LAUSR

Abstract In this research, the equilibrium and kinetics of praseodymium and neodymium extraction from NdFeB magnet-leaching solution with nitrate form of Aliquat 336 ([R4N+][NO3−]) were investigated. The influences of operational parameters including time, the volume ratio of organic to aqueous phase (1–3), pH (2.0–5.0), extractant (0.30–0.85 kmol m−3) and, nitrate ion concentrations (2.2–5.6 kmol m−3) on the extraction process are examined and optimized by slope analysis and response surface methodology, respectively. The combination of extracted species was as the R4N+M(NO3)4− form, and the equilibrium constants of Pr and Nd extraction reactions were 8.4 × 10−2 and 3.4 × 10−2, respectively. The moving drops technique was applied to examine the Pr and Nd extraction kinetics in a single drop column. The impacts of the substantial parameters of column height, nozzle diameter, and the concentrations of Aliquat 336 cation, Pr, Nd, nitrate, and hydrogen ions on the mass transfer rate are scrutinized. The variations in the concentration of a metal ion had no effect on the mass transfer rate of the other metal ion and due to the high viscosity at concentration of 0.85 kmol m−3 [R4N+], a decrease in the mass transfer rate was observed. The multiple linear regression was applied to predict the mass transfer rates that had an error of about 2% less than one by the slope analysis method. The mass transfer rates were obtained as follow: R Pr kmol m − 2 s − 1 = 9.8 × 10 − 7 Pr 3 + 0.94 R 4 N + 0.22 NO 3 − 1.17 H + − 0.13 R Nd kmol m − 2 s − 1 = 9.0 × 10 − 7 Nd 3 + 0.98 R 4 N + 0.34 NO 3 − 1.59 H + − 0.09