Preparation of palladized carbon nanotubes encapsulated iron composites: highly efficient dechlorination for trichloroethylene and low corrosion of nanoiron

A method developed based on the capillary effect and capillary condensation theory was used to synthesize an innovative Fe/C/Pd composite in this study. This composite (Fe@CNTs@Pd) consists of carbon nanotubes (CNTs) with nanoscale zerovalent iron (NZVI) on the inner surface and palladium nanoparticles supported on the outer surface of CNTs. This structure successfully addresses the problems of high iron corrosion rate and lower utilization rate of hydrogen in the application of bimetal nanoparticles for trichloroethylene (TCE) removal. TCE degradation experiments and electrochemical tests were conducted to investigate the material properties and reaction mechanisms of the composite. It is found that the prepared composite material contribute a high level of TCE dechlorination rate and substantially reduced hydrogen production during iron corrosion in water compared with the conventional CNTs-supported bimetal materials (Fe/Pd@CNTs). Hydrogen spillover effect helps the reactivity of Fe@CNTs@Pd for TCE degradation and suppressed the galvanic cell effect, which results in a stronger resistance to corrosion. Although the K(obs) of Fe@CNTs@Pd was 16.87% lower than that of Fe/Pd@CNTs, the hydrogen production rate of Fe@CNTs@Pd was 10 times slower than that of Fe/Pd@CNTs. Therefore, Fe@CNTs@Pd shows a significant reduction in the corrosion rate at a cost of slightly slower degradation of TCE. In sum, the prepared composites demonstrate important characteristics, including alleviating NZVI agglomeration, maintaining high TCE removal efficiency and reducing the corrosion of NZVI.