Search Results (5)

Sorbents based on polyacrylonitrile fiber, containing ferrocyanides of transition metals and manganese oxides (CoMn-PAN and FeMn-PAN) or iron(III) hydroxide (CoFe-PAN) in their structure were obtained, as confirmed by the results of X-ray diffraction and energy-dispersive analyses. The selectivity of the obtained sorbents was investigated, along with their ability to sorb Cs, Ba (as an analog of Ra), P, and Be from various natural media, including river water and seawater with varying salinity of 18.2 and 33.8 ‰. The data show that the sorbents are universal for the recovery of artificial ¹³⁷Cs and natural radionuclides from the natural environments, including complex salt composition (seawater). Researching the obtained sorbents during marine expeditions confirmed the efficiency of the obtained materials based on transition metal ferrocyanides and manganese oxides (CoMn-PAN and FeMn-PAN) for the sorption of ¹³⁷Cs, ⁷Be, ²¹⁰Pb, ²¹⁰Po, ²²⁶Ra, ²²⁸Ra, and ²³⁴Th. Additionally, the sorbent based on transition metal ferrocyanides and iron(III) hydroxide (CoFe-PAN) was effective for the sorption of ¹³⁷Cs, ⁷Be, ³²P, ³³P, ²¹⁰Pb, ²¹⁰Po, and ²³⁴Th. Based on the obtained results, methods for comprehensively determining artificial ¹³⁷Cs and natural radionuclides using these sorbents were developed. Full article

The oxidative C-C cleavage of a C₁₈ substrate is an important transformation in synthetic organic chemistry, facilitating the synthesis of valuable C₈-C₉ acids widely used in many industries. Through a comparative analysis of the catalytic and physicochemical properties of catalysts, comprising mono- (Pd or Au) and bimetallic (PdAu) nanoparticles deposited on oxides, oxyhydroxides and graphite-like carbon material Sibunit (Cp), it was shown that the efficiency of the catalyst in the oxidative cleavage of 9,10-dihydroxystearic acid relies on the nature of the active component, the support and the average size of metal nanoparticles (NPs). The dependency of 9,10-DSA conversion on the average size of metal NPs shows the structural sensitivity of the oxidative cleavage reaction. Notably, catalysts with an average size of gold particles less than 3 nm exhibit the highest activity. The nature of the active component and the support material are crucial factors determining the process selectivity. Among the catalysts studied, the most effective for the oxidative cleavage of 9,10-DSA is a material based on Au NPs deposited on Cp. Full article

For the first time, new sorbents based on polyacrylonitrile (PAN) fiber and transition metal ferrocyanides were obtained. The main difference between the obtained sorbents and the existing ones is the stage of preliminary preparation of the initial support by converting it into the forms PAN-Fe(OH)₃ or PAN-MnO₂, due to which additional ion exchange groups (carboxyl, carbonyl, etc.) are formed, which increases the amount of ferrocyanide fixed to the support. The best components and conditions for the synthesis of new sorbents were determined (concentration (0.1–0.2 mol/L), as well as pH (1 for sorbents based on PAN-Fe(OH)₃, and 1–5—PAN-MnO₂) of potassium ferrocyanide solution, concentration of transition metal salts (0.02 mol/L), temperature conditions). The influence of the studied solution composition (pH, concentration of Na⁺, K⁺, NH₄⁺ ions) on the cesium distribution coefficients during its recovery by the obtained sorbents was assessed. The possibility of cesium recovery from solutions with pH 1–9 containing macro quantities of cations was demonstrated. The sorbents derived were characterized by modern structural methods such as infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy with EDS analysis. A study of the trace amount sorption of ¹³⁷Cs was carried out in comparison with commercially available highly efficient sorbents (FNS-10 and Termoksid-35), and it was shown that the resulting sorbents are not inferior to industrial ferrocyanide sorbents and can be used for ¹³⁷Cs selective sorption from technological solutions and natural waters. Full article

The paper investigates the physicochemical regularities (kinetics and isotherm) of phosphorus and beryllium recovery by sorbents based on polyacrylonitrile (PAN) fiber and Fe(OH)₃ obtained by various methods: PAN or pre-hydrolyzed PAN with precipitation of FeCl₃ with ammonia, using ready-made or electrochemically generated Na₂FeO₄, pre-hydrolyzed PAN treated with an alkaline solution of Na₂FeO₄, as well as their comparison with granular aluminum oxide. The Langmuir, Freudlich and Dubinin–Radushkevich models show high performance of materials for sorption of stable P and Be used as tracers for the release of ⁷Be, ³²P, and ³³P from seawater. The obtained kinetic data are processed using kinetic models of intraparticle diffusion and the pseudo-first-order, pseudo-second-order, and Elovich models. Optimal conditions for obtaining sorbents are established, namely, the effect of NaOH concentration at the stages of preparation on the properties of sorbents based on the PAN fiber and Fe(OH)₃ obtained by various methods. Full article

Sorbents based on Fe(OH)₃ and aluminum oxide are widely used in oceanology for the recovery of cosmogenic radionuclides ⁷Be, ³²Si, ³²P, and ³³P from the seawater. It is also possible to use them for the recovery of the natural radionuclides ²¹⁰Pb, ²³⁴Th. A comparative study of the sorbents based on Fe(OH)₃ and acrylic fiber obtained through various impregnation methods was carried out, and their comparison with granulated aluminum oxide. The possibility of extracting trace amounts of phosphorus and beryllium under laboratory and field conditions with these sorbents was studied. The sorption of ⁷Be, ²¹⁰Pb, and ²³⁴Th on the natural content by the two-column method was investigated. It is shown that fiber samples obtained by oxidation with sodium ferrate and the “classical” method have the highest sorption characteristics. Full article