Biosorption of Cd and Cu by different types of Sargassum biomass

Sargassum seaweed biomass has been established as an excellent biosorbent material for heavy metals. Three different species of non living Sargassum biomass were compared for their equilibrium Cd and Cu uptake from aqueous solutions using experimental sorption isotherms which fitted well the Langmuir sorption model. Uptakes of Cd at the optimum pH 4.5 ranged from q(max) = 87 mgCd/g for S. vulgare, 87 mgCd/g for S. fluitans and 74 mgCd/g for S. filipendula. The amount of Cu uptake at pH 4.5 was q(max) = 59 mgCu/g for S. vulgare, 56 mgCu/g for S. filipendula and 51 mgCu/g for S. fluitans. Potentiometric and conductometric titrations carried out with the biomass of the three Sargassum species revealed a high degree of similarity among these materials. A separate contribution to the metal binding by the strong and weak acidic groups in the biomass could not accurate due to the similarities in their dissociation constants. Estimates of 0.3 mmol/g of strong and 1.5 mmol/g of weak acidic groups were obtained for Sargassum biomass types studied.