Lanthanide-alkali double sulfate precipitation from strong sulfuric acid NiMH battery waste leachate

Antti Porvali, Benjamin P. Wilson, Mari Lundström

Research output: Contribution to journalArticleScientificpeer-review

22 Citations (Scopus)

Abstract

In NiMH battery leaching, rare earth element (REE) precipitation from sulfate media is often reported as being a result of increasing pH of the pregnant leach solution (PLS). Here we demonstrate that this precipitation is a phenomenon that depends on both Na+ and SO4 2− concentrations and not solely on pH. A two-stage leaching for industrially crushed NiMH waste is performed: The first stage consists of H2SO4 leaching (2 M H2SO4, L/S = 10.4, V = 104 ml, T = 30 °C) and the second stage of H2O leaching (V = 100 ml, T = 25 °C). Moreover, precipitation experiments are separately performed as a function of added Na2SO4 and H2SO4. During the precipitation, higher than stoichiometric quantities of Na to REE are utilized and this increase in both precipitation reagent concentrations results in an improved double sulfate precipitation efficiency. The best REE precipitation efficiencies (98–99%) – achieved by increasing concentrations of H2SO4 and Na2SO4 by 1.59 M and 0.35 M, respectively – results in a 21.8 times Na (as Na2SO4) and 58.3 times SO4 change in stoichiometric ratio to REE. Results strongly indicate a straightforward approach for REE recovery from NiMH battery waste without the need to increase the pH of PLS.

Original languageEnglish
Pages (from-to)381-389
Number of pages9
JournalWaste Management
Volume71
DOIs
Publication statusPublished - Jan 2018
MoE publication typeA1 Journal article-refereed

Keywords

  • Double sulfate
  • Hydrometallurgy
  • Nickel metal hydride battery
  • Rare earths
  • Recycling

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