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The wastewaters discharged from chemical industries which may contain heavy metal ions have toxic effect on all the living organisms. Because of this, disposal of them to the environment is a major threat to both human health and ecosystem. So the development of new technologies is required to treat wastewaters as an alternative to traditional physicochemical processes. Biosorption, the process of passive cation binding by dead or living biomass, represents a potentially cost-effective way of eliminating toxic heavy metals from industrial waste waters. While the abilities of microorganisms to remove metal ions in solution have been extensively studied, fungi have been recognized as a promising class of low-cost adsorbents for removal of heavy-metal ions from aqueous waste streams. Algae, fungi and bacteria differ from each other in their constitution, giving rise to different mechanisms of metal biosorption. The paper reviews the biosorption capacities of various fungi (free or immobilized or subjected to physical and chemical treatments) and, chitin and chitosan, important fungal cell wall components, in different reactor systems for heavy metal ions and discusses the fungal biosorption mechanisms. To explore the biosorption mechanisms, it is necessary to identify the functional groups involved in the biosorption process. As single toxic metallic species rarely exist in natural and waste waters, any approach that attempts to removal heavy metals from multi-component systems using fungi would be more realistic. The effects of various combinations of the metal ions on the biosorption capacity of various fungi are discussed and the actions of the metal ion combinations synergistic or antagonistic are identified. Equilibria and capacity relationships for mono-component systems are well established and quantitatively expressed by various types of adsorption isotherms. In the case of multi-metal systems, models should be modified in order to take into account all metals and cover experimental data over a wide range of solution concentrations. The researcher is often puzzled as to what are the basic differences or similarities between the isotherms and what isotherm to select for practical use to predict adsorption capacities or to incorporate it in predicting breakthrough of columnar operations. The paper reviews the range of equilibrium sorption models, and diffusion and sorption models in different reactor systems used by different researchers to correlate experimental data for fungal biosorption.