Equilibrium, kinetics and thermodynamic studies of cadmium(II) biosorption on Nannochloropsis oculata

Abstract

Abstract The marine microalga Nannochloropsis oculata was investigated for its biosorption capacity for the removal of Cd(II) ions from aqueous solution using batch mode experiments. pH (2–5), biomass dosage (0.0191 g/50 mL and 0.392 g/50 mL) and temperature (293–323 K) being the experimental parameters affecting the biosorption process were observed. To describe the experimental equilibrium data, Langmuir and Freundlich isotherms models were applied. The biosorption potential of N. oculata biomass for Cd(II) ions was found to be 232.55 mg/g. The calculated thermodynamic parameters (∆G°, ∆H° and ∆S°) showed that the biosorption of Cd(II) ions onto N. oculata was feasible, spontaneous and exothermic at 298–323 K. Evaluation of experimental data in terms of biosorption kinetics showed that the biosorption of Cd(II) by N. oculata well followed pseudo-second-order kinetics. The FTIR spectra indicated that the functional groups predominantly involved in the biosorption were –OH, COO–, –CH and phosphate groups. The XRD pattern of the biosorbent showed a change in crystallinity of N. oculata biomass after the biosorption. It was concluded that N. oculata can be used as an effective, low-cost and environmentally friendly biosorbent for the removal of Cd(II) from aqueous solution.

Keywords

• Biosorption
• Cadmium(II)
• FTIR
• Isotherms
• Kinetics
• Nannochloropsis oculata