BACKGROUND: Mercury is considered one of the most harmful heavy metals to the environment and human health, so recently remediation processes have been developed to eliminate this metal from wastewaters. Metal retention by natural polymers is a good alternative technique to remove heavy metals from solution. RESULTS: A screening of 25 potential mercury sorbents was carried out at three different pH values in order to find appropriate biomass to remove this metal from polluted waters. High sorption capacities were found for many of the materials studied. Four of these materials were selected for further detailed study. Kinetic studies showed short times to reach equilibrium. For S. muticum, sorption isotherms were obtained at several temperatures and a sorption enthalpy value was obtained. Desorption experiments were performed to determine the possibility for recycling of this brown alga. CONCLUSIONS: Different materials have been found to be potentially good adsorbents of mercury. A detailed study showed that S. muticum is an excellent material with a mercury uptake about 200 mg g(-1). This brown alga has a fast kinetic process (80% of metal is removed from solution in 30 min), and very high metal uptake over a wide pH range, up to 92% elimination for pH values above 3-4. (C) 2009 Society of Chemical Industry