Biosorption of lead(II), nickel(II), and copper(II) on Rhizopus arrhizus from binary and ternary metal mixtures

The biosorption of three divalent metal ions [Pb(II), Ni(II), and Cu(II)] f requently encountered together in industrial waste waters and in binary and ternary systems was studied using Rhizopus arrhizus, a filamentous fungus, in batch stirred reactors. The multimetal biosorption data were evaluated in terms of equilibrium isotherms and adsorption yields. The single-metal e quilibrium data were analyzed using the Freundlich adsorption model. The in dividual Freundlich adsorption constants were determined and used to compar e biosorptive capacity of the microorganism for different metal ions. The e ffects of various combinations of the metal ions on the biosorption capacit y of R. arrhizus are discussed and the actions of the synergistic or antago nistic metal ion combinations were determined. For the two-metal adsorption equilibrium, competitive adsorption isotherms have been also developed. Th e six-parameter empirical Freundlich model, restricted to bicomponent syste ms, was used successfully to characterize simultaneous biosorption of Pb(II ), Ni(II), and Cu(II) ions by R. arrhizus from two-metal systems. The bioso rption capacity of Pb(II) in the two binary and one ternary systems, in agr eement with the single-metal data, was greater than that of the Ni(II) and Cu(II) ions. The relative capacities were Pb(II) > Ni(II) > Cu(II) at pH 5. 0 in single, binary, and ternary systems.