AbstractBiosorption of copper (II) ions on Sargassum angostifolium C.Agardh as brown alga was investigated. The effects of operating parameters such as initial metal ion concentration, temperature, pH, and biomass dose on the copper (II) biosorption were studied. The Langmuir and Freundlich isotherm models were applied to the equilibrium data. The experimental data for copper (II) ions are in good agreement with those calculated using the pseudo-second-order kinetics for the studied parameters. The experiment is designed to predict the role of cooperating parameters on biosorption by using the response surface methodology. The Box Behnken model in the response surface methodology is used for optimal conditions. The maximum uptake conditions were determined as initial pH 6.0, temperature 45°C, biosorbent concentration 0.4 g L-1 and initial copper (II) ion concentration 150 mg L-1.