Investigation of simultaneous biosorption of copper(II) and chromium(VI) on dried Chlorella vulgaris from binary metal mixtures: Application of multicomponent adsorption isotherms

Although the biosorption of single metal ions to various kinds of microorga nisms has been extensively studied and the adsorption isotherms have been d eveloped for only the single metal ion situation, very little attention has been given to the bioremoval and expression of adsorption isotherms of mul timetal ions systems. In this study the simultaneous biosorption of copper( II) and chromium(VI) to Chlorella vulgaris from a binary metal mixture was studied and compared with the single metal ion situation in a batch stirred system. The effects of pH and single- and dual-metal ion concentrations on the equilibrium uptakes were investigated. In previous studies the optimum biosorption pH had been determined as 4.0 for copper(II) and as 2.0 for ch romium(VI). Multimetal ion biosorption studies were performed at these two pH values. It was observed that the equilibrium uptakes of copper(II) or ch romium(VI) ions were changed due to the biosorption pH and the presence of other metal ions. Adsorption isotherms were developed for both single- and dual-metal ion systems at these two pH values, and expressed by the mono- a nd multicomponent Langmuir and Freundlich adsorption models. Model paramete rs were estimated by nonlinear regression. It was seen that the adsorption equilibrium data fitted very well to the competitive Freundlich model in th e concentration ranges studied.