The Analysis of Dissolved Metals in Natural Waters After Preconcentration on Biosorbents of Immobilized Lichen And Seaweed Biomass in Silica

Abstract

A new type of sorbent has been developed in which dried lichen and seaweed biomass is entrapped in silica gel. Biomass of the lichens Bryoria sp., Letharia sp. and the brown seaweed Sargassum sp. were immobilized in silica gel. The immobilized biomass was investigated for use as an absorbent for copper, zinc, cadmium, lead, chromium, nickel, iron, cobalt, aluminum, silver, gold, and mercury. Metal solutions were loaded onto columns containing one gram of biosorbent at pH 5.5 and then stripped 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 completely strip gold. The use of biosorbent columns for preconcentrating metal ions from natural waters was demonstrated by spiking deionized water with Cu, Pb, Cd, and Zn. Recoveries for all metals were close to 100%. Biosorbent columns were used to concentrate dissolved metals ten-fold from drinking waters before analysis by atomic absorption spectrometry. The performance of biomass-based sorbents compared favorably with a commercial iminodiacetate chelating resin. The biosorbents developed are stable and reusable. They have great potential for concentrating metals from solution prior to chemical analysis and for removing toxic metals from waste streams.