CADMIUM ADSORPTION BY THE NONLIVING BIOMASS OF MICROALGAE GROWN IN AXENIC MASS-CULTURE

The freeze-dried (extracted and non-extracted) biomass of 15 microalgal species grown in axenic mass culture and belonging to the Cyanobacteria, Chloro-, Eustigmato-, Phaeo-, Rhodo- and Tribophyceae were investigated for their ability to adsorb cadmium (Cd) ions from aqueous solutions. For comparison, other standard adsorbing materials (activated carbon, silica gel, siliceous earth) were included in the studies. The biomass of 11 microalgae exhibited a higher Cd adsorption than the standard materials. Extraction of the algal biomass increased the Cd adsorption capability of some, but not all microalgae. High Cd adsorption was found in Anabaena lutea, Nodularia harveyana, and Nostoc commune (Cyanobacteria), Chlamydomonas sp. (Chlorophyceae), Bumilleriopsis filiformis (Tribophyceae), and in Ectocarpus siliculosus, Halopteris scoparia and Spermatochnus paradoxus (Phaeophyceae). The specific surface (m(2) cm(-3)) of the various microalgae was determined by means of laser diffractometry. Anabaena inaequalis and A. lutea (Cyanobacteria) and the Phaeophyceae had especially high Cd adsorption per surface unit. Most of the Cd adsorbed to these various materials could be desorbed subsequently with diluted mineral acid (pH 2).