Removal of Cadmium (II) from aqueous solutions onto Dodonaeae Viscose Leg powder using a green process: Isotherms, Kinetics and Thermodynamics

In the present study, Batch adsorption experiments of hazardous cadmium, Cd(II), ions onto low-cost Dodonaeae Viscose Legs (DVL) and processes were conducted with respect to contact time, solution pH, adsorbent dosage, initial Cd concentration and temperature. The DVLs were used without chemical or physical activation processes. Sorption isotherm, kinetic and thermodynamic models were used to describe the equilibrium stage and their constants were determined. The results showed that the adsorption capacity of DVLs for Cd(II) ions was found to be 25.29 mg/g at solution pH 5.26, 50 min and 30oC. The mean free energy was found to be 1.82E-02 using Dubinin-Radushkevich (DRK) isotherm, which indicates that the adsorption of Cd(II) ions onto DVL surface is physical adsorption. The activation energy (Ea) was 3.06 kJ/mole, which confirms that Cd(II)-DVL adsorption process is physical sorption. Pseudo-first-order, pseudo-second-order, Elovich, intra-particle and extra-particle diffusion models were used to describe the adsorption kinetics. The results showed strong correspondence to a pseudo-second-order kinetics. Thermodynamic parameters suggested that the adsorption of Cd(II) ions onto DVL surface is an exothermic process.