Comparison of the heavy metal removal efficiency of biosorbents and granular activated carbons

The adsorption efficiencies of granular activated carbon (GAG) and biosorbents: Saccaromyces cerevisiae yeast (caustic treated and active) immobilized in GAG; Yeast( caustic treated) immobilized in alginate acid, and alginate itself were compared for the removal of Cu2+, Cd2+, Zn2+ from simulated waste waters. Yeast biomass has a high capacity for uptake of heavy metal ions, and can be adsorbed on activated carbon. The alginate used in this study was used as an entrapment material to immobilize yeast. It was observed that the pH of the solution was a critical parameter for the adsorption process; the value chosen in the experiments was 4.5. Two different experimental modes were used, a batch mode and a flow mode were used. In batch mode operation, using biosorbents yeast immobilized on GAC and on alginate, the percentage removal of heavy metal can exceed 90%. When only GAC was used as an adsorbent, acceptable results were obtained. Comparing the two different experimental modes, no difference was observed in the percentage removal of metal ions, although a longer time was needed for the now system to reach adsorption equilibrium compared to batch mode.