Selective separation and recovery of boron from spent Nd-Fe-B magnets leaching solution
[Display omitted] •Proposed a novel boron separation and recovery process from spent Nd-Fe-B leaching solution.•Simultaneous removal and recovery of boron to prepare borax pentahydrate.•High boron selectivity with minimal REEs loss in extraction.•Achieved 99.9% and 99.8% efficiencies in two-stage co...
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Veröffentlicht in: | Separation and purification technology 2024-09, Vol.344, p.127115, Article 127115 |
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•Proposed a novel boron separation and recovery process from spent Nd-Fe-B leaching solution.•Simultaneous removal and recovery of boron to prepare borax pentahydrate.•High boron selectivity with minimal REEs loss in extraction.•Achieved 99.9% and 99.8% efficiencies in two-stage countercurrent extraction and stripping.
The accumulation of boron during the recovery of rare earth elements (REEs) from spent Neodymium-Iron-Boron (Nd-Fe-B) magnets affects the extraction of REEs and causes environmental pollution through the boron-containing wastewater. Given that boron is a globally scarce strategic resource, this study proposes a method for the selective separation and recovery of boron from spent Nd-Fe-B magnets leaching solution. The synergistic extraction of boron adopting 2-ethylhexanol (EHA) and 2-ethyl-1,3-hexanediol (EHD), and the extraction mechanism were investigated. Under optimized conditions (30 % EHA-20 % EHD-50 % sulfonated kerosene, 1:1O/A phase ratio, pH 3.3, 10 min), the two-stage countercurrent extraction achieved a remarkable 99.9 % extraction efficiency with minimal loss of REEs. Slope analysis, Raman, FT-IR, and NMR combined with DFT were used to elucidate the extraction mechanism. Specifically, some of the boric acid molecules complexed with the OH groups of EHD to form stable six-membered ring complexes, while another part bound with both EHA and EHD to form linear complexes containing six-membered rings. Employing 0.4 mol/L NaOH as the stripping agent, the two-stage countercurrent stripping process achieved a stripping efficiency of 99.8 %. Subsequently, borax pentahydrate products exceeding 99 % purity were obtained via evaporative crystallization from the stripping solution. Notably, the raffinate contained only ∼ 5 mg/L of boron, which could be further reduced below the discharge standard via the REEs recovery process, allowing for safe emission. This work offers a novel approach for the selective separation and recovery of boron from spent Nd-Fe-B magnets, eliminating its adverse effects on REEs extraction and the environment, while simultaneously recovering a valuable resource. |
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ISSN: | 1383-5866 1873-3794 |
DOI: | 10.1016/j.seppur.2024.127115 |