Oxalic acid recovery from high iron oxalate waste solution by a combination of ultrasound-assisted conversion and cooling crystallization

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@article{8b9c6abd2a5441e8b27658e47b5ba372,
title = "Oxalic acid recovery from high iron oxalate waste solution by a combination of ultrasound-assisted conversion and cooling crystallization",
abstract = "In order to achieve the global goals related to renewable energy and responsible production, technologies that ensure the circular economy of metals and chemicals in recycling processes are a necessity. The recycling of spent Nd-Fe-B magnets typically results in rare earth elements (REEs) free wastewaters that have a high ferric ion concentration as well as oxalate groups and for which, there are only a few economically viable methods for disposal or reuse. The current research provides a new approach for the effective recovery of oxalic acid and the results suggest that during the initial oxalate groups separation stage, > 99{\%} of oxalate ions can be precipitated as ferrous oxalate  (FeC2O4⋅2H2O) by an ultrasound-assisted iron powder replacement method (Fe/Fe(III) = 2, tu/s = 5 min, T = 50 ºC). Subsequently, almost all of the FeC2O4⋅2H2O was dissolved using 6 mol/L HCl (T = 65 ºC, t = 5 min) and the dissolved oxalates were found to mainly exist in form of H2C2O4. Furthermore, over 80{\%} of the oxalic acid was recovered via crystallization by cooling the oxalate containing HCl solution to 5 ºC. After oxalic acid crystallization, the residual raffinate acid solution can then be recirculated back to the ferrous oxalate leaching stage, in order to decrease any oxalic acid losses. This treatment protocol for high iron REEs-free solution not only avoids the potential harm to the environment due to waste water but also significantly improves the circular economy of metals in the typically utilized permanent magnet recycling processes.",
keywords = "Oxalic acid recycling, Ultrasound-assisted precipitation, Nd-Fe-B magnets, Cooling crystallization",
author = "Fupeng Liu and Chao Peng and Wilson, {Benjamin P.} and Mari Lundstr{\"o}m",
year = "2019",
doi = "10.1021/acssuschemeng.9b04351",
language = "English",
volume = "20",
pages = "17372--17378",
journal = "ACS Sustainable Chemistry and Engineering",
issn = "2168-0485",
publisher = "AMERICAN CHEMICAL SOCIETY",
number = "7",

}

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TY - JOUR

T1 - Oxalic acid recovery from high iron oxalate waste solution by a combination of ultrasound-assisted conversion and cooling crystallization

AU - Liu, Fupeng

AU - Peng, Chao

AU - Wilson, Benjamin P.

AU - Lundström, Mari

PY - 2019

Y1 - 2019

N2 - In order to achieve the global goals related to renewable energy and responsible production, technologies that ensure the circular economy of metals and chemicals in recycling processes are a necessity. The recycling of spent Nd-Fe-B magnets typically results in rare earth elements (REEs) free wastewaters that have a high ferric ion concentration as well as oxalate groups and for which, there are only a few economically viable methods for disposal or reuse. The current research provides a new approach for the effective recovery of oxalic acid and the results suggest that during the initial oxalate groups separation stage, > 99% of oxalate ions can be precipitated as ferrous oxalate  (FeC2O4⋅2H2O) by an ultrasound-assisted iron powder replacement method (Fe/Fe(III) = 2, tu/s = 5 min, T = 50 ºC). Subsequently, almost all of the FeC2O4⋅2H2O was dissolved using 6 mol/L HCl (T = 65 ºC, t = 5 min) and the dissolved oxalates were found to mainly exist in form of H2C2O4. Furthermore, over 80% of the oxalic acid was recovered via crystallization by cooling the oxalate containing HCl solution to 5 ºC. After oxalic acid crystallization, the residual raffinate acid solution can then be recirculated back to the ferrous oxalate leaching stage, in order to decrease any oxalic acid losses. This treatment protocol for high iron REEs-free solution not only avoids the potential harm to the environment due to waste water but also significantly improves the circular economy of metals in the typically utilized permanent magnet recycling processes.

AB - In order to achieve the global goals related to renewable energy and responsible production, technologies that ensure the circular economy of metals and chemicals in recycling processes are a necessity. The recycling of spent Nd-Fe-B magnets typically results in rare earth elements (REEs) free wastewaters that have a high ferric ion concentration as well as oxalate groups and for which, there are only a few economically viable methods for disposal or reuse. The current research provides a new approach for the effective recovery of oxalic acid and the results suggest that during the initial oxalate groups separation stage, > 99% of oxalate ions can be precipitated as ferrous oxalate  (FeC2O4⋅2H2O) by an ultrasound-assisted iron powder replacement method (Fe/Fe(III) = 2, tu/s = 5 min, T = 50 ºC). Subsequently, almost all of the FeC2O4⋅2H2O was dissolved using 6 mol/L HCl (T = 65 ºC, t = 5 min) and the dissolved oxalates were found to mainly exist in form of H2C2O4. Furthermore, over 80% of the oxalic acid was recovered via crystallization by cooling the oxalate containing HCl solution to 5 ºC. After oxalic acid crystallization, the residual raffinate acid solution can then be recirculated back to the ferrous oxalate leaching stage, in order to decrease any oxalic acid losses. This treatment protocol for high iron REEs-free solution not only avoids the potential harm to the environment due to waste water but also significantly improves the circular economy of metals in the typically utilized permanent magnet recycling processes.

KW - Oxalic acid recycling

KW - Ultrasound-assisted precipitation

KW - Nd-Fe-B magnets

KW - Cooling crystallization

U2 - 10.1021/acssuschemeng.9b04351

DO - 10.1021/acssuschemeng.9b04351

M3 - Article

VL - 20

SP - 17372

EP - 17378

JO - ACS Sustainable Chemistry and Engineering

JF - ACS Sustainable Chemistry and Engineering

SN - 2168-0485

IS - 7

ER -

ID: 37256598