Marine Macroalgae as Biosorbents for Cadmium and Nickel in Water

Experimental studies showed that brown marine algae, Sargassum vulgaris and Padina pavonia , can be used to develop an efficient biosorbent for heavy metal removal from aqueous solutions. Sargassum vulgaris exhibited high uptake capacities for cadmium (0.9 to 1.1 mmol Cd/gr) and nickel (0.85 to 1 mmol Ni/gr) that are higher than those of other types of biomass and powdered activated carbon, while P. pavonia showed a broader range of nickel and cadmium uptake capacities (0.7 to 1 mmol Ni/gr and 0.8 to 1.1 mmol Cd/gr). The metal adsorption and desorption processes were rapid, with 70% of the sorption and desorption completed within 10 minutes. The equilibrium data for both algae fit well to Langmuir and Freundlich isotherm models. More than 90% desorption of adsorbed metals from the algae was achieved by hydrochloric acid and ethylenediaminetetraacetic acid (1:1 molar ratio). After eight to nine adsorption and desorption cycles, S. vulgaris showed a 15 to 35% decrease in metal uptake capacities; P. pavonia showed a higher decrease of 50 to 60%.