Surface decoration of amine-rich carbon nitride with iron nanoparticles for arsenite (As(III)) uptake: The evolution of the Fe-phases under ambient conditions.

Abstract A novel hybrid material (gC 3 N 4 -rFe) consisting of amine-rich graphitic carbon nitride (gC 3 N 4 ), decorated with reduced iron nanoparticles (rFe) is presented. XRD and TEM show that gC 3 N 4 -rFe bears aggregation-free Fe-nanoparticles (10 nm) uniformly dispersed over the gC 3 N 4 surface. In contrast, non-supported iron nanoparticles are strongly aggregated, with non-uniform size distribution (20–100 nm). 57 Fe-Mossbauer spectroscopy, dual-mode electron paramagnetic resonance (EPR) and magnetization measurements, allow a detailed mapping of the evolution of the Fe-phases after exposure to ambient O 2 . The as-prepared gC 3 N 4 -rFe bears Fe 2+ and Fe° phases, however only after long exposure to ambient O 2 , a Fe-oxide layer is formed around the Fe° core. In this [Fe°/Fe-oxide] core-shell configuration, the gC 3 N 4 -rFe hybrid shows enhanced As III uptake capacity of 76.5 mg g −1 , i.e., ca 90% higher than the unmodified carbonaceous support, and 300% higher than the non-supported Fe-nanoparticles. gC 3 N 4 -rFe is a superior As III sorbent i.e., compared to its single counterparts or vs. graphite/graphite oxide or activated carbon analogues (11–36 mg g −1 ). The present results demonstrate that the gC 3 N 4 matrix is not simply a net that holds the particles, but rather an active component that determines particle formation dynamics and ultimately their redox profile, size and surface dispersion homogeneity.