One-pot fabrication of nanoscale zero-valent iron scaffolded onto graphitic carbon nitride as bifunctional nanohybrid in sequestering U(VI) and Cr(VI) with boost performance and intrinsic mechanism

In this paper, we reported an innovative one-pot fabrication approach of a bifunctional nanohybrid through scaffolding of nanoscale zero-valent iron onto the inter-layer structure of graphitic carbon nitride in sequestering U(VI) and Cr(VI) in wastewater. The microstructures, morphologies and chemical compositions of the as-fabricated g-C3N4/NZVI nanohybrid before and after U(VI)/Cr(VI) sequestration were exploited in detail by applying various physicochemical and spectroscopic methods. Batch experimental results demonstrated that sequestration of targeted U(VI)/Cr(VI) by g-C3N4/NZVI was higher than those of pure NZVI or g-C3N4 due to the pronounced boost performance, which was ascribed from the introduction of g-C3N4 as matrix inhibited the oxidation of NZVI and improved its reactivity. The pH effect was also elucidated and it was found that lower pH facilitated the sequestration of the negatively-charged Cr(VI), while higher pH benefited the sequestration of the positively-charged U(VI). Moreover, the characterization insights into intrinsic mechanism manifested that sequestration of U(VI)/Cr(VI) was fulfilled through a synergistic effect of adsorption, reduction and coprecipitation. This work is of great significance for understanding the combined sequestration mechanism of U(VI) and Cr(VI), and usage of g-C3N4/NZVI in sequestration of severe dangerous metal ions, especially efficient detoxification of toxic cations and anions in wastewater.