[Cation (K+, Mg2+, Na+, Ca2+) release in Zn(II) biosorption by Saccharomyces cerevisiae]

The biosorption of Zn(II) by the intact yeast of Saccharomyces cerevisiae was investigated for different initial concentration of the metal ion (0.08 - 0.8 mmol x L(-1)) and for different time (0 - 38h) at natural pH of 5.65 without buffer. The metal uptake was 74.84 - 654.8 micromol x g(-1) when the sorbent concentration is about 1 g x L(-1). The pH value increases and the release of physiological cations occurred in the biosorption process. Potassium ion first released rapidly in the order of hundreds of micromol x g(-1), then magnesium and sodium ions release slowly with several to less a hundred of micromol x g(-1), and the release of cadmium ion were rare. The total quantity of release is often larger than that of Zn(II) uptake. Increase in pH value and release of those cations reflected the intrinsic ability of the cell, however the presence of Zn(II) would promote the release of those cations such as K+ and Mg2+, and decrease to absorb H+. Ion exchange was one of the mechanisms for Zn(II) uptake by the biomass.