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A highly efficient photo-Fenton catalyst iron silicate glass was successfully prepared by a simple sol–gel method. The characterization results (XRD, Mössbauer spectroscopy, TEM, and FT- IR) showed that fayalite, clinoferrosilite and hematite nanoparticles were precipitated in the glass system. The catalytic activity of the glass samples was evaluated by measuring the degradation efficiency for organic dyes as well as for a typical persistent organic pollutant phenol, under visible light irradiation, in the presence of hydrogen peroxide (H2O2). The chemical oxygen demand (COD) and total organic carbon (TOC) were measured to see the progress in degradation of phenol. The results showed that the catalyst containing 20% iron had good catalytic properties for the degradation of both types of organic contaminants with superior stability for the degradation of methylene blue dye even after six cycles. Finally, a possible photocatalytic mechanism was proposed.

Chemical stability and good biocompatibility under physiological conditions render nanoparticles made of the spinel oxide magnetite a favorable choice in biomedical diagnostic and therapeutic applications that benefit from high levels of magnetization and superparamagnetism. Under ambient atmosphere, however, magnetite nanoparticles are prone to undesired oxidation leading to an at least partially oxidized form of magnetite. In the present work Fe3-xO4 nanopowders (with a particle size of 10–50 nm) were prepared under different conditions via chemical co-precipitation method, resulting in samples with different oxidation levels. The effect of oxidation of the prepared samples on their morphological, structural, electronic and magnetic properties is followed, respectively, by the means of transmission electron microscopy (TEM), powder X-ray diffractometry (PXRD), 57Fe Mossbauer spectroscopy (MS) and electron magnetic resonance (EMR) spectroscopy measurements. A novel method is applied to decompose the heavily broadened room-temperature 57Fe Mossbauer spectra of the nanoparticles into signals of intermediate valence Fe2.5+ and that of Fe3+ iron species. The results indicate that the cubic lattice parameter of non-stoichiometric magnetite nanoparticles depends on the concentration as well as on the mean oxidation level of the intermediate valence iron species. At the same time, EMR spectra of the samples indicate that oxidation influences the magnetic anisotropy of the nanoparticles, with the magnitude of the nanoparticles' magnetic anisotropy field being correlated with the concentration of the intermediate valence iron species. Malic acid, used as coating agent for several of the samples, is shown to hinder the oxidation of magnetite nanoparticles.

The glass samples with the composition of 40Fe2O3-xAl2O3-(60−x)SiO2 were prepared by sol-gel method. The samples were characterized by XRD, 80 K 57Fe Mossbauer spectroscopy, TEM, FTIR and impedance spectroscopy. In the glass samples with less than 10% alumina, fayalite and hematite were crystallized by addition of hercynite. Whereas nanoparticles of hematite (α-Fe2O3) and maghemite (γ-Fe2O3) doped with Al were confirmed with the increase of alumina contents (15% and 20%). The glass samples exhibit the electronic conduction which is explained by the polaronic conduction mechanism. It is noticed that the catalysts containing a mixture of hematite and maghemite nanoparticles showed higher photocatalytic degradation of Rhodamine B dye than those containing hematite alone. It is suggested from the characterizations of newly developed iron-containing aluminosilicate glass samples that the materials with several bandgaps and without dissolving itself should be developed in the future for water purification under visible light irradiation.

Comparison of the Mossbauer spectra of the as-prepared native iron oxide nanoparticles (IONs) and the citrate-functionalized IONs demonstrates differences in the spectral shapes at room temperature and variations of the 57Fe hyperfine parameters at 80 K. The observed differences are claimed to result from capping the IONs with citrate, thus decreasing the particle-particle interaction while promoting interaction of the outer atomic layers of the IONs with the surface molecular coating.

Nanoparticles of e-Fe2O3 in an amorphous silica matrix were prepared by the sol–gel method without using a precursor. X-ray diffraction patterns reflect a completely amorphous state for the samples even after heat-treated up to 600 °C, while at higher temperatures the formation of crystalline iron oxide phases was observed. Transmission electron microscopy analysis showed a wide size distribution of nanoparticles from 3±0.5 to 46±0.8 nm. The occurrence of e-Fe2O3 particles depends on several factors like annealing temperature, particle size and iron concentration in initial chemicals. Based on the 57Fe Mossbauer spectra, three octahedral and one tetrahedral iron site were identified for e-phase. The optimized conditions for the preparation of e-Fe2O3 rich sample were confirmed and ~ 90% of the e-Fe2O3 phase was obtained with the particle size of 15±0.6 nm. The high coercivity of ~ 1.18 T at room temperature was confirmed for our nanoparticle system.

The research investigated three iron carbonate (siderite) sedimentary concretions from Nagykovacsi, Uri and Delegyhaza, Hungary. To identify possible source rocks and effects of the glaze-like exposed surface of the concretions, we carried on comparative petrological, mineralogical, geochemical and isotopic studies. The samples were microbially mediated siderite concretions with embedded metamorphous and igneous mineral clasts, and had specific rim belts characterized by semi-concentric outer Fe-oxide layers, fluffy pyrite-rich outer belts and siderite inner parts. We investigated the cross section of the Fe-carbonate concretions by independent methodologies in order to identify their rim effects. Their surficial oxide layers showed evidence of degassing of the exposed surface caused most probably by elevated temperatures. The inner rim pyrite belt in the concretions excluded the possibility of a prolonged wet surface environment. Microtextural and mineralogical features did not support desert varnish formation. 10Be nuclide values of the Nagykovacsi and Uri concretions were far above the level of terrestrial in-situ cosmogenic nuclides, but they were consistent with the lowest levels for meteorites. Though the data were not conclusive to confirm any kind of known origin, they are contradictary, and open possibilities for a scenario of terrestrial meteorite origin.

The interaction between Lanthanides (Ln) - ions and Ca-bentonite and the structural changes accompanying were studied. Ln -exchanged bentonites were prepared from Ca-bentonite (Istenmezeje, Hungary) by ion exchange in three consecutive washings with lanthanide solutions. Scanning Eletronmicroscopy Energy Dispersive X-ray spectroscopy (SEM-EDX) studies showed even distribution of Ln s and other components of bentonite. The natural bentonite and the lanthnide exchanged bentonites were characterized by X-ray diffraction (XRD), which revealed the same mineral composition, and the increase of the basal spacing of montmorillonite from 1.465 (Ca 2+ ) to 1.577 nm (REE 3+ ). The d 001 basal spacing of lanthanide montmorillonite increases as the ion radius of the lanthanide cation increases. The Fe 3+ , and Ln s 3+ amount on the bentonite were determined by X-ray-fluorescence spectrometry (XRF) elemental analysis. The amount of exchanged Ln s were determined by washing the Ln -bentonite with 1 M ammonium-acetate, and measuring the amount of Ln released, using inductively coupled plasma optical emission spectrometry (ICP-OES). In most Ln -bentonites, the quantity of the exchanged Ln ions was about 80–90% of the cation exchange capacity (CEC) of the bentonite. In case of some lanthanides bentonite (La 3+ , Ce 3+ , and Gd 3+ ), however, the sorbed quantity of lanthanum ions was higher than the cation exchange capacity. In case of lanthanum-bentonite, the lanthanide quantity is as high as 136% of CEC. Moreover, the iron(III) content of lanthanum bentonite is less than that of the original Ca-bentonite. Mossbauer spectra of the La-, Ce-, and Gd-exchanged samples at 78 K revealed an unexpected magnetically split component that was absent from the Ca-bentonite. This component may belong to interlayer Fe. This iron can be released from the octahedral positions crystal lattice.

The effect of coating with nine different carboxylic acids (glycolic, propionic, lactic, malic, tartaric, citric, mandelic, caproic and caprylic) on nanostructured magnetite (D ~ 10 nm) was studied by Raman and photoacoustic, magnetic and 57Fe Mossbauer measurements. Mossbauer spectra of frozen suspensions showed dominantly magnetically split envelopes at lower temperatures, which were evaluated by hyperfine field distribution method. Mossbauer and Raman spectroscopy indicated similar variation of relative occurrence of magnetite and maghemite phases. These results are discussed on the basis of the hypothesis that different carboxylic acids can promote either the oxidation or reduction of iron oxide nanoparticles.

Microbial cells are well known to be capable of remaining viable when desiccated, and a variety of beneficial microorganisms can thus be preserved for storage. For the ubiquitous widely studied soil bacterium Azospirillum brasilense (wild-type strain Sp7), which has a significant agrobiotechnological potential owing to its plant-growth-promoting capabilities perspective for its use in biofertilisers, Fourier transform infrared (FTIR) spectroscopy (in the diffuse reflectance mode, DRIFT) was used to control the state of biomass, together with 57Fe transmission Mossbauer spectroscopy to monitor intracellular iron speciation in live rapidly frozen cell suspension and in the lyophilised biomass (both measured at T = 80 K). It has been shown for the first time that a relatively large part of ferrous iron in live cells (22% of the whole cellular iron pool, represented by two high-spin Fe(II) forms, in the 18-h culture grown on 57Fe(III) complex with nitrilotriacetic acid as the sole source of iron) gets largely oxidised upon lyophilisation. The remaining part of iron(II) in the resulting dry biomass was found to be ca. 3% only. The major part of ferric iron in the dry biomass was shown to be comprised of ferritin-like ferric species (giving a typical magnetically split sextet at T = 5 K), while the iron(III) formed from cellular iron(II) by oxidation in air in the course of drying remained in a paramagnetic state even at T = 5 K. The possibility of intracellular iron(II) oxidation to iron(III) upon desiccation may be a specific natural strategy to avoid cell damage caused by Fenton-type reactions in dormant (frozen, dried) cells. The results obtained may have important implications related to iron speciation and redox transformations in dried bacterial preparations intended for long-term storage.

Radioactive liquid wastes containing large amounts of nitric acid (approx. 4–7 M) generated in the nuclear fuel cycle are very undesirable by-products. Denitration of highly acidic radioactive liquid wastes with organic reducing agents has sev - eral advantages, such as a significant pH increase, possibility of separation of radioisotopes which can be utilized in other technologies, reduction of volatility of radioisotopes and fixation of certain mono- and divalent radioisotopes with zeolite. In the present work some aspects of denitration of simulated radioactive liquid wastes at laboratory level were investigated. Denitration of HNO 3 with formic acid was investigated for different [HCOOH]/[HNO 3 ] ratios. The changes in the induction time, pH increase and volume reduction were determined. It was shown that by the denitration of simulated radioactive liquid waste high pH values could be achieved which in real systems would create more possibilities in radioactive waste manage- ment. Analysis of solid phases formed after the oxidation of excess HCOOH with H 2 O 2 showed the presence of amorphous fraction as well as goethite and hematite phases, which could remove different radioactive cations from the liquid phase. The immobilization of simulated solid radioactive waste with borosilicate glass matrix was also shown.

Magnetic interaction of the magnetite (Fe3O4) nanoparticles grown on zeolite has been studied. XRD patterns show that in the presence of 25–75 mg of zeolite the average particle size of Fe3O4 decreases to ≈6 nm, but with the increase of zeolite content (75 mg

Iron sulfide (troilite) inclusion extracted from Sikhote-Alin IIAB iron meteorite was examined for its composition, structure and magnetic properties by means of several complementary analytical techniques such as: powder X-ray diffractometry, scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, magnetization measurements, ferromagnetic resonance spectroscopy and 57 Fe Mossbauer spectroscopy with a high velocity resolution. The applied techniques consistently indicated the presence of daubreelite (FeCr 2 S 4 ) as a minority phase beside troilite proper (FeS). As revealed by 57 Fe Mossbauer spectroscopy, the Fe atoms in troilite were in different microenvironments associated with either the ideal FeS structure or that of a slightly iron deficient Fe 1– x S. Phase transitions of troilite were detected above room temperature by ferromagnetic resonance spectroscopy. A novel analysis of 295 and 90 K 57 Fe Mossbauer spectra was carried out and the hyperfine parameters associated with the ideal structure of troilite were determined by considering the orientation of the hyperfine magnetic field in the eigensystem of the electric field gradient at the 57 Fe nucleus.

Iron-oxide nanoparticles were prepared by chemical coprecipitation method in inert gas atmosphere and also in air atmosphere in order to use them as possible nutrition source for plants. The samples were characterized by 57Fe Mossbauer spectroscopy, electron ¨ microscopy and PXRD measurements. The presence of considerable FeII contributions were indicated by 57Fe Mossbauer spectra. Furthermore TEM and XRD reflected nanomagnetite ¨ in washed and lyophilized samples prepared in inert gas atmosphere while the samples prepared in air atmosphere contained much higher amount of FeIII than characteristic of magnetite. In the case of samples prepared in inert gas, it was also shown that the immediate washing after the coprecipitation has a crucial influence on the FeII content of the nanomagnetites.

57Fe Mossbauer spectroscopy, XRD, and TEM were used to investigate the effect of mandelic- and salicylic acid coatings on the iron oxide nanoparticles. These two carboxylic acids have similar molecules size and stoichiometry, but different structure and acidity. Significant differences were observed between the Mossbauer spectra of samples coated with mandelic acid and salicylic acid. These results indicate that the occurrence of iron microenvironments in the mandelic- and salicylic acid-coated iron oxide nanoparticles is different. The results can be interpreted in terms of the influence of the acidity of carboxylic acids on the formation, core/shell structure, and oxidation of coated iron oxide nanocomposites.

A relationship between structure and visible light-activated photocatalytic activity of iron-containing soda lime aluminosilicate (15Na2O⋅15CaO⋅40Fe2O3⋅xAl2O3⋅(30−x)SiO2) glass (xNCFAS) was investigated by means of 57Fe-Mossbauer spectroscopy, X-ray diffractometry (XRD) and UV–visible light absorption spectroscopy (UV–VIS). The 57Fe-Mossbauer spectrum of 11NCFAS glass measured after heat-treatment at 1000 °C for 100 min was composed of a paramagnetic doublet due to FeIII(Td) and two magnetic sextets due to regular hematite (α-Fe2O3) and hematite with larger internal magnetic field. X-ray diffraction patterns of heat-treated xNCFAS samples resulted in decrease of α-Fe2O3 and increase of Ca2Fe22O33 or CaFe2O4 with alumina content. A quick decrease in methylene blue (MB) concentration from 15.6 to 4.7 μmol L−1 was observed in the photocatalytic reaction test with 40 mg of heat-treated 11NCFAS glass under visible light-exposure. The largest first-order rate constant of MB decomposition (k) was estimated to be 9.26 × 10−3 min−1. Tauc’s plot yielded a band gap energy (Eg) of 1.88 eV for heat-treated 11NCFAS glass, which is smaller than previously reported Eg of 2.2 eV for α-Fe2O3. These results prove that addition of Al2O3 into iron-containing soda lime silicate glass is favorable for the preparation of improved visible light-photocatalyst with ‘ubiquitous’ elements.

Frozen aqueous solution of hyperalkaline tin(II)-hydroxide was analysed by 119Sn Mossbauer spectroscopy at low temperature in order to determinate the structure of the hydroxo complex formed under hyperalkaline (pH > 13) conditions. Interestingly, the quadrupole doublet characteristic of this complex in the 119Sn Mossbauer spectrum exhibited asymmetry in the line intensities. Analysis of the temperature dependence of the Mossbauer spectra demonstrated that this phenomenon can be rationalised by the Goldanskii–Karyagin effect. The effect emerges due to the vibrational anisotropy of bonds in the tin complex formed in hyperalkaline solution, similarly to what has been found earlier for SnF2 with analogous Sn bond structure.

A new method is developed to synthesize magnetic carbon microspheres decorated with carbon nanofibers and iron nanoparticles (nanofurry microspheres) for separation techniques in chemistry and biology. Microspheres are synthesized by carbonizing polystyrene–divinylbenzene-based, iron-loaded ion exchange resins. The phase composition, magnetic properties, and surface area and morphology of these materials are characterized by various techniques. It is detected that superparamagnetic (SPM) magnetite is present in microspheres exclusively upon carbonization at 400–500 °C, elemental iron, both α- and γ-Fe, is the major component at 600 °C, and cementite dominates between 700 and 1000 °C. Nanofiber formation is observed to be pronounced at high temperatures. The synthesized carbon microspheres have high surface area (100–300 m2 g−1) and can be separated easily by a magnet or by filtration. Saturation magnetization of selected samples is obtained between 5 and 28 emu g−1, depending on the phase composition. The novel microcomposites are expected to be effective adsorbents or support materials in various chemical processes, for example in water and air cleaning, catalysis, and biotechnological separations. Preliminary experimental studies for Cr(VI) removal from water and for platinum deposition are provided.

In spite of numerous investigations on the various processes of the thermal decomposition and rehydration of layered double hydroxides (LDHs) by a variety sophisticated experimental means, many details are still unexplored and some contradictions are still unresolved. In this work, our efforts were focussed on clarifying the composition, structure and properties of thermally decomposed metaphases originating from CaFe–LDH, heat treated in the 373–973 K temperature range. The structure reconstruction ability of mixed metal oxide phases obtained after heat treatments was also investigated, mainly concentrating on the changes in the microenvironment of Fe(III), in the presence of controlled amount of water vapour (i.e., at different relative humidities). All samples were characterised by X-ray diffractometry, and the iron-containing phases were studied by 57 Fe Mossbauer spectroscopy.

A series of novel [Fe(MeiPrGlyoxH)2(amine)2] complexes have been synthesized [(MeiPrGlyoxH2 = methylisopropylglyoxime, amine = 3,5-dimethylpyridine, 4-(dimethylamino)pyridine, 4-(phenylamino)phenol, 2-imidazolidone)] and characterized by 57Fe Mossbauer, FTIR, UV–Vis spectroscopy, mass spectrometry, AFM and thermoanalytical methods. Quantum chemical (DFT) computations of [Fe(MeiPrGlyoxH)2(3,5-dimethyl-Py)2] (Py = pyridine) complex were also performed. The square-planar structure of [Fe(MeiPrGlyoxH)2] moiety is similar to that of [Fe(MeEtGlyoxH)2]. The incorporation of branching alkyl chains (isopropyl) in the complexes alters the Fe–N bond length and results in high-spin iron(II) state.

The identity of the predominating tin(II)-hydroxide complex formed in hyper-alkaline aqueous solutions (0.2

The effects of firing conditions on the microstructure and physical properties of clay roofing tiles are studied. This research presents the effects of oxidizing and reducing atmosphere on Kanjiža clay material with carbonate content up to 22% by weight and the characterization of the final products. The firing was done both in the laboratory and under industrial conditions. The Fe2+/Fetotal ratio played a decisive role in the sintering process under a reducing atmosphere. The formed glassy phase, with the presence of Fe2+, attacked the earth-alkali oxides after the carbonate decomposition and more effectively filled smaller pores. The obtained results justified the benefits of the reducing firing atmosphere with 5% CO, lower porosity, higher frost resistance values, and changed microstructural characteristics

N-containing fully saturated (L-prolinate) or aromatic (indole-2-carboxylate) heterocyclic anions were immobilised in CaFe-layered double hydroxide with the dehydration-rehydration method from aqueous ethanol or acetone. The structure of the resulting organic-inorganic hybrids was characterised mainly with powder X-ray diffraction and 57Fe Mossbauer spectroscopy, and as supplementary analysis scanning electron microscopy, energy dispersive X-ray spectroscopy with elemental mapping and molecular modelling were also applied. It was found that the solvent mixture used for the synthesis caused enormous difference in the interlayer spacings of the obtained inorganic-organic hybrids.

Aluminium alloy free CS1 type steel (0.06 wt% C, 0.45 wt% Mn) and samples of cold roll bonded steel bimetal alloys (MAS15 and MAS16) were fabricated and investigated by X-ray diffraction (XRD), 57Fe conversion electron Mossbauer spectroscopy (CEMS) at room temperature. XRD has revealed only the existence of the alpha iron solid solution (steel) phase in the steel only sample, while identified steel and metallic Al and Sn constituent phases in the bimetallic alloys. 57Fe Mossbauer spectroscopy revealed the presence of 4 % secondary iron-bearing phase attributed mainly to iron oxide/ oxyhydroxides (ferrihydrite) besides the steel matrix on the surface of the steel sample. A significant difference between the occurrences of the secondary phase of differently prepared bimetal alloys found in their 57Fe CEM spectra allowed to identify the main phase of debris as different iron oxide/ oxyhydroxides.

A relationship between waste-water cleaning ability and local structure of iron-containing soda-lime silicate glass, 15Na2O·15CaO·xFe2O3·(70-x)SiO2 (x = 10–50 in mass%), abbreviated as NCFSx glass, was investigated by means of 57Fe-Mossbauer spectroscopy, redox titration with KMnO4 for the determination of chemical oxygen demand (COD) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Mossbauer spectra of NCFSx glass with “x” of 10 and 30 were composed of two doublets: one due to FeIIIO4 tetrahedra (Td) with isomer shift (δ) of 0.23–0.26 mm s − 1 and quadrupole splitting (Δ) 1.01–1.04 mm s − 1, and the other due to FeIIO6 octahedra (Oh) with δ of 1.00–1.03 mm s − 1 and Δ of 2.03–2.05 mm s − 1. Absorption area for FeII(Td) was decreased from 9.7 to 6.5 and 0.0 % when “x” was increased from 10 to 30 and 50. A leaching test performed with 500 mL of artificial waste water and 2.0 g of NCFS50 revealed waste-water cleaning ability of soda-lime glass, e.g., COD was reduced from 280 to 55.2 mg L − 1 after 10 day-leaching. After 10 day-leaching, it proved that iron was dissolved into waste water to a level of 5.3\(_{7} \times 10^{-1}\) mg L − 1. These results prove that organic matter could be effectively decomposed with iron-containing soda-lime silicate glass.

Novel Sn–Ni–Fe ternary phases, which never occur in the metallurgical alloys, were successfully prepared by deposition from an electrolyte based on sodium gluconate, using DC electrodeposition conditions. 57 Fe and 119 Sn conversion electron Mossbauer spectroscopy and PXRD investigations of these alloys showed that they are amorphous and dominantly ferromagnetic. The occurrence of amorphous Sn–Fe–Ni ternary alloy phase in deposits was found to increase with the current density applied during the deposition. The co-deposition kinetics is mainly governed by the electrodeposition behavior of the tin–gluconate complex that forms in the electrolyte. The high cathodic polarization due to the tin–gluconate discharge causes an apparent mass transfer coupled co-deposition of iron. The nickel deposition rate is independent of the potential and of the partial current of the co-depositing species.

The thermal behavior of tin containing oxalate, EDTA, and inositol-hexaphosphate were investigated. The end products of synthesis were identified by Mossbauer-, XRD analyses, and FTIR studies. The thermal decompose of the samples was studied by DTA-TG analysis. The simultaneously obtained DTA and TG data makes it possible to follow the thermal decomposition of the investigated samples. The tin oxalate decomposed in the temperature range of 520–625 K through tin carbonate formation and finally yielded CO2 and SnO. The tin EDTA complex first lost its hydrate bound water till 520 K. The followed thermal events related to the pyrolysis of anhydrous salt. The intense exothermic process that exists in the temperature range of 820–915 K is due to the formation of SnO2. The tin sodium inositol-hexaposphate lost its hydrate bound water (~10%), up to 460 K. The following sharp exothermic process, in the temperature range of 680–750 K is due to the decomposition and parallel oxidation of organic part of the molecule. At the end of this process, a mixture of phosphorous pentaoxide, sodium carbonate, and tin dioxide is obtained.

The structures of tin(II)-oxalate, tin(IV)Na–EDTA and tin(IV)Na 8 -inositol hexaphosphate were investigated using XRD analysis. Samples were identified using the Mossbauer study, thermal analysis and FTIR spectrometry. The Mossbauer study determined two different oxidation states of tin atoms, and consequently two different tin surroundings in the end products. The tin oxalate was found to be orthorhombic with space group Pnma, a =9.2066(3) A, b =9.7590(1) A, c =13.1848(5) A, V =1184.62 A 3 and Z =8. SnNa–EDTA was found to be monoclinic with space group P2 1 /c 1 , a =10.7544(3) A, b =10.1455(3) A, c =16.5130(6) A, β =98.59(2)°, V =1781.50(4) A 3 and Z =4. Sn(C 6 H 6 Na 8 O 24 P 6 ) was found to be amorphous.

A systematic study on anti-corrosion and anti-fouling effect of hydrophobic Langmuir-Blodgett and self-assembled molecular layers deposited on metal surfaces, as well as anti-microbial adhesion properties of coatings with biocide is presented. Both types of efficiencies produced by LB films are enhanced by Fe 3+ ions built in the molecular film. The quaternary ammonium type biocide embedded into the cross-linked gelatin decreased significantly the microbial adhesion, the biofilm formation.

Double hydroxides of Ba(II) and Fe(III) were prepared by the co-precipitation method. Co-precipitation was facilitated by applying highly alkaline, carbonate free NaOH solutions with varying base concentrations (2-20 M). The substances, thus obtained, were characterised by thermal methods. XRD spectra of samples treated at various temperatures, Mossbauer and X-ray absorption spectroscopies. It was found that in extremely concentrated base solutions (>= 10 M) layered double hydroxides, most probably with intercalated OH ions, were formed, indeed, while at low base concentration the Fe(III) ions were precipitated as various oxyhydroxides and the Ba(II) ions remained dissolved. (C) 2009 Elsevier B.V. All rights reserved.

Surface modification with self-assembled alkyl-phosphonic acid layers is a powerful technique for corrosion protection of different metals. In the present study, passivated, native (covered with air-formed oxide) and metallic iron surfaces were used as substrates. The influence of the oxide on the phosphonate layer formation; the corrosion protective effect of the phosphonate layer and the structure of the modified surfaces were investigated. The layer formation process was monitored directly in the phosphonate-containing solution. It was found that the phosphonate layer formation process depends on the conditions applied during iron passivation, and the oxide layer has an important role in the stability of the protective layer, while the bare metallic iron surface is disadvantageous for phosphonate bonding. Conversion electron Mossbauer spectroscopy (CEMS) and X-ray photoelectron spectroscopy (XPS) proved the presence of phosphonate layer on the top of the passive iron surface, with the thickness around monolayer.

Tin(II/IV) phosphate was prepared by various synthetic methods. The different methods resulted in tin phosphate with different properties, i.e., different crystalline form and behaviour during thermal treatment. The prepared materials have 3 mol water of crystallisation, which they lose in different ways. Total mass loss was between 20 and 30%. This could be connected with water loss, going generally in two steps in parallel with endothermic processes. At the end of thermal treatment, tin pyrophosphate is obtained, irrespective of the method of preparation used.

Aerosol samples in PM 10–2.0 and PM 2.0 size fractions were collected on the platform of a metropolitan underground railway station in central Budapest. Individual aerosol particles were studied using atomic force microscopy, scanning electron microscopy and transmission electron microscopy with energy-dispersive X-ray spectrometry and electron diffraction. The bulk aerosol samples were investigated by 57 Fe Mossbauer spectroscopy, and they were subjected to chemical speciation analysis for Cr. The particles were classified into groups of iron oxides and iron, carbonates, silicates, quartz and carbonaceous debris. Electron micrographs showed that the Fe-rich particles in the PM 2.0 size fraction typically consisted of aggregates of nano-sized hematite crystals that were randomly oriented, had round shapes and diameters of 5–15 nm. In addition to hematite, a minor fraction of the iron oxide particles also contained magnetite. In addition, the PM 2.0 -fraction particles typically had a rugged surface with layered or granular morphologies. Mossbauer spectroscopy suggested that hematite was a major Fe-bearing species in the PM 10–2.0 size fraction; its mass contribution to the Fe was 36%. Further constituents (ferrite, carbides and FeOOH) were also identified. The water soluble amounts of Cr for the underground railway station and city center were similar. In the PM 10–2.0 size fraction, practically all dissolved Cr had an oxidation state of three, which corresponds to ambient conditions. In the PM 2.0 size fraction, however, approximately 7% of the dissolved Cr was present as Cr(VI), which was different from that for the urban aerosol. It is suggested that the increased adverse health effects of aerosol particles in metros with respect to ambient outdoor particles is linked to the differences in the oxidation states, surface properties or morphologies.

Intensive Zn–Pb–Cu mining took place for about 40 years in the Gyongyosoroszi–Matraszentimre region, Matra Mountains, Hungary. The last mine was closed in 1986 without remediation. In 2006, a large-scale project was launched for the complete remediation of the waste dumps (more than 20 sites) and for the proper sealing of the abandoned shafts and adits still releasing acid mine-drainage owing to the large amount of oxidizing pyrite in the walls. During the remediation, full profiles (up to 5–10 m) of old dumps were created, offering a unique opportunity for the systematic sampling of the products of mine-waste alterations. One of these accessible “natural laboratories”, recording 40 years of environmental mineral formation, is the Banyaberc waste dump. Its volume reached 26,000 m 3 , and its bulk pH was around 3.7. We carried out XRD, SEM–EDX and Mossbauer spectroscopic (room temperature, liquid nitrogen) analysis of the minerals present in the altering waste-dump material. Minerals found are pyrite, gypsum, jarosite, hydroniumjarosite, plumbojarosite, anglesite, quartz, the feldspars, goethite, hematite, pickeringite, alunogen, epsomite, hexahydrite, a smectite-group phase, galena, sphalerite, and trace calcite. Rhomboclase and copiapite were identified by XRD in only one

Diverse processes of microbial remote intercellular communication as well as the exchange of molecular signals between microbial cells and their host macroorganisms, involving specific low-molecular-mass diffusible substances (used as a ‘chemical language’), are at the peak of current research in biosciences. This fundamental interest is due to the unique possibility of controlling the microbial behaviour and metabolism by influencing merely their signalling pathways. On the other hand, abiotic impact of the environment (medium) on extracellular molecular signals is also of great importance, as any of their chemical interactions (e.g., complexation or oxidation) represent direct interferences in the process of ‘signal delivery’ through the medium. In this work, chemical interactions of microbial extracellular molecular signals (alkylresorcinols (AR), homoserine lactone (HL) – chemical analogues of microbial autoregulatory substances) with iron(III) were monitored using freeze-quench 57 Fe Mossbauer spectroscopy in moderately acidic aqueous solutions as well as in the dried solids obtained thereof. The conditions applied were designed to simulate possible processes occurring in soils, where ferric iron is commonly ubiquitous. Gradual reduction of iron(III) by AR was observed, coupled to oxidative degradation of the organics, in solution, while iron(II) also remained dominant upon drying, whereas for HL, some iron(II) was detected in the dried solid only. The iron(III) reduction rate in solution for AR with a longer alkyl chain (4- n -C 6 ) was found to be much higher than that for the methyl (5-C 1 )-substituted derivative, pointing to the importance of the structure (i.e., the position and/or the nature of the alkyl substituent) of the alkylresorcinol molecule for the redox process rate. The results obtained indicate that ARs can be readily oxidised abiotically by soil iron(III) in moderately acidic media, thus being excluded from signalling pathways, which is equal to “message undelivery”, directly affecting microbial autoregulation.

Incorporation of fluoride ions into the structure of jarosite, a common precipitate in bioleaching, was studied. Crystalline jarosite was synthesized in the presence of various concentrations of fl ...

Thermal degradation of the solid monomeric Na[FeEDTA(H2O)]·2H2O (EDTA = ethylenediaminetetraacetate anion) complex was studied in air by simultaneous thermogravimetry and differential thermal analysis (TG/DTA) coupled on-line with a quadrupole mass spectrometer for evolved gas analysis (EGA-MS). The solid products were analysed by Mossbauer spectroscopy. A four-step decomposition was observed until 500 °C by TG/DTA–EGA-MS, involving first the release of two molecules of crystal lattice water then one coordinated water molecule and above 200 °C, the release of CO2 as a result of degradation of a carboxylate arm of the EDTA ligand. While releasing CO2, reduction of the ferric iron to ferrous iron was observed by Mossbauer spectroscopy. Two ferrous species have been found to form simultaneously which are assumed to be configurational isomers since their aerial oxidation resulted in the formation of the same μ-oxo dimeric iron(III) species. Reaction pathway for this oxidation is proposed. Finally, the organic residues are burnt out rapidly accompanied by a very sharp exothermic heat effect between 280 and 330 °C; meanwhile magnetite is formed.

Fe[C(SiMe3)3]2 compound, in which iron is coordinated by two carbons, was prepared using the reaction of FeCl2 with (Me3Si)3CLi, and investigated by XRD, 57Fe Mossbauer spectroscopy and DFT calculations. 157.5 T hyperfine magnetic field was found at the site of the iron nucleus of this compound at 20 K. DFT calculations predict the quintet states to be clearly favored energetically over the lower spin states. The population analysis reveals considerable 4s as well as large unpaired 3d electron contributions, which can be responsible for the extremely high hyperfine field.

The mixed zirconium, titanium, hafnium and first-row transition metal oxides (containing phosphorous oxide) were prepared using ion exchange method followed by calcinations at 1020 K during 12 h. The resulted mixed oxides were identified by XRPD method and studied their thermal behaviour by TG-DTA analysis. As a result of thermal analysis there were found one exothermic (with a peak at about 950 K), and one endothermic (with a peak at about 1300 K) processes, both without mass loss. The observation was valid for all investigated samples. The analysis of XRPD patterns of the investigated samples showed well-defined crystal phases characteristic of each oxide. The XRPD analysis also verified the phase transition of tetravalent metal oxides from orthorhombic to tetragonal, observed by DTA analysis.

The speciation of iron in aqueous solutions containing Fe3 + and selected chelates such as EDTA, EDDA, CDTA and HEDTA has been studied using transmission 57Fe Mossbauer spectrometry in frozen solutions. The protonation of various complexes as well as binuclear complex formation could be detected as a function of pH. Autoreduction of Fe3 + to Fe2 + was observed in several cases. Reaction with hydrogen peroxide proved to be rather different for the four ligands, while the dihapto complex [XFe(η 2-O2)]3 − had surprisingly identical Mossbauer parameters for X = EDTA, CDTA or HEDTA. Paramagnetic spin relaxation observed in the Mossbauer spectra was found to be strongly influenced by the identity of the chelating ligand, despite the basically spin-spin origin of the phenomenon.

Phosphonate layer formation on passive iron surface has been investigated by electrochemical, conversion electron Mossbauer spectroscopy (CEMS) and atomic force microscopy (AFM) techniques. Electrochemical methods revealed that the prepassivation of iron surface results in stabilization of the phosphonate layer exhibiting favorable corrosion resistance. The rate of anodic dissolution is continuously decreasing due to the time-dependent formation of a protective phosphonate layer. The large R ct values of 1–20 MΩ cm 2 indicate rather high blocking effect of metal dissolution by the phosphonate layer. The phosphonate layer formation has been also followed by the decrease of capacitance. CEMS investigations were carried out to evaluate the differences in the composition of the passive layer as a result of the phosphonate treatment. Mossbauer spectroscopy indicated the presence of iron phosphonate. Changes in morphology due to the phosphonate layer formation have been observed.

The influence of water on the interaction between iron(III) and indole-3-acetic acid (IAA) was studied in different organic solutions using rapid-scan stopped-flow spectrophotometry and rapid-freeze/quench Mossbauer spectroscopy. Measurements were also performed in ethanol–water and acetone–water mixtures. The results showed that the interaction between FeIII and IAA resulted in dimeric FeIII–IAA complex within 1 s, followed by a slow second step to give Fe2+ and IAA(oxidized). No such products were formed in the absence of water. The visible and Mossbauer spectra reflect the nature of the organic solvent and that of the anion of iron(III) salts.

The effect of FeCl 3 in acetonic medium on the structure of Na-bentonite was studied using X-ray diffraction (XRD), 57 Fe Mossbauer spectroscopy, X-ray fluorescence spectroscopy and infrared spectroscopy to describe the structure of the bentonite before and after treatment. In the samples treated with FeCl 3 , an increase in the basal spacing was found by XRD, while a new magnetically split component assigned to Fe 3+ incorporated within the interlayer regions of montmorillonite showed up in the low-temperature Mossbauer spectra. The Mossbauer parameters observed were close to those of Fe oxyhydroxides, suggesting the presence of some kind of nanoparticles. These results show that the treatment with acetonic FeCl 3 solution is an effective method for introducing Fe into montmorillonite in the form of Fe 3+ accommodated in the interlayer region. The treated samples proved to be efficient Lewis catalysts in the acylation of aldehydes (benzaldehyde and 4-OH-benzaldehyde) by acetic acid anhydride.

A novel aqueous method was used to synthesise mixed chromium-vanadium oxide hydrates with various chromium content, via the reaction of peroxo-polyacids of chromium and vanadium. The resulting materials are gelatinous. The dehydration of the gels result in a brown coloured amorphous powder. Depending on the chromium content, the compounds have a different characteristic crystallisation temperature upon the further heating. The crystalline compounds, except for the low chromium ones, go on a phase transition and decompose with increasing temperature. By refining the XRPD measurement data of the compounds, the type and parameters of the unit cells were determined. The experimental data were in concordance with the calculated values, using the PWC code. The lattice parameters and the crystalline structure were changed with the variation of chromium content.

57Fe Mossbauer spectroscopy, X-ray diffraction, X-ray fluorescence spectroscopy and infrared spectroscopy were used to study the effect of FeCl3 and acetone on the structure of a Na-bentonite. XRD indicated the incorporation of Fe3+ ions into the interlayer space since the basal lattice spacing of montmorillonite increased to 1.6 from 1.24 nm after treatment with FeCl3 dissolved in acetone. Interlayer Na+ ions could be exchanged to Fe3+. Magnetically split Mossbauer subspectra with internal magnetic fields 41 and 46 T at 74 K, were associated with two main Fe3+ microenvironments within the interlayer regions. The resultant Fe-montmorillonite was successfully applied as a catalyst in the preparation of 1,1-diacetates from aromatic aldehydes and acetic acid anhydride.

Our previous studies have revealed that a "hybrid" structure of the amorphous and crystalline phases is formed in the outermost surface region of the austenitic stainless steel tubes of steam generators (SGs) as an undesired consequence of the industrial application of the AP-CITROX (AP: alkaline permanganate; CITROX: citric and oxalic acid) decontamination technology. The formation of this mobile oxide-layer increased the amount of the corrosion products in the primary circuit significantly, resulting in magnetite deposition on fuel assemblies. Owing to the fact that there is no investigation method available for the in-situ monitoring of the inner surfaces of heat exchanger tubes, a research project based on sampling as well as on ex-situ electrochemical and surface analytical measurements was elaborated. Within the frame of this project, comprehensive investigation of the general corrosion state and metallographic features of 36 stainless steel specimens, cut out from various locations of the 21 steam generators of the Paks NPP in the time period of 2000-2007 has been performed. The present work gives a brief overview on the general corrosion state of the heat exchanger tubes of SGs, concerning the long-term effects of the AP-CITROX procedure on the chemical composition and structure of the protective oxide-layer.

The chemical reactions between iron(III) and indole-3-acetic (IAA), -propionic (IPA), and -butyric (IBA) acids were studied in acidic aqueous solutions. The motivation of this work was that IAA is one of the most powerful natural plant-growth-regulating substances (phytohormones of the auxin series). Mossbauer spectra of the frozen aqueous solutions of iron(III) with indole-3-alkanoic acids as ligands (L), showed parallel reactions between Fe3+ and the ligands. Partly, it resulted in a complex formation which precipitated in aqueous solution and partly, in a redox process with iron(II) and the oxidised indole-3-alkanoic acids as products. The Mossbauer parameters of the Fe2+ species suggested a hexaaquo coordination environment. The chemical composition and coordination structure of the precipitated complexes were investigated using elemental analysis, Mossbauer spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopic techniques. The complexes were soluble in some organic solvents. So, Mossbauer, FTIR and solution X-ray diffraction measurements were carried out on the solution of complexes in acetone, hexadeutero acetone and methanol, respectively. The data obtained supported the existence of the μ-dihydroxo-bridging structure of the dimer: [L2Fe FeL2] (where L is indole-3-propionate, -acetate or -butyrate).

The reaction of a diiron(III)-EDTA complex with H 2 O 2 in alkaline medium is studied by Mossbauer spectroscopy in conjunction with the rapid-freeze/quench technique in order to identify possible intermediate species during the formation and decomposition of the purple (EDTA)Fe I I I (η 2 -O 2 ) 3 - complex ion. Starting from the six-coordinate [Fe I I I EDTA] - species at acidic pH, it is demonstrated that mononuclear complexes formed at a pH of about 1 are convert into the diiron(m)-EDTA complex [(EDTA)Fe I I I -O-Fe I I I (EDTA)] 4 - upon raising the pH to around 10.4. H 2 O 2 reacts with the diiron(III) complex to give peroxide/hydroperoxide related adducts. Initially, the reaction tears apart the dimers to form a peroxo adduct, namely the seven-coordinate mononuclear [(EDTA)-Fe I I I (η 2 -O 2 )] 3 - , which is stable only at very high pH. The decomposition of this peroxo adduct gives two new species, which are reported for the first time. The Mossbauer parameters of these species suggest a six-coordinate μ-peroxodiiron(III) complex [(EDTA)Fe I I I -(OO)-Fe I I I (EDTA)] 4 - and a seven-coordinate μ-hydroxo-μ-peroxodiiron(III) complex [(EDTA)Fe I I I -(OO)(OH)-Fe I I I (EDTA)] 5 - . A badly resolved, extremely broad component is observed in the Mossbauer spectra during the conversion of the monomer to dimeric peroxo species, which may be attributed to the short-lived [[EDTA)Fe I I I l -OO] 3 - or [(EDTA)Fe I I I -OOH] 2 - intermediate species.

Amorphous and crystalline (both, α - and γ -forms) titanium phosphate, titanium molybdate and tungstate were irradiated with swift heavy ions of 84Kr and 203Bi at a fluence of 5×1010–1014 ion cm−2. The crystalline structure of the materials was characterized by XRD method before and after irradiation. Comparison of the powder diffraction patterns revealed that the irradiation had practically no effect on the materials with the exception of γ -crystalline structure. This structure was destroyed under the effect of radiation of 84Kr ions and became amorphous above the fluence of 1×1012 ion cm−2. In case of irradiation with 203Bi ions it became amorphous at the lowest fluences applied.

The first-row transition metal salts of zirconium-, titanium-, and hafnium phosphates, respectively were irradiated at various doses with swift heavy ions of 240 MeV 84Kr and 720 MeV 203Bi and with gamma-rays of 60Co at dose of 3×106 Gy. Comparison of powder diffraction patterns of non-irradiated and irradiated samples reveals that the irradiation with gamma-rays has no effect on the materials. Irradiation with swift heavy ions of 84Kr and 203Bi at higher dose caused some degradation of the structure of titanium and hafnium double metal phosphates. The electrical conductivity value of the irradiated samples remained inside the order of magnitude characteristic for untreated materials.

We report on the magnetic and electronic state of iron in Cu-substituted Cr-based thiospinels of the nominal composition Fe1−xCuxCr2S4 ( x = 0.25 , 0.5 , 0.75 ), a class of compounds which recently raised considerable interest in relation with the colossal magnetoresistance effect they display. 57Fe Mossbauer measurements carried out at different temperatures revealed the gradual transformation of iron from the state of Fe2+ (representative for x = 0 ) to the state of Fe3+ (representative for x ⩾ 0.5 ), along with a simultaneous increase in the magnetic ordering temperature. In Fe0.75Cu0.25Cr2S4, where Fe2+ and Fe3+ oxidation states were found to coexist, the Mossbauer–Lamb factor characteristic of Fe3+ sites was found to exceed that characteristic of Fe2+ sites. Special attention is paid to the composition with x = 0.5 . This compound was found to display a Curie temperature T C ≈ 340 K , a value which considerably exceeds the recently reported T C value for a single crystal with the same average composition.