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Fig. 12.5 Raman spectra of
samples that was unreacted:
a ZVI (as-received) b ZVI
(acid-washed) c Ni/Fe
bimetal, and typical sample
spectra after 25 days reaction
of Ni/Fe with d PCP e TeCP
f TCP g DCP
the Ni/Fe bimetal. During the reaction of 2,4,6-TCP and 2,4-DCP with Ni/Fe, various passivating oxides started accumulating on the ZVI surface immediately during the initial reaction period of 1 day when in contact with Ni/Fe. Furthermore,
Raman analysis showed continuous accumulation of such passivating oxides on the
Ni/Fe surface throughout the 25-day reaction period of 2,4,6-TCP and 2,4-DCP with
Ni/Fe. This progressive growth of passive oxides as well as their ageing could lead
to strong entrapment of the adsorbed CP molecules with the oxides/oxyhydroxides
structures and reduce the extraction/desorption potential of such CPs during the
chemical extraction process resulting in poor mass balance recoveries. Based on the
literature, Fe
II oxides have a greater solubility compared to that of Fe
III oxides and