Uranium binding mechanisms of the acid-tolerant fungus

Vzquez-Campos, X.*; Kinsela, A. S.*; Collins, R. N.*; Neilan, B. A.*; Aoyagi, Noboru   ; Waite, T. D.*

The uptake and binding of uranium by a moderately acidophilic fungus, , recently isolated from a uranium mine site, is examined in this work in order to better understand the potential impact of organisms such as this on uranium sequestration in hydrometallurgical systems. Our results show that the viability of the fungal biomass is critical to their capacity to remove uranium from solution. Indeed, live biomass were capable of removing 16 mg U/g dry weight in contrast with dead biomass which removed 45 mg U/g dry weight after 2 h. Furthermore, the uranium binds with different strength, with a fraction ranging from 20-50 % being easily leachable from the exposed biomass by a 10 min acid washing. Results from X-ray absorption spectroscopy measurements show that the strength of uranium binding is strongly influenced by cell viability, with live cells showing a more well-ordered uranium bonding environment, while the distance to carbon or phosphorus second neighbours is similar in all samples. When coupled with laser spectroscopy, the importance of organic acids and phosphates, and polysaccharides, likely released with fungal cell death, appear to be the primary determinants of uranium binding in this system. These results provide an important progression to our understanding with regard to uranium sequestration in hydrometallurgical applications.