Mercury elimination onto brown alga Sargassum muticum has been studied in order to enhance process performance and to go further in the analyses of the combined sorption-reduction mechanism that is taking place. Several chemical treatments of the natural biomass have improved material stability and diminished weight losses, as it was confirmed through TOC analyses. Fast kinetics and high mercury removal capacities (0.9 mmol g(-1)) were found with native and treated material. Competition with dyes has shown that mercury uptake is not affected for these organic compounds in solution; in addition, high metal and dye elimination percentages were obtained simultaneously in mercury/Methylene Blue mixtures. Column experiments have confirmed that mercury interaction with biomass is a complex mechanism where nearly 70% of the metal is reduced and 30% is adsorbed onto material surface. (C) 2013 Published by Elsevier B.V.