This study evaluated the use of the alginate extraction residue (RES) from Sargassum filipendula as biosorbent for the simultaneous biosorption of Cr(III), Ni(II) and Zn(II) applying a mixture design (MD) to evaluate the effects on the total biosorption capacity (q(t)). Inhibitory effects of Cr(III) on the biosorption of the divalent ions were observed, while Zn(II) exhibited contrary effects on the other ions, inhibiting and inducting Cr(III) and Ni(II), respectively. On the other hand, Ni(II) had the lowest interaction effect, inhibiting Zn(II) only. Ion exchange mechanism was verified by characterization analyses, which also revealed a homogenous distribution of metals over the surface of biosorbent. Major involvement of hydroxyl, carboxylic and sulfonic groups was also revealed, but the participation of other acid functions may occur. Cr(III) was favorably adsorbed by RES in all systems, exerting a significant synergic effect on q(t) Ver menos