Ruthenium sorption onto Fe3O4@MnO2: equilibrium, kinetic and thermodynamic study

Abstract

Core–shell magnetic adsorbent Fe3O4@MnO2 was prepared and successfully used to ruthenium adsorption from aqueous solutions with 98% efficiency. The adsorption isotherms, kinetic and thermodynamic parameters for Ru(III) sorption onto Fe3O4@MnO2 were studied via a batch adsorption system. Adsorption isotherm models such as: Langmuir, Freundlich and Temkin were tested while the kinetic adsorption data were analyzed by pseudo-first order, pseudo-second order, and Weber-Morris models. It has been found that the adsorption process of Ru(III) onto Fe3O4@MnO2 can be describe by a Freundlich model whereas mechanism of sorption is presented better by kinetic Weber–Morris model. Freundlich adsorption isotherm constant is equal Kf = 30.62 mg/g and heterogenity factor n = 3.58. Sorption rate constant is k3 = 0.288 mg/(g·min1/2) and intraparticle diffusion rate constant C = 0.174 mg/g. Thermodynamic parameters such as free Gibb’s energy change (ΔG°), enthalpy change (ΔH°), entropy change (ΔS°) and energy activation Ea were determined. Calculated value of activation energy is equal 25.75 kJ/mol. The adsorption process of Ru(III) was found to be both spontaneous and thermodynamically preferable.