Spent Nickel Metal Hydride Research Articles

Characterization of spent nickel–metal hydride batteries and a preliminary economic evaluation of the recovery processes

Valuable metal materials can be recovered from spent nickel–metal hydride (NiMH) batteries. However, little attention has been paid to the metal compositions of individual components of NiMH batteries, although this is important for the selection of the appropriate recycling process. In this study, NiMH batteries were manually disassembled to identify the components and to characterize the metals in each of these. A preliminary economic analysis was also conducted to evaluate the recovery of valuable metals from spent NiMH batteries using thermal melting versus simple mechanical separation. The results of this study show that metallic components account for more than 60% of battery weight. The contents of Ni, Fe, Co, and rare earth elements (REEs) (i.e., valuable metals of interest for recovery) in a single battery were 17.9%, 15.4%, 4.41%, and 17.3%, respectively. Most of the Fe was in the battery components of the steel cathode collector, cathode cap, and anode metal grid, while Ni (>90%) and Co (>90%) were mainly in the electrode active materials (anode and cathode metal powders). About 1.88 g of REEs (Ce, La, and Y) could be obtained from one spent NiMH battery. The estimated profits from recovering valuable metals from spent NiMH batteries by using thermal melting and mechanical processes are 2,329 and 2,531 USD/ton, respectively, when including a subsidy of 1,710 USD/ton. The findings of this study are very useful for further research related to technical and economic evaluations of the recovery of valuable metals from spent NiMH batteries. Implications: The spent nickel–metal hydride (NiMH) batteries were manually disassembled and their components were identified. The metals account for more than 60% of battery weight, when Ni, Fe, Co, and rare earth elements (REEs) were 17.9%, 15.4%, 4.41%, and 17.3%, respectively, in a single battery. The estimated profits of recovering valuable metals from NiMH batteries by using thermal melting and mechanical processing are 2,329 and 2,531 USD/ton, respectively, when including a subsidy of 1,710 USD/ton. These findings are very useful to develop or select the recovery methods of valuable metals from spent NiMH batteries.

Recovery of valuable metals from a spent nickel–metal hydride battery: Selective chlorination roasting of an anodic active material with CCl4 gas

A method for recovery of valuable metals from a spent nickel–metal hydride battery has been investigated. Mischmetal–nickel alloy (MmNi5), which acts as an anode active material, was separated from an electrode scrap mixture using a sedimentation process. The separated MmNi5 contains rare earth metals (14.5mass% Ce, 10.8mass% La, 4.5mass% Nd) and transition metals (49.2mass% Ni, 9.8mass% Co, 4.7mass% Mn). CCl4 gas was employed as a chlorination roasting agent to prevent the formation of rare earth oxychlorides. When MmNi5 was chlorinated at 673K, it was decomposed into rare earth chlorides and nickel alloy. The chlorinated sample was subsequently leached with distilled water to recover these materials. The leaching yields of La, Ce, and Nd reached 96.3, 77.4, and 80.1mass%, respectively, and 85.7mass% of the Ni and 87.1mass% of the Co could be recovered as Ni–Co alloy. The relatively lower recovery ratios of Ce and Nd can be attributed to the stability of Ce and Nd oxychlorides. When the chlorination temperature reached 773K, MmNi5 was completely chlorinated. At 973K and higher, a greenish precipitate was also observed in the low-temperature zone of the reaction tube. Because the vapor pressures of rare earth and transition metal chlorides differ from each other, the transition metal chlorides can be separated by vaporization. Their yields reached 94.6% (La), 95.3% (Ce), and 94.9% (Nd) in the chlorinated residue.

Separation and recovery of rare earth elements from spent nickel–metal-hydride batteries using synthetic adsorbent

The recovery of rare earth elements such as La(III) and Nd(III) from spent nickel–metal hydride (NiMH) battery by novel synthetic adsorbent were investigated. First, layered double hydroxide (LDH)-A (A- anion of carrier) been prepared and characterized by different methods. Second, the separation and recovery of some rare earth elements (La(III) and Nd(III)) from acidic solutions using the synthetic adsorbent were investigated. The adsorption percent of the two metal ions was found to increase with increasing contact time, adsorbent weight and pH from 0 to 1 then it remains constant in the pH range (1–2). La(III) was preferentially adsorbed over Nd(III) in the mixture solution. From characterization of the adsorbent results, the adsorption mechanism of LDH-A adsorbent was proposed with rare earth elements. It was found that the highest separation factor (SLa/Nd) value of 23.2 was obtained with 10g/l (0.1g/10ml) from a mixed solution of 5g/l of each of La(III) and 5g of Nd(III) at pH1 and contact time 2h. Based on the experimental results, a separation method was developed and tested to separate high purity Co(II), Ni(II) and rare earths from Ni-MH batteries leached by 2.0M H2SO4 and the rare earths are leached by 2M HCl. Based on the experimental results, a flow sheet was developed and tested and 1.2g La(III) and 1g Nd(III) were obtained from the leaching process.

Hydrometallurgical separation of rare earth elements, cobalt and nickel from spent nickel–metal–hydride batteries

The separation of rare earth elements, cobalt and nickel from NiMH battery residues is evaluated in this paper. Analysis of the internal content of the NiMH batteries shows that nickel is the main metal present in the residue (around 50% in weight), as well as potassium (2.2–10.9%), cobalt (5.1–5.5%), rare earth elements (15.3–29.0%) and cadmium (2.8%). The presence of cadmium reveals that some Ni–Cd batteries are possibly labeled as NiMH ones. The leaching of nickel and cobalt from the NiMH battery powder with sulfuric acid is efficient; operating variables temperature and concentration of H 2O 2 has no significant effect for the conditions studied. A mixture of rare earth elements is separated by precipitation with NaOH. Finally, solvent extraction with D2EHPA (di-2-ethylhexyl phosphoric acid) followed by Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) can separate cadmium, cobalt and nickel from the leach liquor. The effect of the main operating variables of both leaching and solvent extraction steps are discussed aiming to maximize metal separation for recycling purposes.

Dismantling, Recovery, and Reuse of Spent Nickel–Metal Hydride Batteries

A novel process was developed and optimized for the recycling of spent nickel metal hydride (Ni–MH) batteries. The given process included dismantling, baking, and sieving, dissolving with acid, separating rare earths (La, Ce, Pr, and Nd, shown as RE) and impurities, and synthesizing spherical . By using a specially designed dismantling machine, spent Ni–MH batteries were dismantled with high efficiency and then the battery shells and metal–mesh substrate were separated from the baked residues using a sieving method. The powder residues were dissolved by at 70°C, a solid to liquid (S/L) ratio of 1:10 for 5 h. Then after the separation of RE, Fe, and Cu by adjusting the pH value of the dissolving solution, the recovered solution containing and was used as precursor to synthesize electrode material. Spherical with specific capacity of was finally obtained. The feasibility of the cyclic using of the metal values in Ni–MH batteries is demonstrated in this paper.

Regeneration of hydrogen storage alloy in spent nickel–metal hydride batteries

The hydrogen storage alloy from spent Ni–MH batteries was regenerated by chemical and smelting method. The alloy regenerated by chemical treatment has the same CaCu5 structure, but the electrochemical capacity is lower than that of the original alloy. When the spent alloy was chemically treated and then smelted by arc-melting, its structure and electrochemical properties could be well recovered. It is found that the discharge properties and lifetime of the regenerated alloy can reach the level of the original alloy.

Recovery of Ni-based alloys from spent NiMH batteries

Although spent nickel metal-hydride (NiMH) batteries are not considered hazardous waste, there are valuable materials that could be recovered; therefore the recycling of these batteries should be considered. This paper discusses spent NiMH batteries characterization and describes a simple process to recover valuable materials based on mineral processing techniques, hence the specific objective of this work is to study a process for the recovery of valuable metals from spent NiMH batteries. Batteries were manually dismantled in order to classify their components. The electrodes could be separated during the manual dismantling and were characterized through X-ray diffraction (XRD) analysis. A significant fraction of the batteries, around 37 wt.%, is composed of Ni-based alloy. The spent batteries were treated using laboratory equipment. The treatment that produced the best results was hammer milling, magnetic separation, knife milling, magnetic separation and size separation. The overall metal yield was in the order of 86%. A preliminary economic study is presented to show the feasibility of the process.

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.