Chrysotile Fibers Research Articles

Spectroscopic Analysis of Chrysotile Asbestos and its Environmental Resistance in Asbestos Cement Waste Products

Most asbestos-related studies have focused on asbestos exposure risks, their associated health implications, and waste management issues. Our research introduced a unique perspective that has rarely been explored: the impact of environmental factors on asbestos cement products. The novelty of the study is that, in contrast to previous research, in addition to determining the material quality of asbestos, it analyses the trace materials, additives and the emissive nature of chrysotile fibers. This study aims to identify the chrysotile-asbestos content in three common asbestos cement products found in Hungary, with regard to the release of their fibers upon exposure to the environment and to identify trace elements that could be used to identify the origin and function of each of these products. Our analyses revealed the presence of chrysotile in each tested sample, with spectral matches ranging from 59.6% to 86.7%. Asbestos cement products exposed to various environmental influences for long periods showed a greater chrysotile emission capacity than those unexposed or hermetically sealed ones. Additionally, we established that all asbestos cement products contained glass fibers, with an average spectral match of 62.1%. We further identified polysilicate in the materials with an average spectral match of 66.0%, as it was included in asbestos cement products to enhance their heat resistance. Our results pave the way for a new methodology for assessing asbestos cement products with regard to the implementation of their trace element level assessments.

Peningkatan Produktivitas Karyawan PT. NBI melalui Pelatihan Microsoft Excel sebagai Strategi dalam Pengelolaan Data Perusahaan

PT Nusantara Building Industries (NBI) is one of the national private companies located in Central Java Province which is engaged in the building materials industry in the form of symmetrical corrugated cement chrysotile fiber sheets. PT NBI tries to meet the needs of consumers according to demand and make various innovations in producing its products. Therefore, it is necessary to carry out a training to improve the soft skills of PT NBI employees in the form of Microsoft Excel training. Microsoft Excel is a software application used to carry out various activities, including data analysis, graph making, complex calculations, and various other tasks. Based on the purpose of implementing community service activities, namely increasing employee productivity. So that the implementation of this training is in accordance with the objectives, namely being able to assist PT NBI employees in finding effective ways to manage and analyze company data. In addition, it can increase understanding in the use of Microsoft Excel. The focus of Microsoft Excel training on the AND/OR function is used to perform logical evaluation of several conditions or criteria. This training is designed to introduce the use of AND/OR functions in the company. This method aims to increase the effectiveness and efficiency of work when encountering cases in several conditions or criteria. The evaluation results of the training implementation showed a good level of acceptance from PT NBI employees towards understanding and using the AND/OR formula. Keywords — Enterprise, Microsoft Excel, AND/OR Function, Data Analysis.

Exploring microbial diversity and interactions for asbestos modifying properties

Asbestos poses a substantial environmental health risk, and biological treatment offers a promising approach to mitigate its impact by altering its chemical composition. However, the dynamics of microbial co-inoculation in asbestos bioremediation remain poorly understood. This study investigates the effect of microbial single cultures and co-cultures on modifying crocidolite and chrysotile fibers, focusing on the extraction of iron and magnesium. Seventy bacterial and eighty-three fungal strains were isolated from five diverse sites, characterized phylogenetically using the 16S rRNA gene and ITS region, respectively, and assessed for siderophore and organic acid production. Most bacterial strains were identified as Pseudomonas, while Penicillium predominated among fungal strains. Ten bacterial and 25 fungal strains were found to produce both organic compounds. Four microbial co-cultures (one bacterium-bacterium, two fungus-bacterium, and one fungus-fungus) exhibiting synergistic effects in plate assays, alongside their respective single cultures, were incubated with crocidolite and chrysotile. ICP-OES analysis revealed that in crocidolite, the co-culture HRF19–HRB12 removed more iron than their single cultures, while Penicillium TPF36 showed the highest iron removal. The co-culture of two Pseudomonas strains (HRB12–RB5) exhibited the highest magnesium concentration in the supernatant. In chrysotile, the co-culture HRB12–RB5 removed more iron than their individual cultures, with Penicillium TFSF27 exhibiting the highest iron concentration in the solution. Penicillium TFSF27 and the co-culture TFSF27–TPF36 demonstrated the highest magnesium removal. SEM-XRMA analysis showed a significant reduction in iron and magnesium content, confirming elemental extraction from the fibers' structure. This study significantly broadens the range of microbial strains capable of modifying asbestos fibers and underscores the potential of microbial co-cultures in asbestos remediation.

Microwave-assisted acid treatment for the mineral transformation of chrysotile as an alternative for asbestos waste management

In this work, the effect of microwave-assisted acid treatments on the morphological and crystallochemical characteristics of chrysotile fibers is investigated. A low concentration of nitric acid (0.2 N) is used to remove Mg2+-species located in the octahedral sheet of its structure, thereby causing a crystallo-chemical change forming a skeleton of non-crystalline amorphous silica. This skeleton maintains an elongated morphology but characterized by rounded -not sharp-edges and porous surfaces whose physical resistance under stress is reduced when compared with the initial fibers of chrysotile, favoring a lower pathogenicity of the fibers. Thus, microwave-assisted acid treatment rise as a low-cost, fast and effective option in avoiding the dangerousness associated with asbestos waste management.

ПОЛУЧЕНИЕ ФИБРОЦЕМЕНТНЫХ ИЗДЕЛИЙ С ИСПОЛЬЗОВАНИЕМ ХРИЗОТИЛА – ХРИЗОТИЛЦЕМЕНТНАЯ ПРОМЫШЛЕННОСТЬ

The article discusses the technology of production, the problems of the development of chrysotile and chrysotile cement industries in the countries of independent states. The article provides information on the composition and properties of natural chrysotile fibers, data on the quality of raw materials of cement and chrysotile fibers supplied to chrysotile cement enterprises, characteristics of suspension with them, semi-finished product and properties of solidified chrysotile cement products. The emerging requests of the manufacturers of chrysotile cement products (slate, chrysotile cement pipes) to the mining and processing enterprises of the countries of independent states on the quality of the supplied chrysotile fibers in connection with the apparent violations of the physical and mechanical properties of the slate products are considered.

Impact of air quality on the health of present-day workers in an Asbestos roof manufacturing industry, Sri Lanka.

The study's objective was to determine the air quality in an asbestos-related industry and its impact on current workers' respiratory health. Seventy-seven air and 65 dust samples were collected at 5-day intervals in an asbestos roofing sheets production factory in Sri Lanka having two production facilities. Sampling was performed in ten sites: Defective sheets-storage, Production-plant, Pulverizer, Cement-silo, and Loading-area. A detailed questionnaire and medical screening were conducted on 264 workers, including Lung Function Tests (LFT) and chest X-rays. Asbestos fibres were observed in deposited dust samples collected from seven sites. Free chrysotile fibres were absent in the breathing air samples. Scanning Electron Microscopy confirmed the presence of asbestos fibres, and the Energy Dispersive X-ray analysis revealed Mg, O, and Si in depositions. The average concentrations of trace metals were Cd-2.74, Pb-17.18, Ni-46.68, Cr-81.01, As-7.12, Co-6.77, and Cu-43.04mg/kg. The average Zn, Al, Mg, and Fe concentrations were within 0.2-163g/kg. The highest concentrations of PM2.52.5 and PM1010, 258 and 387µg/m3, respectively, were observed in the Pulverizer site. Forty-four workers had respiratory symptoms, 64 presented LFT abnormalities, 5 indicated chest irregularities, 35.98% were smokers, and 37.5% of workers with abnormal LFT results were smokers. The correlation coefficients between LFT results and work duration with respiratory symptoms and work duration and chest X-ray results were 0.022 and 0.011, respectively. In conclusion, most pulmonary disorders observed cannot directly correlate to Asbestos exposure due to negligible fibres in breathing air, but fibres in the depositions and dust can influence the pulmonary health of the employees.

Defense and Protection of the Marine Coastal Areas and Human Health: A Case Study of Asbestos Cement Contamination (Italy)

Pivotal environmental geology research was carried out in the protected area of Cape Peloro (Messina, NE Sicily, Italy). The main aims were the ascertainment of the presence of Asbestos Cement Materials (ACMs), their mapping, and, consequently, an estimation of the potential risk for human health and marine coastal environments. The beaches surveyed covered 4500 m of coastline. Through high-resolution photographic surveys, over 520 fiber cement fragments were documented on the beaches as well as in beach deposits. The materials, after microscope, SEM-EDS, and FTIR analyses, were found to be composed of Portland cement with chrysotile and crocidolite fibers. Fragments of ACMs showed typical corrugated forms with centimeter-to-decimeter sizes and prevailing well-rounded, platy, and sub-elongate shapes. In a few localities, some fragments were found to be angular or friable. Furthermore, some fragments found on the beach were covered by conspicuous encrustations of marine organisms, testifying to their long staying in shallow-water marine environments. Illicit landfills and abandoned materials were identified in natural sections on the coastal plain. Most of the rounded ACMs were characterized by their surface texture, with mm-size asbestos fibers exposed on the surface due to significant weathering and abrasion. Notably, new fragments appeared after storms. Significant criticisms have been made related to the ACMs, analogously to what was reported for other Italian marine beaches. Possible intervention and reclamation activities cannot limit themselves to removing the fragments on the beach, as fragments are immersed in the coastal sediments at different depths and are also found in the marine deposits. Here, it is underlined that any asbestos removal and reclamation activities, if not designed and based on a multidisciplinary approach and knowledge of local coastal dynamics and the meteo-marine climate, will be very expensive and ineffective.

Lung fibre burden and risk of malignant mesothelioma in shipyard workers: a necropsy-based case-control study.

In Italy, the highest pleural cancer mortality and incidence have been observed among Italian regions where the 2 largest Italian shipyards were (and are) located. The objective of this study was to assess the exposure-response relationship for mesothelioma among male workers employed in the Monfalcone, Italy, shipyard. We conducted a necropsy-based case-control study. Cases (N = 102) were mesothelioma decedents and controls were those with lung cancer (N = 84). Complete job histories were available; the lung fibre content was measured using a scanning electron microscope with X-ray fluorescence, after sample preparation according to the European Respiratory Society guidelines. Odds ratios and 95% confidence intervals of mesothelioma by fibre type and lung fibre burden, as a categorical or continuous variable, were assessed by unconditional logistic regression, adjusted for age and time since exposure cessation. Analyses for the amphibole and chrysotile lung fibre burden were mutually adjusted. We calculated a cumulative exposure index by applying a job-exposure matrix to the job histories of study cases and assessed its correlation with the lung fibre burden. We found an odds ratio of 22.0 (confidence intervals 5.66-85.7) for the highest lung fibre burden category (mean 43.8 million total asbestos fibres per gram of dry tissue) compared with the reference (mean 0.48). Using log10-transformed lung fibre burden, we found that the odds ratio was 3.71 (confidence intervals 2.03-6.79) for a 10-fold lung fibre burden increase. Results for the amphibole lung fibre burden were similar. Odds ratios increased over chrysotile lung fibre burden categories (P-trend = 0.025), and the odds ratio for a 10-fold increase was 4.73 (confidence intervals 0.32-70.4). The cumulative exposure index was correlated with total and amphibole lung fibre burden, but not with chrysotile lung fibre burden. Mesothelioma risk was proportional to total, amphibole, and chrysotile lung fibre burden in shipyard workers.

Cancer mortality in chrysotile miners and millers, Russian Federation: main results (Asbest Chrysotile Cohort-Study)

Background. We investigated mortality in workers of the world’s largest chrysotile mine and enrichment factories located in the town of Asbest, Russian Federation.
 Methods. This historical cohort study included all workers employed for at least 1 year between 1975 and 2010 and follow-up until the end of 2015. Cumulative exposure to dust was estimated based on workers’ complete occupational history linked to dust measurements systematically collected from the 1950s. Exposure to chrysotile fibers was estimated using dust-to-fiber conversion factors. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated as mortality rate ratios in Poisson regression models.
 Results. A total of 30 445 (32% women) workers accumulated 721 312 person-years at risk and 11 110 (36%) died. Of the workers, 54% had more than 30 years since their first exposure. We found an exposure-response between cumulative dust and lung cancer mortality in men. No clear association with dust exposure but a modest increase in the highest category of fiber exposure was seen for lung cancer in women. Mesothelioma mortality was increased (RR=7.64, 95% CI=1.18 to 49.5, to at least 80 fibers per cm3 years and RR=4.56, 95% CI=0.94 to 22.1, to at least 150 mg/m3 years [dust]), based on 13 deaths. For colorectal and stomach cancer, there were inconsistent associations. No associations were seen for laryngeal or ovarian cancer.
 Conclusion. In this large-scale epidemiological study in the world’s largest active asbestos mine, we confirmed an increased risk of mesothelioma with high fiber exposure and an increasing mortality for lung cancer in men with increasing dust exposure. Less clear-cut increased lung cancer mortality was seen in the women. Continued mortality follow-up is warranted.

Cancer mortality in chrysotile miners and millers, Russian Federation: main results (Asbest Chrysotile Cohort-Study).

We investigated mortality in workers of the world's largest chrysotile mine and enrichment factories located in the town of Asbest, Russian Federation. This historical cohort study included all workers employed for at least 1 year between 1975 and 2010 and follow-up until the end of 2015. Cumulative exposure to dust was estimated based on workers' complete occupational history linked to dust measurements systematically collected from the 1950s. Exposure to chrysotile fibers was estimated using dust-to-fiber conversion factors. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated as mortality rate ratios in Poisson regression models. A total of 30 445 (32% women) workers accumulated 721 312 person-years at risk and 11 110 (36%) died. Of the workers, 54% had more than 30 years since their first exposure. We found an exposure-response between cumulative dust and lung cancer mortality in men. No clear association with dust exposure but a modest increase in the highest category of fiber exposure was seen for lung cancer in women. Mesothelioma mortality was increased (RR = 7.64, 95% CI = 1.18 to 49.5, to at least 80 fibers per cm3 years and RR = 4.56, 95% CI = 0.94 to 22.1, to at least 150 mg/m3 years [dust]), based on 13 deaths. For colorectal and stomach cancer, there were inconsistent associations. No associations were seen for laryngeal or ovarian cancer. In this large-scale epidemiological study in the world's largest active asbestos mine, we confirmed an increased risk of mesothelioma with high fiber exposure and an increasing mortality for lung cancer in men with increasing dust exposure. Less clear-cut increased lung cancer mortality was seen in the women. Continued mortality follow-up is warranted.

Application of Organosilicon Modifier Based on Tetraethoxysilane for the Production of Heat-Resistant Chrysotile Fibers and Reinforced Cement Composites

This research is aimed at obtaining boron-containing nanotubular chrysotile fibers with increased neutron absorption capacity. The possibility of using an organosilicon modifier based on tetraethoxysilane to increase the hydrothermal stability of chrysotile, as well as the strength of nanoreinforced composites based on a cement binder is considered. The mechanisms for the synthesis of heat-resistant nanotubular fibers of the composition Mg6(OH)8SiB4O10, which have a chrysotile structure, have been established. To increase the hydrothermal stability of chrysotile, crystalline hydrate phases were localized inside nanotubes using amorphous silica formed as a result of hydrolysis of silicon alkoxide under hydrothermal conditions in an alkaline environment. The modification of chrysotile via amorphous silica increases its hydrothermal stability by 97 °C. It is shown that the introduction of an organosilicon modifier based on tetraethoxysilane into the composition of Portland cement composite material leads to an increase in the structural strength and density of the composite due to the activation of silicate formation processes in the cement matrix, especially under hydrothermal conditions. The experiments showed that the strength of silicon alkoxide-modified samples of composite material increased by 34%.

There is plenty of asbestos at the bottom. The case of magnesite raw material contaminated with asbestos fibres

Although all six asbestos minerals (the layer silicate chrysotile and five chain silicate species actinolite asbestos, amosite, anthophyllite asbestos, crocidolite and tremolite asbestos) are classified as carcinogenic, chrysotile is still mined and used in many countries worldwide. Other countries, like Italy, impose zero tolerance for all asbestos species, but conflicting views repress the development of globally uniform treaties controlling international trade of asbestos-containing materials. Hence, countries with more severe legislations against the use of these hazardous materials lack of an international safety net against importation of non-compliant products. This research reports the first discovery of commercial magnesite raw materials contaminated with white asbestos (chrysotile). X-ray powder diffraction and thermogravimetric/thermodifferential measurements showed the presence of serpentine group minerals in both the semi-processed (powder) and quarried material. The univocal identification of chrysotile in the powders was confirmed by its peculiar Raman bands of the OH stretching vibrations between 3500 and 3800 cm−1, with an intense peak at ∼3695 cm−1 and a weak contribution at ∼3647 cm−1. Transmission electron microscope showed that chrysotile forms fibres up to a few microns long and up to 80 nm thick with a nanotube structure characterized by inner channels as large as 30–40 nm. Fibres size analysis obtained by scanning electron microscopy indicates mean length and diameter of 5.95 and 0.109 μm with medians of 2.62 and 0.096 μm, respectively; some among the fibres analysed exhibit the so-called “Stanton size” (i.e., asbestos fibres longer than 8 μm and thinner than 0.25 μm that are strongly carcinogenic). Quantitative analysis showed a chrysotile content around 0.01 wt% not allowed by current regulations in Italy and many other countries. More generally, our findings demonstrate that without shared policies aimed at regulating asbestos circulation on the global market, “asbestos-free” national policies will inevitably fail.

Diagnostic limitations of lung fiber counts in asbestos-related diseases

Background Lung dust fibre analyses have been used by some pathologists to estimate past asbestos exposure in the workplace and its related health risks. Asbestos, however, especially the predominately applied chrysotile asbestos type, undergoes translocation, clearance and degradation in the lungs. Objectives We quantified the asbestos fibre and ferruginous (asbestos) body (FB) content in human tissue with respect to the German asbestos ban in 1993 and the interim period of more than 20 years in order to evaluate the diagnostic evidence of these analyses for asbestos-related diseases (ARD). Methods Lung dust analyses have been used in empirical assessments of ARD since 1982. Tissue samples of about 2 cm3 were used and processed in standardized manner. FB was analysed by light microscopy and asbestos fibres by scanning transmission electron microscopy (STEM). Results Chrysotile and amphibole fibre concentrations in the lung tissue depend roughly on the cumulative asbestos exposure levels in the workplace. However, the concentration of lung asbestos fibre and FB depends on the year of examination and especially on the interim period. As the interim period increases, the asbestos fibre burden decreases. There is no relationship between FB and chrysotile asbestos fibre concentrations and only a weak correlation between FB and crocidolite fibre concentrations. There was no significant difference in chrysotile and amphibole fibre concentrations as well as in FB counts between the different ARD. Conclusions Due to the length of interim periods, a past exposure to chrysotile or amphibole asbestos can no longer be detected with FB or asbestos fibre measurement in lung tissue. This means that negative results of such measurements cannot disprove a qualified occupational case history of asbestos exposures and the related health risks due to the fibrogenic and carcinogenic potential of asbestos.

Highly efficient iodine capture by hydrophobic bismuth-based chrysotile membrane from humid gas streams

Because of their non-toxicity and low cost, bismuth-based materials have received considerable attention for the capture of gaseous iodine, especially for the removal of radioactive iodine in nuclear post-processing plants. In the actual operation conditions of reprocessing plant, the presence of water vapor must be considered as an important factor because it will significantly affect the iodine capturing efficiency for most iodine-capturing materials. To address this problem, we successfully synthesized a hydrophobic bismuth-based chrysotile membrane, which was modified by the silane coupling agent KH570. The chrysotile fiber was chosen to provide rich reactive sites for bismuth loading, and the bismuth was chosen due to its high affinity to iodine. The hydrophobic surface endowed by KH570 acts as a ‘protecting layer’ when water vapor exists during iodine adsorption. The maximum of iodine capture efficiency of the prepared membrane reached 483.37 mg/g in air, and 443.04 mg/g under 75 % relative humidity. Comparing hydrophobic membrane with one that non-modified by KH570, the hydrophobic membrane increases about 54 % iodine adsorption capacity in humid condition. This study provides a certain reference value for the application of bismuth-based materials in iodine removal under humid conditions.

Modernization of drive of vertical hammer crusher VMD-105 at Orenburg Minerals

The authors inform briefly about the Russian mining company—JSC Orenburg Minerals, which produces chrysotile asbestos and chrysotile fiber. With an increase in production volume, it became necessary to increase productivity of crushing process on vertical hammer crushers (24 pcs.) installed at the stages of fine crushing. For this purpose, modernization of the drive of vertical hammer crusher VM -105 was proposed, which allowed to increase its productivity by 10% owing to changed gear ratio of the V-belt transmission from 1.64 to 1.4 after replacement of pulleys (the diameter of the drive pulley was increased from 335 mm to 355 mm, and the diameter of the driven pulley was reduced from 550 mm to 500 mm). At the same time, the existing design of the basic parts was used and, in particular, the axial distance of the V-belt transmission was preserved. Thus, the proposed modernization avoids structural changes to the body parts and, thereby, provides a fairly simple and efficient replacement of the drive. The calculations show that the implementation of the design solutions enables a reduction in the cost of one ton of mined ore by 0.94%, tan increase in the profitability of products by 5.19% and an increase in the labor productivity by 2.95%. Additional capital costs for the modernization of all 24 vertical hammer crushers installed at the stages of fine crushing amount to about 8 million rubles and pay off in less than 6.5 months. The project is effective, pays off quickly and is recommended for the implementation at JSC Orenburg Minerals and other mining companies. 

The Potential Contribution of Hexavalent Chromium to the Carcinogenicity of Chrysotile Asbestos.

Chrysotile asbestos is a carcinogenic mineral that has abundantly been used in industrial and consumer applications. The carcinogenicity of the fibers is partly governed by reactive Fe surface sites that catalyze the generation of highly toxic hydroxyl radicals (HO•) from extracellular hydrogen peroxide (H2O2). Chrysotile also contains Cr, typically in the low mass permille range. In this study, we examined the leaching of Cr from fibers at the physiological lung pH of 7.4 in the presence and absence of H2O2. Furthermore, we investigated the potential of cells from typical asbestos-burdened tissues and cancers to take up Cr leached from chrysotile in PCR expression, immunoblot, and cellular Cr uptake experiments. Finally, the contribution of Cr to fiber-mediated H2O2 decomposition and HO• generation was studied. Chromium readily dissolved from chrysotile fibers in its genotoxic and carcinogenic hexavalent redox state upon oxidation by H2O2. Lung epithelial, mesothelial, lung carcinoma, and mesothelioma cells expressed membrane-bound Cr(VI) transporters and accumulated Cr up to 10-fold relative to the Cr(VI) concentration in the spiked medium. Conversely, anion transporter inhibitors decreased cellular Cr(VI) uptake up to 45-fold. Finally, chromium associated with chrysotile neither decomposed H2O2 nor contributed to fiber-mediated HO• generation. Altogether, our results support the hypothesis that Cr may leach from inhaled chrysotile in its hexavalent state and subsequently accumulate in cells of typically asbestos-burdened tissues, which could contribute to the carcinogenicity of chrysotile fibers. However, unlike Fe, Cr did not significantly contribute to the adverse radical production of chrysotile.

Identification of iron compounds in chrysotile from the Balangero mine (Turin, Italy) by micro‐Raman spectroscopy

AbstractChrysotile, one of the six regulated asbestos minerals, is classified as carcinogenic to humans by the International Agency for Research on Cancer. The Balangero mine (Turin, Italy) was the largest asbestos mine in Europe, providing extraction of chrysotile fibers until 1990. Chrysotile from Balangero is currently of great interest in fibers toxicity studies focused on the understanding of the mechanisms that induce lung malignancies. One of the crucial factors in the biochemical reactions is the presence of Fe at the fibers surface. Surface reactivity is responsible for the generation of reactive oxygen species, which play an important role in asbestos cyto‐genotoxicity. Moreover, the dissolution of Fe‐bearing phases in the acidic environment of the lysosomes might be considered as possible release of hazardous Fe ions in the lungs. Here, chrysotile from Balangero was characterized by micro‐Raman spectroscopy and scanning electron microscope‐energy dispersive system (SEM‐EDS) analysis to identify the Fe‐bearing impurities associated with asbestos fibers. Micrometric crystals were recognized as Fe oxides, carbonates, and sulfides. Uncommonly reported phases in asbestos minerals were also identified, mainly as mackinawite (Fe(II)S), in different forms. The nature of the Fe compounds containing both Fe(II) and Fe(III) species was verified by micro‐Raman spectroscopy combined with SEM‐EDS analysis.

Engineering siderophore production in Pseudomonas to improve asbestos weathering.

SummaryIron plays a key role in microbial metabolism and bacteria have developed multiple siderophore‐driven mechanisms due to its poor bioavailability for organisms in the environment. Iron‐bearing minerals generally serve as a nutrient source to sustain bacterial growth after bioweathering. Siderophores are high‐affinity ferric iron chelators, of which the biosynthesis is tightly regulated by the presence of iron. Pyoverdine‐producing Pseudomonas have shown their ability to extract iron and magnesium from asbestos waste as nutrients. However, such bioweathering is rapidly limited due to repression of the pyoverdine pathway and the low bacterial requirement for iron. We developed a metabolically engineered strain of Pseudomonas aeruginosa for which pyoverdine production was no longer repressed by iron as a proof of concept. We compared siderophore‐promoted dissolution of flocking asbestos waste by this optimized strain to that by the wild‐type strain. Interestingly, pyoverdine production by the optimized strain was seven times higher in the presence of asbestos waste and the dissolution of magnesium and iron from the chrysotile fibres contained in flocking asbestos waste was significantly enhanced. This innovative mineral weathering process contributes to remove toxic iron from the asbestos fibres and may contribute to the development of an eco‐friendly method to manage asbestos waste.

Cement Compositions Modified with Dispersed Magnesium Silicate Dihydrate- and Carbon-Based Additives

This study is based on the hypothesis that carbon black and chrysotile nanofibers, due to their ability to act as micro-reinforcement of the cement matrix and stimulate the formation of additional amounts of calcium silicate hydrates, can be used together as modifying additives in order to replace the expensive carbon nanotubes in cement-based compositions. The presented paper describes the results of experimental studies on the influence of these additives and their combinations on the physical and mechanical characteristics of the cement matrix. It was experimentally confirmed that the introduction of a complex additive based on chrysotile fibers and carbon black into the composition of the cement matrix leads to an increase in the strength of the material at the age of 28 days by 30.8% in compression and 21.6% in bending compared to the reference composition. The results of infrared spectroscopy, X-ray phase and microstructural analysis of the cement matrix are also presented. Physical and chemical analysis methods revealed a decrease in the content of the crystalline phases and the formation of amorphous hydration products in the structure of the matrix, characteristic of low-basic calcium silicate hydrates, which are responsible for the increased strength of the cement stone.

Modification-scavenging hydroxyl groups of natural mineral fiber separators to boost initial coulombic efficiency of lithium-ion battery

The recently reported inorganic separator is promising for advanced lithium-ion batteries (LIBs) with excellent electrochemical performance and high safety. However, then with most of inorganic separators suffered from low initial Coulombic efficiency (ICE). In this work, the chrysotile fiber (CF) separator was researched as a hydroxyl-rich inorganic separator, and the relationship between the hydroxyl groups on the surface of the CF separators and the ICE of batteries was studied. It was found that the rich hydroxyl groups on the surface of the CF separators induced the decomposition of LiPF6, thus leading to low ICE. Modified CF separators (LSO) were prepared by acid leaching and lithium ions modification. Modification-scavenging the hydroxyl groups on the surface of the CF separators can effectively promote the ICE of the Li|LiFePO4 cell (93%). Furthermore, the Li|LiFePO4 cell with LSO exhibited an excellent rate performance and high-rate cycle stability (109.4 mAh g−1 at 5C after 1000 cycles). This work provided a new strategy for improving electrochemical performance that reducing the number of hydroxyl groups on the surface of natural mineral fibers is effective to improve the ICE of inorganic separators.