Cystoseira barbata is an edible brown seaweed, traditionally used in the Black Sea area as functional food. Both alginate and brown seaweed biomass are well known for their potential use as adsorbents for heavy metals. Alginate was extracted from C. barbata recovered from the Romanian coast on the Black Sea with a yield of 19 ± 1.5% (w/w). The structural data for the polysaccharide was obtained by HPSEC-MALS, ¹H-NMR. The M/G ratio was determined to be 0.64 with a molecular weight of 126.6 kDa with an intrinsic viscosity of 406.2 mL/g. Alginate beads were used and their adsorption capacity with respect to Pb²⁺ and Cu²⁺ ions was determined. The adsorption kinetics of C. barbata dry biomass was evaluated and it was shown to have an adsorption capacity of 279.2 ± 7.5 mg/g with respect to Pb²⁺, and 69.3 ± 2 with respect to Cu²⁺. Alginate in the form of beads adsorbs a maximum of 454 ± 4.7 mg/g of Pb²⁺ ions and 107.3 ± 1.7 mg/g of Cu²⁺ ions.