Note
Due to the increasing awareness of toxic heavy metals contamination to the environment, studies of metal accumulation from the view point of metal removal from contaminated water have been performed (Kuyucak and Volesky, 1988; Darnall et al., 1986). Conventional methods including precipitation, oxidation, reduction, ion exchange, filtration, electrochemical treatment, membrane technologies and evaporation recovery are expensive or ineffective, especially when the metal concentrations are very low in the order of 1 to 100 mg/L (Volesky, 1990).