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%.