Journal
WASTE MANAGEMENT
Volume 71, Issue -, Pages 381-389Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.wasman.2017.10.031
Keywords
Nickel metal hydride battery; Hydrometallurgy; Double sulfate; Rare earths; Recycling
Categories
Funding
- TEKES
- EU
- Vipuvoimaa EU:lta
- Norilsk Nickel
- CrisolteQ
- Akkuser
- Kuusakoski
- Jyvaskylan Energia
- Luvata
- Boliden Harjavalta
- municipality of Pori
- municipality of Harjavalta
- Strategic Research Council at the Academy of Finland [303454]
- NoWASTE [297962]
- Mine-WEEE [7100/31/2016]
- Academy of Finland (AKA) [303454, 303454] Funding Source: Academy of Finland (AKA)
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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 SO42- 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 degrees C) and the second stage of H2O leaching (V = 100 ml, T = 25 degrees 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. (C) 2017 The Authors. Published by Elsevier Ltd.
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