Heterogeneous and mechanochemical syntheses of new materials based on titanium, calcium, and magnesium phosphates were developed for the first time. The products demonstrated high efficiency as sorbents for the removal of heavy metal cations and radionuclides from solutions. The joint action of the sorption components ensures high sorption capacity towards various cations over a wide pH range. The optimal conditions providing products with a specified phase composition were identified. The use of a solution of a phosphorus-containing agent and solid precursors taken in a stoichiometric ratio, together with mild hydrothermal conditions make it possible to minimize the amount of liquid waste. In the first step of the synthesis, precipitation of titanium phosphate and formation of the precursor needed for the second step (formation of calcium and magnesium phosphates) take place simultaneously. Thus, the synthesis protocol complies with the green chemistry principles.

The highly alkaline multicomponent systems TiO2–H2SO4–Na2SiO3–NaOH–H2O and TiO2–H2SO4–(NH4)2SO4–Na2SiO3–NaOH–H2O have been studied under conditions of hydrothermal synthesis, which gives new products with specified technical properties. It has been shown that, by a targeted selection of structure-forming components, in particular, titanium compounds, together with optimal parameters of hydrothermal treatment of the formed precursor, one can obtain compounds with given chemical composition and particle size and morphology. It has been found that the rate of structural transformations in the synthesis depends on the phase composition of titanosilicate precursors. Their hydrothermal treatment involves the alkaline and thermal hydrolysis followed by dehydration of the hydrolyzed phases of titanium(IV) and silicon. This is accompanied by the localization of free bonds ensuring the formation of Ti–O–Si–O bridges and their subsequent transformation into new structured species.

The paper presents a new low-temperature method for the synthesis of highly dispersed powders of double phosphates LiCoPO4 and LiNiPO4 using low-waste technology. It has been shown that the morphology and particle size of the obtained materials depend on the type of initial precursors. The obtained compounds are characterized by elemental, XRD, SEM, cyclic volammetry, cyclic chronopotentiometry analyses. A new approach to the synthesis of submicron powders of lithium double phosphates and transition metal (nickel, cobalt) is more effective compared to current methods.

Pilot-plant testing of a laboratory technology for producing alkaline titanosilicate sorbent from the current titanium-containing technogenic waste from the enrichment of the Khibiny apatite–nepheline ore shows that this technology can be modeled on an enlarged (pilot-plant) scale. The parameters of the main technological operations in systems of various salt compositions are checked and optimized. For example, in the ammonium sulfate systems, a two-phase precipitate is formed, which consists of phases similar to the minerals zorite and ivanyukite at their weight ratio of about 1 : 0.8–1.0. A one-phase precipitate in the form of ivanukite crystals is formed in the sulfate system. A study of the technical and sorption properties characterized in the tests of sorbents finds that the absorption of the Cs + cation is due to the substitution for the Na + cation in the interframework space of the crystal. The Sr 2+ cation is also substituted for Na + and is additionally deposited on the sorbent particles due to the alkaline reaction of its surface. The sorption capacities of powder and granules for Sr 2+ are, on average, 170 and 160 mg g –1 , respectively; and for Cs+, 275 and 245 mg g –1 , respectively. Tests will be continued as pilot batches of the sorbent with stable structure and properties are produced for testing in specialized organizations.

The paper presents a new low-temperature method for the synthesis of fine powders of double phosphates LiCoPO 4 and LiNiPO 4 using a low-waste technology. It has been shown that the morphology and particle size distribution of the synthesized materials are determined by the type of precursor used. The resulting compounds are characterized by chemical analysis, X-ray powder diffraction analysis, scanning electron microscopy, cyclic voltammetry, and cyclic chronopotentiometry. The new approach to the synthesis of submicron powders of lithium and transition metal (nickel or cobalt) double phosphates is more efficient than the existing conventional methods.

Generalizing analysis of the ecological aspects of the development and application of materials and chemical technologies, promising for management of the Arctic zone and cold regions is carried out. The requirements to the Arctic materials and technologies both in their functionality and in relation to minimization of environmental impact are discussed. The problems related to the arrangement of Arctic raw material processing at mining sites are discussed.

A scheme was proposed for the first time to produce analogs of the natural minerals sampleite NaCaCu 5 (PO 4 ) 4 Cl⋅5H 2 O and lavendulan NaCaCu 5 (AsO 4 ) 4 Cl⋅5H 2 O from intermediate products produced by AO Apatit and AO Kol’skaya GMK. The obtained compounds are promising functional materials: they exhibit antiferromagnetic properties in a magnetic field and can be used, e.g., in designing memory cells operating at low temperatures, and also as ionic conductors.

The sorption of 137Cs and 90Sr radionuclides from model and real solutions of various salt compositions has been studied on a synthetic powder and pelletized titanosilicate represented by ivanyukite (SIV), the technology of which was developed at the Kola Science Center, Russian Academy of Sciences. Titanosilicate sorbents successfully recover Cs and Sr from mixed multicomponent solutions in a broad pH range (from 4 to 11) at a salt content of up to 10 g/L with a purification coefficient of more than 200 in the case of powder materials. In the case of a pelletized sorbent, the distribution coefficient Kd decreases due to the partial dissolution (peptization) of silicate binder, which results in a decrease in the effective specific surface of sorbent. When there is no salt background, the sorption of radionuclides by SIV significantly decreases. This fact is caused by the protonation of the sorbent and, consequently, competition between hydrogen ions and radionuclides. The extraction ability of SIV towards 137Cs and 90Sr, as well as 51Cr, 54Mn, and 60Co, in the presence of the salts of other elements in the form of unfiltered suspension allows one to carry out sorption without a preliminary water preparation stage, which is represented by precipitation with iron or aluminum salts. The sorption characteristics of SIV have been compared to the Termoksid-35 ferrocyanide sorbent employed in industry for the recovery of 137Cs. The possibility of using one type of sorbent, SIV, for deactivating liquid radioactive waste (LRW) instead of the conventional purification scheme employed at an enterprise would remarkably facilitate the sorption scheme of processing of LRW. Considering this feature of SIV, one can expect a decrease in the volume of secondary radioactive waste in the form of spent sorbents for subsequent utilization. Verifying the process in dynamic mode has confirmed the effectiveness of SIV for processing LRW. The possibility of utilizing the spent sorbent in the form of ceramic material of SYNROC type possessing high radiation and chemical stability is an important potential advantage of SIV.

The possibility to synthesize titanium phosphate from crystalline titanium salts has been shown for the first time. Optimal synthesis conditions have been found to provide preparation of monophase product of composition Ti(HPO4)2 · H2O or TiO(OH)H2PO4 · 2H2O by heterogeneous reaction of titanium-containing precursors with phosphoric acid. The process has been found to proceed for 3–5 h at stoichiometric consumption of the components and provides more environmentally benign and profitable conditions as compared with the known methods of synthesis.

В настоящей работе рассматривается возможность создания подземных хранилищ газа в гидратном состоянии на 11 перспективных площадях Вилюйской синеклизы. Для этого были определены границы зоны стабильности гидратов природного газа Средневилюйского газоконденсатного месторождения и метана в пресной воде и в растворе хлорида натрия (минерализация 51,77 г/л). Путем сопоставления мощностей зоны стабильности гидратов природного газа и многолетнемерзлых толщ выбраны наиболее подходящие для создания подземных хранилищ газа площади.

Layered microporous titanosilicate AM-4 (Aveiro-Manchester-4) is a synthetic analog of microporous lintisite-type minerals. We applied the hydrothermal method to synthesize AM-4 compound from different titanium sources, i.e. titanium (III) chloride solution, titanyl-sulfate (titanite ore treatment product) and sodium metasilicate by stepwise cooling of an initial titanium-silicate mixture. In acid solution the crystal structure of AM-4 transformed into a novel layered titanosilicate SL3 (synthetic decationated lintisite) with a unique topology that consists of Ti2Si4O10(OH)4 nano-blocks. It was found that SL3 compound had a tendency for uptake of Ag from the standard test copper-nickel electrolyte. A possibility of repeated use of SL3 as a renewable sorbent was shown on the example of sorption Ca2+ cations. Both AM-4 and SL3 compounds can be considered as new functional materials of renewable and thermally stable nature with potential application for sorption and immobilization of the radioactive iodine isotopes.

В связи с осуществляемой программой по очистке арктического побережья России от жидких радиоактивных отходов (ЖРО), накопленных за время функционирования атомного флота, возникает проблема дезактивации больших объемов регламентных ЖРО, а также малых и средних объемов ЖРО, для которых технологические регламенты переработки отсутствуют. В настоящее время не существует технологических процессов, позволяющих производить комплексную одностадийную очистку жидких радиоактивных отходов с возможностью дальнейшего долговременного захоронения продуктов очистки. Наши исследования показали, что для очистки нерегламентных ЖРО может быть успешно использован новый нанокристаллический сорбент LHT-9 (слоистый титанат гидразина), способный удалять из водных растворов более 50 химических элементов, в том числе большинство радионуклидов, включая 137Cs, 90Sr, 93Zr, 151Sm, 154Eu, 99Tc, 79Se, 107Pd, 126Sn, 238U, 235U, 239Pu, 237Np, 243Am. Быстрая одноактная очистка регламентных ЖРО реакторов водно-водяного энергетического типа от радионуклидов Cs, Sr и Co может быть проведена при помощи еще одного нового сорбента – минерала иванюкита (микропористый титаносиликат натрия), селективного в отношении этих элементов. Одновременное либо последовательное использование разработанных сорбентов с учетом их устойчивости в растворах любой кислотности-щелочности позволяет полностью решить проблему дезактивации и отверждения ЖРО практически любого химического состава. В статье вводится понятие «геоника» – инженерно-технологическое воспроизведение и использование уникальных свойств природных минералов для решения прикладных задач, по аналогии с бионикой.

Using X-ray diffraction study of the solid phases formed in an alkaline titanosilicate system with an invariable concentration of components upon process temperature variation in the 180–210°C range and time variation from 1 to 7 days, structural genesis of the solid phases was established. This allowed predicting the final result, consisting in the formation of an ion exchange material as a powder or granules with a high sorption capacity for Cs+ and Sr2+ cations. The formation of granules of the titanosilicate sorbent with a colloidal silicon binder induced agglomeration of particles with partial isolation of their pore system, which decreased the sorption capacity for Cs+ by a factor of 1.5. Simultaneously, the uptake of Sr2+ increased by 10–15% due to the formation of insoluble Sr2+ silicate or hydroxide on the surface with pH of 8.5–9.5.

Using a titania–silica precursor with the composition SiO 2 ∙ TiO 2 ∙ х H 2 O, isolated via hydrochloric acid treatment of a process waste from the dressing of apatite–nepheline ore, we have prepared a hybrid composite containing silica as a matrix for an α-Ti(HPO 4 ) 2 ∙ H 2 O functional filler (STP). The key step of the synthesis process is a solution-phase reaction of the precursor with phosphoric acid. Our results demonstrate that a preferable sequence of steps begins with the mechanical activation of the components of the precursor, with their phase transformations. Using a combination of subsequent heat treatment with phosphoric acid with different concentrations under atmospheric conditions and in an autoclave, we have found conditions for chemical reactions that change the composition and structure of the final product and, accordingly, its sorption activity for cesium and strontium cations. The synthesized hybrid inorganic material can be effectively used to remove radionuclides and heavy nonferrous metal cations from liquid discharges. The proposed technology significantly surpasses known processes in economic and environmental characteristics.

6 Институт геохимии и аналитической химии (ГЕОХИ) РАН, Москва Аннотация.Рассмотрены основные структурные особенности прототипов различных функциональных материалов минералов класса титаносиликатов из массивов Кольской щелочной провинции, используемых в качестве сорбентов, молекулярных сит и ионообменников, прекурсоров для дубителей, нелинейнооптических материалов и фотокатализаторов (семейство линтисита-кукисвумита, группа мурманита, каменевит, группа иванюкита, ситинакит, группа зорита, натисит, группа лабунцовита).Ионообменные и сорбционные свойства титаносиликатов обуславливают их применение для очистки жидких радиоактивных отходов с надёжной фиксацией радионуклидов