Two types of gold-bearing ore are identified at the Shiraldjin deposit (Kyrgyz Republic): (1) a sulfide-rich ore (approx. 60%), containing coarse native gold particles (> 70 mu m); and (2) an ore type dominated by Fe oxides and hydroxides (approx. 80%) with finely disseminated gold. The latter is considered refractory owing to its complex mineral composition and, in particular, the fine intergrowth of gold with iron and manganese phases. Impurities such as manganese (up to 10%), copper, and bismuth hinder gold extraction by conventional methods. Mineralogical studies have revealed that fine gold particles are frequently encapsulated within goethite and pyrolusite, while copper occurs both as dispersed secondary oxides (e.g., malachite, cuprite) and as sulfides (chalcopyrite, chalcocite) with intergrown textures. These minerals possess similar physical properties (e.g., density and surface characteristics), making selective separation by gravity or flotation inefficient. Technological constraints are outlined, and approaches are proposed, including a combination of gravity pre-concentration, bacterial leaching, and selective flotation as a practical strategy for enhancing gold recovery from complex oxide ores.

Titanium carbide and titanium oxycarbide have been obtained from gravity concentrate of natural titaniumbearing sandstones (Pizhemskoye deposit, Russia) in which titanium is associated with ilmenite alteration products - pseudorutile (electromagnetic fraction P4em) and rutile (non-magnetic fraction P4nm). The P4em is dominated by the products of the exogenous-hypergenic alteration of ilmenite: low-crystalline oxyhydroxide titanium phases, primarily pseudorutile (Fe2Ti3O9). The total content of low crystalline titanium phases is approximately 60-65 %. The P4nm is represented by highly crystalline rutile (approximately 65 %). For the first time, hypercoal obtained from low-grade coal was used as a reducing agent. Carbothermic reduction in of electromagnetic and non-magnetic fractions of gravity concentrates an inert atmosphere at 1500 degrees C lead to formation of cubic and hexagonal TiC phases. The lattice parameter calculated from the structural reflection (220) belongs to the ordered Ti2C phase for samples synthesised using electromagnetic fraction. The samples obtained by non-magnetic fraction reduction the formation of titanium oxycarbide have been detected. Titanium carbide particles of two morphological types have been synthesised. The shape of crystals of the first morphological type is characterised by an isometric habitus close to cubic. Aggregates of the second morphotype are represented by dendrite-like aggregates of titanium carbide crystals. FeSi particles are found on the surface of titanium carbide aggregates in the form of spherical inclusions with a diameter of 2-3 mu m. Thermodynamic analysis of the reactions was carried out and the mechanism of pseudorutile reduction with formation of titanium carbide or oxycarbide was proposed as follows: Fe2Ti3O9 -> TiO2/TiO + Fe -> TiO + Fe -> TiCxOy/TiCx square(1-x).

Design of affordable photocatalytically active materials is of a great interest, but overcoming the bandgap limitation of catalysts to shift the photocatalytic effect of titanium dioxide from the characteristic UV to the visible region of the spectrum is a major challenge. Advanced materials based on nanostructures can be obtained from natural raw materials with isomorphous impurities. Titania 1D structures have been synthesized from the non-magnetic component of titanium-bearing sandstone (Pizhemskoe deposit, Middle Timan, Russia). The presence of Fe and V as isomorphic impurities included in its composition leads to the formation of allowed levels in the bandgap of the catalyst, which enhance its activity. The photocatalytic efficiency has been evaluated on the example of the test reaction of trichlorofnol decomposition in aqueous medium. Titania nanotubes synthesized from commercially available chemically pure precursor were used as reference material to compare the efficiency of the photocatalyst derived from natural raw material.

Binary CaO-MgO-Al2O3-SiO2 (CMAS) ceramics composites of anorthite-cordierite composition were synthesized from natural raw materials (kaolin and dolomite rock). The change of SiO2/Al2O3 ratio in kaolin/dolomite mixtures (12, 24, and 36 wt.%) and synthesized composites along with analysis of their phase composition transformations (X-ray diffraction) during heat treatment (thermogravimetric and differential thermal analysis) give the controlled design of aluminosilicate matrices. The obtained ceramic composites are represented by anorthite, a cordierite-like phase whose ratio varies from 1.3:1 to 2.8:1. Mullite crystals, also included in the composition, reinforce the anorthite-cordierite matrix. The morphostructural features of the samples were studied using optical and scanning electron microscopy. The porosity ranges from 7.8% to 24.2% depending on dolomite content. The impurities of iron and titanium interfering with obtaining a qualitative product are leveled by the presented technique including the heat treatment scheme justified by thermogravimetric analysis. Obtained CMAS-ceramics of anorthite-cordierite composition correspond to industrial international standards by their technical characteristics and exceed the requirements for heat-insulating and chemically resistant materials by compressive strength.

The intracellular or intercellular microspace effectively enables various enzymatic reactions in organisms to proceed efficiently and orderly. Inspired from nature, this study combined the advantages of both natural enzymes and nanozymes to construct a microencapsulated reactor that simulates the enzymatic cascade reaction in vivo. First, the natural aluminosilicate mineral halloysite nanotubes (HNTs) were used as a carrier to in situ generate iron tetroxide (Fe3O4) with horseradish peroxidase-like activity on its surface. Then, it was used as a capsule wall material to encapsulate natural glucose oxidase (GOx), forming the GOx@Fe3O4-HNTs microcapsule reactor. When glucose is added into the system, the GOx within microcapsule reactor will first convert the glucose into gluconic acid and hydrogen peroxide (H2O2), and the H2O2 will continue to be catalyzed by Fe3O4 from the capsule wall and converted into hydroxyl radicals, triggering the color development of the substrate 3,3',5,5'-tetramethylbenzidine(TMB). Among them, Fe3O4-HNTs not only serves as the capsule wall material to protect GOx from environmental interference, but also can conduct a cascade catalytic reaction system with GOx. This kind of enzyme-nanozyme microencapsulation cascade system makes it have better catalytic performance and reaction stability than the natural enzyme systems. In addition, due to the participation of magnetic Fe3O4, the material is also recyclable and reusable. This enzyme-nanoenzyme composite microcapsule reactor provides a new method for simulating a multi-enzyme reaction system in the confined environment of organisms, and also lays a foundation for subsequent research in the fields of bioanalysis and biomimetic catalysis.

Increasing the safety of use of water and land resources, improving the quality of life of the population and reducing the risk of diseases are urgent scientific challenges for modern society. Zeolites are cost-effective natural sorbents suggested to solve environmental problems. The paper presented data on the sorption activity of analcime-bearing rocks (ABR) widespread in the north-east of the European part of Russia. The obtained data testified to promising application of ACR in sorption processes. We determined that ABR were characterized by a high sorption activity to radium, uranium, and thorium, the extraction of which from aqueous solutions amounted to 99.6, 99.4, and 100%, respectively, and had a potential for the rehabilitation of radiation-contaminated areas. We reported a significant decrease in various pollutants resulted from purification of drinking water and waste water from enterprises using ABR.

We carried out experimental studies of the dependence of the sorption of phosphate ion with ilmenite-leucoxene ore (non-magnetic fraction of the gravitational concentrate, Pizhemskoe deposit, Middle Timan, Russia) on the concentration of sodium phosphate solution and pH of the medium. Phosphorus sorbed mainly in the form of HPO42– and H2PO4– ions on the surface of leucoxene mineral phases causing a change in pH of the medium. The result was a change in the magnitude and sign of the surface charge. The experiments have confirmed the idea that leucoxene is most likely the main geochemical barrier for phosphorus under hypergenesis conditions.

The lack of reserves of high-quality bauxite raw justifies increased attention to refractory bauxites of the Middle Timan (Russia). The objects of research are bauxites of the Vezhayu-Vorykvinskoe deposit, which are distinguished by a complex mineral composition together with a dispersed structure and incomplete crystallinity of the mineral matrix. We used a complex of physical methods of mineralogical analysis to obtain reliable information on their composition and structure. We specified the data of the composition of bauxites of the Vezhayu-Vorykvinskoe deposit and discussed proposals for improving processing technologies.

The purpose of this article is to develop a special modeling approach, which simulates the synthesis of a mullite from kaolinite and allows controlling its physical and structural properties. A Taguchi experimental design is implemented to reveal significant PTX-parameters in comparison with insignificant ones for the synthesis of a mullite nanocomposite and prototyping of the optimal synthesis protocol. The objects of the study are ceramic nanocomposites: morphostructural characteristics of mullite synthesized from kaolinite and its structural transformations during heat treatment. 2D contour plots of the intensity of mullite XRD-peaks and content of the mullite phase were used to visualize the influence of input factors and point out the optimal ones. Furthermore, we rearranged the previously proposed simple mathematical model of structural transformations "kaolinite - mullite", which allows controlling the synthesis protocol and properties of the mullite matrix of nanocomposite depending on the PTX-parameters of mullite synthesis.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was used to identify and mapping of industrially and environmentally important iron oxides and hydroxides in red mud dumps. In paper we were focused on specified region of interests - one of the largest boxite processing manufactory in Russia Ural Aluminum Plan (UAP). Initially we use ASTER L1T images. The graph of processing includes band relationship, principal component analysis and spectral angle mapper procedures for identifying spatial distribution of targeted minerals. Several minerals were mapped within red mud dumps No 2 and No 3: Hematite, Goetite, Jarosite and Magnetite. At the next stage the Scanning Electronic Microscopy (SEM) of red mud mineral samples was carried out. The results show a good correlation between remote sensing techniques and standard mineralogical analysis (SEM) method. In both cases the principal iron oxides and hydroxides were observed. Combination of remote sensing and traditional mineralogical analysis methods allows to increase the reliability of assessing ore potential and efficiency of planning utilization technologies for wastes in technogenic deposits. In addition, processing of several ASTER images from different time gap (2004 and 2015) allows to trace in dynamics the transformation of mineral composition in red muds.

The economic importance of titanium oxides and hydroxides results in the active development of titanium deposits. Considering world trends in the development of titanium ores and taking into account their mineralogical features, a comparative study of stages of titanium minerals formation in nature (mineralogenesis) and their transformations in technological processing or synthesis (technogenesis) under hydrothermal conditions at the macrolevel (textural), micro-level (structural) and nanoscale (heterogeneity of individuals and microaggregates, including the synthesis of nanostructures) was made. The natural mechanism of mineral formation of titanium ores in the geological system (titanium ore – hydrothermal conditions) have been successfully used to simulate the synthesis of titanium nanotubes: a trigger for the redeposition of ore matter with the formation of new mineral phases and restructuring at the macro-, micro- and nanoscale is the energy of the geological system/its model, which is sufficient to create conditions for inhomogeneiting (destabilizing) the initial structure of titanium minerals due to external influences (P, T, pH). The relationship between the stages of mineral formation processes in nature and experiment as a promising strategy for the “smart” materials industry was discussed.

Technological mineralogy of titanium ores is the basis for assessing their complexity. It enables, from a unified standpoint, to trace the entire course of changes in mineral matter through operating procedures, including beneficiation, processing, and obtaining target industrial products. The study targets are Pizhemskoye ilmenite-leucoxene sandstones, which are distinguished by a complex polymineral composition. Along with the main ore components, there are other metals with different speciation (isomorphic admixture, independent mineral phases). The optimal set of mineralogical analysis methods for the predictive assessment of their further use is substantiated exemplified by titanium ores of the Pizhemskoye deposit, which are complex, noted for a variable content of iron oxides and contain rare earth metals. Examinations by X-ray phase analysis and scanning electron microscopy confirm that the main titanium phases of sandstones are pseudorutile and a polymineral aggregate, “leucoxene”. Considering the granulometric peculiarities of the magnetic and non-magnetic fractions of the gravity concentrate, the prospects of technologies for processing titanium raw materials are discussed. Along with the problems of obtaining high-quality raw materials, the transformations of mineral phases as a result of extreme impacts and their physicochemical properties as a consequence of isomorphic substitution of a part of Ti atoms with natural modifier agents (Fe and V) in the synthesis of titanium oxide nanostructures for industrial applications are considered (photocatalytic nanoreactor).

The scientific basis for the development of innovative materials (microporous, nanostructured, composite) based on natural (technogenic and synthetic) aluminosilicate raw materials determine prototypes of new technologies in modern industry. Inspired by this, we studied interphase boundary interactions of the “aluminosicate resource – nanoproduct” type system as a key factor of aggregation and nanostructuring in the processes of mineral formation and synthesis. To study features of the heterogeneity of the structure and their correlations with the thermodynamic parameters of the formation of mineral aggregates and individuals, instrumental and methodological resources were used. Based on previous and current studies of natural, synthesized and technogenic aluminosilicates (zeolites, clays, halloysite, fly ash, halloysite nanotubes, etc., features of the constitution and surfaces, sorption, ion-exchange, catalytic, –QS and +QS, biocompatibility, nontoxicity and other useful properties) the prospects for promotion of their industrial application were considered.

Технологическая минералогия титановых руд является основой оценки их комплексности и позволяет с единых позиций проследить весь ход изменений минерального вещества через технологические процессы, включая обогащение, переработку, получение целевых индустриальных продуктов. Объекты исследования – пижемские ильменит-лейкоксеновые песчаники, которые отличаются сложным полиминеральным составом: наряду с главными рудными компонентами присутствуют другие металлы, форма нахождения которых различна (изоморфная примесь, самостоятельные минеральные фазы). Обоснован оптимальный комплекс методов минералогического анализа для прогнозной оценки их дальнейшего использования на примере титановых руд Пижемского месторождения, которые являются комплексными, отличаются переменным содержанием оксидов железа и содержат редкоземельные металлы. На основании экспертиз рентгенофазового анализа и сканирующей электронной микроскопии подтверждено, что основными титансодержащими фазами песчаников являются псевдорутил и полиминеральный агрегат – «лейкоксен». С учетом особенностей гранулометрии магнитной и немагнитной фракций гравитационного концентрата обсуждаются перспективы технологий переработки титанового сырья. Наряду с проблемами получения качественного сырья рассматриваются трансформации минеральных фаз в результате экстремальных воздействий и их физико-химические свойства как результат изоморфного замещения части атомов Ti природными агентами-модификаторами (Fe и V) при синтезе наноструктур титановых оксидов для индустриальных приложений (фотокаталитического нанореактора).

The growing demand for mullite raw materials, which meet industrial requirements originates the search for new and alternative sources, as well as efficient technologies for obtaining the target products (nanocomposites). The article suggests a method for obtaining mullite from kaolinite experimentally (Vezhayu-Vorykvinsky deposit, Russia). Structural kaolinite transformations (Al-Si-O-Me system), mineral phases transformations, and thermodynamics of the process have been studied. Based on the estimation of the thermodynamics of the reactions, the preferable reaction of mullite formation was determined. The article shows, that formation of the target product, mullite nanocomposite, has several intermediate phases (metakaolinite, pseudomullite). The transformations of the initial kaolinite structure include the removal of structural water and separation of the silica-oxygen tetrahedral and alumina-oxygen octahedral layers, the decomposition into free oxides, breaking of bonds between the silica-oxygen tetrahedrons and the partial increase in the coordination number of aluminium ions, the formation of mullite and cristobalite from free oxides. The proposed approach controls the ratio of Al2O3 and SiO2 phases at certain stages, which will further improve the mechanical and other properties of the matrix of the obtained raw materials for the target prototypes of industrial products.

A linear correlation established between TiO2 and P2O5 contents in rocks based on a large dataset substantiates that titanium (together with calcium and iron oxides) serves as a geochemical barrier for phosphorus. The most probable mechanism in the supergene processes is phosphate sorption on titanium dioxide and hydroxide, in particular, on leucoxene, which was confirmed by experimental data.

Рост потребности в муллитовом сырье, соответствующем промышленным требованиям, инициирует поиск его новых и альтернативных источников, а также эффективных технологий получения целевых продуктов (нанокомпозитов). В статье апробирован метод получения муллита из каолинита экспериментальным путем (Вежаю-Ворыквинское месторождение, Россия). Изучены структурные преобразования каолинита (системы Al-Si-O-Me), трансформации минеральных фаз и термодинамика процесса. На основе оценки термодинамики протекания реакций определена предпочтительная реакция образования муллита. Показано, что образование целевого продукта – муллитового нанокомпозита – имеет ряд промежуточных фаз (метакаолинит, псевдомуллит). Преобразования структуры исходного каолинита включают удаление структурной воды с разделением кремнекислородного тетраэдрического и алюмокислородного октаэдрического слоев, распад на свободные оксиды, разрыв связей между кремнекислородными тетраэдрами и частичное повышение координационного числа ионов алюминия, образование из свободных оксидов муллита и кристобалита. Предложенный подход контролирует соотношение фаз Аl2О3 и SiO2 на определенных этапах, что в дальнейшем позволит улучшить механические и другие свойства матрицы получаемого сырья для целевых прототипов промышленных продуктов.

Various enzymatic reactions or enzymatic cascade reactions occur efficiently in biological microsystems due to space constraints or orderly transfer of intermediate products.Inspired by this,the horseradish peroxidase(HRP)-like nanozyme(Fe-aminoclay)was in situ synthesized on the surface of alkali-activated halloysite nanotubes and the natural enzyme(glucose oxidase,GOx)was immobilized on it to construct a high-efficiency GOx-FeAC@AHNTs cascade nanoreactor.In which,FeAC@AHNTs can not only be used as a carrier for immobilized enzymes,but also help its catalytic activity to cooperate with glucose oxidase in a cascade reaction.The microcompartments and substrate channel effect of this enzyme-nanozyme microsystem exhibit a superior catalytic performance than that of natural enzyme system,and exhibits excellent long-term stability and recyclability.Subsequently,the GOx-FeAC@AHNTs cascade nanoreactor was employed as a glucose colorimetric platform,which displayed a low detection limit(0.47 μmol/L)in glucose detection.This enzyme-nanoenzyme nanoreactor provides a simple and effective example for constructing a multi-enzyme system with limited space,and lays the foundation for subsequent research in the fields of biological analysis and catalysis.