Biosorption of toxic metal ions by alkali-extracted biomass of a marine cyanobacterium, Phormidium valderianum BDU 30501

Alkali-extracted biomass of Phormidium valderianum BDU 30501, a marine fila mentous, non-heterocystous cyanobacterium adsorbed more than 90% of cadmium ions from solutions containing 0.1-40 mM. Cadmium binding accounted up to 18% of biomass weight (w/w). The algal biosorbent was also efficient is seq uestering metal ions (Cd2+, Co2+, Cu2+, Ni2+) from a mixture. Biosorbent pl aced in dialysis tubing could concentrate Cd2+ (50-65%) from 1 l solution ( 10 and 100 ppm) at equilibrium. Biosorbent immobilized in polyvinyl foam al so removed cadmium and cobalt efficiently, but required longer contact time s (24 h). Most of the bound metal ions ( > 80%) could be desorbed with 0.1 M HCl or EDTA, while other reagents were less efficient in the order: H2SO4 > NH4Cl > CaCl2 > Na2SO4 > KSCN > KCl > NH4OH > NaHCO3. The regenerated bi osorbent retained 80% of the initial binding capacity for Cd2+ and 50% bind ing capacity for Co2+ up to three cycles of reuse. Infrared spectra of the biosorbent preparation suggested carboxyl groups to be the primary sites fo r metal binding.