IMMOBILIZATION OF ALGAE CELLS ON SILICA-GEL AND THEIR CHARACTERIZATION FOR TRACE-METAL PRECONCENTRATION

Algae cells were successfully immobilized on a silica substrate and used In a chromatographic separation procedure that removed Pb from synthetic solutions. Characterization of the resin in a chromatographic extraction mode revealed acceptable flow rates and efficient metal stripping by both HNO3 and HCI. Variability associated with the growth, harvesting, immobilization, and column packing procedures were evaluated. Results revealed excellent reproducibility for the immobilization procedure, and the greatest source of variation was associated with the algae growing process. The adsorption capacity of the algas resin declined by 15 % over 20 adsorption-elution cycles, and attempts to identify and control the source(s) of the degradation were not successful. Equilibrium parameters governing the metal adsorption process were obtained by Schatchard analysis of the Pb binding data for both the free and immobilized algae. Comparison of the extrapolated saturation values for the free (449 +/- 49-mu-mol of sites/g of algae) and immobilized algae (278 +/- 25-mu-mol of sites/g of algae) reveal a 40 % loss of adsorption efficiency as a result of the immobilization procedure. However, close agreement of the equilibrium constants calculated from the slope of the fitted regression lines at high Pb concentrations for free (0.031 +/- 0.003) and immobilized (0.025 +/- 0.002) algas indicate the immobilization process has minimal effect on the integrity of the remaining adsorption sites. The density of adsorption sites on the algae resin was also measured by a chromatographic procedure (267 +/- 6-mu-mol of sites/g of algae) and the results are In good agreement with the Scatchard method of data analysis.