Preparation and characterization of bimetallic zero-valent iron nanocatalysts for nitrophenol degradation

Background: p-Nitrophenol (4-NP) is an organic pollutant found in wastewater discharged from agricultural facilities worldwide. This pollutant is considered as hazardous and toxic by the US Environmental Protection Agency (USEPA).Methods: The spherical chain-shaped nanophase zero-valent-iron (nZVI) with different metal (Ag, Cr, Cu) loadings was used for wastewater simulation to form bimetallic nanocatalyst (BNC). Moreover, the nZVI and BNC was synthesized and characterized for 4-NP removal. The as-synthesized nZVI and BNCs were used to degrade 4-NP in wastewater, where a higher conversion of 4-NP to aminophenol (4-AP) was observed. The core-shell shape of nZVI@Cu BNCs was also investigated with small angle X-ray scattering (SAXS) to demonstrate the parameters of core-shell model in SAS View.Significant findings: Experimentally, the Cu removal efficiencies at different loading ratios were nZVI@Cu-800> nZVI@Cu-400> nZVI@Cu-200> nZVI@Cu-100. The thermal induced aggregations of nZVI were demonstrated with SAXS, where the 55 degrees C group displayed 181% increase in size when compared with the 25 degrees C group. The XANES/EXAFS spectra revealed the presence of Cu2O in nZVI@Cu, a phenomenon which provided the reductive degradation mechanism of the chemical reactions. In this study, heavy metal absorbed onto nZVI and BNCs reduced 4-NP heavy metal contaminants to less toxic 4-AP. Thus, the as-synthesized nZVIs could effectively convert harmful 4-NP in wastewater into useful and high-value 4-AP by-products.

Automated summary

This study used spherical chain-shaped nanophase zero-valent-iron (nZVI) with different metal loadings to simulate wastewater, forming bimetallic nanocatalysts (BNC). The Cu removal efficiency was highest in nZVI@Cu-800. The size of nZVI was found to increase by 181% at 55 degrees C compared to 25 degrees C. XANES/EXAFS spectra analysis revealed the presence of Cu2O in nZVI@Cu, indicating a reductive degradation mechanism. Overall, this study demonstrates that nZVI and BNCs can effectively convert harmful 4-NP into useful and high-value 4-AP.