Biosorption of heavy metals by Zoogloea ramigera: Use of adsorption isotherms and a comparison of biosorption characteristics

The biosorption of lead(II), copper(II), nickel(II) and iron(III) ions on Zoogloea ramigera, an activated sludge bacterium, was studied with respect to adsorption pH and temperature in order to determine the optimum conditions for heavy metal removal. Optimum initial pH for the biosorption of lead(II),nickel(II) and copper(II) ions by Z. ramigera was determined as 4.0-4.5 whereas higher biosorptive uptake of iron(III) ions by Z. ramigera was obtained at pH 2.0. Maximum biosorption rates of nickel(II) and copper(II) ions by Z. ramigera were obtained at 25 degrees C, while the initial biosorption rates and the adsorptive capacity of the biomass for lead(II) and iron(III) ions increased with increasing temperatures in the range 25-45 degrees C. The adsorption isotherms were developed for optimum conditions and it was seen that the adsorption equilibrium data fit both Freundlich and Langmuir isotherms within the metal ion concentrations studied (25-200 mg 1(-1)). The adsorption constants for lead(II) and iron(III) were higher than those for nickel(II) and copper(II) for both Langmuir and Freundlich models.