Ternary biosorption equilibria of chromium(VI), copper(II), and cadmium(II) onRhizopus arrhizus

A process of competitive biosorption of Cr(VI), Cu(II), and Cd(II) ions to Rhizopus arrhizus from ternary mixtures was described. Three-dimensional biosorption isotherm surfaces were used to evaluate the three-metal biosorption system performance. Triangular equilibrium diagrams, which could incorporate all the experimental data of the ternary system, were also constructed. The multimetal biosorption equilibria were described by the multicomponent Langmuir and Freundlich models. Of the two models examined, the Langmuir-type model showed the best fit for the three-metal biosorption data, whereas the Freundlich-type multicomponent model did not adequately describe the biosorption results of Cr(VI) ions on R. arrhizus from ternary mixtures. The multimetal biosorption results indicated that Cr(VI) and Cu(II) significantly inhibited the biosorption of Cd(II). The Cr(VI)+Cu(II)+Cd(II) combination showed synergistic interaction on the biosorption of Cr(VI) ions.