Removal of cadmium(II) from aqueous solutions by biosorption onto the brown macroalga (Dictyota dichotoma)

This paper presents the characteristics of Cd(II) biosorption from aqueous solution using the brown alga (Dictyota dichotoma) as a function of pH, biomass dosage, contact time and temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherms of Cd(II) by D. dichotoma biomass. The monolayer biosorption capacity of D. dichotoma biomass for Cd(II) ions was found to be 75 mg/g. The mean free energy calculated from D-R isotherm indicated that the biosorption of Cd(II) onto D. dichotoma macroalga took place by chemisorption. Kinetic evaluation of the experimental data showed that the biosorption process followed pseudo-second-order model.The calculated thermodynamic parameters Delta [GRAPHICS] , Delta [GRAPHICS] and Delta [GRAPHICS] , showed that the biosorption of Cd(II) onto D. dichotoma biomass was feasible, spontaneous and exothermic under examined conditions. X-ray photoelectron spectroscopy (XPS) and FT-IR analysis of D. dichotoma revealed the chelating character of the ion coordination to carboxyl groups. It was confirmed that carboxyl, ether, alcoholic and amino groups are responsible for the binding of the metal ions.