Abstract:   Biomass of nonliving brown seaweed Sargassum fluitans pretreated by different methods is capable of taking up more than 10% (11 mEq/g) of its dry weight in aluminum at pH 4.5. There are indications that the biomass hydroxyl groups were involved in sequestering the aluminum in the form of polynuclear aluminum species. Aluminum-alginate complex (like cotton candy) was formed in the aluminum sorption solution as alginate was partially released from the biomass. Aluminum uptake of S. fluitans biomass was independent of residual alginate content in the biomass. Sodium ion added for pH adjustment was not adsorbed at all in the presence of aluminum ion.