Electrospun Bimetallic Nanoparticle-Containing Polymer Nanofibers: Preparation And Enviromental Remediation Application

In recent years, nanotechnology has received much attention in many fields, and the synthesis and application of nanomaterials are the hot spot in the field of materials science in particular. For environmental remediation applications, the unique properties of nanostructured materials such as high surface area to volume ratio can improve the degradation effects of materials to the pollutants. Iron-based bimetallic nanopaticles (NPs), a representative nanomaterial used in environmental remediation, have exhibited excellent capacity because of their superior physical and chemical properties in the dechlorination of chlorinated organic contaminants, in the sequestration of toxic metal ions, and in the decoloration of dyes and so on. However, the formed NPs are prone to agglomeration during the process of contaminant degradation and their transport process in the subsurface environment. This often leads to a reduced reactivity, which is a critical drawback in the environmental application of iron-based bimetallic NPs. Although some promising new synthetic methods have been developed to produce more dispersible and stable the NPs, NPs dispersed in water could cause second pollution. So, immobilizing iron-based bimetallic NPs onto a continuous medium with a high surface area to volume ratio and good porosity is anticipated to meet the requirements for environmental remediation applications.Electrospinning technology has recently emerged as a straightforward method for synthesizing various polymeric nanofibers and nanostructured materials. In this study, polyacrylic acid (PAA)/polyvinyl alcohol (PVA)-containing nanofibers were fabricated using the electrospinning method. Then, Fe/Ni or Fe/Pd NPs were synthesized and immobilized in the electrospun polymer nanofibers through in situ reducing of ferric (or ferrous, or nickelous) ions complexed with nanofibrous mats, forming functional nanostructured materials for wastewater treatment. We focused on the study of synthesis, characterization and the application of Fe/Ni or Fe/Pd NP-containing composite nanofibrous mats.Meanwhile, we also evaluated the environmental remediation capability of Fe/Ni or Fe/Pd NP-immobilized composite nanofibrous mats through decoloration of representative dyes in printing and dyeing wastewater (orange G), and degradation of chlorinated organic contaminant trichloroethylene (TCE).In this paper, to retain the nanofibrous structure of PAA, we electrospun PAA and PVA mixture solution to form PAA/PVA nanofibers. Then thermal treatment was introduced to crosslink PAA/PVA nanofibers, resulting in water-stable PAA/PVA nanofibers. SEM results showed that PAA/PVA nanofibers exhibited smooth and uniform morphology with a mean diameter of 217±65 nm. Bimetallic NPs were directly immobilized into the PAA/PVA nanofibers after chemical reducing metallic cations complexed with PAA/PVA nanofibers. We show that the Fe/Ni or Fe/Pd NP-immobilized composite nanofibers still retain uniform fibrous structure with a smooth surface similar to the electrospun PAA/PVA nanofibers without bimetallic NPs. The mean diameter of Fe/Ni or Fe/Pd NP-immobilized composite nanofibers was 248±44 nm or 245±48 nm, and 303±52 nm. TEM morphological studies show that the Fe/Ni or Fe/Pd NPs are uniformly distributed in the cross-sections of PAA/PVA nanofibers with a mean size among 0.8-2.4 nm and 2-4 nm nm. Orange G decoloration experiment demonstrated that the orange color of orange G solution was obviously decolorized after 5 min exposure of Fe/Ni NP-immobilized composite nanofibrous mats. The composite nanofibrous mats were easy reusable and recyclable. Similarly, the Fe/Pd NP-immobilized composite nanofibrous mats can enhance the dechlorination efficiency to TCE, and also showed high reusability and recyclability.In summary, we report a facile approach to synthesizin and immobilizing bimetallic NPs onto or into nanofibrous mats, preventing the agglomeration and second pollution of the NPs. Meanwhile, the concept of using electrospun nanofibers as nanoreactors might open a new avenue in the fabrication of various three-dimensional porous nanostructured hybrid materials for various applications.