Mossbauer Spectroscopy and X-Ray Diffraction of Oxide Precipitates Formed from FeSO4 Solution. Part II

The chemical and structural properties of Fe-oxides formed from FeS04 solutions are strongly dependent on the [Fe2+]/[OH-] concentration ratio at the beginning of the precipitation process,· on the rate of oxygenation, the time of precipitation, the temperature, and the kind of alkali (NH40H or NaOH). Goethite (a-FeOOH) of varyingcrystallinity and/er substoichiometric magnetite (Fe3-\u27 04) were precipitated at 90 -c. Differences in the crystallinity of a-FeOOH were revealed by Mossbauer spectroscopy, as well as by X-ray diffraction. The stoichiometry of Fe3_x04 varied from Fe2.9104 to the one close to Fe2.6704. The X-ray diffraction showed only the presence of Fe3-x04, but not of maghemite (y-Fe203). The formation of hematite (a-Fe203), under specific experimental conditions, was also observed. Amorphous iron(III) hydroxyde precipitated at room temperature. The mechanism of precipitation of Fe-oxides from FeS04 solution is discussed

Potentiometric Determination of Chlorides Formed by Radiolysis of Chlorobenzene in n-Hexane

The method of potentiometric titration was used to determine the yield of chlorides radiolytically produced 1n solution of chlorobenzene inn-hexane. The results obtatned suggest that this method is convenient for the determination of chlorides present in nonaqueous solution and could be applied particularly in chemic.al dosimetry

Mossbauer Spectroscopy, X-ray Diffraction and IR Spectroscopy of Oxide Precipitates Formed from FeSO4 Solution

Iron oxyhydroxides and oxides were precipitated from FeS04 solution at low oxygen content. The composition and structure, stoichiometry, particle size and nuclear magnetism of the precipitates were studied using Mossbauer spectroscopy, X-ray diffraction and IR spectroscopy. The standard iron oxyhydroxides and oxides were also characterized using the same instrumental techniques. The results have indicated a strong dependence of the chemical composition and structure of the precipitates on the [FeS04] i [NaOH] concentration ratio. a-FeOOH of poor crystallinity was isolated at low pH values. a-Fe203 was formed by internal crystallization of a-FeOOH. At 90 aC, a mixture of Fe(OH)2iFe(OHh was transformed, with the time of heating, to nonstoichiometric Fe304, a-FeOOH and further to a-Fe203. Nonstoichiometric Fe304 was the final precipitation product in suspension with the [Fe2+]i [NaOH] stoichiometric ratio. The importance of these results for the corrosion science of steel in the presence of sulfates has been discussed

Synthesis and Microstructural Properties of Fe-TiO 2 Nanocrystalline Particles Obtained by a Modified Sol-Gel Method

Abstract. A series of iron/titanium oxide nanocrystalline particles with Fe/Ti molar ratios up to 0.15 were synthesized by a modified sol-gel technique using Ti(IV)-isopropoxide and anhydrous Fe(II)-acetate. The precursors were mixed and subsequently hydrolyzed with water molecules generated in situ by an esterification reaction between acetic acid and ethanol. As-synthesized samples were amorphous for XRD, independently of the relative amount of doped iron. The undoped samples and samples with the molar ratio Fe/Ti = 0.01, treated at up to 500 • C, contained anatase as the dominant phase and rutile as the minor phase. The samples with the Fe/Ti molar ratio of 0.15, treated at the same temperature, contained anatase (major phase), rutile (minor phase) and a very small amount of an unidentified phase. The crystallite size of the dominant phase in the samples was estimated from the XRD line broadening using the Scherrer formula. Thermogravimetric analysis showed that weight loss was accelerated and completed at lower temperatures as the relative concentration of iron in the Fe-TiO 2 samples increased. The strong exothermic peak in the DTA curve between 300 and 450 • C in the undoped TiO 2 sample shifted to the lower temperatures and became much more asymmetrical with increased iron doping. This DTA peak corresponded to the amorphous-to-anatase-transition and it included several steps such as (i) the thermal degradation of strongly bound organic molecules, (ii) the condensation of unhydrolyzed -OR groups, (iii) the sintering and growth of particles and (iv) the rearrangement of newly formed chemical bonds. The center of the most intense Raman band of the E g mode at 143.8 cm −1 in the undoped TiO 2 sample continually shifted to higher wave numbers and the full-width at half maximum increased with iron doping. Transmission electron microscopy revealed decrease of the mean particle size from 16.3 nm in undoped sample to 9.7 nm in the highest iron doped sample. The particle size distribution becomes * To whom all correspondence should be addressed. 6Šijaković-Vujičić et al. narrower with iron doping. The narrowest particle size distribution was found in sample with the Fe/Ti molar ratio of 0.05, calcined at 500 • C. Scanning electron microscopy of undoped samples calcined at 580 • C showed irregular aggregates having a relatively flat surface. On the contrary, the samples doped with 15 mol% of iron and treated at the same temperature exhibited a non-uniform sponge-like surface with distributed micrometer holes

Mossbauer Spectra of Iron(III) Iodate and Periodates

The Mossbauer spectra of iron(III) iodate and periodate are studied at room temperature. The spectrum of iron(III) iodate shows a single line of absorption, while that of iron(III) periodate exhibits quadrupole splitting. The results are discussed in terms of ionic character and covalency of the chemical bond between iron(III) and oxy-anfons

Mössbauer and photocatalytic studies of CaFe2O4 nanoparticle-containing aluminosilicate prepared from domestic waste simulated slag

The relationship between local structure and visible-light activated photocatalytic effect of simulated domestic waste slag glass–ceramics (R-NaWSFe) was investigated. The largest pseudo-first-order rate constant of 9.75 × 10−3 min−1 was estimated for methylene blue decomposition test under the visible-light irradiation using R-NaWSFe with additional 30 mass% of Fe2O3 heat-treated at 900 °C for 100 min. The reason for the high photoactivity of this sample was mainly due to nanoparticles of CaFe2O4 and α-Fe2O3 confirmed by the Mössbauer spectrum measured at 77 K. It is concluded that the nanoparticles of magnetic components in silica are essential for exhibiting visible-light activated catalytic effect

Mössbauer and photocatalytic studies of CaFe2O4 nanoparticle-containing aluminosilicate prepared from domestic waste simulated slag

The relationship between local structure and visible-light activated photocatalytic effect of simulated domestic waste slag glass–ceramics (R-NaWSFe) was investigated. The largest pseudo-first-order rate constant of 9.75 × 10−3 min−1 was estimated for methylene blue decomposition test under the visible-light irradiation using R-NaWSFe with additional 30 mass% of Fe2O3 heat-treated at 900 °C for 100 min. The reason for the high photoactivity of this sample was mainly due to nanoparticles of CaFe2O4 and α-Fe2O3 confirmed by the Mössbauer spectrum measured at 77 K. It is concluded that the nanoparticles of magnetic components in silica are essential for exhibiting visible-light activated catalytic effect

Chemically and thermally stable silica nanowires with a β-sheet peptide core for bionanotechnology

Background: A series of amyloidogenic peptides based on the sequence KFFEAAAKKFFE template the silica precursor, tetraethyl orthosilicate to form silica-nanowires containing a cross-β peptide core. Results: Investigation of the stability of these fibres reveals that the silica layers protect the silica-nanowires allowing them to maintain their shape and physical and chemical properties after incubation with organic solvents such as 2-propanol, ethanol, and acetonitrile, as well as in a strong acidic solution at pH 1.5. Furthermore, these nanowires were thermally stable in an aqueous solution when heated up to 70 °C, and upon autoclaving. They also preserved their conformation following incubation up to 4 weeks under these harsh conditions, and showed exceptionally high physical stability up to 1000 °C after ageing for 12 months. We show that they maintain their β-sheet peptide core even after harsh treatment by confirming the β-sheet content using Fourier transform infrared spectra. The silica nanowires show significantly higher chemical and thermal stability compared to the unsiliconised fibrils. Conclusions: The notable chemical and thermal stability of these silica nanowires points to their potential for use in microelectromechanics processes or fabrication for nanotechnological devices

Physical Activity, Screen Time, and Sleep Duration of Children Aged 6-9 Years in 25 Countries: An Analysis within the WHO European Childhood Obesity Surveillance Initiative (COSI) 2015-2017

Background: Children are becoming less physically active as opportunities for safe active play, recreational activities, and active transport decrease. At the same time, sedentary screen-based activities both during school and leisure time are increasing. Objectives: This study aimed to evaluate physical activity (PA), screen time, and sleep duration of girls and boys aged 6–9 years in Europe using data from the WHO European Childhood Obesity Surveillance Initiative (COSI). Method: The fourth COSI data collection round was conducted in 2015–2017, using a standardized protocol that included a family form completed by parents with specific questions about their children’s PA, screen time, and sleep duration. Results: Nationally representative data from 25 countries was included and information on the PA behaviour, screen time, and sleep duration of 150,651 children was analysed. Pooled analysis showed that: 79.4% were actively playing for >1 h each day, 53.9% were not members of a sport or dancing club, 50.0% walked or cycled to school each day, 60.2% engaged in screen time for 1 h/day, 8.2–85.6% were not members of a sport or dancing club, 17.7–94.0% walked or cycled to school each day, 32.3–80.0% engaged in screen time for <2 h/day, and 50.0–95.8% slept for 9–11 h/night. Conclusions: The prevalence of engagement in PA and the achievement of healthy screen time and sleep duration are heterogenous across the region. Policymakers and other stakeholders, including school administrators and parents, should increase opportunities for young people to participate in daily PA as well as explore solutions to address excessive screen time and short sleep duration to improve the overall physical and mental health and well-being of children.The authors gratefully acknowledge support from a grant from the Russian Government in the context of the WHO European Office for the Prevention and Control of NCDs. Data collection in the following countries was made possible through funding. Albania: WHO through the Joint Programme on Children, Food Security and Nutrition “Reducing Malnutrition in Children” (the Millennium Development Goals Achievement Fund) and the Institute of Public Health; Bulgaria: Ministry of Health, National Centre of Public Health and Analyses, WHO Regional Office for Europe; Croatia: Ministry of Health, Croatian Institute of Public Health and WHO Regional Office for Europe; Czechia: grants AZV MZČR 17–31670 A and MZČR – RVO EÚ 00023761; Denmark: Danish Ministry of Health; Estonia: Ministry of Social Affairs, Ministry of Education and Research (IUT 42–2), WHO Country Office, and National Institute for Health Development; France: Sante Publique France, the French Agency for Public Health; Georgia: WHO; Ireland: Health Service Executive; Italy: Ministry of Health and Italian National Institute of Health; Kazakhstan: Ministry of Health of the Republic of Kazakhstan and WHO Country Office; Kyrgyzstan: WHO; Latvia: Ministry of Health, Centre for Disease Prevention and Control; Lithuania: Science Foundation of Lithuanian University of Health Sciences and Lithuanian Science Council and WHO; Malta: Ministry of Health; Montenegro: WHO and Institute of Public Health of Montenegro; Poland: National Health Programme, Ministry of Health; Portugal: Ministry of Health Institutions, the National Institute of Health, Directorate General of Health, Regional Health Directorates and the kind technical support from the Center for Studies and Research on Social Dynamics and Health (CEIDSS); Romania: Ministry of Health; San Marino: Health Ministry, Educational Ministry, Social Security Institute and Health Authority; Spain: Spanish Agency for Food Safety and Nutrition (AESAN); Turkmenistan: WHO Country Office in Turkmenistan and Ministry of Health; Turkey: Turkish Ministry of Health and the World Bank