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

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.