Bolat Uralbekov

Uranium series radionuclides in surface waters from the Shu river (Kazakhstan)

The concentrations of (238)U, (234)U, (226)Ra, (210)Po and (210)Pb have been determined in surface waters collected along the course of the Shu River, lying on the border between Kazakhstan and Kyrgyzstan. In the study area, the river runs through some of the largest uranium deposits worldwide, which were actively exploited during the nuclear weapons and nuclear energy programmes of the former Soviet Union. The data show an increasing trend in uranium concentrations downstream the river from the city of Tokmak to the city of Shu, with good correlation between total uranium concentrations and total dissolved solids. Data on uranium isotopes disequilibrium show the presence of technogenic uranium inputs into the Shu River downstream from the city of Karasu, evidenced by a decrease in the measured (234)U/(238)U isotopic ratio from 1.63 in uncontaminated sites to 1.29 in sites affected by past mining activities.

Mechanochemical synthesis of colloidal silver chloride particles in the NH4Cl–AgNO3–NH4NO3 system

Silver chloride nanoparticles prepared by exchange mechanochemical reaction NH4Cl + AgNO3 + zNH4NO3 = (z + 1)NH4NO3 + AgCl in ammonium nitrate matrix (diluent and side reaction product) at dilution parameters z = 7.22 and 3.64 are studied by X-ray diffraction and thermal analysis, electron microscopy, and dynamic light scattering. It is shown that free-form AgCl nanoparticles can be obtained after removal of ammonium nitrate by washing-out with water or thermal annealing at 300°C.

Synthesis of Core/Shell ZnO/rGO Nanoparticles by Calcination of ZIF-8/rGO Composites and Their Photocatalytic Activity

A facile two-step method was developed to prepare core/shell ZnO/rGO particles from ZIF-8/rGO composites. ZIF-8 particles were first grown at the surface of rGO sheets. Next, ZIF-8 particles were transformed into ZnO particles by thermal decomposition under air at 500 °C. All materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller analyses. Results obtained show that ZIF-8 particles strongly associate with rGO sheets and that the calcination of this material produces porous core/shell ZnO/rGO particles with an average diameter of ca. 40 nm. The wt % of rGO associated with ZIF-8 particles was varied from 5 to 20%. The ZnO/rGO (10%) particles exhibit the highest photocatalytic activity for the degradation of the Orange II dye under simulated solar light irradiation of weak intensity (5 mW/cm2). This high photocatalytic activity was demonstrated to originate from superoxide O2•– radicals due to the efficient trapping of photogenerated electrons in ZnO by rGO.

KBaR(BO 3 ) 2 orthoborates (R = REE): Synthesis and study

The search for compounds with the formula composition KBaR(BO3)2 has been performed by solid-phase synthesis and differential thermal analysis. The compounds synthesized in this series are KBaPr(BO3)2 and KBaNd(BO3)2, which are isostructural to KBaY(BO3)2, are isotypical to butschliite K2Ca(CO3)2, and crystallize in a trigonal system with space group R3m. The structural characteristics of compounds calculated for the entire series of REEs are given.

Synthesis of New Isostructural Orthoborates NaBaR(BO3)2 with R = Tb, Dy, Ho, Er, Tm and Lu

Six new rare-earth orthoborates NaBaR(BO3)2, with R = Tb, Dy, Ho, Er, Tm, Lu were synthesized using a multiple-step solid-state reaction. These new orthoborates continue the previously described isostructural lines of three-cation orthoborates NaBaR(BO3)2, by R = Sc, Y, Yb. The structure of synthesized solid compounds is isotypic with the mineral eitelite, Na2Mg(CO3)2, crystallizing in the trigonal system with space group R3. All prepared borates are isostructural, as evidenced by the presence of the same vibration modes in Raman spectra and of the same diffraction peaks in X-ray patterns. The photoluminescence of NaBaTb(BO3)2 have been investigated in a detail.

Heavy metals and natural radionuclides in the water of Syr Darya River, Kazakhstan

This study deals with concentrations of heavy metals and the main uranium series radionuclide in the Syr Darya surface waters (Kazakhstan). Large proportion of studied heavy metals were transported with suspended matter (> 0.45 μm), while large proportion of U (98–100 %) and Mo (81–100 %) were in dissolved forms and colloidal fraction (< 0.45 μm).

Comparison of Approaches in Slovenia and Kazakhstan in Managing Exposure to Radon

Increasing attention has been paid to radon in both Slovenia and Kazakhstan. The paper reviews their activities in radon measurements and dose estimates for radon exposure mitigation. Slovenia succeeded to accomplish the main goal of managing exposure to radon in homes and at workplaces at acceptably low levels, while in Kazakhstan there are still quite a number of dwellings with potential radon risk needing further monitoring and mitigation measures.

Mechanochemical synthesis of colloidal silver bromide particles in the NaBr–AgNO3–NaNO3 system

X-ray diffraction and thermal analyses, electron microscopy, and dynamic light scattering have been employed to study silver bromide nanoparticles obtained by the mechanochemical exchange reaction NaBr + AgNO3 + zNaNO3 = (z + 1)NaNO3 + AgBr in sodium nitrate matrix (diluent and side reaction product) at z = z1 = 8.06 and z = z2 = 4.31. AgBr nanoparticles have been obtained in the free form by dissolving the matrix in water, and their activity in the photodegradation of methylene blue dye has been studied.