately, in grams per liter, 23.4 Ni, 1.7 Co, 3.4 Fe, 0.72 Zn, 0.46 Al, 1.2 Mn, 4.2 La, 0.26 Ce, 0.82 Pr, 2.6 Nd and 0.074 Sm, as well as 50 Cl. The pH of the solution was around 1.2. The rare earth values can be readily recovered from the leach liquor by the use of a solvent extraction circuit with 25% bis(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene, in which a two-stage counter-current extraction at an O:A ratio of 3:1 at an equilibrium pH of 2.0, a single-stage cobalt scrubbing with 0.3 M hydrochloric acid at an O:A ratio of 22:1, and a stripping operation with 2.0 M hydrochloric acid in one contact at an O:A ratio of 5:1 are involved. A mixed rare earth oxide of over 99% purity was obtained by selective precipitation with oxalic acid, and calcination of the precipitate. The total yield of rare earths approached 98%. The cobalt and nickel in the raffinate are effectively separated by selective extraction of cobalt with 25% TOA in kerosene after concentration (up to [Cl−]≈220 g l−1). Nearly complete recovery of cobalt can be achieved by using a three-stage counter-current extraction at an O:A ratio of 2:1, followed by stripping with a dilute hydrochloric acid solution (pH 2.0) in a single stage at an O:A ratio of 4:1. Subsequently the cobalt in the strip liquor and the nickel remained in the raffinate are separately recovered as oxalates by the addition of ammonium oxalate. A pure cobalt product and a nickel oxalate with a purity close to 99.9% were obtained. The total recoveries of cobalt and nickel were found to be approx. 98% and 96%, respectively.

Recovery of metal values from spent nickel–metal hydride rechargeable batteries

Abstract A hydrometallurgical process is developed for the separation and recovery of metal values such as nickel, cobalt and rare earths from spent nickel–metal hydride (Ni–MH) rechargeable batteries. After removal of the external case, the electrode materials are dissolved in 2 M sulfuric acid solution at 95°C. The resulting liquor contains typically (g l−1), 10.6 Ni, 0.85 Co, 1.70 Fe, 0.36 Zn, 0.21 Al, 0.54 Mn, 1.73 La, 0.10 Ce, 0.33 Pr, 1.10 Nd and 0.032 Sm. The pH is around 0.4. The rare earth values are recovered from the liquor by means of a solvent extraction circuit with 25% bis(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene, followed by precipitation with oxalic acid. A mixed rare earth oxide of about 99.8% purity is obtained after calcination of the precipitate. The total yield of rare earths approaches 93.6%. The cobalt and nickel in the raffinate are effectively separated by solvent extraction with 20% bis(2,4,4-tri-methylpenthyl) phosphinic acid (Cyanex 272) in kerosene. The individual cobalt and nickel are then recovered as oxalates by the addition of oxalic acid. Cobalt and nickel oxalates with purities close to 99.6% and 99.8%, respectively, are obtained. The overall recoveries are over 96% for both cobalt and nickel. A total flowsheet of the process for recovery of rare earths, cobalt and nickel from spent Ni–MH batteries is proposed.

Direct observation of the polymer and monomer Langmuir-Blodgett films with the atomic force microscope

Abstract Molecular arrangement of two kinds of Langmuir–Blodgett monolayers composed of poly(N-dodecylacrylamide) and N-octadecylacrylamide were characterized with the atomic force microscope (AFM). The dodecyl side chains in the polymer Langmuir–Blodgett monolayer were observed as random molecular arrangement. In contrast, alkyl chains in N-octadecylacrylamide monomer Langmuir–Blodgett film were highly ordered to form two dimensional crystals. The X-ray diffraction patterns of the monomer and polymer Langmuir–Blodgett films were consistent with the AFM observation. The polymer Langmuir–Blodgett monolayer was not destroyed by AFM tip scanned in the contact mode, indicating that the monolayer is mechanically appreciably stable.

Ag+ ion sensing by the polymer Langmuir-Blodgett films containing 1-aza-15-crown 5-ether group

Abstract The 1-aza-15-crown 5-ether functional group can be incorporated into polymer Langmuir-Blodgett (LB) films as a comonomer of N-dodecylacrylamide. The surface pressure-area isotherms of the copolymers indicated the formation of the stable condensed monolayers on the air-water interface. The copolymer monolayers could be transferred onto solid substrates by the LB technique (Y-type deposition). The result of voltammetric measurement indicated that the functionalized electrodes covered with copolymer monolayers could collect the Ag+ by soaking them in the AgNO3 aqueous solution.