Sustainable Recycling of Rare-Earth Elements from NdFeB Magnet Swarf: Techno-Economic and Environmental Perspectives
Rare-earth elements (REEs) are increasingly susceptible to supply risks due to their limited geographical availability and growing demand in clean energy applications such as neodymium-iron-boron (NdFeB) magnets used in electric vehicles and wind turbines. When NdFeB magnets are produced, 6–73% of swarf is generated during the manufacturing steps. This paper presents an innovative technology that utilizes copper nitrate to dissolve REEs in NdFeB magnet swarf and subsequently recovers ∼97% of them as mixed rare-earth oxides (REOs) of purity higher than 99.5%. Techno-economic analysis (TEA) and life cycle assessment (LCA) quantified the economic and environmental impacts of adopting the proposed acid-free dissolution technology, projecting a net profit margin of 12–43% and a global warming impact reduction by up to 73% compared to the prevailing REO production routes in China. As copper nitrate is the single largest contributor to the cost and environmental footprint, recycling of copper nitrate was investigated as well as using alternative copper salts (e.g., copper acetate), revealing significant improvements in TEA and LCA results. Dysprosium was a major revenue source, highlighting the importance of targeting electric vehicle magnets that are rich in dysprosium. As the REO market is volatile, sensitivity analysis was employed to evaluate the profitability of the proposed technology under different REO prices over the last 11 years. Overall, our results confirmed the economic and environmental viability of the proposed technology for sustainable recycling of REEs from the NdFeB magnet swarf.
LCI data for producing 1 kg of REO from NdFeB magnet swarf with a copper nitrate recycling efficiency of 90% using acid-free dissolution technique. The REE leached efficiency in the baseline, high, and low bound scenarios is 97 percent, 96 percent, and 99 percent, respectively.
InputBaselineHighLowUnitCopper (II) nitrate hemi(pentahydrate)0.560.560.54kgAmmonium hydroxide (14.5 N)13.3113.4613.05LOxalic acid8.398.488.23kgWater70.9871.7669.58kgElectricity (roasting)16.0016.1815.69kWhElectricity (heating)3.763.803.68kWhElectricity (stirring)0.000.000.00kWhElectricity (filtration)0.630.630.61kWhElectricity (pumping)0.030.030.03kWhCalcium chloride2.842.872.78kgCalcium oxide1.581.591.55kgPotassium bisulfate6.916.996.78kgCalcium nitrate tetrahydrate10.1910.319.99kgOutputBaselineHighLowUnitNeodymium oxide0.880.880.88kgPraseodymium oxide0.110.110.11kgDysprosium oxide0.020.020.02kgIron (II)/(III) oxide1.81.91.8kgDirect emissionBaselineHighLowUnitIron (II)/ Iron (III) hydroxide6.906.986.77kgCalcium oxalate24.7825.0524.29kgOther solid waste2.152.182.11kgCarbon dioxide0.780.790.77kgCalcium sulfate5.885.945.76kgAmmonium chloride10.3610.4710.15kg
Sustainable Recycling of Rare-Earth Elements from NdFeB Magnet Swarf
Monte Carlo simulation of characterized environmental impact results for producing 1 kg of Nd2O3production through (a) acid-free recycling process of NdFeB magnet swarf, (b) 92% mixed REO production from Bayan Obo ores, (c) ≥99.5% individual REO production from Bayan Obo ores, (d) 92% mixed REO production from ion adsorption clay, and (e) ≥99.5% individual REO production from ion adsorption clay (Method: TRACI 2.1 V1.05/ US 2008 and Cumulative Energy Demand, confidence interval 95%). SD, CV, and SEM represent the standard deviation, coefficient of variation, and standard error of the mean. 2.5% and 97.5% indicate the percentile 80values of the uncertainty distribution of the environmental impacts.
S10Non carcinogenicsCTUh2.1E-052.1E-054.6E-0621%1.6E-053.3E-051.5E-07Respiratory effectskg PM2.5 eq2.7E-012.7E-012.8E-0210%2.2E-013.3E-018.8E-04EcotoxicityCTUe1.1E+031.1E+031.8E+0216%8.6E+021.6E+035.8E+00Fossil fuel depletionMJ surplus1.9E+021.9E+021.9E+0110%1.6E+022.3E+026.0E-01Cumulative energy demandMJ1.7E+031.7E+031.5E+0296%1.4E+032.0E+034.8E+008687(d)Impact categoryUnitMeanMedianSDCV2.5%97.5%SEMOzone depletionkg CFC-11eq4.1E-064.0E-065.5E-0713%3.3E-065.4E-061.7E-08Smogkg O3 eq4.3E+004.3E+002.3E-015%4.0E+004.9E+007.4E-03Acidificationkg SO2 eq3.9E-013.9E-011.7E-024%3.6E-014.3E-015.4E-04Eutrophicationkg N eq4.1E+004.1E+004.1E-021%4.0E+004.2E+001.3E-03CarcinogenicsCTUh9.5E-068.5E-064.2E-0644%5.5E-061.8E-051.3E-07Non carcinogenicsCTUh5.8E-055.7E-051.2E-0520%4.6E-057.5E-053.7E-07Respiratory effectskg PM2.5 eq5.2E-025.1E-024.9E-039%4.6E-026.5E-021.5E-04EcotoxicityCTUe2.7E+032.6E+033.9E+0214%2.2E+033.7E+031.2E+01Fossil fuel depletionMJ surplus5.7E+015.7E+014.3E+007%5.0E+016.7E+011.4E-01Cumulative energy demandMJ8.4E+028.3E+026.4E+0162%7.3E+029.9E+022.0E+00 Rare-Earth Elements from NdFeB Magnet Swarf
Life cycle impacts of producing 1 kg of Nd2O3 with ≥99.5in two different qualities: 1) ≥99.5% pure individual Nd2O3 and 2) 92% pure mixed REOs from two dominant REE production sources: 1) bastnasite and monazite in Bayan Obo, China14,15 and 2) ion adsorption clays in Southern China.15,16 Economic allocation was applied, using the most recent REO prices.
Economic allocation factors for recycling NdFeB swarf. REO unit prices were discounted by 20%. The baseline scenario assumes 0.48% Dy contained in the initial NdFeB magnet swarf, the worst case assumes 0% Dy, and the best case assumes 6% Dy in the magnet swarf.
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