Tatiana Vereshchagina - Academia.edu (original) (raw)

Papers by Tatiana Vereshchagina

Research paper thumbnail of Hydrothermal synthesis and sorption performance to Cs(I) and Sr(II) of zirconia-analcime composites derived from coal fly ash cenospheres

Chimica Techno Acta

The paper is concerned with (i) the hydrothermal synthesis of hydrous zirconium dioxide (HZD) bea... more The paper is concerned with (i) the hydrothermal synthesis of hydrous zirconium dioxide (HZD) bearing analcime (HZD-ANA, zirconia-analcime) and (ii) its sorption properties with respect to Cs+ and Sr2+. The HZD-ANA particles were synthesized from coal fly ash cenospheres composed of aluminosilicate glass with (SiO2/Al2O3)wt.=3.1 and characterized by PXRD, SEM-EDS, STA, and low-temperature N2 adsorption. The non-radioactive simulant solutions of different acidity (pH=2–10) and Cs+/Sr2+ content (0.5–50.0 mg/L) were used in the work. The effect of synthesis conditions on the HZD-ANA particle size, zirconia content and localization as well as the sorption behavior with respect to Cs+ and Sr2+ (capacity, KD) were clarified. It was found that the small-sized HZD-ANA composites surpasses the Zr free analcime and large-sized HZD-ANA material in the Cs+ and Sr2+ sorption parameters (KD ~104–106 mL/g). The conditions to synthesize the zirconia-analcime composite of the highly enhanced sorptio...

Research paper thumbnail of Cenosphere-Based Zeolite Precursors of Lutetium Encapsulated Aluminosilicate Microspheres for Application in Brachytherapy

Materials

Coal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass p... more Coal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass phase—95.4; (SiO2/Al2O3)glass—3.1; (Si/Al)at. = 2.6) were used to fabricate lutetium-176 encapsulated aluminosilicate microspheres as precursors of radiolabeled microspheres applied for selective irradiation of tumors. To incorporate Lu3+ ions into cenosphere’s aluminosilicate material, the following strategy was realized: (i) chemical modification of cenosphere globules by conversion of aluminosilicate glass into zeolites preserving a spherical form of cenospheres; (ii) loading of zeolitized microspheres with Lu3+ by means of ion exchange 3Na+ ↔ Lu3+; (iii) Lu3+ encapsulation in an aluminosilicate matrix by solid-phase transformation of the Lu3+ loaded microspheres under thermal treatment at 1273–1473 K. Two types of zeolitized products, such as NaX (FAU) and NaP1 (GIS) bearing microspheres having the specific surface area of 204 and 33 m2/g, accordingly, were prepared and their Lu3+ sor...

Research paper thumbnail of Sorption Properties of ZrO2-Analcime Composites in Relation to Cs(I) and Sr(II)

Journal of Siberian Federal University. Chemistry, 2021

Composite zeolite sorbents based on analcime with inclusions of hydrated zirconium dioxide (ZrO2-... more Composite zeolite sorbents based on analcime with inclusions of hydrated zirconium dioxide (ZrO2-analcime) have been obtained by hydrothermal treatment of coal fly ash cenospheres with a high glass phase content in the presence of a zirconium compound and an alkaline activating agent at 150 °C and different stirring modes of the reaction mixture. The synthesis products were characterized by XRD, SEM-EDS, STA and low-temperature nitrogen adsorption; their sorption properties with respect to Cs+ and Sr2+ were studied in the pH range of 2–10. It was found that the ZrO2-analcime compositions surpass unmodified analcime by 2–5 times in terms of sorption of Cs+ and Sr2+ and by two orders of magnitude in terms of the distribution coefficient value (KD ~106 ml/g). The process of high-temperature solid-phase transformation of Cs+/Sr2+-exchanged forms of the compositions was studied, which simulates the process of conversion of water-soluble forms of Cs‑137 and Sr‑90 radionuclides into a mine...

Research paper thumbnail of Hydrothermal Co-Processing of Coal Fly Ash Cenospheres and Soluble Sr(II) as Environmentally Sustainable Approach to Sr-90 Immobilization in a Mineral-like Form

Materials, 2021

Co-processing of radioactive effluents with coal fly ash-derived materials is recognized as a res... more Co-processing of radioactive effluents with coal fly ash-derived materials is recognized as a resource-saving approach for efficient stabilization/solidification of radioactive components of wastewater. In this context, the paper is focused on the hydrothermal synthesis of Sr2+-bearing aluminosilicate/silicate phases as analogs of a mineral-like 90Sr waste form using hollow glass-crystalline aluminosilicate microspheres from coal fly ash (cenospheres) as a glassy source of Si and Al (SiO2-Al2O3)glass) and Sr(NO3)2 solutions as 90Sr simulant wastewater. The direct conversion of cenosphere glass in the Sr(NO3)2-NaOH-H2O-(SiO2-Al2O3)glass system as well as Sr2+ sorption on cenosphere-derived analcime (ANA) in the Sr(NO3)2-H2O-ANA system were studied at 150–200 °C and autogenous pressure. The solid and liquid reaction products were characterized by SEM-EDS, PXRD, AAS and STA. In the Sr(NO3)2-NaOH-H2O-(SiO2-Al2O3)glass system, the hydrothermal processing at 150–200 °C removes 99.99% of t...

Research paper thumbnail of Cenosphere-sourced hydrothermal synthesis of pollucite-analcime solid solutions as a low-temperature method to immobilize 137Cs in a mineral-like form

Journal of Nuclear Materials, 2020

h i g h l i g h t s g r a p h i c a l a b s t r a c t Microspheres with a composite mullite/ANA w... more h i g h l i g h t s g r a p h i c a l a b s t r a c t Microspheres with a composite mullite/ANA wall are produced as a Cs mineral-like form. Analcime-pollucite phases with nonsignificant difference in Si/Al ratios were obtained. Mullite provides the preservation of a spherical shape of crystallized microspheres. The average Cs content in solid products is 23e32 wt %.

Research paper thumbnail of Magnetic Composite Sorbents for Trapping Heavy Metals from Liquid Waste and Their Immobilization in a Mineral-Like Matrix

Journal of Siberian Federal University. Chemistry, 2019

Magnetic sorbents were prepared by addition of ferrospheres to zirconia-silica gel followed by th... more Magnetic sorbents were prepared by addition of ferrospheres to zirconia-silica gel followed by thermal treatment at 500 °C. The ferrosphere narrow fraction E -0.063+0.050 mm from fly ash resulted from combustion of Ekibastuz coal was used as a magnetic component. The surface of magnetic composites was additionally functionalized by grafting of – POONa and – NH2 groups. Under equilibrium conditions sorption capacities of the sorbents with respect to Се3+ used as a U4+/Th4+ simulator and Pb2+ were measured by means of determination of sorption isotherms which were fitted by the Langmuir model. It was established that extraction of Се3+ and Pb2+ from aqueous solutions is characterized by distribution coefficients of 104–106 ml/g. Temperature conditions for solid-phase crystallization of the sorbents resulting in polyphase systems with the content of zircon phase of 50 wt. % were found

Research paper thumbnail of Preparation and Properties of Zr-Bearing Sorption Materials Based on Coal Fly Ash Microspheres

Journal of Siberian Federal University. Chemistry, 2019

The influence of hydrothermal conditions on synthesis of analcime and a composite material ZrO2- ... more The influence of hydrothermal conditions on synthesis of analcime and a composite material ZrO2- analcime as well as zirconomolybdate coverings with ion exchange properties was studied using narrow fractions of aluminosilicate microspheres with a high content of a glass phase (91-95 wt. %). The possibility to synthesize ZrO2-analcime composites of narrow particle size distributions with maximum of about 40 μm and 6 μm under hydrothermal treatment at 150 °С was demonstrated starting from microspheres with Si/Al=2.7 and applying different regimes of a reaction mixture agitation. A microsphere material of a “core-shell” type such as ZrMo2O7(OH)2(H2O)2@(SiO2-Al2O3)glass with the nanostructured covering was prepared. Sorption properties of the materials regarding Nd3+, Sr2+ and Cs+ were studied under equilibrium conditions by means of determination of sorption isotherms and their fitting by the Langmuir model. Sorption parameters were determined including distribution coefficients which ...

Research paper thumbnail of Microsphere Zirconomolybdate Sorbents for Extraction of Lanthanides (III) from Aqueous Solutions

Journal of Siberian Federal University. Chemistry, 2017

Micromesoporous zirconomolybdates with a specific surface area of 200 m 2 /g and pore sizes in th... more Micromesoporous zirconomolybdates with a specific surface area of 200 m 2 /g and pore sizes in the range of 10-40 Å (D max~1 5 Å) were synthesized under hydrothermal conditions (150 °С, 72 h). Microsphere composites were prepared by deposition of the zirconomolybdates on a microsphere hollow carrier with a macroporous shell (D pore ~ 2-10µm) resulted from the NH 4 F-HCl-H 2 O etching of a cenosphere narrow fraction (-0,08+0,071 mm) separated from coal fly ash of Reftinskaya power station. The morphological type "cenospheres with a porous shell and a smooth surface" predominates in the fraction. The sorption properties of zirconomolybdates and microsphere composites with different Mo/Zr ratio were studied regarding Nd 3+ cations as a surrogate of trivalent actinides. It was established that the thin-layer mode of zirconomolybdate deposition on the carrier and the increasing of a Mo/Zr ratio in its composition provides the enhanced distribution coefficient (up to 10 4 ml/g) and efficiency of Nd 3+ sorption (up to 85 %).

Research paper thumbnail of ZrMo2O7(OH)2(H2O)2 coated microsphere glass supports derived from coal fly ash cenospheres as a novel sorbent for radionuclide trapping

Journal of Environmental Chemical Engineering, 2019

The nanostructured polycrystalline ZrMo 2 O 7 (OH) 2 (H 2 O) 2 coating was synthesized on coal fl... more The nanostructured polycrystalline ZrMo 2 O 7 (OH) 2 (H 2 O) 2 coating was synthesized on coal fly ash cenosphere derived microsphere glass supports via a two-step mild hydrothermal procedure resulting in a microsphere composite of a hollow core-shell structure. Sorption properties of the microsphere composite with respect to Cs + , Sr 2+ and Nd 3+ as non-radioactive imitators of 137 Cs, 90 Sr and actinides (III) were estimated. The nanostructured design of the coating was shown to enhance the Nd 3+ , Sr 2+ ,Cs + sorption in comparison with pure microsized ZrMo 2 O 7 (OH) 2 (H 2 O) 2. Nd 3+ , Sr 2+ , Cs + sorption distribution coefficients were determined (0.52•10 4 , 0.40•10 3 and 0.92•10 2 mL/g, respectively) and preferential Nd 3+ sorption was explained on the basis of ZrMo 2 O 7 (OH) 2 (H 2 O) 2 structure.

Research paper thumbnail of One-step immobilization of cesium and strontium from alkaline solutions via a facile hydrothermal route

Journal of Nuclear Materials, 2018

Analcime-pollucite solid solutions crystallize as host phases immobilizing Cs þ. Cs þ and Sr 2þ w... more Analcime-pollucite solid solutions crystallize as host phases immobilizing Cs þ. Cs þ and Sr 2þ were immobilized by hydrothermal treatment of coal fly ash cenospheres. Sequestration of Cs and Sr from alkaline solutions was 90e99%.

Research paper thumbnail of Composite Zirconomolybdate Sorbents for Immobilization of f-Metal (III) Cations in a Mineral-Like Matrix

Journal of Siberian Federal University. Chemistry, 2016

Composite zirconomolybdate sorbents of different compositions were prepared by agglomeration of l... more Composite zirconomolybdate sorbents of different compositions were prepared by agglomeration of layered zirconomolybdate with a SiO 2 gel followed by impregnation of a sodium salt of bis-(2,4,4trimethylpentyl)-phosphinic acid (Cyanex 272). Sorption properties of two composites with respect to Nd 3+ , as an actinide (Am, Cm) surrogate, and possibility of Nd 2 Zr 3 (MoO 4) 9 phase formation, which is similar by structure to a kosnarite mineral, by high-temperature phase conversion were studied. It was shown that the inorganic and hybrid composites trap Nd 3+ cations from solutions with distribution coefficients of about 10 4 mL/g and limit sorption capacities of 30 and 50 mg/g, accordingly. It was established that solid-phase crystallization of both composites with sorbed Nd 3+ takes place at 650 °С resulting in a polyphase system with the content of the target phase Nd 2 Zr 3 (MoO 4) 9 of about 30 %.

Research paper thumbnail of Solidification of Cs-137-Bearing Radioactive Waste in Cenosphere-Based Mineral-Like Hosts for Long-Term Disposal in Granithoids

Journal of Siberian Federal University. Chemistry, 2015

Theoretical and practical possibility to stabilize Cs-137(Na)-bearing liquid radioactive waste in... more Theoretical and practical possibility to stabilize Cs-137(Na)-bearing liquid radioactive waste in mineral-like forms which are geochemically compatible with granithoids in its long-term disposal was demonstrated. Perforated cenospheres (SiO 2 /Al 2 O 3 =3.4) of fly ash generated from combustion of kuznetskii coal was used as an aluminosilicate precursor. It was established that solidification of Cs-bearing solutions at 750-1100 °С via the proposed route resulted in glass-crystalline compounds incorporating 53-79 wt. % pollucite with the Cs leaching rate being by 2-3 order of magnitude lower than the standard parameter accepted in Russia for solidified high level waste.

Research paper thumbnail of Synthesis and structure of analcime and analcime-zirconia composite derived from coal fly ash cenospheres

Microporous and Mesoporous Materials, 2017

Cubic analcime and analcime-zirconia composite with the Si/Al ratio of 2.04 and 2.16, respectivel... more Cubic analcime and analcime-zirconia composite with the Si/Al ratio of 2.04 and 2.16, respectively, was synthesized by hydrothermal treatment of coal fly ash cenospheres (Si/Al ¼ 2.7) at 150 C. The scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), synchronous thermal analysis (STA) methods were used to study the morphology, composition and structure of the products. Two main types of analcime bearing particles were obtained, such as hollow microspheres with attached analcime icositetrahedra of 5 e50 mm in size and individual analcime crystals of a narrow particle size distribution (D m ¼ 41 mm) with incorporated zirconia (4.8 wt% Zr). The high quality of the crystalline fractions allowed an accurate fullprofile PXRD analysis of complete analcime crystal structure and composition including anisotropic displacement parameters of all atoms and H-positions of water molecules.

Research paper thumbnail of Immobilization of Liquid Radioactive Waste in Mineral-Like Matrices Derived From Inorganic Cenosphere-Based Sorbents as Precursors

MRS Proceedings, 2008

The progress in study of immobilization of liquid radioactive waste in mineral-like aluminosilica... more The progress in study of immobilization of liquid radioactive waste in mineral-like aluminosilicate matrices (feldspar and feldspathoids) derived from cenosphere-based microspherical zeolite sorbents is reported. Based on the analysis of ‘composition – morphology –C characteristics’ correlation obtained for more than 70 cenosphere products with a high content of one morphological type of imperforated cenospheres, optimal ranges of cenospheres composition were identified for the synthesis of zeolites with the predetermined structural type. Given that the cenosphere-based zeolite sorbents are precursors of the final waste form, further activity proceeds toward developing a highly efficient zeolite sorbent of NaP1 type, which would ensure the effective trapping of Cs+ and/or Sr2+ ions and the phase transformation under relatively mild conditions (T≤1000°C). The paper details the main criteria for realization of the ‘precursor’ approach for fixation of Cs-Sr fraction using cenosphere-ba...

Research paper thumbnail of Solid-Phase Transformation of Cs+- and Sr2+-Bearing Zeolite Sorbents Derived From Cenospheres to Mineral-Like Forms

MRS Proceedings, 2009

The paper describes the studies of the transformation of Cs+- and Sr2+-containing zeolite sorbent... more The paper describes the studies of the transformation of Cs+- and Sr2+-containing zeolite sorbents synthesized from fly ash cenospheres to crystalline mineral composition, suitable for the long-term disposal. Series of Cs+- and Sr2+-exchanged NaP1-containing sorbents were subjected to the thermochemical transformation in the temperature range 40-1100°C at atmospheric pressure in air and the progress of reaction was monitored by DSC and XRD analysis. It was shown that initial sodium zeolite undergoes two-step transformation at 736-785°C and 892-982°C forming nepheline as the principle product, with the conversion temperatures being dependant on the heating rate.The thermal treatment of Cs+-bearing zeolite sorbent led to formation of a complex multiphase system, the principal components of which were nepheline and pollucite. Increasing cesium content in the samples led to a monotonous shift of crystallization peak to the higher temperature range (1005-1006°C). A more complicated behav...

Research paper thumbnail of Porous Materials Based on Cenospheres of Coal Fly Ash for Fixation of Cs-137 and Sr-90 in Mineral-like Aluminosilicates

MRS Proceedings, 2006

ABSTRACTAmong the crystalline matrices being developed for immobilization of 137Cs and 90Sr are f... more ABSTRACTAmong the crystalline matrices being developed for immobilization of 137Cs and 90Sr are framework aluminosilicates like feldspars and feldspathoids. A novel approach to obtain mineral-like aluminosilicate forms of 137Cs and 90Sr with using porous materials based on hollow aluminosilicate microspheres of coal fly ash (cenospheres) has been demonstrated. Two modifications of microspherical porous materials have been developed, (i) moulded porous matrices based on consolidated cenospheres and (ii) zeolite sorbents obtained by hydrothermal zeolitization of cenospheres. The first includes impregnation of Cs- or Sr-containing solutions into porous matrices, drying and calcining at temperatures (700-900°C) lower than the softening point of the porous matrix material, at which solid phase crystallization takes place with formation of framework aluminosilicates, such as Cs-nepheline, pollucite or Sr-anorthite. Using zeolite sorbents, immobilization of Cs+ and Sr2+ proceeds through th...

Research paper thumbnail of Removal of radioactive and other hazardous material from fluid waste

Hollow glass microspheres obtained from fly ash (cenospheres) are impregnated with extractants/io... more Hollow glass microspheres obtained from fly ash (cenospheres) are impregnated with extractants/ion-exchangers and used to remove hazardous material from fluid waste. In a preferred embodiment the microsphere material is loaded with ammonium molybdophosphonate (AMP) and used to remove radioactive ions, such as cesium-137, from acidic liquid wastes. In another preferred embodiment, the microsphere material is loaded with octyl(phenyl)-N-N-diisobutyl-carbamoylmethylphosphine oxide (CMPO)

Research paper thumbnail of Open-cell glass crystalline porous material

An open-cell glass crystalline porous material made from hollow microspheres which are cenosphere... more An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, he...

Research paper thumbnail of One-step fabrication of hollow aluminosilicate microspheres with a composite zeolite/glass crystalline shell

Microporous and Mesoporous Materials, 2013

ABSTRACT One-step procedure to fabricate hollow aluminosilicate microspheres with a composite NaA... more ABSTRACT One-step procedure to fabricate hollow aluminosilicate microspheres with a composite NaA(NaX)/glass/mullite composite shell was demonstrated by the direct conversion of low-silica cenospheres (Si/Al = 1.8) separated from coal fly ash. The reported method does not involve seeding and structure-directing reagents. Composition of cenospheres and the stirring of reactants at the optimal synthesis temperature (T = 80 °C) and alkaline molarity (2.5 M NaOH) are parameters affected the formation of a monozeolitic phase (NaA or NaX). The influence of the silica–alumina composition of cenospheres on the type of zeolite phase formation is only revealed under stirring conditions. In the case of the low-silica cenospheres, NaA (LTA) zeolite crystallizes as a dominant phase (43 wt.%) (Si/Al = 1.8) under stirring of reactants, while the static conditions favor formation of the NaX (FAU) zeolite phase (45 wt.%).

Research paper thumbnail of Microsphere zeolite materials derived from coal fly ash cenospheres as precursors to mineral-like aluminosilicate hosts for 135,137Cs and 90Sr

Journal of Nuclear Materials, 2013

Hollow microsphere zeolite materials with a bilayered zeolite/glass crystalline shell bearing NaP... more Hollow microsphere zeolite materials with a bilayered zeolite/glass crystalline shell bearing NaP1 zeolite were synthesized by the hydrothermal treatment of coal fly ash cenospheres (Si/Al = 2.7) in an alkaline medium. Cs + and/or Sr 2+ forms of zeolitized cenospheres with the different Cs + and/or Sr 2+ loading were prepared by the ion exchange from nitrate solutions. The resulted (Cs,Na)P1, (Sr,Na)P1 and (Cs,Sr,Na)P1 bearing microsphere zeolites were converted to glass ceramics by heating at 900-1000°C. The differential scanning calorimetry and quantitative phase analysis were used to monitor the solidphase transformation of the initial and ion exchanged zeolite materials. It was established that the final solidified forms of Cs + and/or Sr 2+ are glass-crystalline ceramic materials based on pollucite-nepheline, Sr-feldspar-nepheline and Sr-feldspar-pollucite composites including $60 wt.% of the major host phases (pollucite, Sr-feldspar) and 10-20 wt.% of glass. The 137 Cs leaching rate of 4.1 Â 10 À7 g cm À2 day À1 was determined for the pollucite glass-ceramic according to Russian State Standard (GOST) No. 52126 P-2003 (7 day, 25°C, distilled water).

Research paper thumbnail of Hydrothermal synthesis and sorption performance to Cs(I) and Sr(II) of zirconia-analcime composites derived from coal fly ash cenospheres

Chimica Techno Acta

The paper is concerned with (i) the hydrothermal synthesis of hydrous zirconium dioxide (HZD) bea... more The paper is concerned with (i) the hydrothermal synthesis of hydrous zirconium dioxide (HZD) bearing analcime (HZD-ANA, zirconia-analcime) and (ii) its sorption properties with respect to Cs+ and Sr2+. The HZD-ANA particles were synthesized from coal fly ash cenospheres composed of aluminosilicate glass with (SiO2/Al2O3)wt.=3.1 and characterized by PXRD, SEM-EDS, STA, and low-temperature N2 adsorption. The non-radioactive simulant solutions of different acidity (pH=2–10) and Cs+/Sr2+ content (0.5–50.0 mg/L) were used in the work. The effect of synthesis conditions on the HZD-ANA particle size, zirconia content and localization as well as the sorption behavior with respect to Cs+ and Sr2+ (capacity, KD) were clarified. It was found that the small-sized HZD-ANA composites surpasses the Zr free analcime and large-sized HZD-ANA material in the Cs+ and Sr2+ sorption parameters (KD ~104–106 mL/g). The conditions to synthesize the zirconia-analcime composite of the highly enhanced sorptio...

Research paper thumbnail of Cenosphere-Based Zeolite Precursors of Lutetium Encapsulated Aluminosilicate Microspheres for Application in Brachytherapy

Materials

Coal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass p... more Coal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass phase—95.4; (SiO2/Al2O3)glass—3.1; (Si/Al)at. = 2.6) were used to fabricate lutetium-176 encapsulated aluminosilicate microspheres as precursors of radiolabeled microspheres applied for selective irradiation of tumors. To incorporate Lu3+ ions into cenosphere’s aluminosilicate material, the following strategy was realized: (i) chemical modification of cenosphere globules by conversion of aluminosilicate glass into zeolites preserving a spherical form of cenospheres; (ii) loading of zeolitized microspheres with Lu3+ by means of ion exchange 3Na+ ↔ Lu3+; (iii) Lu3+ encapsulation in an aluminosilicate matrix by solid-phase transformation of the Lu3+ loaded microspheres under thermal treatment at 1273–1473 K. Two types of zeolitized products, such as NaX (FAU) and NaP1 (GIS) bearing microspheres having the specific surface area of 204 and 33 m2/g, accordingly, were prepared and their Lu3+ sor...

Research paper thumbnail of Sorption Properties of ZrO2-Analcime Composites in Relation to Cs(I) and Sr(II)

Journal of Siberian Federal University. Chemistry, 2021

Composite zeolite sorbents based on analcime with inclusions of hydrated zirconium dioxide (ZrO2-... more Composite zeolite sorbents based on analcime with inclusions of hydrated zirconium dioxide (ZrO2-analcime) have been obtained by hydrothermal treatment of coal fly ash cenospheres with a high glass phase content in the presence of a zirconium compound and an alkaline activating agent at 150 °C and different stirring modes of the reaction mixture. The synthesis products were characterized by XRD, SEM-EDS, STA and low-temperature nitrogen adsorption; their sorption properties with respect to Cs+ and Sr2+ were studied in the pH range of 2–10. It was found that the ZrO2-analcime compositions surpass unmodified analcime by 2–5 times in terms of sorption of Cs+ and Sr2+ and by two orders of magnitude in terms of the distribution coefficient value (KD ~106 ml/g). The process of high-temperature solid-phase transformation of Cs+/Sr2+-exchanged forms of the compositions was studied, which simulates the process of conversion of water-soluble forms of Cs‑137 and Sr‑90 radionuclides into a mine...

Research paper thumbnail of Hydrothermal Co-Processing of Coal Fly Ash Cenospheres and Soluble Sr(II) as Environmentally Sustainable Approach to Sr-90 Immobilization in a Mineral-like Form

Materials, 2021

Co-processing of radioactive effluents with coal fly ash-derived materials is recognized as a res... more Co-processing of radioactive effluents with coal fly ash-derived materials is recognized as a resource-saving approach for efficient stabilization/solidification of radioactive components of wastewater. In this context, the paper is focused on the hydrothermal synthesis of Sr2+-bearing aluminosilicate/silicate phases as analogs of a mineral-like 90Sr waste form using hollow glass-crystalline aluminosilicate microspheres from coal fly ash (cenospheres) as a glassy source of Si and Al (SiO2-Al2O3)glass) and Sr(NO3)2 solutions as 90Sr simulant wastewater. The direct conversion of cenosphere glass in the Sr(NO3)2-NaOH-H2O-(SiO2-Al2O3)glass system as well as Sr2+ sorption on cenosphere-derived analcime (ANA) in the Sr(NO3)2-H2O-ANA system were studied at 150–200 °C and autogenous pressure. The solid and liquid reaction products were characterized by SEM-EDS, PXRD, AAS and STA. In the Sr(NO3)2-NaOH-H2O-(SiO2-Al2O3)glass system, the hydrothermal processing at 150–200 °C removes 99.99% of t...

Research paper thumbnail of Cenosphere-sourced hydrothermal synthesis of pollucite-analcime solid solutions as a low-temperature method to immobilize 137Cs in a mineral-like form

Journal of Nuclear Materials, 2020

h i g h l i g h t s g r a p h i c a l a b s t r a c t Microspheres with a composite mullite/ANA w... more h i g h l i g h t s g r a p h i c a l a b s t r a c t Microspheres with a composite mullite/ANA wall are produced as a Cs mineral-like form. Analcime-pollucite phases with nonsignificant difference in Si/Al ratios were obtained. Mullite provides the preservation of a spherical shape of crystallized microspheres. The average Cs content in solid products is 23e32 wt %.

Research paper thumbnail of Magnetic Composite Sorbents for Trapping Heavy Metals from Liquid Waste and Their Immobilization in a Mineral-Like Matrix

Journal of Siberian Federal University. Chemistry, 2019

Magnetic sorbents were prepared by addition of ferrospheres to zirconia-silica gel followed by th... more Magnetic sorbents were prepared by addition of ferrospheres to zirconia-silica gel followed by thermal treatment at 500 °C. The ferrosphere narrow fraction E -0.063+0.050 mm from fly ash resulted from combustion of Ekibastuz coal was used as a magnetic component. The surface of magnetic composites was additionally functionalized by grafting of – POONa and – NH2 groups. Under equilibrium conditions sorption capacities of the sorbents with respect to Се3+ used as a U4+/Th4+ simulator and Pb2+ were measured by means of determination of sorption isotherms which were fitted by the Langmuir model. It was established that extraction of Се3+ and Pb2+ from aqueous solutions is characterized by distribution coefficients of 104–106 ml/g. Temperature conditions for solid-phase crystallization of the sorbents resulting in polyphase systems with the content of zircon phase of 50 wt. % were found

Research paper thumbnail of Preparation and Properties of Zr-Bearing Sorption Materials Based on Coal Fly Ash Microspheres

Journal of Siberian Federal University. Chemistry, 2019

The influence of hydrothermal conditions on synthesis of analcime and a composite material ZrO2- ... more The influence of hydrothermal conditions on synthesis of analcime and a composite material ZrO2- analcime as well as zirconomolybdate coverings with ion exchange properties was studied using narrow fractions of aluminosilicate microspheres with a high content of a glass phase (91-95 wt. %). The possibility to synthesize ZrO2-analcime composites of narrow particle size distributions with maximum of about 40 μm and 6 μm under hydrothermal treatment at 150 °С was demonstrated starting from microspheres with Si/Al=2.7 and applying different regimes of a reaction mixture agitation. A microsphere material of a “core-shell” type such as ZrMo2O7(OH)2(H2O)2@(SiO2-Al2O3)glass with the nanostructured covering was prepared. Sorption properties of the materials regarding Nd3+, Sr2+ and Cs+ were studied under equilibrium conditions by means of determination of sorption isotherms and their fitting by the Langmuir model. Sorption parameters were determined including distribution coefficients which ...

Research paper thumbnail of Microsphere Zirconomolybdate Sorbents for Extraction of Lanthanides (III) from Aqueous Solutions

Journal of Siberian Federal University. Chemistry, 2017

Micromesoporous zirconomolybdates with a specific surface area of 200 m 2 /g and pore sizes in th... more Micromesoporous zirconomolybdates with a specific surface area of 200 m 2 /g and pore sizes in the range of 10-40 Å (D max~1 5 Å) were synthesized under hydrothermal conditions (150 °С, 72 h). Microsphere composites were prepared by deposition of the zirconomolybdates on a microsphere hollow carrier with a macroporous shell (D pore ~ 2-10µm) resulted from the NH 4 F-HCl-H 2 O etching of a cenosphere narrow fraction (-0,08+0,071 mm) separated from coal fly ash of Reftinskaya power station. The morphological type "cenospheres with a porous shell and a smooth surface" predominates in the fraction. The sorption properties of zirconomolybdates and microsphere composites with different Mo/Zr ratio were studied regarding Nd 3+ cations as a surrogate of trivalent actinides. It was established that the thin-layer mode of zirconomolybdate deposition on the carrier and the increasing of a Mo/Zr ratio in its composition provides the enhanced distribution coefficient (up to 10 4 ml/g) and efficiency of Nd 3+ sorption (up to 85 %).

Research paper thumbnail of ZrMo2O7(OH)2(H2O)2 coated microsphere glass supports derived from coal fly ash cenospheres as a novel sorbent for radionuclide trapping

Journal of Environmental Chemical Engineering, 2019

The nanostructured polycrystalline ZrMo 2 O 7 (OH) 2 (H 2 O) 2 coating was synthesized on coal fl... more The nanostructured polycrystalline ZrMo 2 O 7 (OH) 2 (H 2 O) 2 coating was synthesized on coal fly ash cenosphere derived microsphere glass supports via a two-step mild hydrothermal procedure resulting in a microsphere composite of a hollow core-shell structure. Sorption properties of the microsphere composite with respect to Cs + , Sr 2+ and Nd 3+ as non-radioactive imitators of 137 Cs, 90 Sr and actinides (III) were estimated. The nanostructured design of the coating was shown to enhance the Nd 3+ , Sr 2+ ,Cs + sorption in comparison with pure microsized ZrMo 2 O 7 (OH) 2 (H 2 O) 2. Nd 3+ , Sr 2+ , Cs + sorption distribution coefficients were determined (0.52•10 4 , 0.40•10 3 and 0.92•10 2 mL/g, respectively) and preferential Nd 3+ sorption was explained on the basis of ZrMo 2 O 7 (OH) 2 (H 2 O) 2 structure.

Research paper thumbnail of One-step immobilization of cesium and strontium from alkaline solutions via a facile hydrothermal route

Journal of Nuclear Materials, 2018

Analcime-pollucite solid solutions crystallize as host phases immobilizing Cs þ. Cs þ and Sr 2þ w... more Analcime-pollucite solid solutions crystallize as host phases immobilizing Cs þ. Cs þ and Sr 2þ were immobilized by hydrothermal treatment of coal fly ash cenospheres. Sequestration of Cs and Sr from alkaline solutions was 90e99%.

Research paper thumbnail of Composite Zirconomolybdate Sorbents for Immobilization of f-Metal (III) Cations in a Mineral-Like Matrix

Journal of Siberian Federal University. Chemistry, 2016

Composite zirconomolybdate sorbents of different compositions were prepared by agglomeration of l... more Composite zirconomolybdate sorbents of different compositions were prepared by agglomeration of layered zirconomolybdate with a SiO 2 gel followed by impregnation of a sodium salt of bis-(2,4,4trimethylpentyl)-phosphinic acid (Cyanex 272). Sorption properties of two composites with respect to Nd 3+ , as an actinide (Am, Cm) surrogate, and possibility of Nd 2 Zr 3 (MoO 4) 9 phase formation, which is similar by structure to a kosnarite mineral, by high-temperature phase conversion were studied. It was shown that the inorganic and hybrid composites trap Nd 3+ cations from solutions with distribution coefficients of about 10 4 mL/g and limit sorption capacities of 30 and 50 mg/g, accordingly. It was established that solid-phase crystallization of both composites with sorbed Nd 3+ takes place at 650 °С resulting in a polyphase system with the content of the target phase Nd 2 Zr 3 (MoO 4) 9 of about 30 %.

Research paper thumbnail of Solidification of Cs-137-Bearing Radioactive Waste in Cenosphere-Based Mineral-Like Hosts for Long-Term Disposal in Granithoids

Journal of Siberian Federal University. Chemistry, 2015

Theoretical and practical possibility to stabilize Cs-137(Na)-bearing liquid radioactive waste in... more Theoretical and practical possibility to stabilize Cs-137(Na)-bearing liquid radioactive waste in mineral-like forms which are geochemically compatible with granithoids in its long-term disposal was demonstrated. Perforated cenospheres (SiO 2 /Al 2 O 3 =3.4) of fly ash generated from combustion of kuznetskii coal was used as an aluminosilicate precursor. It was established that solidification of Cs-bearing solutions at 750-1100 °С via the proposed route resulted in glass-crystalline compounds incorporating 53-79 wt. % pollucite with the Cs leaching rate being by 2-3 order of magnitude lower than the standard parameter accepted in Russia for solidified high level waste.

Research paper thumbnail of Synthesis and structure of analcime and analcime-zirconia composite derived from coal fly ash cenospheres

Microporous and Mesoporous Materials, 2017

Cubic analcime and analcime-zirconia composite with the Si/Al ratio of 2.04 and 2.16, respectivel... more Cubic analcime and analcime-zirconia composite with the Si/Al ratio of 2.04 and 2.16, respectively, was synthesized by hydrothermal treatment of coal fly ash cenospheres (Si/Al ¼ 2.7) at 150 C. The scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), synchronous thermal analysis (STA) methods were used to study the morphology, composition and structure of the products. Two main types of analcime bearing particles were obtained, such as hollow microspheres with attached analcime icositetrahedra of 5 e50 mm in size and individual analcime crystals of a narrow particle size distribution (D m ¼ 41 mm) with incorporated zirconia (4.8 wt% Zr). The high quality of the crystalline fractions allowed an accurate fullprofile PXRD analysis of complete analcime crystal structure and composition including anisotropic displacement parameters of all atoms and H-positions of water molecules.

Research paper thumbnail of Immobilization of Liquid Radioactive Waste in Mineral-Like Matrices Derived From Inorganic Cenosphere-Based Sorbents as Precursors

MRS Proceedings, 2008

The progress in study of immobilization of liquid radioactive waste in mineral-like aluminosilica... more The progress in study of immobilization of liquid radioactive waste in mineral-like aluminosilicate matrices (feldspar and feldspathoids) derived from cenosphere-based microspherical zeolite sorbents is reported. Based on the analysis of ‘composition – morphology –C characteristics’ correlation obtained for more than 70 cenosphere products with a high content of one morphological type of imperforated cenospheres, optimal ranges of cenospheres composition were identified for the synthesis of zeolites with the predetermined structural type. Given that the cenosphere-based zeolite sorbents are precursors of the final waste form, further activity proceeds toward developing a highly efficient zeolite sorbent of NaP1 type, which would ensure the effective trapping of Cs+ and/or Sr2+ ions and the phase transformation under relatively mild conditions (T≤1000°C). The paper details the main criteria for realization of the ‘precursor’ approach for fixation of Cs-Sr fraction using cenosphere-ba...

Research paper thumbnail of Solid-Phase Transformation of Cs+- and Sr2+-Bearing Zeolite Sorbents Derived From Cenospheres to Mineral-Like Forms

MRS Proceedings, 2009

The paper describes the studies of the transformation of Cs+- and Sr2+-containing zeolite sorbent... more The paper describes the studies of the transformation of Cs+- and Sr2+-containing zeolite sorbents synthesized from fly ash cenospheres to crystalline mineral composition, suitable for the long-term disposal. Series of Cs+- and Sr2+-exchanged NaP1-containing sorbents were subjected to the thermochemical transformation in the temperature range 40-1100°C at atmospheric pressure in air and the progress of reaction was monitored by DSC and XRD analysis. It was shown that initial sodium zeolite undergoes two-step transformation at 736-785°C and 892-982°C forming nepheline as the principle product, with the conversion temperatures being dependant on the heating rate.The thermal treatment of Cs+-bearing zeolite sorbent led to formation of a complex multiphase system, the principal components of which were nepheline and pollucite. Increasing cesium content in the samples led to a monotonous shift of crystallization peak to the higher temperature range (1005-1006°C). A more complicated behav...

Research paper thumbnail of Porous Materials Based on Cenospheres of Coal Fly Ash for Fixation of Cs-137 and Sr-90 in Mineral-like Aluminosilicates

MRS Proceedings, 2006

ABSTRACTAmong the crystalline matrices being developed for immobilization of 137Cs and 90Sr are f... more ABSTRACTAmong the crystalline matrices being developed for immobilization of 137Cs and 90Sr are framework aluminosilicates like feldspars and feldspathoids. A novel approach to obtain mineral-like aluminosilicate forms of 137Cs and 90Sr with using porous materials based on hollow aluminosilicate microspheres of coal fly ash (cenospheres) has been demonstrated. Two modifications of microspherical porous materials have been developed, (i) moulded porous matrices based on consolidated cenospheres and (ii) zeolite sorbents obtained by hydrothermal zeolitization of cenospheres. The first includes impregnation of Cs- or Sr-containing solutions into porous matrices, drying and calcining at temperatures (700-900°C) lower than the softening point of the porous matrix material, at which solid phase crystallization takes place with formation of framework aluminosilicates, such as Cs-nepheline, pollucite or Sr-anorthite. Using zeolite sorbents, immobilization of Cs+ and Sr2+ proceeds through th...

Research paper thumbnail of Removal of radioactive and other hazardous material from fluid waste

Hollow glass microspheres obtained from fly ash (cenospheres) are impregnated with extractants/io... more Hollow glass microspheres obtained from fly ash (cenospheres) are impregnated with extractants/ion-exchangers and used to remove hazardous material from fluid waste. In a preferred embodiment the microsphere material is loaded with ammonium molybdophosphonate (AMP) and used to remove radioactive ions, such as cesium-137, from acidic liquid wastes. In another preferred embodiment, the microsphere material is loaded with octyl(phenyl)-N-N-diisobutyl-carbamoylmethylphosphine oxide (CMPO)

Research paper thumbnail of Open-cell glass crystalline porous material

An open-cell glass crystalline porous material made from hollow microspheres which are cenosphere... more An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, he...

Research paper thumbnail of One-step fabrication of hollow aluminosilicate microspheres with a composite zeolite/glass crystalline shell

Microporous and Mesoporous Materials, 2013

ABSTRACT One-step procedure to fabricate hollow aluminosilicate microspheres with a composite NaA... more ABSTRACT One-step procedure to fabricate hollow aluminosilicate microspheres with a composite NaA(NaX)/glass/mullite composite shell was demonstrated by the direct conversion of low-silica cenospheres (Si/Al = 1.8) separated from coal fly ash. The reported method does not involve seeding and structure-directing reagents. Composition of cenospheres and the stirring of reactants at the optimal synthesis temperature (T = 80 °C) and alkaline molarity (2.5 M NaOH) are parameters affected the formation of a monozeolitic phase (NaA or NaX). The influence of the silica–alumina composition of cenospheres on the type of zeolite phase formation is only revealed under stirring conditions. In the case of the low-silica cenospheres, NaA (LTA) zeolite crystallizes as a dominant phase (43 wt.%) (Si/Al = 1.8) under stirring of reactants, while the static conditions favor formation of the NaX (FAU) zeolite phase (45 wt.%).

Research paper thumbnail of Microsphere zeolite materials derived from coal fly ash cenospheres as precursors to mineral-like aluminosilicate hosts for 135,137Cs and 90Sr

Journal of Nuclear Materials, 2013

Hollow microsphere zeolite materials with a bilayered zeolite/glass crystalline shell bearing NaP... more Hollow microsphere zeolite materials with a bilayered zeolite/glass crystalline shell bearing NaP1 zeolite were synthesized by the hydrothermal treatment of coal fly ash cenospheres (Si/Al = 2.7) in an alkaline medium. Cs + and/or Sr 2+ forms of zeolitized cenospheres with the different Cs + and/or Sr 2+ loading were prepared by the ion exchange from nitrate solutions. The resulted (Cs,Na)P1, (Sr,Na)P1 and (Cs,Sr,Na)P1 bearing microsphere zeolites were converted to glass ceramics by heating at 900-1000°C. The differential scanning calorimetry and quantitative phase analysis were used to monitor the solidphase transformation of the initial and ion exchanged zeolite materials. It was established that the final solidified forms of Cs + and/or Sr 2+ are glass-crystalline ceramic materials based on pollucite-nepheline, Sr-feldspar-nepheline and Sr-feldspar-pollucite composites including $60 wt.% of the major host phases (pollucite, Sr-feldspar) and 10-20 wt.% of glass. The 137 Cs leaching rate of 4.1 Â 10 À7 g cm À2 day À1 was determined for the pollucite glass-ceramic according to Russian State Standard (GOST) No. 52126 P-2003 (7 day, 25°C, distilled water).