Abstract:

The increased circulation of toxic metals through the soils, water, air and their inevitable transfer to the human food chain remains an importantenvironmental issue. A number of methods have been developed for the removal of heavy metals from liquid wastes such as precipitation,evaporation, electroplating, ion exchange, membrane processes etc. However, these methods have several disadvantages such as unpredictable metalion removal, high reagent requirement, generation of toxic sludge, etc. In this respect, the search for a new ecofriendly, economical and effectivemetal adsorbent is focused on biomaterials such as bacterial and algal biomass. Biosorption is a promising alternative method to treat industrialeffluents, mainly because of its low cost and high metal binding capacity. Biosorption may occur actively through metabolism or passively throughsome physical and chemical processes. Biosorption technology based on the utilization of dead biomass offers certain major advantages such aslack of toxicity constraints, non-requirement of nutrient supply, and recovery of bound metal species by an appropriate desorption method. Algae,bacteria, cyanobacteria, fungi and yeasts have proved to be potential metal biosorbents, due to metal sequestering properties and can decrease theconcentration of heavy metals ions in solution. The biosorbents contains variety of functional sites including carboxyl, imidazole, sulphydryl,amino, phosphate, sulfate, thioether, phenol, carbonyl, amide and hydroxyl moieties. Biosorbents are cheaper, more effective alternatives for theremoval of metallic elements, especially heavy metals from aqueous solution. This review provides an overview of biosorption and microbial sorbents.

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