Biosorption of heavy metal from aqueous solutions

Metal contaminated water is known to have negative impacts on health and the environment and it keeps increasing. Solving this problem is a challenge since the conventional physical and chemical methods of treatment is costly. This chapter presents an overview of an alternative method, “biosorption,” of inorganic contaminated effluent. Principally, biosoption is a mass transfer process by which a substance is transferred from the liquid phase to the surface of biomaterials including dead bacterial or plant biomass and also agricultural waste, and then this inorganic element becomes bound by physical or chemical interactions by phenomena of complexation, coordination, chelation, ion exchange, adsorption, or inorganic microprecipitation. Brief overviews of biosorbents efficiency for metal removal form solutions are also discussed. The overall process of biosorption is affected by the environmental conditions such as pH, temperature, and ionic strength of the solution so it is most valuable to express the set of equations to organize and predict metal uptake performance under those different conditions. This chapter also discusses the biosorption isotherms which can be represented by empirical and mechanistic models. The first empirical models are simple mathematical relations including Langmuir and Freundlich isotherms and their extensions which is capable of representing experimental trends but without informative or predictive committed. The mechanistic models are theoretically derived supposing a set of reactions between biosorbent active binding sites and ionic species in solution which not only represent but also interpret and predict the effects of the employing factors on equilibrium metal distribution. Kinetic data in batch experiments and column studies which are normally characterized by empirical models are also presented here.