Adsorption of inorganic mercury from aqueous solutions onto dry biomass of <i>Chlorella vulgaris</i>: 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.