Composite Biosorbents of Metal Ions Based on Yeast Cells and Diatomite

Abstract

The possibility of removing Cu2+ and Pb2+ ions from solutions by the yeast cells Rhodotorula glutinis and diatomite (natural mineral) was studied. It is shown that at the concentration of CuSO4 and Pb(NO3)2 10-3 mol/l the removal of metal ions by yeast cells was 59.1 and 72.4% for the ions of Cu2+ and Pb2+. The yeast cells surface includes amino, hydroxyl, phosphate and carboxyl groups which activates sorption ability, because these groups can bind metal ions by ion exchange, donor acceptor and electrostatic interactions. The removal degree of metal ions by diatomite under the same conditions was for Cu2+ 91.6% and for Pb2+ 94.7%. To increase the removal degree of metal ions from solutions, the yeast cells were immobilized on the surface of diatomite. In order to attach the negatively charged cells of microorganisms with negatively charged surface of the mineral, the surface of diatomite was modified by polyethylenimine (PEI). As a result, the immobilization degree of Rhodotorula glutinisto the surface of diatomite at the concentration of PEI 0.02 base-mol/l increased from 62 to 88%, which is explained by the existence of electrostatic contacts between the negatively charged functional groups of the cell surface and amino groups of PEI, that has covered the surface of diatomite by PEI. It is shown that the obtained composite biosorbent removes 97.8% of Cu2+ ions and 99.4% of Pb2+ ions.