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Serpentinites are metamorphic rocks constituted primarily by serpentine-group minerals (antigorite, chrysotile, lizardite) resulting from the transformation and low-temperature hydration of previous olivine-rich ultramafic rocks, such as dunite, lherzolite, wehrlite, and harzburgite. The peculiar features of the serpentinites such as the greenish color and the intricate vein and mesh-like texture, as well as their role in CO[sub.2] sequestration when carbonated, have hugely increased interest in studying these rocks over recent decades. Moreover, since antiquity, serpentinites have long been exploited, traded, and exported worldwide as daily tools, as well as in buildings and decorative stones in both internal and external architectural elements, because of their aesthetic appeal, attractiveness, and durability. In this work, we analyzed and compared petrographic features, geochemical signatures, and physical–mechanical properties of serpentinites from historical quarries from Andalusia (southern Spain), Basilicata, and Calabria (southern Italy) where they have been used as dimension stones in religious and civil buildings and as construction materials. We aim to evaluate and assess differences in petrographic, carbonation, uniaxial compressive strength, and seismic behavior, that could affect the efficiency when these serpentinites are used as either building and construction materials or for preservation/renovation purposes in cultural heritage. Results obtained from petrophysical investigations of serpentinites from these regions highlight that these materials are suitable for use in construction to various extents and are considered a valuable georesource, behind a detailed characterization carried out before their implementation in construction or conservation/restoration of architectural heritage.

Waste generated during asbestos manufacturing contains substantial quantities of iron, nickel, magnesium, and silicon. The existing techniques for processing chrysotile-asbestos waste (CAW) cannot fully recover these elements. Therefore this paper presents a hydrometallurgical method for processing the CAW of the Zhitikara deposit in the Kostanay region of Kazakhstan. Batch reactors are used in both laboratory and pilot experiments, and initial trials are conducted in a recently constructed industrial Ti reactor at the Kostanay Minerals JSC plant in the Kostanay region of Zhitikara. The primary benefits of the industrial reactor include operation without excessively grinding the feedstock and creation of a pulp with enhanced filtration properties. A moderate agitation speed (10 rpm) helps ensure a consistent pulp density and prevent the production of silica gel. Optimal leaching conditions are determined as a fraction size of CAW between − 1.25 and 0.25 mm, hydrochloric acid concentration of 18 wt%, temperature of ~ 85–90 °C, pressure of 1 atmosphere, and duration of 2 h. An investigation of the process kinetics reveals that diffusion is the rate-controlling step. Further, the activation energies are determined to be 54.4 kJ.mol − 1 , and the leaching rates of Mg, Fe, and Ni under these conditions are 96.0, 87.8, and 81.3%, respectively. Washing and recycling water enhances helps to increase the recovery of magnesium chloride. Implementing pilot-scale hydrometallurgical processing of CAW can effectively address environmental issues that pose a threat to human health and provide commercial advantages.

Methyl orange (MO) is a common anionic azo dye that is harmful to the environment and biology, so it must be treated innocuously before it can be discharged. Adsorption is an effective method to remove anionic dyes. Nanotube mineral is a natural one-dimensional adsorption material, and its unique morphology and structure endow it with good adsorption capacity. Although there are many related studies, there is a lack of in-depth discussions on the influence of nanotube’s composition and structure on the adsorption of dyes and other pollutants. In this paper, two kinds of natural one-dimensional silicate minerals [halloysite nanotubes (HNTs) and chrysotile nanotubes (ChNTs)] with similar morphology but slightly different compositions and crystal structures were used as adsorbents, and MO solution was used as simulate pollutants. It is the first time to discuss in depth the influence of the composition and structure of nanotube minerals on their charge properties and the adsorption performance of methyl orange dyes. It is found that HNTs and ChNTs have different adsorption capacity due to the difference of electronegativity between Al 3+ and Mg 2+ in the crystal, so they possess negative and positive charges respectively in near-neutral solution, which leads to the adsorption capacity of MO by ChNTs with positive charges which is greater than that of HNTs.

A group of phyllosilicate nanoscrolls conjoins several hydrosilicate layered compounds with a size mismatch between octahedral and tetrahedral sheets. Among them, synthetic Mg[sub.3]Si[sub.2]O[sub.5](OH)[sub.4] chrysotile nanoscrolls (obtained via the hydrothermal method) possess high thermal stability and mechanical properties, making them prospective composite materials fillers. However, accurate determination of these nano-objects with Young's modulus remains challenging. Here, we report on a study of the mechanical properties evolution of individual synthetic phyllosilicate nanoscrolls after a series of heat treatments, observed with an atomic force microscopy and calculated using the density functional theory. It appears that the Young's modulus, as well as shear deformation's contribution to the nanoscrolls mechanical behavior, can be controlled by heat treatment. The main reason for this is the heat-induced formation of covalent bonding between the adjacent layers, which complicate the shear deformation.

Introduction. The article considers the issue of modifying the initial chrysotile fiber and its bundles by the action of hydration products of Portland cement and various acidity value of the treated medium. A brief justification of the relevance of the research topic is provided. It is noted that recently, issues of production of composite materials based on natural and man-made raw materials, which are a promising area of modern economics, have aroused great scientific and practical interest. The availability and low cost of raw materials, as well as low energy, transportation, and overhead costs, contribute to reducing the cost of composite materials. At the same time, the high contractual prices and strong demand in both domestic and foreign markets provide incentives for increasing production volumes. The aim of the research is to study the behavior of the initial chrysotile fibers and their aggregates in the composition of the cement component under the influence of different acidity of the treated medium. Research objective: to investigate the behavior of chrysotile cement dust components under an aggressive environmental condition with electron microscopy examination; calculation of the number and dimensional characteristics of nanofibers and dust particles under the influence of various exposure times of the aggressive factor; microdifraction studies of the nanostructure of the studied samples after exposure to acidic media. Materials and methods. The materials used in the research and their characteristics are given, in particular, chrysotile cement dust containing fibers of commercial chrysotile, acidity of the medium, exposure time, micro- and nanofibers obtained after exposure to aggressive medium. Samples of chrysotile cement dust were taken at the slate production No.1 of JSC \"BelACI\" and collected at the place of sawing of chrysotile cement products, underwent the stage of dispersion using a centrifugal separator. In the work chrysotile cement dust was used as an object of environmental pollution and its further use in the production of composite chrysotile cement products. Results. The results of studies on the influence of aggressive environment on the components of chrysotile-cement dust, their size characteristics, and structural nano-changes are presented. The studied samples have been examined in a scanning ion-electron microscope at magnifications of 200x, 500x, 5000x, 10000x, and their chemical composition have been analyzed. Discussion. The results of analysis of the obtained experimental data are given. Quantitative composition of fibers and aggregates of fibers in chrysotile cement dust changes after its exposure in acidic medium in comparison with their quantity in initial chrysotile cement dust, and the quantity of separate thin fibers increases, it is explained by the fact that in acidic medium there is not only destruction of cement stone, but also splitting of bundles of chrysotile fibers into micro- and nanofibers. Conclusions. Electron microscopic examination of initial commercial chrysotile fibers and their bundles in cement dust have shown changes in their dimensional and quantitative characteristics, including the products of Portland cement hydration under the influence of the factor of aggressiveness of the environment.

ObjectiveInvestigate cancer mortality in workers of the world’s largest chrysotile mine and its enrichment factories in Asbest, Sverdlovsk region of the Russian Federation.Material and MethodsThe Asbest chrysotile cohort study includes 30 445 workers, whereof 32% are women, employed for at least 1 year between 1975 and 2010 and followed up until the end of 2015. Individual cumulative exposure to dust (and modelled conversion to asbestos fibres) was estimated based on workers’ occupational history linked to dust measurements systematically collected from the 1950s to 2010. Relative risks (RRs) by exposure were estimated as mortality rate ratios in Poisson regression models within the cohort, and standardized mortality ratios (SMRs) were calculated for selected cancer sites compared to the population of Sverdlovsk region for the years 1980-2015.ResultsAn exposure-response between cumulative dust and lung cancer mortality in men was observed with a RR 1.40, 95%-confidence interval (CI) 1.03-1.90 in the ≥150 mg/m3-years category and a p-value for trend of 0.02, while in women no clear association was seen but a modest increase in the highest category of exposure to fibres. Mesothelioma mortality was increased (RR 7.64, CI 1.18 to 49.5) in the highest exposure category to fibres (≥ 80 fibres/cm3-years). Comparing the cohort vs. Sverdlovsk region for lung cancer showed SMR 1.20, CI 1.10-1.30 in men and 1.35, CI 0.97-1.83 in women. No or no consistent associations were seen for stomach, colorectal, laryngeal, or ovarian cancer.ConclusionsThis is the first international study to examine cancer mortality in the Russian chrysotile industry. We observed increased risks of mesothelioma and of lung cancer in men. Our comparison with the mortality of the region confirms the observed exposure-depended excess in lung cancer, especially in men.

Growing requirements in the field of environmental protection and waste management result in the need to search for new and effective methods of recycling various types of waste. From the perspective of technical and natural sciences, the disposal of hazardous waste, which can lead to environmental degradation, is of utmost importance. A particularly hazardous waste is asbestos, used until recently in many branches of the economy and industry. Despite the ban on the production and use of asbestos introduced in many countries, products containing it are still present in the environment and pose a real threat. This paper presents the results of research related to the process of asbestos neutralization, especially the chrysotile variety, by the thermal decomposition method. Changes in the mineralogical characteristics of asbestos waste were studied using the following methods: TG-DTA-EGA, XRD, SEM-EDS and XRF. The characteristics of the chrysotile asbestos sample were determined before and after thermal treatment at selected temperatures. The second part of the study focuses on the kinetic aspect of this process, where the chrysotile thermal decomposition process was measured by two techniques: ex situ and in situ. This study showed that the chrysotile structure collapsed at approximately 600–800 °C through dehydroxylation, and then the fibrous chrysotile asbestos was transformed into new mineral phases, such as forsterite and enstatite. The formation of forsterite was observed at temperatures below 1000 °C, while enstatite was created above this temperature. From the kinetic point of view, the chrysotile thermal decomposition process could be described by the Avrami–Erofeev model, and the calculated activation energy values were ~180 kJ mol−1 and ~220 kJ mol−1 for ex situ and in situ processes, respectively. The obtained results indicate that the thermal method can be successfully used to detoxify hazardous chrysotile asbestos fibers.