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In this review, the structure of iron-containing soda-lime aluminosilicate glass–ceramics prepared by domestic waste slag from waste combustion plants in Japan and its simulated composite was investigated by 57Fe-Mössbauer spectroscopy. The photo-Fenton catalytic ability of the samples was evaluated by a degradation test using an aqueous methylene blue (MB) solution. The photo-Fenton catalytic efficacy of the specimens was assessed through a degradation examination employing an aqueous methylene blue (MB) solution. The MB degradation test recorded a k value of 2.25–2.65 × 10–3 min−1 using the composite of (silicate + iron oxide nanoparticles) prepared from domestic waste slag. The 57Fe-Mössbauer spectra were mainly composed of three sextets due to nanoparticles of Fe3O4 and α-Fe2O3. After exploring the chemical composition of soda lime iron aluminosilicates as domestic waste-modeled slag, we revealed that heat-treated simulated slag samples of 5Na2O-41.4CaO-20Al2O3-27.6SiO2-6Fe2O3 glass showed the largest k value of 115 × 10–3 min−1 under photo-Fenton reaction which highly covalent distorted FeIIIO4 caused. It is concluded that municipal waste slag can be a starting material for the Photo-Fenton catalyst with high activity, which contributes purification of wastewater. [ABSTRACT FROM AUTHOR]

The mixed‐valent, solid solution series FeMo1−nVnO4 (0≤n≤0.3) was synthesized and characterized by x‐ray diffraction, and thermal analysis. Assignments of individual Fe‐species stem from 57Fe‐Mössbauer spectroscopy and DFT‐calculations of the electric field gradients. The incorporation of smaller ions (FeIII, VV) represents an internal "chemical pressure" effect stabilizing the low‐temperature α‐polymorph with increasing n. The site‐preference and distribution of vanadium on individual Mo‐sites impacts the α→β transition temperatures around 650 K, and causes distinct differences in charge mobility in this hole‐doped semiconductor around 225 K. We assign the charge localization in α‐FeMo1−nVnO4 to enhanced electron‐phonon coupling within a polaronic scenario. [ABSTRACT FROM AUTHOR]

The relationship between local structure and visible-light-activated photocatalytic ability of glass–ceramics prepared from Municipal Solid Waste (MSW) was investigated. The samples were characterized by XRD, 57Fe Mössbauer spectroscopies, TEM and DRS. From the Mössbauer spectrum, it was found that iron ions are present in FeIII(tetrahedral) and FeII(tetrahedral) coordinations. A high covalent iron magnetic component (FeIV) with small isomeric shifts is also confirmed in the Model Slag (MS-x) samples. The energy band gap values of the samples can easily be tuned by simple adjusting the initial iron concentration and heat treatment. The largest degradation of 99.56% was estimated for methylene blue dye under the visible-light irradiation using MS-15. It is concluded that a small change of chemical composition in MSW contributed to a large change of first-order-rate kinetics and local structure. This study provides a novel approach for the removal of contaminants using MSW and sheds new insights into the presence of FeIV species enhancing photocatalytic activity. [ABSTRACT FROM AUTHOR]

This study aims to find a suitable method to transform the amorphous iron oxides obtained from the incineration of combustible waste slag into hematite. The resulting samples were utilized as heterogeneous photocatalysts for the photo-Fenton degradation of methylene blue (MB) aqueous solution. A good correlation was found between the MB degradation and the amount of hematite phase as confirmed by XRD and Mössbauer measurements. The largest rate constant (k) was (4.1 ± 0.08) × 10−2 min−1 for MB decomposition under visible-light for the sample N5-50-800. The results are promising for both low-cost photocatalysts and recycling of combustible waste slags. [ABSTRACT FROM AUTHOR]

Local structure and the photo-Fenton reactivity of iron-containing glasses and glass-ceramics prepared from Japanese domestic waste slag were investigated. The largest rate constant (k) of (2.8 ± 0.08) × 10−2 min−1 was recorded for the methylene blue degradation test by using H2O2 with a heat-treated 'model slag'. The 57Fe Mössbauer spectrum was composed of a paramagnetic doublet with isomer shift of 0.18 ± 0.01 mm s−1 attributed to distorted FeIIIO4 tetrahedra. These results indicate that the paramagnetic Fe3+ provided strong photo-Fenton catalytic ability, and that waste slag can thus be recycled as an effective visible-light activated photocatalyst. [ABSTRACT FROM AUTHOR]

Biotic and abiotic pathways for the transformation of phosphorus (P) in the sediment of Taihu Lake, a eutrophic shallow freshwater lake in southeastern China, were studied using the oxygen isotope ratios of phosphate (δ18O P) along with sediment chemistry, X-ray diffraction, and 57Fe-Mössbauer spectroscopic methods. The results showed that δ18O P values of sediment P pools significantly deviated from equilibrium and thus allowed distinguishing potential P sources or pathways of transformation. Isotope values of authigenic P being lighter than equilibrium suggests the re-mineralization of organic matter and subsequent precipitation of apatite as the major pathway of formation of authigenic P. The δ18O P values of the Al-bound P pool (18.9–23.5‰) and ferric Fe-bound P (16.79–19.86‰) could indicate potential terrestrial sources, but the latter being closer to equilibrium values implies partial overprinting of potential source signature, most likely due to reductive dissolution and release of P and followed by partial biological cycling before re-sorption/re-precipitation with newly formed ferric Fe minerals. Oxic/anoxic oscillation and dissolution/re-precipitation reactions and expected isotope excursion are corroborated by sediment chemistry and Mössbauer spectroscopic results. These findings provide improved insights for better understanding the origin and biogeochemical cycling of P associated with eutrophication in shallow freshwater lakes. Unlabelled Image • Sediment P pools provide information on the size of labile P and recalcitrant P sinks. • δ18O P values can differentiate sources and pathways of formation of P pools. • Isotopes of Al bound P is a better recorder of terrestrial P sources than Fe-bound P pool. [ABSTRACT FROM AUTHOR]

Abstract The mixed cation diphosphate of composition NH 4 FeP 2 O 7 has been prepared by heating of adequate mixtures of NH 4 (H 2 PO 4) and Fe(NO 3) 3 ⋅9H 2 O in concentrated phosphoric acid, and characterized by X-ray powder diffractometry. Its infrared and Raman spectra were recorded and briefly analyzed on the basis of the structural peculiarities of the P 2 O 7 4− anion and the NH 4 + cation, which is demonstrated, do not rotate freely in the lattice. Its 57Fe- Mössbauer spectrum shows that the typical high-spin FeIIIO 6 octahedra present in the compound exhibit almost no distortion. Graphical abstract Image 109559 Highlights • NH4FeP2O7 was prepared by heating of NH4(H2PO4)/Fe(NO3)3⋅9H2O mixtures in 85% H3PO4. • FTIR and Raman spectra were analyzed on the basis of its structural peculiarities. • It is demonstrated that the NH4+ cation does not rotate freely in the lattice. • Mössbauer spectra show that the FeIIIO6 octahedra are very little distorted. [ABSTRACT FROM AUTHOR]

• Under the current density of 50 mA g−1, the highest SIB performances with the large discharge capacities of 153 and 137 mAh g−1 were achieved by heat-treated 20ZFV and 0ZCFV. • The heat-treated 20ZFV and 0ZCFV have a high electrical conductivity of 1.8 × 10−2 and 6.7 × 10−1 S cm−1 due to electron hopping. • The stability of crystalline phases precipitated due to the heat treatment of 20ZFV and 0ZCFV glass is essential for applying them as a cathode active material of SIB. Glass-ceramics x ZrO 2 •10Fe 2 O 3 •(90- x)V 2 O 5 with ' x ' between 0 and 30 mol% and y ZrO 2 ･(20- y)CaO･10Fe 2 O 3 ･70 V 2 O 5 glass with ' y ' between 0 and 20 mol%, respectively abbreviated as x ZFV and y ZCFV, before and after heat treatment at 500 °C for 100 min, were evaluated as potential cathode-active materials for sodium-ion batteries (SIBs). Relationships between physical properties and local structure of x ZFV and y ZCFV glass-ceramics were investigated by 57Fe-Mössbauer spectroscopy, V K -edge X-ray absorption near edge structure (XANES), X-ray diffractometry (XRD), DC four-probe method and differential thermal analysis (DTA). SIBs containing heat-treated x ZFV glass-ceramics showed the highest discharge capacity of 153 mA h g−1 under a current density of 50 mA•g−1, which exhibited a high electrical conductivity of 1.8 × 10−2 Scm−1. Precipitation of V 0.05 Zr 0.95 O 2 and Fe 2 V 4 O 13 nanoparticles were confirmed from the XRD pattern of the heat-treated 20ZFV glass, consistent with the lower energy of the pre-edge peak at 5467 eV in the V K -edge XANES spectrum. This result is associated with the reduction of vanadium ions from VV to VIV. It is concluded that the precipitation of stable vanadium bronze phases with high electrical conductivity and structural stability effectively enable the high SIB capacity of these materials. [ABSTRACT FROM AUTHOR]

A relationship between local structure, thermal endurance, chemical durability and electrical conductivity of alkaline iron tungsten vanadate glass, 20R2O•10Fe2O3•xWO3•(70− x)V2O5, R=Na and K, x =0–50mol.%, abbreviated as RFWV was investigated by 57Fe-Mössbauer spectroscopy, X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), differential thermal analysis (DTA), leaching test using 20vol.% HCl and dc-probe method. Mössbauer spectra of 20Na2O•10Fe2O3•xWO3•(70− x)V2O5 glass (NFWV) consisted of one paramagnetic doublet with a stable isomer shift (δ) of 0.40mms−1 and an increasing quadrupole splitting (Δ) from 0.68 to 0.82mms−1 with the increase of “x” from 0 to 50mol.%, indicating that local distortion of FeIIIO4 tetrahedra increased with WO3 content. After isothermal annealing at 500°C for 100min, Δ decreased to 0.62, 0.59, 0.67 and 0.67mms−1 for NFWV glass with “x” of 0, 10, 20 and 30, showing that local distortion of FeIIIO4 tetrahedra was reduced due to the structural relaxation. Original NFWV glass exhibited a slightly decreasing electrical conductivity (σ) from 2.9×10−6 to 5.5×10−8 Scm−1 with the increase of “x” from 0 to 50. The isothermal annealing of NFWV glass caused a remarkable increase in σ of 4.5×10−3, 6.2×10−4 and 9.8×10−4 Scm−1 with “x” of 0, 10 and 20, all of which showed a small activation energy for electron hopping (W H) of 0.21, 0.20 and 0.15eV, respectively. On the other hand, increases in glass transition temperature (T g), crystallization temperature (T c) and activation energy for crystallization (E a) were observed for NFWV glass with WO3 content, proving that the tungsten ion contributes to enhancement of chemical bond strength of NFWV glass. Similar results of an increase in σ and a decrease in dissolution rate due to annealing were observed for KFWV glass. It is concluded that structure, physical and chemical properties of RFWV glass can be controlled by introduction of WO3. [ABSTRACT FROM AUTHOR]

Abstract: Two partly new [Fe(intz)6](BF4)2 complexes with n =3 and 4 (i3tz =1-isopropyl-1H-tetrazole, i4tz =1-isobutyl-1H-tetrazole) were synthesized and characterised by X-ray powder diffraction, magnetic susceptibility measurements, vibrational, electronic and 57Fe–Mößbauer spectroscopy as well as DSC. The [Fe(i3tz)6](BF4)2 complex was re-investigated and shows an incomplete spin transition at T c ∼109K, while the [Fe(i4tz)6](BF4)2 features a complete but rather gradual spin transition with T ½ =223K. In the lack of suitable crystals of [Fe(intz)6](BF4)2 with n =3 and 4, we synthesized crystals of [Ni(intz)6](BF4)2 with n =3 and 4, determined their X-ray crystal structures, and proved them to be homeotypic with the respective Fe-complexes by X-ray powder diffraction. DSC measurements showed an endothermic peak for the [Fe(i3tz)6](BF4)2 around T =260K not corresponding to a spin transition and suggesting a structural phase transition at this temperature. A well-developed peak at T p =225K matches the spin-transition temperature T ½ =223K for [Fe(i4tz)6](BF4)2. [Copyright &y& Elsevier]

Local structure and thermal durability of semiconducting xBaO·(90 − x)V2O5 · 10Fe2O3 glasses ( x = 20, 30 and 40), NTA glass TM, before and after isothermal annealing were investigated by 57Fe-Mössbauer spectroscopy and differential thermal analysis (DTA). An identical isomer shift ( $\mathit{\delta}$ ) of 0.39 ± 0.01 mm s − 1 and a systematic increase in the quadrupole splitting ( Δ) were observed from 0.70 ± 0.02 to 0.80 ± 0.02 mm s − 1 with an increasing BaO content, showing an increase in the local distortion of FeIIIO4 tetrahedra. From the slope of the straight line in the T g– Δ plot of NTA glass TM, it proved that FeIII plays a role of network former. Large Debye temperature ( Θ D) values of 1000 and 486 K were respectively obtained for 20BaO · 70V2O5 · 10Fe2O3 glass before and after isothermal annealing at 400°C for 60 min, respectively. This result also suggests that FeIII atoms constitute the glass network composed of tetrahedral FeO4, tetrahedral VO4 and pyramidal VO5 units. The electric conductivity of 20BaO · 70V2O5 · 10Fe2O3 glass increased from 1.6 × 10 − 5 to 5.8 × 10 − 2 S cm − 1 after isothermal annealing at 450°C for 2,000 min. These results suggest that the drastic increase in the electric conductivity caused by heat treatment is closely related to the structural relaxation of the glass network structure. [ABSTRACT FROM AUTHOR]

Samarium–iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th2Zn17-type and a TbCu7-type structure, respectively. Structure comparison between these types was investigated for Sm–Fe intermetallic compounds and their nitrides by 57Fe-Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

The most commonly used route in the hydrometallurgical extraction of zinc and copper from a sulphide ore is the concentrate–roast–leach–electro winning process. In the present investigation a zinc–copper ore from the Maranda mine, located in the Murchison Greenstone Belt, South Africa, containing sphalerite (ZnS) and chalcopyrite (CuFeS2), was studied. The 57Fe-Mössbauer spectrum of the concentrate yielded pyrite, chalcopyrite and clinochlore, consistent with XRD data. Optimal roasting conditions were found to be 900°C for 3 h and the calcine produced contained according to X-ray diffractometry equal amounts of franklinite (ZnFe2O4) and zinc oxide (ZnO) and half the amount of willemite (Zn2SiO4). The Mössbauer spectrum showed predominantly franklinite (59%), hematite (6%) and other Zn- or Cu-depleted ferrites (35%). The latter could not be detected by XRD analyses as peak overlapping with other species occurred. Leaching was done with HCl, H2SO4 and HNO3, to determine which process would result in maximum recovery of Zn and Cu. More than 80% of both were recovered by using either one of the three techniques. From the residue of the leaching, the Fe-compounds were precipitated and <1% of the Zn and Cu was not recovered. [ABSTRACT FROM AUTHOR]

• Electrically conductive sodium phospho-vanadate glass (x NPV) was successfully introduced into a cathode active material of a Na-ion battery. • The highest performances of the discharge capacities were recorded at 184 and 173 mAh g −1 for the Na-ion battery including 25NVP before and after heat-treatment as the cathode, respectively. • An isothermal heat-treatment of the studied glass caused the reductions of local distortion in the NWF sites and the oxidation number in vanadium ions which were respectively observed from the 57Fe-Mössbauer and XANES spectra. A relationship between local structure and electrical property of x Na 2 O·10P 2 O 5 ·(90− x)V 2 O 5 glass (x = 5, 25 and 45 mol%, abbreviated as x NPV) was investigated by means of 57Fe-Mössbauer spectroscopy(FeMS), X-ray absorption fine structure (XAFS), X-ray diffractometry (XRD), impedance spectroscopy (IS), and cathode active performance test of Na-ion battery (SIB). XAFS of x NPV glasses showed that the oxidation number of the vanadium in x NPV glasses was reduced after the heat treatment. FeMS of x Na 2 O·10P 2 O 5 ·(89− x)V 2 O 5 ·57Fe 2 O 3 glass showed a decrease in the isomer shift and quadrupole splitting with an increase of Na 2 O content. DC conductivity was decreased with increasing Na 2 O content and the glass samples exhibit electronic conduction which is explained by the polaronic conduction mechanism. The charge-discharge capacity of x NPV glasses showed a larger initial capacity than that of heat-treated samples. A large initial capacity of 184 mAh g −1 was recorded for 25NPV glass, suggesting that the sodium phospho-vanadate glass can be used as a good cathode of SIB. [ABSTRACT FROM AUTHOR]

Members of the lazulite–scorzalite (MgAl2- (PO4)2(OH)2-FeAl2(PO4)2(OH)2) solid-solution series were synthesized in compositional steps of 12.5 mol% at T = 485 °C and P = 0.3 GPa under hydrothermal conditions and controlled oxygen fugacities of the Ni/NiO-buffer. X-ray powder diffraction and 57Fe-Mössbauer studies show that under these conditions a complete solid-solution series is formed which is characterized by the substitution of Mg2+ and Fe2+ on the octahedral Me2+ site. The 57Fe-Mössbauer spectra which reveal the presence of both ferrous and ferric iron and the compositional data were interpreted in terms of a defect model with a distribution of the ferric ions over both the Me2+ and the Al3+ positions and vacancies on the Me2+ site. The 57Fe-Mössbauer parameters of the synthetic compounds correspond to those of natural lazulites except for the total absorption ratio of the ferric iron A(Fe3+)/(A(Fe3+)+A(Fe2+)), which is significantly higher in natural lazulites of the same composition. The total absorption ratio of the ferric iron increases from 4% in pure scorzalite to 15% in a Mg-rich solid-solution with xFe = 12(1)% [ABSTRACT FROM AUTHOR]

57Fe -Mössbauer spectra of eleven Fe-Mg-bearing staurolite samples, synthesized at 5, 20 and 25 kbar and 680°C, ranging in composition from xFe =1.00 to xFe =0.15, and of two Zn-Fe-bearing staurolite samples, synthesized at 20 kbar and 700°C with xFe =0.10 and xFe =0.32 were collected at room temperature. The spectra reveal that about 80% of Fetot (in case of Fe-Mg-bearing staurolite) and about 70% of Fetot (in case of Fe-Zn-bearing staurolite) are located as Fe2+ at the three subsites Fe1, Fe2 and Fe3 of the tetrahedral T2-site. The refinement of the spectra results in almost identical values for the isomer shift (IS) (±1.0 mm/s) but significantly different values for the quadropole splitting (QS) for the three subsites which is in accordance with the different distortions of these sites. About 8% of Fetot (in case of Fe-Mg-bearing staurolite) and 13% of Fetot (in case of Fe-Zn-bearing staurolite) are located as Fe2+ at the octahedral M4 site, while the remainder percents of Fetot indistinguishably occur as Fe2+ at the octahedral M1 and M2 sites of the kyanite-like part of the structure. Within the whole Fe-Mg-staurolite solid solution series the Mössbauer parameters QS of the sites M4 and (M1, M2) vary systematically with composition whereas IS remains constant. There is a high negative correlation of the total Mg-content with Fe-occupation of all the Fe-bearing sites indicating a continuous substitution of Fe2+ by Mg on all these sites. Synthetic Fe-staurolites show no increasing occupation of the octahedral sites by two-valent cations with pressure, as was assumed by several authors. [ABSTRACT FROM AUTHOR]

Glass samples with composition x Fe 2 O 3 ・ y Al 2 O 3 ・(100- x - y)SiO 2 abbreviated as x F y AS for photo-Fenton catalyst were prepared by a sol-gel method and heat-treated at 1000 °C for 100 min. It was found that when alumina was added to the Fe 2 O 3 + SiO 2 glass matrix, the photo-Fenton activity tested with methylene blue degradation increased, so did the photoactivity with visible light. From Mössbauer and XRD results, it was noticed that hercynite phase appeared that showed higher photoactivity even for the samples having lower hematite content and that the Fe+3 (T d) content increased with Al 2 O 3 content. In these samples, the more Fe+3 (T d) found, the more effective was the photo-Fenton degradation. • Sol-gel synthesized and heated 30F y AS, 40F y AS and 50F y AS samples with ' y ' of 10, 15, and 20 resulted in the precipitation of hematite and hercynite (FeAl 2 O 4) with photocatalytic properties. • As for the photo-Fenton degradation ability by adding H 2 O 2 , the best sample was 40F20AS yielding the highest first-order rate constant of 8.61 × 10−2 min−1. • These results indicate that Fe3+ ions also show photo-Fenton catalytic abilities and light-scattering ability caused by the introduction of Al 2 O 3 is effective for the visible light photocatalytic activity. [ABSTRACT FROM AUTHOR]

Potential release of phosphorus (P) bound to iron (Fe) is critical because of the aggravating effects on P load in aquatic ecosystems. However, the process is largely unknown due to the absence of in-situ high-resolution evidence. Dissolved oxygen (DO), ferrous ion (Fe2+), and dissolved reactive phosphate (DRP) in interstitial water of sediment columns from a eutrophic shallow lake were measured using the novel colorimetric planar optode imaging method and ZrO-Chelex DGT technology during controlled experimental episodes. The solid Fe and P fractions in sediments were also simultaneously evaluated by employing sequential extraction procedure and spectra scanning analysis including SEM-EDS and 57Fe-Mössbauer spectroscopy. The results demonstrated that the DO penetration depths were accordingly regulated with time, the depths depended on the oxygen supply patterns, and oxygen depletion occurred at anaerobic intervals. Considerable increases of concentrations and diffusion of Fe2+ and DRP in interstitial water upward from the deep layer into the overlying water were mirrored by decreased concentrations of solid Fe bound P and mineral phase Fe(II) during an anaerobic episode. This confirmed that the re-dissolution of solid Fe bound P pools is the most important source of labile P, and aggravates the P budget in lake water via anaerobic intervals. The reduction-precipitation mechanism of Fe bound P during different oxidation scenarios indicated that the Fe bound P in sediments can act as intermediates between Po and Ca bound P, and result in the permanent burying of authigenic Ca bound P. Significantly positive correlations (R2 ≥ 0.7783, n = 74) between labile Fe2+ and DRP on both redox conditions also provided explicit evidence for the critical role of redox controlling Fe in labile P cycling at the lacustrine sediment-water interface. These findings provide improved insight for potential controlling effort of Fe coupled P to labile P depending on the oxygen supply in shallow-water hypereutrophic lakes. Unlabelled Image • Oxygen penetration depth vibrations for different redox conditions were visually explored. • Solid P pools of the sediment significantly varied with the redox conditions. • Diffusion of PO 4 3− and Fe2+ into water during hypoxia was observed with high resolution. • Increased solid ferrous iron minerals during hypoxia showed potential for solid P release. • Fe bound P concentration potentially controls the labile P load in shallow eutrophic lakes. [ABSTRACT FROM AUTHOR]