Use of fourier transform infrared spectroscopy to examine the Fe(II)-Catalyzed transformation of ferrihydrite

Adding Value to Waste Minerals in a Circular Economy Framework: Ochre-Derived Layered Double Hydroxide Catalysts in Fatty Acid Ketonisation

“…Regarding the Saltburn ochre sample, the peaks observed at 797 and 885 cm −1 can be attributed to those characteristic of goethite, due to the deformation of the O-H bonds [35][36][37], supporting the data obtained from the XRD. Taken together, XRD, TGA and FTIR analysis all confirm that the original ochre is comprised mainly of goethite and the material has been substantially, if not completely, reprecipitated as an LDH material.…”

“…The data is characteristic of LDHs [42,43], supporting the XRD data above regarding a successful synthesis of the desired LDH material. The latter can also be supported with the FTIR plot of the Saltburn ochre observed in Figure 3, with the characteristic goethite peaks at 797 and 885 cm −1 [35][36][37] and their total disappearance in the LDH spectra. No sharp absorbance was observed circa 3700 cm −1 , which would also indicate the presence of a brucite (Mg(OH) 2 ) phase.…”

“…Principle adsorptions corresponding to the LDH are a broad adsorption band from 3000 to 3500 cm −1 , with an observable peak at 3410 cm −1 , corresponding to hydrogen-bonded -OH and interlayer water [20,31], and a distinctive intense absorption at 1356 cm −1 corresponding to carbonate anti-symmetric stretching, as well as an observable shoulder close to 2900 cm −1 related to stretching bonding of H-bonded molecules (O-H bonded to the CO 2− 3 in the interlayer) [26,29,33,34]. Regarding the Saltburn ochre sample, the peaks observed at 797 and 885 cm −1 can be attributed to those characteristic of goethite, due to the deformation of the O-H bonds [35][36][37], supporting the data obtained from the XRD. Taken together, XRD, TGA and FTIR analysis all confirm that the original ochre is comprised mainly of goethite and the material has been substantially, if not completely, re-precipitated as an LDH material.…”

Decreases in Iron Oxide Reducibility during Microbial Reductive Dissolution and Transformation of Ferrihydrite

“…Such low ratios presumably resulted in low concentrations of ferrihydrite-associated Fe II that are known to catalyze its transformation into goethite through a dissolution-reprecipitation mechanism. 12,14,15,26,27,30,36 At donor-to-acceptor ratio of 1:1 (Figure 1e), ferrihydrite transformed into a final mixture of 32% goethite-Fe III and 62% magnetite-Fe III (6% unreacted ferrihydrite). The EM image in Figure 1h shows goethite needles (lengths and widths of up to 100 nm and ≈ 10 nm, respectively) in close association with diamond-shaped magnetite particles (diameters of 80-300 nm; in agreement with crystallite sizes of ≈ 177 nm that we estimated from the X-ray diffractograms in Figure S13a).…”

“…[23][24][25] The importance of microbial reductive dissolution and transformation of poorly crystalline iron oxides is well documented. [14][15][16][26][27][28][29][30] However, earlier studies primarily focused on two aspects: First, the quantification of Fe II formation during microbial Fe III reduction (e.g. by colorimetric assays) and second, the characterization of changes in iron oxide mineralogy (e.g., by spectroscopic techniques).…”