Nonprecious bimetallic (Mo, Fe)-N/C nanostructures loaded on PVDF membrane for toxic Cr(VI) reduction from water

Abstract

Nonprecious bimetallic molybdenum and iron embedded into N-doped carbon (MoFe-NC) hybrids were designed and fabricated by pyrolysis of mixed precursors and then immobilized on poly (vinylidene fluoride) (PVDF) films via a phase inversion process to obtain novel catalytic membranes (MoFe-NC@PVDF) for toxic Cr(VI) reduction. The catalytic membranes are highly active for aqueous Cr(VI) reduction using formic acid (FA) as a sacrificial electron donor under mild conditions. The results demonstrated that the parameters of synthesis process can efficiently adjust the morphology and textural properties of the as-synthesized MoFe-NC@PVDF membrane, and thus have a significant impact on the catalytic behavior. Cr(VI) reduction rates significantly increased with increasing FA concentrations (0.234-0.936 M) and reaction temperature (5-35℃), but declined with the increase of Cr(V) concentrations (5-40 mg/L) and pH values of solution (1.87-4.62). Mo-Nₓ, Fe-Nₓ, and C-Nₓ are the active sites, boosting the dissociation of FA molecules into active H* species for effective catalytic reduction of Cr(VI). The catalytic PVDF membrane exhibited distinct porous structure and numerous interaction sites, which not only stabilized metallic nanoparticles, but also promoted mass transfer across the membrane. This cost-effective catalytic membrane provides a new approach toward the treatment of Cr(VI)-containing water.