In this study, we present a new approach for the synthesis of Pt/SnO₂ catalysts using microwave radiation. Pt(IV) and Sn(IV) inorganic precursors (H₂PtCl₆ and SnCl₄) and ammonia were used, which allowed the controlled formation of platinum particles on the anisotropic SnO₂ support. The synthesized Pt/SnO₂ samples are mesoporous and exhibit a reversible physisorption isotherm of type IV. The XRD patterns confirmed the presence of platinum maxima in all Pt/SnO₂ samples. The Williamson-Hall diagram showed SnO₂ anisotropy with crystallite sizes of ~10 nm along the c-axis (< 00l >) and ~5 nm along the a-axis (< h00 >). SEM analysis revealed anisotropic, urchin-like SnO₂ particles. XPS results indicated relatively low average oxidation states of platinum, close to Pt metal. ¹¹⁹Sn Mössbauer spectroscopy indicated electronic interactions between Pt and SnO₂ particles. The synthesized samples were used for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of excess NaBH₄. The catalytic activity of the Pt/SnO₂ samples for the reduction of 4-NP to 4-AP was optimized by varying the synthesis parameters and Pt loading. The optimal platinum loading for the reduction of 4-NP to 4-AP on the anisotropic SnO₂ support is 5 mol% with an apparent rate constant k = 0.59 × 10^–2 s^–1. The Pt/SnO₂ sample showed exceptional reusability and retained an efficiency of 81.4% after ten cycles.

The Boda Claystone Formation (BCF) is an extended sedimentary sequence formed in a shallow-water salt lake under semi-arid to arid climatic conditions during the middle Permian period. The rock was formed predominantly from denuded and altered products of three primary felsic sources, the Mórágy Metagranite Complex, the Baksa Metamorphic Complex and the rhyolitic Gyűrűfű Formation, resulting in the recent dominant sheet silicate components, illite and chlorite. BCF has been considered a potential host rock for high-level nuclear waste, too. Thus, it has been characterized by several powerful methods so far (X-ray diffraction (XRD), transmission electron microscopy (TEM), etc.). ⁵⁷Fe Mössbauer spectroscopy may provide a unique additional tool to study iron-bearing minerals. Iron is dominantly present in a ferrous form in minerals of the fresh parent rocks (in the biotite group and amphibole), and in a ferric oxide, hematite, in altered Gyűrűfű Formation. During transformations of biotite group minerals and amphibole, the partial release of ferrous iron or its conversion to ferric form takes place with the stabilization of recent illite and chlorite, while the original layered structure is still preserved. Mössbauer spectroscopy revealed the dominant presence of ferrous iron located in cis-M2 octahedral sites both in parent biotite group minerals and in the final illite, as well as chlorite in both stages. The proportion of ferrous iron in biotite group minerals was halved during the stages of evolution by conversion to ferric iron still in sheet silicate illite or by segregation into separate hematite inclusions. The transformation process of biotite group minerals and amphibole of the source rocks is connected only to the iron-bearing smaller fraction of sheet silicates in the BCF clay mineral assemblage. Determination of Fe²⁺/Fe³⁺ ratios in sheet silicates was also pertinent in two sections of BCF. Namely, in samples from the Gorica region, Fe³⁺ was dominant, siting in illite, whereas Fe²⁺ was also present in significant portions in chlorite in samples from the Western Mecsek Anticline. The interpretation is deduced in correspondence with results of extended XRD, and high-resolution TEM studies.

Potassium ferrate(VI) (K₂FeO₄) as a particularly strong oxidant represents an effective and environmentally friendly waste water treatment material. When produced by anodic oxidation in highly alkaline aqueous solution, the K₂FeO₄ product is separated and sealed in inert plastic bags with the retention of some liquid phase with high pH. This method proved to be excellent for long-term storage at moderately low temperature (5 °C) for industrial applications. It is still imperative to check the ferrate(VI) content of the product whenever it is to be used. Fe-57 Mössbauer spectroscopy is an excellent tool for checking the ratio of ferrate(VI) to the degradation product iron(III) in a sample. For this purpose, normally the spectral areas of the corresponding subspectra are considered; however, this approximation neglects the possible differences in the corresponding Mössbauer–Lamb factors. In this work, we have successfully determined the Mössbauer–Lamb factors for the ferrate(VI) and for the most common iron(III) degradation products observed. We have found superparamagnetic behavior and low-temperature phase transformation for another iron(III) degradation product that made the determination of the Mössbauer–Lamb factors impossible in that case. The identities of a total of three different iron(III) degradation products have been confirmed.

The effect of swift heavy ion irradiation on sol–gel-prepared maghemite nanoparticles was studied by ⁵⁷Fe transmission Mössbauer spectroscopy and X-ray diffractometry (XRD). The room temperature Mössbauer spectra of the non-irradiated nano-maghemite showed poorly resolved magnetically split, typical relaxation spectra due to the superparamagnetic state of the nanoparticles. Significant changes in the line shape, indicating changes in the superparamagnetic state, were found in the Mössbauer spectra upon irradiation by 160 MeV and 155 MeV ¹³²Xe²⁶⁺ ions with fluences of 5 × 10¹³ ion cm⁻² and 1 × 10¹⁴ ion cm⁻². XRD of the irradiated maghemite nanoparticles showed a significant broadening of the corresponding lines, indicating a decrease in the crystallite size, compared to those of the non-irradiated ones. The results are discussed in terms of the defects induced by irradiation and the corresponding changes related to the change in particle size and consequently in the superparamagnetic state caused by irradiation.