Application of Two-Parameter and Three-Parameter Isotherm Models at Uranium Biosorption by Baker's Yeast

In this work, the ability of free and immobilized deactivated baker's yeast saccharomyces cerevisiae to remove uranium ions was investigated using a batch biosorption procedure with respect to the initial pH (3.0-6.0), contact time (24 h), initial ion concentration (50-400 mg/g) and presence of secondary ions (Cr (VI)). The removal of uranium was approximately 90% and 50% at low concentrations, whereas it was about 80% and 15% at high concentrations at an optimum pH of 5 and 5.5, using 1 g/l of adsorbent in 24 h of equilibration time for immobilized and free baker's yeast, respectively. Experimental results at 30ºC indicated that the uptake capacity of uranium ions by immobilized baker's yeast biomass on calcium alginate was reduced by the presence of secondary ions. The experimental data obtained at the optimum have been analyzed using two two-parameter models, Langmuir and Freundlich, and one three-parameter model, Redlich–Peterson. Taking into three statistical error functions, the data were best fitted to the Redlich–Peterson model. Using the Langmuir equation, the saturated monolayer sorption capacities of uranium ions onto immobilized and free baker's yeast were 592.8 and 73 mg/g, respectively at 30ºC.