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[Display omitted] • A fast reduction of U6+ to U4+ occurs on semiconductors during XPS measurement. • Slower breakage of uranyl occurs on non-semiconductors under X-ray irradiation. • XPS measurement could change the elements state even if far from the center of beam. • Measures are proposed to reduce the beam induced effects in XPS measurement. X-ray photoelectron spectroscopy (XPS) is an efficient technique for recognizing the state of elements. However, the effects of X-ray irradiation on change in the chemical state are sometimes ignored, which may impair the understanding of the environmental behavior of these elements. This study determined the change in the U 4f spectra induced by X-ray irradiation during XPS detection. For U(VI) on non-semiconductors, X-ray irradiation led to a negative shift of U 4f 7/2 to ∼ 380.8 eV due to the break of the uranyl molecules, but not resulting in U(IV) species. However, owing to the photocatalytic reduction of U(VI), the irradiation of U(VI) loaded semiconductors rapidly induced the negative shift of U 4f 7/2 peak to ∼ 379.8 eV, which is the characteristic of U(IV). Moreover, apparent photo-reduction occurred even if the samples were far from the center of the X-ray beam (>3971 μm). Based on these findings, methods for reducing potential error due to X-ray irradiation are suggested, including using the minimum scan time, measuring uranium-containing samples first or independent of other samples, and using X-ray of lower intensity. The results indicated that X-ray induced alteration to the chemical states must be considered when using X-ray techniques. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Co-culture of A. niger did not change the structures of kaolinite and illite. • U(VI) sorption on kaolinite and illite depended on pH and/or ionic strength. • A. niger changed the sorption mechanism of U(VI) on kaolinite and illite. • U(VI) complexed with various functional groups on the bio-composites. • U(VI) was partly reduced by A. niger to noncrystalline U(IV). [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Co-culture of A. niger did not change the structures of kaolinite and illite. • U(VI) sorption on kaolinite and illite depended on pH and/or ionic strength. • A. niger changed the sorption mechanism of U(VI) on kaolinite and illite. • U(VI) complexed with various functional groups on the bio-composites. • U(VI) was partly reduced by A. niger to noncrystalline U(IV). [ABSTRACT FROM AUTHOR]

• Pb(II) sorption on micas strongly depended on pH or/and ionic strength. • Pb2+ could enter the interlayer of biotite and phlogopite causing expanded interlayer. • Co-culture of micas and T. viride resulted in the weathering of micas. • Sorption capacity of Pb(II) on micas was greatly improved in the presence of T. viride. • T. viride caused biomineralization of Pb(II) on micas forming lead phosphates. In this study, batch and spectroscopic approaches were used to explore the sorption of Pb(II) on micas (i.e., muscovite, biotite and phlogopite) in the presence of Trichoderma viride (T. viride). Batch sorption showed that ion exchange, outer-sphere complexes (OSCs) and inner-sphere complexes (ISCs) contributed to Pb(II) sorption on biotite and phlogopite in the pH range of 2.0–7.4, whereas the ISCs were predominant for Pb(II) sorption on muscovite. X-ray diffraction and Fourier transform infrared (FT-IR) analyses have confirmed the changes of structure and surface properties of micas after co-culturing with T. viride , which could improve the sorption capacity of micas to Pb(II). Scanning electron microscopy revealed the bio-mineralization of Pb(II) on T. viride and mica– T. viride composites forming lead phosphates. Furthermore, FT-IR analysis showed that the groups of Si−OH, Al−OH from micas, and carboxyl, phosphate and amino groups from T. viride were synergistically contributing to Pb(II) sorption on mica– T. viride composite. X-ray photoelectron spectroscopy further confirmed that both OSCs and ISCs formed for Pb(II) sorption on micas; however, in the case of mica– T. viride composites, the synergistic effects of T. viride and micas were contributing to Pb(II) sorption through forming the ISCs and biomineralization. [ABSTRACT FROM AUTHOR]