HEAVY-METAL REMOVAL BY CAUSTIC-TREATED YEAST IMMOBILIZED IN ALGINATE

Saccharomyces cerevisiae yeast biomass was heated in 0.75 M NaOH at 70 -90 degrees C for 10-15 min to increase its biosorption for heavy meta ls, and then immobilized in alginate gel. Biosorption for Cu2+, Cd2+ a nd Zn2+ on alginate gel, native yeast, native yeast immobilized in alg inate gel, and caustic-treated yeast immobilized in alginate gel, were all compared. Immobilized yeasts (native yeast and caustic-treated ye ast) could be reactivated and reused in a manner similar to ion-exchan ge resins. Immobilized caustic-treated yeast has high heavy metal bios orption capacity and high metal removal efficiency over a rather wide pH region. The biosorption isotherm of immobilized caustic-treated yea st was studied and empirical equations were obtained. The initial pH o f polluted water affected the metal removal efficiency in extreme pH r egions, and the biosorption capacity almost remained constant over a w ide pH range. The equilibrium biosorption appeared to be temperature i ndependent in the range from 7 degrees C to 45 degrees C at low initia l metal concentration.