The use of marine algae for the removal of Cu²⁺ and Co²⁺ from aqueous solutions

The present work aims to evaluate the effectiveness and efficiency of Chlorella vulgaris as a low-cost biosorbent for the removal of Cu 2+ and Co 2+ from aqueous solutions. The analyzed biosorbents were characterized by various methods such as FTIR, pH pzc , SEM, and elemental analysis. The adsorption isotherm models, including the Freundlich, Langmuir, BET, extended Langmuir, and Jain-Snoeyink models, were analyzed. The biosorption of Cu 2+ and Co 2+ on Chlorella vulgaris occurred mainly according to the pseudo-second kinetic model, and the uptake was satisfactorily described by the Langmuir and the Freundlich models. The results suggest that Chlorella vulgaris acts as a microporous adsorbent, and the adsorption mechanism is monolayer. The values of the n parameter in the Freundlich equation indicate that the adsorption process is characterized by high efficiency and the adsorbent surface is heterogeneous. The results of the maximum adsorption capacity indicated that the adsorption process was more effective for Cu 2+ ions, for which q max was 30.3 mg·g -1 (in single systems). In the case of binary systems, the qmax values were on average 22.2 mg·g -1 for Cu 2+ and 19.6 mg·g -1 for Co 2+ . The intraparticle diffusion model indicated that the key factor controlling the sorption process of Cu 2+ and Co 2+ ions is diffusion inside the sorbent pores.