Biosorption of monovalent and divalent ions on bakerʹs yeast

Biosorption of monovalent ions Na+ and K+, by deactivated protonated yeast (Saccharomyces cerevisiae) at controlled pH, was compared with biosorption of divalent ions Ca2+ and Mg2+ to help to understand the underlying binding mechanisms. The adsorption for monovalent ions was accompanied by H+ release. Divalent ions were sorbed by proton displacement, and also an additional mode not accompanied by release of H+. The sorption uptake of both monovalent and divalent metal ions increased with pH in the range 3–7 peaking at 6.75. Equilibrium sorption isotherms at pH=6.75 showed that the total maximum biosorptive capacity for metal ions decreased in the following order: Ca>Mg>Na K.