Heavy metals removal from aqueous solutions using Saccharomyces cerevisiae in a novel continuous bioreactor–biosorption system

• The possibility of on-line production of yeast S. cerevisiae and biosorption of Cu2+ and Pb2+ was investigated.
• Diffusion and chemical-based kinetics models were used to study the adsorption behaviour of yeast cells.
• Continuous adsorption system was an effective and inexpensive method for removal of heavy metals.

The adsorption behaviour of unmodified yeast cells of Saccharomyces cerevisiae to remove Pb(II) and Cu(II) ions from aqueous solutions in continuous mode was studied. Yeast biomass showed mediocre capacity for Cu(II) ions compared to that of Pb(II) ions in the metals concentrations range of 10–180 mg/l. Metal-binding capacity of yeast cells reached to a maximum of 29.9 mg/g and 72.5 mg/g for Cu(II) and Pb(II) ions, respectively, under similar experimental conditions. The rate of biosorbent production in the continuous bioreactor, governed by dilution rate equal to maximum specific growth rate of the cells, was the limiting factor of the biosorption system. At low metal concentration, Cu(II) removal by yeast cells was higher than previously studied heat-deactivated yeast biomass suggesting involvement of both intracellular and surface-based sequestrations. The removal efficiencies of the test metals decreased as the initial metal concentrations increased. Equilibrium adsorption of the metals by yeast cells was well described by the Langmuir isotherm model. The adsorption kinetics data fitted to diffusion-based and chemical reaction-based models showed intracellular diffusion as the rate controlling step at low metal loads. The results obtained suggest that the use of live yeast cells in a self-contained continuous adsorption system is an effective method for removal of heavy metals from industrial effluents reducing biomass pretreatment and preparation steps as well as achieving on-line adsorbent production, biosorption, and effluent treatment.