Katsutoshi Inoue

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.

Adsorptive separation of some metal ions by complexing agent types of chemically modified chitosan

Two kinds of chemically modified chitosan immobilizing the ligands of ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) or diethylenetriamine-N,N,N′,N″,Ni″- pentaacetic acid (DTPA) onto polymer matrices of chitosan (EDTA– and DTPA–chitosan) were prepared by interacting the anhydrides of these complexing agents with chitosan. By incorporating these ligands, the adsorption of metal ions are much enhanced compared with original chitosan. For example, adsorption of Cu(II) takes place at pH=0–1 on these chemically modified chitosan, while it takes place at pH=4–6 on original chitosan. The observed order of selectivity for some metal ions are nearly the same for both of EDTA– and DTPA–chitosan in the adsorption from sulfuric acid solution: Ga(III)=In(III)=Fe(III)>Cu(II)=Mo(VI)>Ni(II)>V(IV)≫Zn(II)=Co(II)≫Al(III)≫Mn(II). This is nearly the same as the order of the stability of these metal chelates with these complexing agents, suggesting that the chelating ability of these ligands is still maintained after immobilizing these on polymer matrices of chitosan. Based on these basic data obtained in batchwise experiments, breakthrough and elution tests were carried out using a column packed with the EDTA– or DTPA–chitosan together with glass beads for some pairs of metal ions: e.g. same dilute concentrations of Co(II) and Ni(II) as well as small amounts of Co(II) together with a large excess of Al(III). These tests demonstrated that very clear-cut mutual separations between these pairs of metal ions can be successfully achieved by these complexing agent types of chemically modified chitosan.

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.

Removal and recovery of phosphorus from water by means of adsorption onto orange waste gel loaded with zirconium

Orange waste, an available biomass, was immobilized with zirconium(IV) to investigate its feasibility for phosphate removal from an aquatic environment. Kinetics, effects of pH and foreign anions, and the adsorption isotherm for phosphate have been examined. The adsorption capacity has been compared to that of two commercially available adsorbents such as zirconium ferrite and MUROMAC XMC 3614. The prepared gel was an effective adsorption gel for phosphate removal with a reasonably high sorption capacity of 57mg-P/g, which was four times higher than that of zirconium ferrite. The highest removal of phosphate was observed at low pH, whereas higher pH suppressed phosphate removal, but even up to pH 9 more than 85% phosphate removal was observed. Adsorbed phosphate was eluted by NaOH solution. Fixed bed column-mode experiments confirmed the complete adsorption of phosphate in continuous-mode operation. Throughout the operating conditions, zirconium was not leaked.

ADSORPTIVE REMOVAL OF ARSENIC USING ORANGE JUICE RESIDUE

A novel adsorbent has been prepared by simple chemical modification of orange juice residue (OJR) with the substitution of phosphate groups on the alcoholic analog of cellulose. Phosphorylated gel was further loaded with iron(III). The loading capacity for iron(III) on the gel was as high as 3.7 mol/kg. Adsorption studies on iron(III) loaded gel were carried out both batch wise and by using a column. Arsenic(III) adsorption was found to have been favored at alkaline condition (pH=7–11) while that of arsenic(V) was at acidic condition (pH=2–6). Maximum adsorption capacity for As(V) and As(III) was evaluated as 0.94 and 0.91 mol/kg at their optimum pH values 3.1 and 10.0, respectively. Experimental results indicate that iron-loaded phosphorylated OJR can be potentially applied for the removal and recovery of arsenic from various aqueous media.

Adsorption behavior of heavy metals onto chemically modified sugarcane bagasse

A new process for the xanthation of sugarcane (Saccharum officinarum) bagasse was investigated for the separation of cadmium, lead, nickel, zinc and copper from their aqueous solutions. Adsorption capacity of the charred xanthated sugarcane bagasse (CXSB) was found to be significantly more than the several biosorbents reported in the literatures. The modified material was characterized by FTIR and elemental analysis. The kinetics of sorption of the tested metals was fast, reaching equilibrium within 20-40 min. The maximum adsorption capacities evaluated in terms of mol/kg dry gel were 1.95 for Cd(II), 1.58 for Pb(II), 2.52 for Ni(II), 2.40 for Zn(II) and 2.91 for Cu(II), respectively. The high adsorption capacity and the kinetics results indicated that CXSB can be used as the selective adsorbent for the removal of these respective metal ions from wastewater.

Extraction and selective stripping of molybdenum(VI) and vanadium(IV) from sulfuric acid solution containing aluminum(III), cobalt( II), nickel(II) and iron(III) by LIX 63 in Exxsol D80

Abstract 5,8-diethyl-7-hydroxydodecane-6-oxime (LIX 63), a commercially available reagent, has been used in this work to investigate the extraction of molybdenum(VI) and vanadium(IV) from sulfuric acid solution in the presence of various other metals, such as aluminum(III), cobalt(H), nickel(II) and iron(III). Molybdenum(VI) and vanadium(IV) were extracted preferentially and separated completely from the coexisting metals involved at low pH (e.g., around 1.5) with LIX 63 dissolved in Exxsol D80. Vanadium(IV) in the loaded organic phase was selectively stripped by contacting with a 2 M sulfuric acid solution and isolated from molybdenum(VI). Molybdenum(VI) in the organic solvent, after the removal of vanadium(IV), was easily stripped by employing an aqueous ammonia solution as stripping agent and excellent phase separation performance (rapid phase separation, no formation of a second organic phase and no generation of an emulsion) in the stripping process was observed in all cases. A special emphasis, at least as an example of potential application, has been put on the extraction recovery of molybdenum(VI) and vanadium(IV) with LIX 63 extractant from the acidic sulfate liquor containing a sufficient quantity of aluminum(III), an appreciable amount of cobalt(II) and nickel(II), as well as a small amount of iron(III), resulting from the sulfuric acid leaching of spent hydrodesulfurization catalysts. The results obtained using the synthetic solution are in good agreement with those using the real leach liquor.

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.

Liquid membrane transport of amino acids by a calix[6]arene carboxylic acid derivative

Calix[6]arene hexacarboxylic acid was found to be a useful carrier for transporting amino acids through a liquid membrane. The calix[6]arene, which has a cyclic structure to include a guest molecule of the amino acid ester and bears six ionizable carboxylic acids to contribute electrostatic interaction, exhibited a high transport efficiency compared to its monomer analog and the other calix[n]arene derivatives. The novel carrier successfully transported hydrophobic amino acid esters from the feed phase to the receiving phase. The transport rate could be controlled by changing the pH gradient between the feed and receiving aqueous phases because the complexation proceeds by a proton-exchange mechanism. Furthermore, an optical resolution system was constructed by applying an enantioselective enzymatic reaction for a chiral separation of the amino acids. In the enzyme reaction, the l-form ester was selectively hydrolyzed to the free amino acid. The free amino acid hydrolyzed was not transported, while the unhydrolyzed d-form ester effectively moved to the receiving phase through the liquid membrane containing the calix[6]arene as a mobile carrier.

Grape waste as a biosorbent for removing Cr(VI) from aqueous solution.

Grape waste generated in wine production is a cellulosic material rich in polyphenolic compounds which exhibits a high affinity for heavy metal ions. An adsorption gel was prepared from grape waste by cross-linking with concentrated sulfuric acid. It was characterized and utilized for the removal of Cr(VI) from synthetic aqueous solution. Adsorption tests were conducted in batch mode to study the effects of pH, contact time and adsorption isotherm of Cr(VI), which followed the Langmuir type adsorption and exhibited a maximum loading capacity of 1.91 mol/kg at pH 4. The adsorption of different metal ions like Cr(VI), Cr(III), Fe(III), Zn(II), Cd(II) and Pb(II) from aqueous solution at different pH values 1-5 has also been investigated. The cross-linked grape waste gel was found to selectively adsorb Cr(VI) over other metal ions tested. The results suggest that cross-linked grape waste gel has high possibility to be used as effective adsorbent for Cr(VI) removal.