Two-stage biosorption of selenium from aqueous solution using dried biomass of the baker's yeast Saccharomyces cerevisiae

Abstract

In the present study, the biosorption of selenium ion onto dried biomass of baker's yeast, Saccharomyces cerevisiae, in an aqueous system was investigated. An optimization of selenium biosorption was performed by varying the pH, the initial ion concentration and the biomass dosage. Selenium sorption isotherms were obtained at optimal conditions and the sorption equilibrium data fitted to the Sips isotherm model. The maximum uptake capacity by the Sips model was about 39.0mgg−1. The mass balance equations permitted a theoretical determination of the selenium concentration and the amount of biosorbent needed for achieving the required heavy metal removal. It was observed that two adsorption stages and 2g of baker's yeast biomass biosorbent were required to remove 96.10% of 50mgL−1 selenium from 100ml aqueous solution. In this condition, the percentage removal of selenium in stage one was 88.10% and stage two was 67.20%. The thermodynamic study revealed that the biosorption process of selenium has an endothermic and spontaneous nature and is promoted by increasing the temperature from 298 to 318K. The results also showed that the pseudo-second-order kinetic model correlated well with the experimental data, with an activation energy of 40.67kJmol−1. Based on the results of the percentage removal in the two-stage biosorption system, it could be concluded that the dried biomass of S. cerevisiae is a suitable sorbent for the removal of selenium ions from aqueous solution.