Copper adsorption by inactivated cells of Mucor rouxii: Effect of esterification of carboxyl groups

Inactivated copper-sensitive and copper-tolerant strains of Mucor rouxii cultured at high copper concentration were tested for their potential to adsorb Cu(II) ions from solution. We performed batch experiments to determine the pH profile for Cu(II) binding, binding capacity, and the possibility of removing the Cu(II) that had been adsorbed. The biomasses studied showed a high affinity for Cu(II) ions as the pH increased from 2 to 5. The copper-tolerant strain exhibited a higher copper adsorption than the copper-sensitive strain. Most of the Cu(II) adsorbed by the inactivated cells was desorbed by treatment with 0.1 M HCl. We investigated one of the mechanisms involved in Cu(II) binding through chemically modifying the possible carboxyl groups present on the inactivated cells of Mucor rouxii by esterification with methanol. Cu(II) binding decreased approximately 25% after the carboxyl groups were esterified. The Cu(II) binding ability of the esterified carboxyl groups was regained after base hydrolysis. These preliminary findings suggest that the carboxyl groups could be one of the mechanisms responsible for Cu(II) binding. This phenomenon can have useful applications for metal removal from contaminated water.