THE ANALYSIS OF DISSOLVED METALS IN NATURAL-WATERS AFTER PRECONCENTRATION ON BIOSORBENTS OF IMMOBILIZED LICHEN AND SEAWEED BIOMASS IN SILICA

A new type of sorbent has been developed in which dried lichen and sea weed bi-ass is entrapped in silica gel. Biomass of the lichens Bryoria sp., Letharia sp. and the brown seaweed Sargassum sp. were immobilize d in silica gel. The immobilized biomass was investigated for use as a n absorbent for copper, zinc, cadmium, lead, chromium, nickel, iron, c obalt, aluminum, silver, gold, and mercury. Metal solutions were loade d onto columns containing one gram of biosorbent at pH 5.5 and then st ripped with 0.05 M sodium or ammonium acetate solution at pH 1.5-2 or 1 M HNO3. A complexing agent such as 0.1 M thiourea was required to co mpletely strip gold. The use of biosorbent columns for preconcentratin g metal ions from natural waters was demonstrated by spiking deionized water with Cu, Pb, Cd, and Zn. Recoveries for all metals were close t o 100%. Biosorbent columns were used to concentrate dissolved metals t en-fold from drinking waters before analysis by atomic absorption spec trometry. The performance of biomass-based sorbents compared favorably with a commercial iminodiacetate chelating resin. The biosorbents dev eloped are stable and reusable. They have great potential for concentr ating metals from solution prior to chemical analysis and for removing toxic metals from waste streams.