Two stage leaching process for selective metal extraction from spent nickel metal hydride batteries

Meshram P., Somani H., Pandey B. D., Mankhand T. R., DEVECİ H., Abhilash A.

JOURNAL OF CLEANER PRODUCTION, vol.157, pp.322-332, 2017 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 157
  • Publication Date: 2017
  • Doi Number: 10.1016/j.jclepro.2017.04.144
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.322-332
  • Keywords: Spent NiMH batteries, Baking, Sulfuric acid, Water, Reductive leaching, RARE-EARTH-ELEMENTS, SOLVENT-EXTRACTION, RECOVERY, KINETICS, COBALT
  • Karadeniz Technical University Affiliated: Yes


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 degrees C, 2 mL H2SO4 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 H2SO4 at 95 degrees 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. (C) 2017 Elsevier Ltd. All rights reserved.