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.