Kinetic and isotherm analysis for selective thorium(IV) retrieval from aqueous environment using eco-friendly cellulose composite

Thorium reclamation was studied using nano-iron oxide-impregnated cellulose acetate beads to gain insights into the adsorption mechanism, kinetics and thermodynamics. The designed experiments were thoroughly investigated as a function of solution pH, initial thorium( IV) ion concentration, adsorbent dose and nano-iron oxide loading in the cellulose acetate matrix. The batch adsorption of Th(IV) ions revealed the highly pH dependent (pH range 3.0–9.0) behaviour with maximum sorption at pH 6.0 and equilibrium being achieved within 2 h for maximum concentration of 100 mg/L at 298 K. Rapid adsorption of 50 ± 0.2 % was observed within first 10 min. The kinetics data are best described by the pseudofirst- order kinetic model (R² = 0.9996) and intraparticle diffusion model. The equilibrium adsorption process was fitted with the Langmuir, Freundlich, Dubinin–Radushkevich and Temkin models which yield good fit with Langmuir isotherm equation indicating monolayer adsorption process. The calculated thermodynamics parameter reveals spontaneous and exothermic adsorption process. Further, the desorption was Th(IV) ions that was easily achieved using 0.05 N HNO₃ which suggests the reusability of the adsorbent for multiple use.