Cadmium Removal by Two Strains of Desmodesmus pleiomorphus Cells

The capacity of microalgae to accumulate heavy metals has been widely investigated for its potential applications in wastewater (bio)treatment. In this study, the ability of Desmodesmus pleiomorphus (strain L), a wild strain isolated from a polluted environment, to remove Cd from aqueous solutions was studied, by exposing its biomass to several Cd concentrations. Removal from solution reached a maximum of 61.2 mg Cd g biomass by 1 day, at the highest initial supernatant concentration used (i.e., 5.0 mg Cd L), with most metal being adsorbed onto the cell surface. Metal removal by D. pleiomorphus (strain ACOI 561), a commercially available ecotype, was also assessed for comparative purposes; a removal of 76.4 mg Cd g biomass was attained by 1 day for the same initial metal concentration. Assays for metal removal using thermally inactivated cells were also performed; the maximum removal extent observed was 47.1 mg Cd g biomass, at the initial concentration of 5 mg Cd L. In experiments conducted at various pH values, the highest removal was achieved at pH 4.0. Both microalga strains proved their feasibility as biotechnological tools to remove Cd from aqueous solution.