Investigation of operational parameters in the separation factor of praseodymium and neodymium from model NdFeB magnet-leaching solution in the solvent extraction: Optimization by response surface methodology

Document Type : Article


1 School of Chemical, Petroleum and Gas Engineering, Iran University of Science and Technology, Tehran, Iran

2 Catalysts and Organic Synthesis Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran 16846{13114, Iran



In this study, the separations of praseodymium (Pr) and neodymium (Nd) from model NdFeB Magnet-leaching solution were evaluated by two different mixtures, namely Aliquat 336/toluene (system I) and Cyanex 272/kerosene (system II). The operational parameters such as Aliquat 336 concentration (0.30-0.85 mol/L), Cyanex 272 concentration (0.23-0.57 mol/L), pH (2.0-5.0), organic to aqueous phase (O/A) ratio (1-3), and ammonium nitrate (AN) concentration (2.2-5.6 mol/L) were investigated. The impact of the studied parameters on the separation factor were modeled, compared, and optimized by response surface methodology (RSM) based on the central composite design (CCD). The parameters had relatively consistent impact on the extraction efficiency and selectivity of the system I but inconsistent impact for the system II. According to the optimization results of the operational selectivity, the system I was more fitted in which the extraction efficiencies of Pr and Nd were obtained 74.8% and 61.2%, respectively, and the separation factor was 2.10. The obtained values for Aliquat 336 concentration, O/A ratio, pH, and AN concentration were 0.85 mol/L, 1, 5.0, 3.9 mol/L, respectively. Finally, the stripping of metal ions from the loaded organic phase was effectively conducted with 0.1 M hydrochloric acid solution within a contact time of 5 minutes.


[1]    Voncken, J.H.L. "Applications of the Rare Earths", In The rare earth elements: an introduction, pp. 89-106, Springer, (2016).
[2]    Balaram, V. "Rare earth elements: A review of applications, occurrence, exploration, analysis, recycling, and environmental impact", Geosci. Front., 10(4), pp. 1285-1303 (2019).
[3]    Parhi, P., Sethy, T., Rout, P. et al. "Separation and recovery of neodymium and praseodymium from permanent magnet scrap through the hydrometallurgical route", Sep. Sci. Technol., 51(13), pp. 2232-2241 (2016).
[4]    Zhang, J., Zhao, B., and Schreiner, B. "Solvent Extraction in Metal Hydrometallurgy", In Separation hydrometallurgy of rare earth elements, pp. 55-78, Springer, (2016).
[5]    Naumov, A. "Review of the world market of rare-earth metals", Russ. J. Non-Ferr. Met., 49(1), pp. 14-22 (2008).
[6]    Welsbach, C.A.v. "Die Zerlegung des Didyms in seine Elemente", Montshe. Chem. Verw. Teile Anderer Wiss., 6(1), pp. 477-491 (1885).
[7]    Liu, Y., Jeon, H.S., and Lee, M.S. "Solvent extraction of Pr and Nd from chloride solution by the mixtures of Cyanex 272 and amine extractants", Hydrometallurgy, 150, pp. 61-67 (2014).
[8]    Wu, D., Zhang, Q., and Bao, B. "Solvent extraction of Pr and Nd (III) from chloride-acetate medium by 8-hydroquinoline with and without 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester as an added synergist in heptane diluent", Hydrometallurgy, 88(1-4), pp. 210-215 (2007).
[9]    Yamaguchi, M. "Extractive separation of praseodymium and neodymium by di (2-ethylhexyl) phosphoric acid in the presence of water-soluble complexing agents using an electrostatic liquid-liquid contactor", Chem. Eng. Res. Des., 75(4), pp. 447-452 (1997).
[10]   Liu, Y., Jeon, H.S., and Lee, M.S. "Solvent extraction of Pr and Nd from chloride solutions using ternary extractant system of Cyanex 272, Alamine 336 and TBP", J. Ind. Eng. Chem., 31, pp. 74-79 (2015).
[11]   Liu, Y., Jeon, H.S., and Lee, M.S. "Solvent extraction of Pr and Nd from chloride solution by mixtures of acidic extractants and LIX 63", Korean J. Met. Mater., 54(8), pp. 592-597 (2016).
[12]   Banda, R., Jeon, H., and Lee, M. "Solvent extraction separation of Pr and Nd from chloride solution containing La using Cyanex 272 and its mixture with other extractants", Sep. Purif. Technol., 98, pp. 481-487 (2012).
[13]   Banda, R., Jeon, H.S., and Lee, M.S. "Solvent extraction separation of La from chloride solution containing Pr and Nd with Cyanex 272", Hydrometallurgy, 121, pp. 74-80 (2012).
[14]   Padhan, E. and Sarangi, K. "Solvent extraction of praseodymium using different extractants–a synergistic study", Sep. Sci. Technol., 53(2), pp. 295-302 (2018).
[15]   Shaohua, Y., Wenyuan, W., Zhang, B. et al. "Study on separation technology of Pr and Nd in D2EHPA-HCl-LA coordination extraction system", J. Rare Earths, 28, pp. 111-115 (2010).
[16]   Scal, M.L.W., Seruff, L.A., and Vera, Y.M. "Study of the separation of didymium from lanthanum using liquid-liquid extraction: Comparison between saponification of the extractant and use of lactic acid", Miner. Eng., 148, pp. 106200 (2020).
[17]   Banda, R.J., Jeon, H.S., and Lee, M.S. "Extraction behavior of REEs (La, Pr, and Nd) in the presence of EDTA from chloride solutions", Korean J. Met. Mater., 51(6), pp. 421-427 (2013).
[18]   Minagawa, Y. "Selective extraction of praseodymium ions from neodymium solution using a non-equilibrium extraction method", J. Alloy. Compd., 192(1-2), pp. 126-128 (1993).
[19]   Matsuyama, H., Azis, A., Fujita, M. et al. "Analysis of extraction rate and selectivity of Pr/Nd separation by solvent extraction in the presence of diethylenetriaminepentaacetic acid in aqueous phase", J. Chem. Eng. Jpn., 28(6), pp. 830-836 (1995).
[20]   Padhan, E. and Sarangi, K. "Recovery of Nd and Pr from NdFeB magnet leachates with bi-functional ionic liquids based on Aliquat 336 and Cyanex 272", Hydrometallurgy, 167, pp. 134-140 (2017).
[21]   Nakayama, C., Uemiya, S., and Kojima, T. "Separation of rare earth metals using a supported liquid membrane with DTPA", J. Alloy. Compd., 225(1-2), pp. 288-290 (1995).
[22]   He, Y., Chen, K., Srinivasakannan, C. et al. "Intensified extraction and separation Pr (III)/Nd (III) from chloride solution in presence of a complexing agent using a serpentine microreactor", Chem. Eng. J., 354, pp. 1068-1074 (2018).
[23]   Rho, B.J., Sun, P.P., and Cho, S.Y. "Recovery of neodymium and praseodymium from nitrate-based leachate of permanent magnet by solvent extraction with trioctylphosphine oxide", Sep. Purif. Technol., 238, pp. 116429 (2020).
[24]   Banda, R., Jeon, H.S., and Lee, M.S. "Separation of Nd from mixed chloride solutions with Pr by extraction with saponified PC 88A and scrubbing", J. Ind. Eng. Chem., 21, pp. 436-442 (2015).
[25]   Thakur, N., Jayawant, D., Iyer, N. et al. "Separation of neodymium from lighter rare earths using alkyl phosphonic acid, PC 88A", Hydrometallurgy, 34(1), pp. 99-108 (1993).
[26]   Sun, P., Huang, K., and Liu, H. "Separation of adjacent rare earth elements enhanced by “external push-pull” extraction system: An example for the separation of Pr and Nd", Hydrometallurgy, 189, pp. 105136 (2019).
[27]   Wang, X., Huang, K., Cao, W. et al. "Enhanced separation of praseodymium and neodymium by kinetic “push and pull” system of [A336][NO3]-DTPA in a column extractor", J. Rare Earths, 38(2), pp. 203-212 (2020).
[28]   Nishihama, S., Hirai, T., and Komasawa, I. "Selective extraction of Y from a Ho/Y/Er mixture by liquid− liquid extraction in the presence of a water-soluble complexing agent", Ind. Eng. Chem. Res., 39(10), pp. 3907-3911 (2000).
[29]   Ghorbanzadeh, M., Gorzin, H., and Eshtehardi, H.A. "Precipitation and solvent extraction of magnesium from lithium-chloride solution by di-(2-ethylhexyl) phosphoric acid in the presence of lactic acid as a complexing agent", Mater. Res. Express, 5(8), pp. 086512 (2018).
[30]   De Carvalho Gomes, R., Seruff, L.A., Scal, M.L.W. et al. "The influence of lactic acid concentration on the separation of light rare earth elements by continuous liquid–liquid extraction with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester", Metall. Mater. Trans. B, 49(1), pp. 460-465 (2018).
[31]   Bauer, D.J. and Lindstrom, R.E., "Differential extraction of rare-earth elements in quaternary ammonium compound-chelating agent systems", US Department of Interior, Bureau of Mines, pp. 1-15 (1971).
[32]   Kumari, A., Sahu, K.K., and Sahu, S.K. "Solvent Extraction and Separation of Nd, Pr and Dy from Leach Liquor of Waste NdFeB Magnet Using the Nitrate Form of Mextral® 336At in the Presence of Aquo-Complexing Agent EDTA", Metals, 9(2), pp. 269 (2019).
[33]   Sun, P.P., Kim, D.H., and Cho, S.Y. "Separation of neodymium and dysprosium from nitrate solutions by solvent extraction with Cyanex 272", Miner. Eng., 118(pp. 9-15 (2018).
[34]   Bezerra, M.A., Ferreira, S.L.C., Novaes, C.G. et al. "Simultaneous optimization of multiple responses and its application in Analytical Chemistry–A review", Talanta, 194, pp. 941-959 (2019).
[35]   Safarzadeh, M.S., Agarwal, V., and Hayes, L. "New insights into the separation of Nd from Pr in hydrochloric and sulfuric acid solutions", Polyhedron, 153, pp. 82-87 (2018).
[36]   Lu, D., Horng, J., and Hoh, Y. "The separation of neodymium by quaternary amine from didymium nitrate solution", J. Less-Common Met., 149, pp. 219-224 (1989).
[37]   Preston, J. "The recovery of rare earth oxides from a phosphoric acid byproduct. Part 4. The preparation of magnet-grade neodymium oxide from the light rare earth fraction", Hydrometallurgy, 42(2), pp. 151-167 (1996).
[38]   Batchu, N.K., Jeon, H.S., and Lee, M.S. "Solvent extraction of praseodymium (III) from chloride solutions by a mixture of Cyanex 301 and LIX 63", J. Ind. Eng. Chem., 26, pp. 286-290 (2015).
[39]   Xie, F., Zhang, T.A., Dreisinger, D. et al. "A critical review on solvent extraction of rare earths from aqueous solutions", Miner. Eng., 56, pp. 10-28 (2014).
[40]   Pospiech, B. and Chagnes, A. "Highly selective solvent extraction of Zn (II) and Cu (II) from acidic aqueous chloride solutions with mixture of Cyanex 272 and Aliquat 336", Sep. Sci. Technol., 50(9), pp. 1302-1309 (2015).
[41]   Gorzin, H., Ghaemi, A., Hemmati, A. et al. "Studies on effective interaction parameters in extraction of Pr and Nd using Aliquat 336 from NdFeB magnet-leaching solution: Multiple response optimizations by desirability function", J. Mol. Liq., 324, pp. 115123 (2021).
[42]   Gorzin, H., Ghaemi, A., Hemmati, A. et al. "Equilibrium and kinetics of praseodymium and neodymium extraction from NdFeB magnet-leaching solutions with [R4N+][NO3−] using single drop column", J. Mol. Liq., 318, pp. 114376 (2020).
[43]   Moore, F. "Improved Extraction Method for Isolation of Trivalent Actinide-Lanthanide Elements from Nitrate Solutions", Anal. Chem., 38(3), pp. 510-512 (1966).
[44]   Kawashima, M. and Freiser, H. "Mixed ligand chelate extraction of lanthanides in 8-quinolinol-tetra-n-heptylammonium chloride systems", Anal. Chem., 53(2), pp. 284-286 (1981).
[45]   Černá, M., Volaufová, E., and Rod, V. "Extraction of light rare earth elements by amines at high inorganic nitrate concentration", Hydrometallurgy, 28(3), pp. 339-352 (1992).
[46]   Marcus, Y. and Abrahamer, I. "Anion exchange of metal complexes—VII The lanthanides-nitrate system", J. Inorg. Nucl. Chem., 22(1-2), pp. 141-150 (1961).
[47]   Li, K.a. and Freiser, H. "Extraction of Lanthanide metals with b.ts (2,4,4-trimethylpentyl) phosphinic acid", Solvent Extr. Ion Exc., 4(4), pp. 739-755 (1986).
[48]   Bezerra, M.A., Santelli, R.E., Oliveira, E.P. et al. "Response surface methodology (RSM) as a tool for optimization in analytical chemistry", Talanta, 76(5), pp. 965-977 (2008).
[49]   Ayanda, O.S., Adekola, F.A., Baba, A.A. et al. "Application of Cyanex extractant in cobalt/nickel separation process by solvent extraction", Int. J. Phys. Sci., 8(3), pp. 89-97 (2013).