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Abstract: Five different brown seaweeds, Bifurcaria bifurcata, Saccorhiza polyschides, Ascophyllum nodosum, Laminaria ochroleuca and Pelvetia caniculata were studied for their ability to remove cadmium from aqueous solution. Kinetics of cadmium adsorption by all the algae were relatively fast, with 90% of total adsorption occurring in less than 1h. These experiments could be accurately described by a pseudo-second-order rate equation, obtaining values between 1.66×10−3 and 9.92×10−3 g/mgmin for the sorption rate constant k. Several equilibrium adsorption isotherms were obtained for the quantitative description of cadmium uptake. The use of the Langmuir isotherm led to values between 64 and 95mg/g for q max and between 0.036 and 0.094L/mg for b. The effect of pH on biosorption was also studied. Acid–base properties of algae were studied by potentiometry to determine pK values (from 3.54 to 3.98) and the total number of acid groups. [Copyright &y& Elsevier]