In recent years, studies on the more efficient use of natural materials in adsorption processes have increased significantly. Thus, obtaining new adsorbents from marine algae biomass with higher adsorptive performance will ensure a better use of these renewable resources. In this study, the adsorption of Cu(II) ions from aqueous solution was done using three types of adsorbent materials obtained from marine red algae biomass (Callithamnion corymbosum sp.), namely: alginate (Alg), algae waste biomass resulted after alginate extraction (AWB) and iron nanoparticles functionalized with alginate (Fe-NPs-Alg), compared to raw marine red algae biomass (RAB). FTIR spectra and SEM images recorded for each type of adsorbent indicate a porous structure and the presence of various superficial functional groups who may be involved in the retention of Cu(II) ions. The biosorption experiments were performed in a batch system, at different initial Cu(II) ion concentrations and contact times, maintaining a constant initial solution pH (4.4), adsorbent dose (2.0 g/L), and temperature (25 ± 1 °C). The obtained results indicate that the retention of Cu(II) ions requires a maximum of 60 min to reach equilibrium, and the maximum adsorption capacity increases in order: RAB (47.62 mg/g) < Fe-NPs-Alg (52.63 mg/g) < AWB (83.33 mg/g) < Alg (166.66 mg/g). The quantitative removal of Cu(II) ions from aqueous effluents can be done in two successive adsorption stages, using AWB (in the first stage) and Fe-NPs-Alg (in the second stage), when the treated solution has a Cu(II) ions concentration below the maximum permissible limit. The quantitative recovery of retained Cu(II) ions (over 97%) can be done by treating these exhausted adsorbent materials with 0.1 N HNO3 solution. Therefore, the extraction of alginate from marine red algae biomass could be a viable solution to obtain efficient adsorbent materials for Cu(II) ions removal from aqueous media, and allow for a better valorisation of marine red algae biomass.