Lanthanide-alkali double sulfate precipitation from strong sulfuric acid NiMH battery waste leachate
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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2018-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
381-389
Series
Waste Management, Volume 71
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.Description
Keywords
Double sulfate, Hydrometallurgy, Nickel metal hydride battery, Rare earths, Recycling
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Citation
Porvali , A , Wilson , B P & Lundström , M 2018 , ' Lanthanide-alkali double sulfate precipitation from strong sulfuric acid NiMH battery waste leachate ' , Waste Management , vol. 71 , pp. 381-389 . https://doi.org/10.1016/j.wasman.2017.10.031
