Biosorption of heavy metals by marine algae.

The ability of four different algae (three brown and one red) that have not been previously studied to adsorb Cr(3+), Co(2+), Ni(2+), Cu(2+), and Cd(2+) ions was investigated. The metal uptake was dependent on the type of biosorbent, with different accumulation affinities towards the tested elements. The HCl-treated biomass decreased the metal biosorptive capacity particularly in the case of Cr(3) adsorption with Laurencia obtusa. The extent of uptake of the different metals with the tested algae was assessed under different conditions such as pH, time of algal residence in solution with the metal, and concentration of algal biomass. The rate of uptake of the different metals was very fast in the first 2 h; thereafter the increase in metal uptake was insignificant. The amount of the metal uptake (5-15 mg range) increased steeply by increasing the weight of the biomass. An exception was L. obtusa, where a parallel increase of the uptake of different metals was observed on increasing the algal mass from 5 to 50 mg.