The capability of Sargassum angustifolium in removing nickel (Ni) (II) and zinc (Zn) (II) from single and binary metal solution was determined. In binary solution the presence of the secondary metal inhibited the sorption of the primary metal by S. angustifolium but the inhibitory effect of Ni during sorption of Zn is stronger than the inhibitory effect of Zn in absorption of Ni. The total metal (Ni + Zn) sorbed from the binary metal solution by S. angustifolium cells always remained lower than the total sorption of individual metals from their respective single metal solutions, thereby suggesting competition between Ni(II) and Zn(II) for the common binding sites on S. angustifolium. The maximum uptake capacities of the S. angustifolium, which was collected near Bushehr, Persian Gulf, Iran in the natural form, at the optimal conditions for Ni(II) and Zn(II) ions in single metal solutions were approximately 0.71 and 0.93 mmol/g dry S. angustifolium, respectively. Under the binary system Ni(II) and Zn(II) uptake capacities were 0.41 mmol Ni/g and 0.36 mmol Zn/g, respectively. Better fitness of equilibrium metal sorption data to the Langmuir than the Freundlich model suggests multilayer adsorption of test metals onto the cell surface.
