Adsorptive Removal of Organic dyes by Hydrothermally Synthesized Binary Rare Earth Oxide Pr6O11: Isotherms, Optimization, Kinetic and Thermodynamic Studies.

Abstract

This study explored the potential of rare earth oxide, praseodymium oxide (Pr₆O₁₁) as an adsorbent for removing Erichrome Black T (EBT) dye from aqueous solution. Pr₆O₁₁ with a surface area (24.07 m²/g), was synthesized using hydrothermal method and characterized using various analytical techniques (XRD, SEM, TEM, BET, XPS). The influence of initial dye concentration, temperature, adsorbent dose, and pH on adsorption capacity, kinetics, and isotherms was investigated. Optimal conditions were: 60 mg/L initial dye, 0.03g adsorbent, 90 min contact time, and pH around 7–8. The heterogeneous adsorption of dyes by the prepared catalyst was best described by Freundlich adsorption isotherm model which favours multilayer adsorption of EBT dye onto Pr₆O₁₁ surface. Kinetic study confirms the progress of adsorption via pseudo-second-order kinetics. Different thermodynamic considerations such as ΔG⁰, ΔH⁰, ΔS⁰ calculated during the experiment suggested a favourable, spontaneous, and exothermic physisorption process (30–50°C). The material exhibited reusability with minimal capacity loss after each cycle.