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

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 sorption ability with respect to Sr2+ (KD ~106 mL/g) were determined. The high-temperature solid-phase re-crystallization of Cs+/Sr2+-exchanged HZD-ANA composites was shown to occur at 1000 °C resulting in a polyphase system based on nepheline, tetragonal ZrO2, and glass phase

Preparation of Cenosphere-Derived Lutetium-Aluminosilicate Microspheres as Precursors of Radiation Sources for Brachytherapy

Полые алюмосиликатные микросферы (ценосферы) стабилизированного состава (стеклофаза – 95.4 мас.%; (SiO2/Al2O3) стекло – 3.1), выделенные из летучих зол от сжигания угля, были использованы для получения лютеций-алюмосиликатных микросфер в качестве прекурсоров микросферических источников β-излучения на основе Lu‑177, применяемых для селективной радиационной терапии опухолей. Для включения ионов Lu3+ в алюмосиликатный материал ценосфер была реализована следующая стратегия: (1) химическая модификация глобул ценосфер путём превращения алюмосиликатного стекла в цеолиты с сохранением сферической формы ценосфер; (2) сорбционное концентрирование Lu3+ в цеолитном слое микросфер путем ионного обмена 3Na+ ↔ Lu3+; (3) капсулирование Lu3+ в алюмосиликатной матрице микросфер путём высокотемпературного твердофазного превращения сорбированной формы Lu3+ при 1000 и 1200 оС в малорастворимые формы. Получены цеолитизированные микросферы, содержащие фазу цеолита NaP1 (GIS), и исследованы его сорбционные свойства в отношении Lu3+. Установлено, что сорбционная ёмкость цеолитизированного продукта в отношении Lu3+ составляет около 70 мг/г Lu3+. Обнаружено, что длительное нагревание Lu3+/NaP1-микросфер в неподвижном слое при 1000 оС приводит к кристаллизации фазы моноклинного пиросиликата лютеция (Lu2Si2O7), в то время как в результате быстрого цикла нагрева-охлаждения при 1200 оС в движущемся слое происходит аморфизация цеолитного компонента без формирования кристаллической фазы лютеция с сохранением сферической формы прекурсора. Микросферы как с кристаллической, так и аморфной формами лютеция характеризуются низкой скоростью выщелачивания лютеция (Rn не выше 3×10–7 г/см2×сут) в растворе 0.9 % NaCl, имитирующем состав кровиCoal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass phase – 95.4 wt.%; (SiO2/Al2O3) glass – 3.1) were used to fabricate lutetium-aluminosilicate microspheres as precursors of Lu‑177 bearing β-irradiation sources applied for the selective radiation therapy of tumors. To incorporate Lu3+ ions into cenosphere’s aluminosilicate material, the following strategy was realized: (1) chemical modification of cenosphere globules by conversion of aluminosilicate glass into zeolites preserving a spherical form of cenospheres; (2) the loading of zeolitized microspheres with Lu3+ by means of ion exchange 3Na+ ↔ Lu3+; (3) Lu3+ encapsulation in an aluminosilicate matrix by solid-phase transformation of the Lu3+ sorbed form into insoluble forms under the thermal treatment at 1000–1200 oC. The zeolitized microspheres containing the zeolite phase NaP1 (GIS) were synthesized and their sorption properties with respect to Lu3+ were studied. It was established that the sorption capacity of the zeolitized products is about 70 mg/g Lu3+. It was found that the long-time heating of the Lu3+-loaded zeolite precursor at 1000 oC in a fixed bed resulted in the crystallization of a monoclinic lutecium pyrosilicate (Lu2Si2O7). The fast heating–cooling cycle at 1200 oC in a moving bed resulted in amorphization of the zeolite component without the formation of the lutecium crystal phase preserving the precursor spherical form. The microspheres based on both crystalline and amorphous Lu forms are characterized by the low Lu leachability rate (Rn ≤ 3×10–7 g/cm2×day) in 0.9 % NaCl solution imitating bloo

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

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 = 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 5–50 mm in size and individual analcime crystals of a narrow particle size distribution (Dm = 41 mm) with incorporated zirconia (4.8 wt% Zr). The high quality of the crystalline fractions allowed an accurate full-profile PXRD analysis of complete analcime crystal structure and composition including anisotropic displacement parameters of all atoms and H-positions of water molecules

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

Получены композитные циркономолибдатные сорбенты различного состава путем агломерации слоистого циркономолибдата с гелем SiO2 с последующим нанесением на неорганическую композицию бис-(2,4,4-триметилпентил)-фосфината натрия (Cyanex 272). Изучены сорбционные свойства двух композиций в отношении катионов Nd3+ как имитатора актиноидов (Am, Cm) и возможность формирования фазы Nd2Zr3(MoO4)9, изоструктурной минералу коснарит, посредством высокотемпературного фазового превращения сорбента. Показано, что неорганическая и гибридная композиции извлекают катионы Nd3+ из растворов с коэффициентом распределения порядка 104 мл/г и предельной сорбционной ёмкостью 30 и 50 мг/г соответственно. Установлено, что при 650 °С обе композиции с сорбированными катионами Nd3+ претерпевают твердофазную кристаллизацию с образованием полифазной системы, в которой содержание целевой фазы Nd2Zr3(MoO4)9 составляет в среднем около 30 %.Composite zirconomolybdate sorbents of different compositions were prepared by agglomeration of layered zirconomolybdate with a SiO2 gel followed by impregnation of a sodium salt of bis-(2,4,4- trimethylpentyl)-phosphinic acid (Cyanex 272). Sorption properties of two composites with respect to Nd3+, as an actinide (Am, Cm) surrogate, and possibility of Nd2Zr3(MoO4)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 Nd3+ cations from solutions with distribution coefficients of about 104 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 Nd3+ takes place at 650 °С resulting in a polyphase system with the content of the target phase Nd2Zr3(MoO4)9 of about 30 %

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

Получены композитные циркономолибдатные сорбенты различного состава путем агломерации слоистого циркономолибдата с гелем SiO2 с последующим нанесением на неорганическую композицию бис-(2,4,4-триметилпентил)-фосфината натрия (Cyanex 272). Изучены сорбционные свойства двух композиций в отношении катионов Nd3+ как имитатора актиноидов (Am, Cm) и возможность формирования фазы Nd2Zr3(MoO4)9, изоструктурной минералу коснарит, посредством высокотемпературного фазового превращения сорбента. Показано, что неорганическая и гибридная композиции извлекают катионы Nd3+ из растворов с коэффициентом распределения порядка 104 мл/г и предельной сорбционной ёмкостью 30 и 50 мг/г соответственно. Установлено, что при 650 °С обе композиции с сорбированными катионами Nd3+ претерпевают твердофазную кристаллизацию с образованием полифазной системы, в которой содержание целевой фазы Nd2Zr3(MoO4)9 составляет в среднем около 30 %.Composite zirconomolybdate sorbents of different compositions were prepared by agglomeration of layered zirconomolybdate with a SiO2 gel followed by impregnation of a sodium salt of bis-(2,4,4- trimethylpentyl)-phosphinic acid (Cyanex 272). Sorption properties of two composites with respect to Nd3+, as an actinide (Am, Cm) surrogate, and possibility of Nd2Zr3(MoO4)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 Nd3+ cations from solutions with distribution coefficients of about 104 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 Nd3+ takes place at 650 °С resulting in a polyphase system with the content of the target phase Nd2Zr3(MoO4)9 of about 30 %

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

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+ sorption abilities were studied. As revealed, the Lu3+ sorption capacities of the zeolitized products are about 130 and 70 mg/g Lu3+ for NaX and NaP1 microspheres, respectively. It was found that the long-time heating of the Lu3+-loaded zeolite precursors at 1273 K in a fixed bed resulted in the crystallization of monoclinic Lu2Si2O7 in both zeolite systems, which is a major component of crystalline constituents of the calcined microspheres. The fast heating–cooling cycle at 1473 K in a moving bed resulted in the amorphization of zeolite components in both precursors and softening glass crystalline matter of the NaX-bearing precursor with preserving its spherical form and partial elimination of surface open pores. The NaX-bearing microspheres, compared to NaP1-based precursor, are characterized by uneven Lu distribution over the zeolite-derived layer. The precursor based on gismondin-type zeolite provides a near-uniform Lu distribution and acceptable Lu content (up to 15 mol.% Lu2O3) in the solid phase

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

Получены композитные цеолитные сорбенты на основе анальцима с включениями гидратированного диоксида циркония (ZrO2-анальцим) путем гидротермальной обработки ценосфер летучих энергетических зол с высоким содержанием стеклофазы в присутствии соединения циркония и щелочного активирующего агента при 150 °C и различном режиме перемешивания реакционной смеси. Продукты синтеза охарактеризованы методами РФА, РЭМ-ЭДС, СТА и низкотемпературной адсорбции азота, изучены их сорбционные свойства в отношении Cs+ и Sr2+ в интервале рН = 2–10. Установлено, что композиции ZrO2-анальцим превосходят немодифицированный анальцим в 2–5 раз по величине сорбции Cs+ и Sr2+ и на два порядка по величине коэффициента распределения (KD ~106 мл/г). Изучен процесс высокотемпературного твердофазного превращения Cs+/Sr2+-обменных форм композиций, моделирующий процесс перевода водорастворимых форм радионуклидов Cs‑137 и Sr‑90 в минералоподобную форму. Показано, что при 1000 °C композиции ZrO2-анальцим с сорбированными катионами Cs+ и Sr2+ претерпевают фазовое превращение с образованием полифазной системы близкого состава на основе фаз нефелина, тетрагонального ZrO2 и стеклофазыComposite 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 mineral-like form. It was shown that at 1000 °C the ZrO2-analcime compositions with sorbed Cs+ and Sr2+ undergo the phase transformation resulting in polyphase systems of similar composition based on nepheline, tetragonal ZrO2, and glass phas

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

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.The nanostructured polycrystalline ZrMo2O7(OH)2(H2O)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+, Sr2+ and Nd3+ as non-radioactive imitators of 137Cs, 90Sr and actinides (III) were estimated. The nanostructured design of the coating was shown to enhance the Nd3+, Sr2+,Cs+ sorption in comparison with pure microsized ZrMo2O7(OH)2(H2O)2. Nd3+, Sr2+, Cs+ sorption distribution coefficients were determined (0.52∙104, 0.40∙103 and 0.92∙102 mL/g, respectively) and preferential Nd3+ sorption was explained on the basis of ZrMo2O7(OH)2(H2O)2 structure

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

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.Hydrothermal treatment of coal fly ash cenospheres (Si/Al = 2.7) as a glassy source of Si and Al was carried out in 1.5 M NaOH at 150°C in the presence of Cs+ and Sr2+ to study the possibility of Cs+ and Sr2+ immobilization in mineral-like compounds. Systems Na2O–H2O– (SiO2–Al2O3) glass, Na2O–Cs2O–H2O– (SiO2–Al2O3) glass with Cs+/Na+ ratios of 0.05 and 0.5, and Na2O–SrO–H2O– (SiO2–Al2O3) glass with Sr2+/Na+ ratios of 0.25 and 0.025 were under study. Structure, composition and morphology of solid products were characterized by PXRD, SEM-EDS and STA methods. In the Cs+/Sr2+ free systems the deep crystallization of cenosphere glass takes place resulting in hollow polycrystalline analcime microspheres. Microsphere solids including phases of ANA topology (analcime, pollucite or analcime-pollucite solid solutions) and Cs+/Sr2+ silicates are produced as Cs+ and Sr2+ immobilized forms in the Cs+/Sr2+ bearing systems. The degree of Cs+ and Sr2+ recovery from alkaline solutions was 90–99%

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

Методом гидротермального синтеза (150 °С, 72 ч) получены микромезопористые циркономолибдаты с удельной поверхностью около 200 м2/г и размером пор в интервале 10-40 Å (Dmax ~ 15 Å), а также микросферические композиции путем нанесения циркономолибдатов на микросферический полый носитель с макропористой оболочкой (Dпор ~ 2-10 μm). В качестве носителя использовали продукт травления NH4F-HCl-H2O узкой фракции ценосфер (-0,08+0,071 мм) из летучей золы Рефтинской ГРЭС с преимущественным содержанием морфологического типа «ценосферы с пористой оболочкой и гладкой поверхностью». Изучены сорбционные свойства циркономолибдата и микросферических композиций с различным отношением Mo/Zr в отношении катионов Nd3+ как имитатора трехвалентных актиноидов. Установлено, что тонкослойное нанесение циркономолибдата на носитель и увеличение отношения Mo/Zr в его составе способствует повышению коэффициента распределения (до 104 мл/г) и эффективности процесса сорбции Nd3+ (до 85 %)Micromesoporous zirconomolybdates with a specific surface area of 200 m2/g and pore sizes in the range of 10-40 Å (Dmax~15 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 (Dpore ~ 2-10μm) resulted from the NH4F-HCl-H2O 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 Nd3+ 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 104 ml/g) and efficiency of Nd3+ sorption (up to 85 %