Characterization of Cadmium Removal Processes from Seawater by the Living Biomass of Three Microalgae with Different Tolerance to This Metal

Pollution of the marine environment is a current problem. One of the main pollutants is cadmium. This heavy metal is toxic for living beings. For this reason, the removal of cadmium from seawater solutions is a relevant problem. However, there are few studies on the elimination of this metal in seawater. Biosorption is a technique that uses the properties of living or dead biomass to remove pollutants from solutions in an efficient and environmentally friendly way. Microalgal biomass has shown good results in this field. In this work, the ability of the living biomass of three species of marine microalgae (Phaeodactylum tricornutum, Tetraselmis suecica and Dunaliella salina) to remove cadmium from seawater was studied. Growth, kinetics, equilibrium isotherms, cadmium adsorbed to the cell surface and intracellular cadmium were studied. The efficiency of the three species in removing cadmium was compared, showing significant differences both in kinetics and in amount of cadmium removed. After 96h P. tricornutum was able to remove 27.48 ± 1.05 milligrams of cadmium per gram of biomass, T. suecica 78.11 ± 2.08 and D. salina 10.72 ± 0.28. The percentage of cadmium removed by adsorption was higher than the intracellular, except for the lowest cadmium concentrations in P. tricornutum and T. suecica.