Adsorption, bioconcentration and transformation of radioactive U(VI) on filamentous fungi <italic>Aspergillus Niger</italic>

Abstract

The adsorption, bioconcentration and transformation of radionuclides U(VI) by Aspergillus niger (A. niger) were studied. Batch experiments showed that the adsorption of U(VI) by A. niger was influenced by time, adsorbent concentration, pH value and temperature. The adsorption reached equilibrium within 48 h, and the adsorption kinetics complied with the pseudo-second-order kinetics model. The Langmuir model was more consistent with the adsorption isotherm than the Freundlich model, and the maximum adsorption of U(VI) by mycelia was 83.73 mg/g at pH 6.0 and T=298 K, which was higher than other biosorbents. After bioconcentration of U(VI) by A. niger, the intracellular and extracellular morphological structures changed significantly, and the concentrations of intracellular H 2 O 2 , malonaldehyde (MDA) and thiol compounds in mycelia increased obviously. X-ray absorption near-edge structure (XANES) analysis confirmed that the intracellular U(VI) of A. niger was reduced to U(IV), and EXAFS data indicated that the U(IV) product was a phase composed of mononuclear U(IV) atoms closely surrounded by light element shells. The results showed that the filamentous fungus A. niger can be used as a potential biological material for radionuclide removal, which has important scientific significance and potential application value.