@conference{
author = "Petrović, Nataša M. and Cvetković, Vesna. S and Prasakti, Laras and Feldhaus, Dominic and Friedrich, Bernd and Jovićević, Jovan J. and Petrović, Nataša",
year = "2024",
abstract = "In the progressive energy transition process, rare earth elements (REE) became key components in crucial products
that play a central role in the development of renewable energy and low-carbon technologies. With China currently
producing more than 90 % of the world's REE output, many of the world's economies are facing REE supply risk [1].
To address this problem, many countries need to look for alternative resources of rare earths, e.g. recycling of these
elements from REE-containing end-of-life products. A new route for recovery of REE from NdFeB magnet scrap,
using a combination of pyrometallurgical treatment of spent NdFeB magnets, and a subsequent molten salt
electrolysis process, has been investigated in the authors’ laboratory [2]. The magnet recycling derived oxides
(MRDO), were produced from spent NdFeB magnets by oxidation in air and subsequent carbothermal reduction
under an 80 mbar Ar gas atmosphere. High-temperature molten salt electrolysis was introduced as an option that
enables the separation of rare earth elements from fluoride-based molten salts using produced MRDO [3]. One of
the challenges in this electrochemical approach for REE electrowinning is effective control of the anode effects to
make the electrolytic production of rare earths more environmentally friendly [3,4]. Minimizing the perfluorocarbon
compounds emission (PFC), in rare earth electrolysis, should be the primary goal, owing to their high global
warming potential [4,5].
In the present work, we investigated the off-gases emissions during the REE electrolysis from NdFeB magnet scrap
using in-situ FTIR-spectrometry, in order to understand the formation pathways of CO, CO2, and perfluorocarbon
gases (CF4 and C2F6) made at the anode. The electrolytic extraction of rare earths from fluoride-based molten salts
with different contents of MRDO present was performed using molybdenum (Mo) as a cathode, tungsten (W) as a
reference electrode, and a glassy carbon (GC) electrode as an anode. It was found that depending on the content
of the starting material, the dissolution of MRDO in their corresponding fluoride molten salts most probably induces
the formation of different oxyfluoride complexes and their subsequent reactions on the GC anode. The anode
reactions in the fluoride-based melts are, most likely, results of either oxide or fluoride formation by exchange with
the fluoride or oxide complexes present in the electrolyte. The produced oxygen subsequently reacts with carbon
to generate CO and CO2. With F− present, PFC compounds such as CF4 and C2F6 can also be formed from a GC anode.
The anode gas products are composed mainly of CO and CO2. The average CO2 concentration was approximately
450 ppm, while CO concentration was around 40 ppm. CF4 emissions in off-gas products were detected periodically,
except for some spikes, and even then, the concentration was below 4 ppm. C2F6 was not detected. The results
indicate that the electrodeposition of REE within the applied potential range occurs at the expense of their
corresponding oxides, provided by MRDO. To develop a more efficient RE recovery process, we opted for a low
deposition overpotential to suppress the emission of greenhouse gases and further enhance the control of their
emission in rare earth electrolysis.",
publisher = "Serbian Chemical Society",
journal = "9th Regional Symposium on Electrochemistry - South-East Europe, Book of Abstract, 3 to 7 June, 2024, Novi Sad, Serbia",
title = "Off-gases emission during the rare earth electrolysis from magnet recycling derived oxides",
pages = "123-123",
doi = "10.5281/zenodo.11194247"
}
