The Mechanism of Heavy Metal Biosorption on Green Marine Macroalga Enteromorpha linza

Abstract

The biosorption mechanism of divalent Ni(II), Cd(II), and Pb(II) ions onto calcium treated Entemorpha linza was investigated as a function of pH, contact time, biomass dose, and temperature. The experimental data were evaluated by Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The uptake capacity of the tested metal ions was markedly influenced by pH in the range of 2-3.5 and maximum rates were observed at pH 5-5.5. The kinetics of the metal ions adsorption were rather rapid, with 90% of adsorption occurring within 10min. In addition to batch sorption tests, the functional groups on the cell wall matrix of the biomass were revealed by potentiometric titration data and Fourier transform infrared analysis. The relative contribution of the chemical groups involved in metal biosorption such as carboxyl, amino, sulfonate was evaluated to characterize their binding mechanisms using these instrumental techniques. The density of strong and weak acidic functional groups in the biomass was found to be 0.25 and 0.95mmolg(-1) biomass, respectively. In conclusion, the present work showed that the marine algae E. linza could be used as a potentially cost-effective biosorbent for the treatment of complex wastewater containing heavy metals.