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• The preparation and characterization of biochar were introduced. • The photocatalytic activity of biochar was summarized. • The photocatalytic process and mechanism of biochar were discussed in detail. • The effects of environmental factors on the photocatalytic reaction were summarized. Biochar has attracted significant attention due to its excellent environmental benefits and extensive applications. Recently, a consensus has been accepted that biochar can act as a photocatalyst and trigger effective photocatalytic reactions in the environment, which is important to energy conversion and the cycle of elements. However, its photocatalytic processes and the corresponding environmental impacts need to receive more and due attention. In this review, we provide a comprehensive summary of the underlying correlations among the pyrolytic evolution of biomass, the structure characteristic of biochar, and the resultant photocatalytic performance. Moreover, the photocatalytic processes and the influence of environmental factors were elaborately investigated on biochar. Finally, future tendencies and challenges in the photocatalysis of biochar have been prospected in the environmental field. This review has offered innovative insights into the photocatalytic essential of biochar and highly enhanced the understanding of its environmental impact. [Display omitted] [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]

• Recent progress of heterogeneous U(VI) photoreduction was reviewed for the first time. • The influence of environmental factors on the photocatalytic reduction of U(VI) was discussed. • Photoconversion mechanisms of U(VI) were discussed in detail. • Future perspectives of the photocatalytic U(VI) reduction were presented. The utilization of light-driven heterogeneous photocatalytic technology is extremely appealing for the uranium(VI) reduction since it is promising in seawater uranium extraction and uranium wastes treatment. U(VI) recovery through heterogeneous photocatalysis is more efficient, economic, non-pollutant, and of high selectivity compared to other methods. However, the systematic summarization on U(VI) photocatalytic reduction from water system is indeed scarce, especially, there are several discrepant hypotheses on the photocatalytic process and mechanisms of the reduction of U(VI). Therefore, this review would provide an overview and recent progress in the photocatalytic U(VI) reduction for the first time. The background of the photocatalytic U(VI) reduction is firstly introduced, followed by the discussion of the photocatalytic reduction mechanisms of U(VI). Thereafter, the photocatalysts widely used in the photocatalytic reduction of U(VI) are summarized. Subsequently, the influence of environmental factors such as organic matters, pH, coexisting ions, and dissolved oxygen on the photocatalytic U(VI) reduction is described. Finally, the challenges and the future perspectives of the photocatalytic reduction of U(VI) are addressed. [ABSTRACT FROM AUTHOR]