Abstract
The reactivity of nanoscale zero-valent iron is limited by surface passivation and particle agglomeration. Here, Ni/Fe bimetallic nanoparticles embedded into graphitized carbon (NiFe@GC) were prepared from Ni/Fe bimetallic complex through a carbothermal reduction treatment. The Ni/Fe nanoparticles were uniformly distributed in the GC matrix with controllable particle sizes, and NiFe@GC exhibited a larger specific surface area than unsupported nanoscale zero-valent iron/nickel (FeNi NPs). The XRD results revealed that Ni/Fe bimetallic nanoparticles embedded into graphitized carbon were protected from oxidization. The NiFe@GC performed excellently in 2,4,6-trichlorophenol (TCP) removal from an aqueous solution. The removal efficiency of TCP for NiFe@GC-50 was more than twice that of FeNi nanoparticles, and the removal efficiency of TCP increased from 78.5% to 94.1% when the Ni/Fe molar ratio increased from 0 to 50%. The removal efficiency of TCP by NiFe@GC-50 can maintain 76.8% after 10 days of aging, much higher than that of FeNi NPs (29.6%). The higher performance of NiFe@GC should be ascribed to the significant synergistic effect of the combination of NiFe bimetallic nanoparticles and GC. In the presence of Ni, atomic H* generated by zero-valent iron corrosion can accelerate TCP removal. The GC coated on the surface of Ni/Fe bimetallic nanoparticles can protect them from oxidation and deactivation.
Highlights
Accepted: 25 May 2021Recently, nanoscale zero-valent iron in pollutant remediation has attracted significant attention because nZVI can maximize the benefits of ZVI [1,2]
The morphology of the Ni/Fe embedded into graphitic carbon (NiFe@GC)-50 and Ni/Fe nanoparticle distribution was characterized by the transmission electron microscopy (TEM)
The core–shell structure is obvious, as seen from the high-resolution TEM (HRTEM) image in Figure 1b, indicating that the Ni/Fe nanoparticles were coated with carbon shell, and the carbon shell was highly graphitized due to the catalytic effect of Ni/Fe nanoparticles at a high temperature
Summary
Accepted: 25 May 2021Recently, nanoscale zero-valent iron (nZVI) in pollutant remediation has attracted significant attention because nZVI can maximize the benefits of ZVI [1,2]. Owing to the nanoscale particle size, nZVI has a much larger specific surface as compared to ZVI, and more reactivity can be provided for targeted contaminant adsorption and reduction [3]. The following major problems inhibit the practical application of nZVI: (1) nZVI particles are prone to agglomeration due to the small particle size, large surface energy, and strong magnetic properties, resulting in decreased specific surface area and reactive sites [4]; (2) nZVI is prone to be oxidized under ambient environmental conditions, and the generated iron oxide passivation layer would inhibit the electron transfer [5]; (3). In order to enhance the stability and anti-passivation properties of nZVI, great efforts have been focused on surface modification technology. In the second metal-doped nZVI system, Fe0 acts as a reactive electron donor, while the second metals serve as the carrier and catalyst to adsorb H2 and Published: 27 May 2021
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