Coppering nanoscale zero-valent iron particles for enhanced decontamination: implications of synthesis conditions on particle architecture and reactivity

Abstract

Doping of the surface of nanoscale zero-valent iron (nZVI) particles with noble metals enhances their reactivity and efficiency of pollutant removal. In this study, we explored the effects of different synthesis procedures on the performance of Cu-doped nZVI particles in the removal of trichloroethylene (TCE). The abundance, speciation, and distribution of Cu on the Cu-nZVI particle surface were analysed by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDX) mapping, and X-ray photoelectron spectroscopy (XPS). Based on the measurements of oxidation-reduction potential (ORP), pH, and dissolved Cu concentration, a 60 min reaction time was found to be optimal for the Cu-nZVI synthesis. The particles prepared with Cu(ii) chloride and sulfate removed 67% more TCE than the non-modified nZVI particles in eight days, degrading it mainly to ethene. In contrast, particles synthesized with Cu(ii) nitrate showed no increase the removal efficiency due to (i) higher pH of the dispersions, (ii) more passivated surface, and (iii) the presence of Cu in an amorphous form. Increasing the Cu loading above 1% did not improve the TCE removal rate likely due to the more extensive particle surface passivation. These findings provide insights into optimizing the synthesis and performance of metal-doped (n)ZVI particles for pollutant removal.