Adsorption of inorganic mercury from aqueous solutions onto dry biomass of Chlorella vulgaris: kinetic and isotherm study

ABSTRACT

This study focused on kinetics and equilibrium isotherms of mercury biosorption from water using dry biomass of Chlorella vulgaris as biosorbent at pH 5.0. Biosorption tests were performed at 2.0 g/L biomass dosage varying initial Hg concentration from 11.0 to 90.6 mg/L. The Lagergren equation was found to best describe the process, with R² of 0.984 and specific rate constant of 0.029 ± 0.004 min⁻¹. Although equilibrium data were well fitted by the Dubinin and Radushkevich isotherm (R² = 0.870; q_DR = 16.6 mg/g), important insights on phenomenological events occurring at equilibrium were concurrently provided by the Lamgmuir one (R² = 0.826; q₀ = 32.6 mg/g; K_L = 0.059 L/mg). FT-IR analysis confirmed that Hg biosorption took place via physisorption. Since C. vulgaris is a fresh-water microalga that can be easily cultivated anywhere, these promising results suggest its possible use as an effective, low-cost biosorbent to treat industrial effluents contaminated by this metal.

GRAPHICAL ABSTRACT

KEYWORDS:

• Mercury biosorption
• Chlorella vulgaris; kinetics
• equilibrium
• FT-IR

Acknowledgements

The authors thank Prof. Elisabetta Finocchio for helpful discussion and interpretation of FT-IR data.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge the financial support of the Ministero dell'Istruzione, dell'Università e della Ricerca [Italian Ministry of Education, University and Research] to the Scientific Research Program of Relevant National Interest 2010-2011 (PRIN) ‘Emerging contaminants in air, soil, and water: from source to the marine environment’ [grant number 2010WLNFY2_003].