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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.

The mafic sills intruding into the dolostone in the uppermost part of the Vempalle Formation, Cuddapah Supergroup, have caused extensive metasomatism in the dolostone, resulting in serpentinisation and hydrothermal chrysotile mineralisation in the Pulivendla asbestos belt. Three different coloured varieties of serpentine, namely black, green, and yellow serpentine, have developed successively away from the mafic sill-dolostone contact. These serpentines belong to the lizardite variety and occur in the form of massive bands, irregular replacement patches, and stylolite fills in dolostone. Due to high XH2O activity and lesser silica activity, in some portions of dolostone, brucite has formed in excess of lizardite. This is the first report of brucite mineralisation from this asbestos belt. Major and trace element data indicate a greater contribution from the mafic sill for the formation of black serpentine and a greater role of dolostone in the formation of yellow and green serpentine. A simple mixing model of the 143Nd/144Nd values also supports the contribution of the mafic sill and carbonate in the proportion of 60:40 in the formation of black serpentine. Variation in the concentration of transition metals Fe, V, Cr, Co and Ni is possibly responsible for the development of serpentine having different colours. Serpentinised dolostone commonly shows depletion in δ13C and δ18O values ranging from –1.43 to –0.76‰ and –18.01 to –17.06‰, respectively, compared to those of unaltered dolostone (δ13C: 0.35–0.97‰ and δ18O: –7.11 to –8.75‰). The depletion in δ13C and δ18O values in the serpentinised dolostone is inferred to be caused by decarbonation and interaction with the mafic magma. Serpentinisation of dolostone was accompanied by extensive fracturing and development of stylolites, and followed by hydrothermal fluid flow when some of the early formed serpentines were dissolved in the hydrothermal fluid and re-precipitated as chrysotile filling fractures and stylolites.Research highlightsDolostone in the uppermost part of Vempalle Formation was serpentinised upon emplacement of mafic sill.Chrysotile mineralisation occurred after the serpentinisation of dolostone by dissolution and re-precipitation of previously formed lizardite variety of serpentine.Incidence of brucite mineralisation in serpentinised dolostone of Pulivendla asbestos belt is identified and reported for the first time.

The purpose of this research was to study the particularities of the immune status of workers in the field of chrysotile asbestos production, depending on their work experience and professional risk of being affected by chrysotile dust. The research covered 125 men, who were workers at the only enterprise dealing with the extraction and beneficiation of chrysotile ores in Kazakhstan. Indicants of cell immunity were detected by flow cytometry; IgA, IgM, and IgG were detected by a multiplex immunological assay. It was found that, among workers impacted by chrysotile asbestos for more than 15 years, compared with individuals who were not impacted by asbestos dust, the level of CD3+ T-cells was decreased (t = −8.76, p < 0.001), as well as the number of CD4+ T-cells (U = 1246.0, p < 0.001). Moreover, CD8+ T-cells increased (t = 5.308, p = 0.001), and neutrophil phagocytic activity also increased, by 1.2 times (U = 305.5, p < 0.001). It was found that working under the condition of professional contact with chrysotile asbestos dust modifies the indicants of humoral immunity, IgA, IgM, and IgG, to a lesser extent than those of cellular immunity.

Zimbabwe has two major factories that have been manufacturing chrysotile asbestos cement products since the 1940s. Exposure monitoring of airborne fibres has been ongoing since the early 1990s. This study examines trends in personal exposure chrysotile asbestos fibre concentrations for the period 1996–2016. Close to 3000 historical personal exposure measurements extracted from paper records in the two factories were analysed for trends in exposure. Exposure over time was characterised according to three time periods and calendar years. Mean personal exposure chrysotile asbestos fibre concentrations generally showed a downward trend over the years in both factories. Exposure data showed that over the observed period 57% and 50% of mean personal exposure chrysotile asbestos fibre concentrations in the Harare and Bulawayo factories, respectively, were above the OEL, with overexposure being exhibited before 2008. Overall, personal exposure asbestos fibre concentrations in the factories dropped from 0.15 f/mL in 1996 to 0.05–0.06 f/mL in 2016—a decrease of 60–67%. These results can be used in future epidemiological studies, and in predicting the occurrence of asbestos-related diseases in Zimbabwe.