Adsorptive capacity and kinetic studies of PK216 resin for the extraction of Pr, Gd, and Dy rare earth elements

BACKGROUND: The 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. RESULTS: The 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 degrees 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. CONCLUSION: The 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. (c) 2023 Society of Chemical Industry