New insights into the sorption of U(VI) on kaolinite and illite in the presence of Aspergillus niger

The regulation effect of Aspergillus niger to the sorption behavior of U(VI) on kaolinite and illite was studied through investigating the enrichment of U(VI) on kaolinite-Aspergillus niger and illite-Aspergillus niger composites. Kaolinite-or illite-A. niger composites were prepared through co-culturation method. Results showed that U(VI) sorption on kaolinite and illite in different pH ranges could be attributed to ion exchange, outer-sphere complexes (OSCs), and inner-sphere complexes (ISCs), while only the ISCs on the bio-composites. Moreover, micro spectroscopy tests revealed that U(VI) coordinate with phosphate, amide, and carboxyl groups on illite-and kaolinite-A. niger composites. X-ray photoelectron spectroscopy (XPS) further found that U(VI) was partly reduced to non-crystalline U(IV) by A. niger in the bio-composites, occurring as phosphate coordination polymers or biomass-associated monomers. The findings herein provide further insight into the immobilization and migration of uranium in environments.

Automated summary

The regulation effect of Aspergillus niger on the sorption behavior of U(VI) on kaolinite and illite was studied, showing that only inner-sphere complexes were present on the biocomposites. Microspectroscopy tests revealed coordination of U(VI) with phosphate, amide, and carboxyl groups on the biocomposites, while XPS found partial reduction of U(VI) to U(IV) in the presence of A. niger.