Separation and preconcentration of copper and cadmium ions from multielemental solutions using Nostoc muscorum-based biosorbents

Nostoc-based biosorbents (AlgaSORBs) useful as chromatographic column-packi ng materials were prepared by immobilizing cyanobacteria onto solid support in three different fashions: (i) cyanobacterial biofilm (Nostoc-dimethylfo rmamide slurry) over polymer-modified silica gel, (ii) cyanobacterial biofi lm over bare silica gel, and (iii) cyanobacteria as such onto polymer-modif ied silica gel. The materials were characterized for their stabilities and metal sorption/elution conditions under static and dynamic equilibrations. Preconcentrated metals from a test sample were detected following 'standard addition' method using a differential pulse anodic stripping voltammetric technique. All sorbents showed 100% affinity for Cd2+ ion in a multielement al sample at pH 6.9 and a flow rate of 0.5 ml/min with a preconcentration f actor varying between 28- and 75-fold. The first type of AlgaSORB was also found to be selective for Cu2+ ion multielemental analysis at pH 5.2 and a flow rate of 1.0 ml/min with a preconcentration factor of 75. The low capac ity and favourable kinetics of these sorbents for Cu2+, Cd2+, Zn2+ and Pb2 ions reflect the suitability of AlgaSORB columns for satisfactory performa nce in single column ion-chromatography. The polymer spacer between cyanoba cterial biofilm and silica gel plays a vital role in holding the immobilize d biofilm resulting in better endurance and recyclability for the first typ e of biosorbent.