Alginate and pure algal-beads are prepared by homogeneous ionotropic gelation. PEI incorporation in algal beads improves Pd(II) and Pt(IV) sorption at pH 2.5. Uptake kinetics are controlled by the resistance to intraparticle diffusion. Alginate and algal-beads are more selective sorbents for Pd(II) against Pt(IV). Metal speciation has a critical impact on sorption mechanism and performance.