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This study focuses on the extraction of rare-earth elements (REE) using eight newly formulated synergist extractants and the performance was compared with that using the conventional extractants. Extraction was conducted on selected REE namely praseodymium (Pr), gadolinium (Gd) and dysprosium (Dy) representing light, medium and heavy REE, respectively. The synergist extractant of A336-[C 2 mim][NTf 2 ] appeared to be the most positive synergist extractant, especially in the extraction of Pr and Dy based on a 90% increase in the extraction efficiency compared to the conventional extractant of A336. Apparently, the presence of the ionic liquid [C 2 mim][NTf 2 ] in the synergist extractant altered the anion exchanger of A336 and successfully formulated extractant with a high extraction efficiency. The characterisation studies of A336-[C 2 mim][NTf 2 ] show the synergist compatibility between A336 and [C 2 mim][NTf 2 ]. Apparently, not all synergist extractants could elevate the extraction potential until conducting a sequence of tests.

This work studies on the performance of synergist extractants on the extraction of Cerium (Ce) alone. Conventional extractant, 4,4,4-trifluoro-1-(2-thienyl)-1,3butanedione (HTTA) was combined with 3-methylimidazolium bis(triflouromethylsulfonyl)imide [C n mim][NTf 2 ], n=2,4 at different ratios to identify the best mixing ratio between HTTA and ionic liquid respectively. The effect of pH and temperature were also investigated on synergist extractant. Liquid-liquid extraction (LLE) was conducted by mixing synergist extractant with aqueous phase of Ce in the ratio of 1:1. The studies on pH and temperature were conducted in a range of 1.5-5.5 and 25-45 o C respectively. synergist extractant of HTTA-[C 4 mim][NTf 2 ] was found to have better extraction efficiency compared to HTTA-[C 2 mim][NTf 2 ] under the optimum pH of 4.5-5.5 and temperature of 45°C. HTTA-[C 4 mim][NTf 2 ] also exhibits better Ce extraction when the extractant was at independent mode i.e. HTTA or [C 4 mim][NTf 2 ]. In conclusion, the synergist extractant is more efficient at extraction of Ce compared to independent extractant under the pH value of 5 at 45°C.

BACKGROUNDThe removal of rare earth elements (REE) ions from aqueous solutions is a challenging task, and it requires a cost‐effective and readily available adsorbent material with excellent performance. In this study, PK216 resin was utilized for the adsorption kinetics and mechanism studies of REE ions owing to its outstanding performance, low cost, and easy availability.RESULTSThe findings revealed that higher loading resulted in increased adsorption capacity, while pH and temperature adjustments had minimal effects on the adsorption process, which remained constant within the pH range of 1–6 and a temperature range of 25–85 °C. Moreover, the thermodynamic parameters showed that the adsorption reaction for praseodymium (Pr) and gadolinium (Gd) was spontaneous and exothermic, whereas for dysprosium (Dy) it was endothermic due to its high hydration enthalpy. This characteristic nature of Dy requires additional energy from the surroundings to dissociate from the aqueous phase and proceed to the PK216 resin surface compared to Pr and Gd. The Langmuir model and pseudo‐second‐order reaction were found to be the fitting models for the adsorption process on PK216 resin. Additionally, the chemisorption of Pr, Gd, and Dy resulted in monolayer coverage. The diffusion process was found to be intraparticle and film diffusion, as it fitted the Boyd kinetic model as opposed to the Weber–Morris intraparticle model.CONCLUSIONThe results indicate that higher loading enhances the adsorption capacity, and the Langmuir model and pseudo‐second‐order reaction are the most suitable models for the adsorption process on PK216 resin. © 2023 Society of Chemical Industry