An ionic liquid-mesoporous silica blend as a novel adsorbent for the adsorption and recovery of palladium ions, and its applications in continuous flow study and as an industrial catalyst

Abstract

In this work, we report the synthesis of Aliquat-336 (ionic liquid) impregnated SBA-15 mesoporous silica, showing its effective interaction and high adsorption capacity for palladium(II) ions. The physicochemical properties of the adsorbent prior to and after adsorption of palladium(II) ions were characterized extensively using FT-IR, XRD, SEM, TEM, EDX, surface area (BET), and pore size analysis. The plausible interaction envisaged between Aliquat-336 impregnated SBA-15 and Pd(II) could be charge and ion-pair interactions. Different isotherm models were utilized to obtain the sorption parameters and the experimental data fitted adequately with the Langmuir isotherm model, with an adsorption capacity of 212.76 mg g⁻¹. The kinetics of the adsorption process agreed well with the pseudo-second order kinetic model, and the exothermic nature of the adsorption process was revealed through thermodynamic parameters. The Aliquat-336 impregnated SBA-15 adsorbent was regenerated using thiourea. The continuous flow studies were carried out using the Thomas model and this gave an adsorption capacity of 453.89 mg g⁻¹ and 376.38 mg g⁻¹ at flow rates of 4 and 6 mL min⁻¹ respectively. Furthermore, the present scheme was tested for the adsorption of palladium recovered from a spent catalyst containing 5% Pd on activated carbon.