Dissolution and oriented aggregation: transformation from lepidorocite to goethite by the catalysis of aqueous Fe(ii)

Abstract

At a low temperature, lepidocrocite-to-goethite transformation occurred in the presence of Fe(ii) ions, whereas lepidocrocite was stable in the absence of Fe(ii) ions.

Nanoparticle Assembly Leads to Mackinawite Formation

“…When the pH subsequently increased fast from 4 to 7, very large aggregates formed possibly under an OA or cluster-to-cluster aggregation mechanism (Figure 8d). Self-assembly of particles through OA has been reported for many other mineral systems (e.g., magnetite, goethite, apatite, ferrihydrite), 28,[31][32][33][34][35] and the crystallization of these minerals through particle aggregation was reported to include stages of multiple ion complexes and all the way to transformations to fully formed nanocrystals. 36 Our results demonstrate that in the iron-sulfide system, an initial nanocrystalline FeSnano transforms into more stable and poorly crystalline 4.0 4.5 5.0 6.0 7.0 pH mackinawite via aggregation or self-assembly of the structure.…”

Effects of Rare Earth Elements’ Physicochemical Properties on Their Stabilization during the Fe(II)aq-induced Phase Transformation of Ferrihydrite

“…After that, 48 h were needed to equilibrate the anoxic condition with the anaerobic atmosphere. The stock solution of 57 Fe(II) was prepared inside the anoxic chamber, 5 M HCl was used to dissolve the enriched 57 Fe(0) (Isoflex, 57 Fe > 96%) metal, then the enriched 57 Fe(II) solution was diluted to 100 mM. Ln(III) solutions (100 mM) were prepared with their corresponding chloride salts being dissolved inside the anoxic chamber.…”

“…The details of analytical procedures were consistent with those previously described. 37 After measuring the total counts over all four channels (i.e., 54 Fe, 56 Fe, 57 Fe and 58 Fe), each isotope channel was divided by the sum of the total counts to obtain the iron isotope fractions (f). Then, the iron atom exchange percentages in the solids were calculated according to the following equation: 44,45…”

Structural change from Pbnm to R3̅c phase with varying Fe/Mn content in (1-x) LaFeO3.xLaMnO3 solid solution leading to modifications in octahedral tilt and valence states

“…The literature reveals that Fe-2p3/2 and Fe-2p1/2 peaks for low-spin iron (II) are narrow and are separated by -13 eV, whereas for high-spin iron (III) the features are broader, separated by -13.5 eV and shows an extensive satellite structure. The broadness of the spin components is due to multiplet splitting and is a cause for the satellite feature [75,76].…”