Study of the mechanisms of Cu2+ biosorption by ethanol/caustic-pretreated baker's yeast biomass

Baker's yeast biomass was pretreated by ethanol and caustic soda, and then the pristine baker's yeast, ethanol pretreated baker's yeast (ethanol-baker's yeast) and caustic soda pretreated baker's yeast (caustic-baker's yeast) were utilized as biosorbents to adsorb Cu2+ in aqueous solution. The influence of different parameters on Cu2+ uptake by the three biomasses, such as initial Cu2+ concentration, initial pH of solution, contact time and temperature, was studied. The mechanism of Cu2+ binding by biomass was investigated by a number of techniques. Evidence from potentiometric titration revealed that the concentration of carboxyl and amino groups is higher on the caustic and ethanol-baker's yeast compared to the pristine baker's yeast and FTIR spectra confirmed carboxyl, and amino groups on the surface of baker's yeast could be available for characteristic coordination bonding with Cu2+. In addition, SEM and Zeta potential of the three samples show that caustic and ethanol-pretreatment resulted in the change of baker's yeast surface structure and charge which is relative to adsorption. These results demonstrate that the increase of biosorption capacity for Cu2+ by ethanol and caustic-baker's yeast was attributed to the increase and exposure of carboxyl and amino groups on the surface of biomass sample. (C) 2010 Elsevier B.V. All rights reserved.