Heavy metal biosorption by the fungus, Mucor rouxii

The present study evaluated the potential of the fungus Mucor rouxii to remove lead, cadmium, nickel and zinc from aqueous solutions. Live M. rouxii biomass exhibited a higher biosorption capacity than autoclaved biomass for metal ions, because the biomass had a high surface area due to its filamentous form. Pretreatment using alkaline chemicals and some salts enhanced metal removal capacity of autoclaved biomass, but a loss of biomass mass resulted from the pretreatment.; The pH of the metal solution strongly affected the degree and kinetics of biosorption of lead, cadmium, nickel and zinc on pretreated biomass. At an initial pH of 4.0 or under, little biosorption of metal ions occurred. Biosorption of metal ions was inhibited at a pH of 2.0 (except for nickel) but increased sharply when the pH was increased from 5.0 to 6.0. Beyond a pH of 6.0, biosorption tended to be stable for lead and increased to a lesser extent for cadmium, nickel and zinc. At an initial pH of 5.0, biosorption reached an equilibrium in 7, 13, 10 and 12 hours for lead, cadmium, nickel and zinc, respectively. The kinetics of metal ion biosorption on pretreated biomass could be adequately described by both the Lagergren and Ho's models.; Nitric acid solution with a low concentration of 0.05 M was effective in desorbing the biosorbed metal ions from the biomass. After desorption, the biomass was regenerated with 0.2M sodium hydroxide solution. The regenerated biomass could be used for at least five cycles of biosorption, without losing its metal removal capacity. However, desorption and regeneration resulted in a loss of biomass mass.; Batch and column experiments showed that the biomass immobilized in the form of beads was able to remove lead, cadmium, nickel and zinc ions from aqueous solutions. The biosorption capacity of the beads was calculated to be 3.66, 1.12, 0.25 and 1.35 mg metal ions per gram of beads for lead, cadmium, nickel and zinc, respectively.; Carboxyl, amine, phosphate groups and lipids present in the M. rouxii biomass were found to be the main biosorption sites for lead, cadmium, nickel and zinc. Biosorption of the metal ions on pretreated biomass released sodium, potassium, calcium and magnesium ions from the biomass, indicating a possible ion-exchange mechanism in biosorption of the metal ions. (Abstract shortened by UMI.)...