Biosorption of total chromium from aqueous solution by red algae (Ceramium virgatum): Equilibrium, kinetic and thermodynamic studies

This study focused on the biosorption of total chromium onto red algae (Ceramium virgatum) biomass from aqueous solution. Experimental parameters affecting biosorption process such as pH, contact time, biomass dosage and temperature were studied. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherms. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The biosorption capacity of C. virgatum biomass for total chromium was found to be 26.5 mg/g at pH 1.5 and 10 g/L biomass dosage, 90 min equilibrium time and 20 °C. From the D-R isotherm model, the mean free energy was calculated as 9.7 kJ/mol, indicating that the biosorption of total chromium was taken place by chemisorption. The calculated thermodynamic parameters (ΔG°, ΔH°and ΔS°) showed that the biosorption of total chromium onto C. virgatum biomass was feasible, spontaneous and exothermic at 20-50 °C. Kinetic evaluation of experimental data showed that the biosorption processes of total chromium followed well pseudo-second-order kinetics.