Biosorption of Copper by Saccharomyces cerevisiae: From Biomass Characterization to Process Development

Abstract

Biosorption offers a competitive technological solution to the removal of heavy metals from wastewaters. Nevertheless, large-scale application of biosorption is still hindered by the absence of systematic methodologies for product and process design. Crucial role is played by the development of models that can describe the effect of operating conditions on biosorption equilibrium and kinetics and thus drive the rational process design. In this contribution, biosorption of copper onto a wild-type strain of Saccharomyces cerevisiae is analyzed. The analysis is structured in a way that allows reviewing and discussing the main stages of process development. Type and concentration of the biomass active sites were determined by fitting mechanistic equilibrium models accounting for the distribution of the site protonation constants to potentiometric titration data. Equilibrium biosorption tests were performed to determine the dependence of the biosorption capacity on pH (3 and 5) and metal liquid concentration (0–120 ppm). The immobilization of biomass by calcium alginate was performed to produce composite sorbent beads with different biomass contents. An experimental analysis was performed to characterize the kinetics and the equilibrium of copper biosorption onto the produced beads. These data were exploited to identify kinetic and equilibrium models describing the competitive biosorption of protons and copper ions onto the beads. A mathematical model was derived to describe the transport of copper and protons in a biosorption column packed by the produced beads. The column mathematical model was validated by recourse to the experimental data derived by the operation of lab-scale packed column (length 15 cm, diameter 1.7 cm).