| Title |
Oxalic Acid Recovery from High Iron Oxalate Waste Solution by a Combination of Ultrasound-Assisted Conversion and Cooling Crystallization |
| ID_Doc |
6585 |
| Authors |
Liu, FP; Peng, C; Wilson, BP; Lundström, M |
| Title |
Oxalic Acid Recovery from High Iron Oxalate Waste Solution by a Combination of Ultrasound-Assisted Conversion and Cooling Crystallization |
| Year |
2019 |
| Published |
Acs Sustainable Chemistry & Engineering, 7, 20 |
| Abstract |
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 element (REE)-free wastewater that has 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 group separation stage, >99% of oxalate ions can be precipitated as ferrous oxalate (FeC2O4 center dot 2H(2)O) by an ultrasound-assisted iron powder replacement method (Fe/Fe(III) = 2, t(u/s) = 5 min, T = 50 degrees C). Subsequently, almost all FeC2O4 center dot 2H(2)O was dissolved using 6 mol/L HCl (T = 65 degrees C, t = 5 min) and the dissolved oxalates were found to mainly exist in the form of H2C2O4. Furthermore, over 80% of the oxalic acid was recovered via crystallization by cooling the oxalate containing HCl solution to 5 degrees C. After oxalic acid crystallization, the residual raffinate acid solution can then be recirculated back to the ferrous oxalate leaching stage, to decrease any oxalic acid losses. This treatment protocol for high-iron REE-free solution not only avoids the potential harm to the environment due to the wastewater but also significantly improves the circular economy of chemicals in the typical utilization in permanent magnet recycling processes. |
| PDF |
https://doi.org/10.1021/acssuschemeng.9b04351
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