Two stage leaching process for selective metal extraction from spent nickel metal hydride batteries. (20th July 2017)

• Record Type: Journal Article
• Authors: Meshram, Pratima; Somani, Hemant; Pandey, Banshi Dhar; Mankhand, Tilak Raj; Deveci, Haci; Abhilash,
• Is Part Of: Journal of cleaner production. Volume 157(2017)
• Page Start: 322
• Page End: 332
• Publication Date: 2017-07-20
• Subjects: Spent NiMH batteries -- Baking -- Sulfuric acid -- Water -- Reductive leaching; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2017.04.144
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: In this study, a closed loop two-stage leaching process has been experimentally and theoretically established for the selective dissolution of metals from electrode material of spent Ni-MH batteries. In the first step, baking parameters, such as temperature, acid concentration, and duration were optimized as 300 °C, 2 mL H2 SO4 for 1.5 g of cathode powder, 90 min. The thermodynamic feasibility of the process ascertained the spontaneous formation of water-soluble sulfates of nickel, zinc, and rare earth elements during the acid baking. Post-baking, a two-stage leaching was performed for leaching of different metals present in the baked material. In first stage leaching with water, 91.73% Ni, 94% Zn, 91% rare earth elements were extracted with a low recovery of 36.5% Co, 22.1% Fe, 23.5% Mn at 75 °C in 1 h. Owing to the low recovery of Co and Mn, 2nd stage leaching was performed using NaHSO3 in H2 SO4 at 95 °C for 1 h, improving extraction to Co (55%) and Mn (74%). The overall recovery of the metals was found to be 98.2% Ni, 91.4% Co, 98% Zn, 97.8% Mn and 96% rare earth elements. The two-stage process (baking and leaching) outperforms direct sulfuric acid leaching of cathode powder due to lower acid consumption and its selectivity of metals. Graphical abstract: Highlights: Two stage process intensified treatment of spent NiMH for selective metal dissolution. 1st stage water leaching of baked powder dissolved 91–94% Ni, Zn, REEs; low Co, Mn. 55% Co, 74% Mn reductively leached using NaHSO3 with H2 SO4 in 2nd stage. Overall leaching efficiency (base metals): 98.2% Ni, 91.4% Co, 98% Zn, 97.8% Mn. Overall leaching efficiency (REEs):80.4% La, 98.8% Ce, 98.2% Nd, 98.5% Pr, 99.2% Sm.