In this study a systematic comparison in morphology, long-term degradation, regeneration and reuse were conducted between palladized and sulfidized nanoscale zero-valent iron (Pd-Fe and S-Fe). Pd-Fe and S-Fe were prepared, after the synthesis of precursor Fe0 nanoparticles (spherical, ~35 nm radius) for carbon tetrachloride (CTC) treatment. With HAADF-TEM-EDS characterization, dispersive Pd islets were found on the Fe core of Pd-Fe. However, the Fe core was covered by the FeSx shell of S-Fe (FeS/FeS2 = 0.47). With an excessive Pd dose (10 mol%), the Pd-Fe were dramatically deformed to dendritic structures which significantly decreased reactivity. For CTC degradation, Pd-Fe (0.3 atomic% Pd) increased the degradation rate by 20-fold (ksa = 0.580 Lm−2 min−1) while S-Fe presented a greater life time. The major intermediate chloroform (CF) was further degraded and less than 5% CF was observed after 24 h using Pd-Fe or S-Fe while above 50% CF remained using Fe. During aging, the Fe core was converted to FeOOH and Fe3O4/γ-Fe2O3. The restoration of Fe0 was achieved using NaBH4, which regenerated Fe and Pd-Fe. However, the formed FeSx shell on S-Fe was disappeared. The results suggest that S-Fe extends longevity of Fe, but the loss of FeSx after aging makes S-Fe eventually perform like Fe in terms of CTC degradation.
|Journal||Chemical Engineering Journal|
|State||Published - Aug 15 2020|
Bibliographical noteFunding Information:
This work was supported by the NIEHS-SRP grant P42ES007380 ; partial support was also provided by NSF KY EPSCoR grant (Grant no: 1355438 ).
© 2020 Elsevier B.V.
- Chloro-organics removal
- Long-term study
ASJC Scopus subject areas
- Chemistry (all)
- Environmental Chemistry
- Chemical Engineering (all)
- Industrial and Manufacturing Engineering