This paragraph justifies Fe-P interaction
Since there does not appear to be mechanistic grounds for interaction
between Si and Fe or Si and P, we believe that the interaction of Fe and
P species in solution is responsible for the remarkable uptake of Fe
within the prepared SBA-15. The interaction of Fe and P species in
acidic media has been studied and based on both spectrophotmetric and
potentiometric data, the concnetration of
[FeHnPOn+4 ]
species ranges from 100 to 10000 times higher than the
[Fe3+][H3PO4]
for pH ranging from 1 to 2 , suggesting iron phosphates can readily form
under our synthesic conditiosn.17 Pre-calcination XRD
patterns in figure t, acquired after filtration and washing show complex
behaviour reminiscient of a variety of hydrated iron phosphates and
minerals. While an exact identification by XRD was not possible, there
is a clear trend of \(\alpha\) or tridimyte iron phosphates diffracting
above 20° while hydrates exhibit additional peaks below. This is likely
due to the much larger unit cell dimensions necessary to accommodate
water of crystalization, and hence greater interplanar spacings.
Introduce concept of nanodomain encapsulation. How it would determine on
kinetics. XPS discrepancy supporting mesoprous shape of Fe P domain.