Characterization of uranium binding to residual biomass in distillery spent wash

The solid component of spent wash from a whiskey distillery, consisting primarily of non-living yeast and bacteria, was recovered and its ability to take up uranium from solution has been examined. Under optimal conditions the biomass had a maximum biosorption capacity (qmax) of 180 mg U/g (dry weight) biomass. The biomass exhibited maximal binding at 18°C and little or no change was detected when the temperature was increased to 60°C. The qmax decreased dramatically, however, when the temperature was decreased to 2°C. Kinetic studies demonstrated that binding reactions were relatively rapid with over 75% binding occurring within 10 min at 60°C. Kinetic studies also demonstrated that binding of uranium to the biomass was temperature dependant. The optimum pH for binding of uranium to the biomass was pH 5.0 and binding was inhibited in the presence of sea-water. Binding of uranium to the biomass was also inhibited to varying degrees by Fe and Cu. Electron microscopy demonstrated that remnants of both bacterial and fungal cells contained bound uranium and the intracellular mass of the material played an important role in biosorption.