Removal of divalent heavy metal mixtures from water by Saccharomyces Cerevisiae using crossflow microfiltration

Abstract

The removal of heavy metal ions, Ni 2+, Cu 2+ and Pb 2+ using yeast ( Saccharomyces cerevisiae) as carriers in a crossflow microfiltration is investigated. The effects of yeast cell and electrolyte concentrations on the transient and steady-state permeate flux and metal ion rejections are established. It is found that the metal ion rejection reaches a plateau if yeast cell concentration is greater than ∼2 g/l as a result of cell aggregation. The binding affinity of the metals to yeast cell is Pb 2+>Cu 2+>Ni 2+, which is also reflected in the metal ion rejection under identical process conditions. Because of the formation of yeast cell flocks in the presence of Pb 2+, permeate flux is also higher for this metal. The presence of NaCl decreases both rejection and permeate flux for Ni 2+ and Cu 2+ but not for Pb 2+. When binary or ternary metal mixtures are used, the rejection of the individual metals is reduced except that of Pb 2+. It is found that the pseudo-gel concentration is unaffected by the presence of metal ions.