Abstract Uniaxial and isothermal compression tests of kaolinite were carried out using molecular dynamics simulations. Five different temperatures (300, 400, 500, 600 and 700 K) and pressures ranging from 0.0001 to 50 GPa were selected to study the temperature and pressure effects on the mechanical properties of kaolinite. As kaolinite may undergo a phase transition at ~1572 K, a highest temperature of 700 K was chosen to avoid such structural change. The Young's modulus, strength and elastic constants of kaolinite under various temperatures were calculated, and the relative change of the elastic constant C33 with temperature was found to be almost 12 times greater than the relative change of the interlayer constant C11. The microstructures under various compressive strains were tracked and they exhibited various failure modes in three directions. The temperature and pressure effects on the mechanical properties of three crystal directions were analysed. The results showed that the Young's modulus of the z-direction is the most affected by temperature; however, the influence of temperature on the strengths of the three crystal directions was the same. In addition, the structure of the z-direction was the most sensitive to temperature under the same hydrostatic pressure due to the weak interactions between layers.
{"title":"A molecular dynamics study of the mechanical properties of kaolinite under uniaxial and isothermal compression at various temperatures","authors":"Y. Cui, H. Wang, H. Zhao, H. Yang","doi":"10.1180/clm.2022.21","DOIUrl":"https://doi.org/10.1180/clm.2022.21","url":null,"abstract":"Abstract Uniaxial and isothermal compression tests of kaolinite were carried out using molecular dynamics simulations. Five different temperatures (300, 400, 500, 600 and 700 K) and pressures ranging from 0.0001 to 50 GPa were selected to study the temperature and pressure effects on the mechanical properties of kaolinite. As kaolinite may undergo a phase transition at ~1572 K, a highest temperature of 700 K was chosen to avoid such structural change. The Young's modulus, strength and elastic constants of kaolinite under various temperatures were calculated, and the relative change of the elastic constant C33 with temperature was found to be almost 12 times greater than the relative change of the interlayer constant C11. The microstructures under various compressive strains were tracked and they exhibited various failure modes in three directions. The temperature and pressure effects on the mechanical properties of three crystal directions were analysed. The results showed that the Young's modulus of the z-direction is the most affected by temperature; however, the influence of temperature on the strengths of the three crystal directions was the same. In addition, the structure of the z-direction was the most sensitive to temperature under the same hydrostatic pressure due to the weak interactions between layers.","PeriodicalId":10311,"journal":{"name":"Clay Minerals","volume":"57 1","pages":"131 - 138"},"PeriodicalIF":1.5,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45901286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fatemeh Ahmadi, H. Ghanbari, Faraz Shabani Moghaddam, R. Naghizadeh
Abstract In polymer composites, montmorillonite nanosheets are crucial as fire retardants, reinforcers, anti-corrosives, detoxifying agents and ultraviolet-protection agents. However, the quality of montmorillonite nanosheets can be improved by optimizing the raw bentonite purification process in which undesirable phases are removed. Optimization of Iranian calcium bentonite purification for nanomontmorillonite synthesis considering various parameters based on various physical approaches to dispersion and ultrasonication was investigated; the calcium bentonite purification was performed using sodium hexametaphosphate followed by either sedimentation or centrifugation, and the nanomontmorillonite synthesis was performed using ultrasonic treatment. The effects of suspension concentration, milling type, pH and centrifugation duration and speed on the separation of various impure phases were evaluated qualitatively and optimized. The raw and purified bentonite and the synthesized nanomontmorillonite were characterized using X-ray powder diffraction, X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy. The cation-exchange capacity was also measured in the raw and purified samples. Optimal experimental conditions in the dispersed samples were achieved at a 2.5 wt.% concentration of bentonite suspension and planetary milling at pH 7. While the ultrasonic treatment was more effective than the dispersion approach for cristobalite elimination, a smaller lateral size of the montmorillonite sheets, optimized at 0.5 wt.% concentration of the suspension, was achieved. The increased cation-exchange capacity after the purification improved the exfoliation and delamination of montmorillonite nanosheets in the presence of cetyltrimethylammonium bromide as the surfactant. The interplanar spacing of (001) planes of 15 Å in raw bentonite shifted to 21 Å and 19 Å in purified and non-purified samples, respectively, after synthesis.
{"title":"Optimized purification procedure for Iranian calcium bentonite for producing montmorillonite nanosheets","authors":"Fatemeh Ahmadi, H. Ghanbari, Faraz Shabani Moghaddam, R. Naghizadeh","doi":"10.1180/clm.2022.29","DOIUrl":"https://doi.org/10.1180/clm.2022.29","url":null,"abstract":"Abstract In polymer composites, montmorillonite nanosheets are crucial as fire retardants, reinforcers, anti-corrosives, detoxifying agents and ultraviolet-protection agents. However, the quality of montmorillonite nanosheets can be improved by optimizing the raw bentonite purification process in which undesirable phases are removed. Optimization of Iranian calcium bentonite purification for nanomontmorillonite synthesis considering various parameters based on various physical approaches to dispersion and ultrasonication was investigated; the calcium bentonite purification was performed using sodium hexametaphosphate followed by either sedimentation or centrifugation, and the nanomontmorillonite synthesis was performed using ultrasonic treatment. The effects of suspension concentration, milling type, pH and centrifugation duration and speed on the separation of various impure phases were evaluated qualitatively and optimized. The raw and purified bentonite and the synthesized nanomontmorillonite were characterized using X-ray powder diffraction, X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy. The cation-exchange capacity was also measured in the raw and purified samples. Optimal experimental conditions in the dispersed samples were achieved at a 2.5 wt.% concentration of bentonite suspension and planetary milling at pH 7. While the ultrasonic treatment was more effective than the dispersion approach for cristobalite elimination, a smaller lateral size of the montmorillonite sheets, optimized at 0.5 wt.% concentration of the suspension, was achieved. The increased cation-exchange capacity after the purification improved the exfoliation and delamination of montmorillonite nanosheets in the presence of cetyltrimethylammonium bromide as the surfactant. The interplanar spacing of (001) planes of 15 Å in raw bentonite shifted to 21 Å and 19 Å in purified and non-purified samples, respectively, after synthesis.","PeriodicalId":10311,"journal":{"name":"Clay Minerals","volume":"57 1","pages":"120 - 130"},"PeriodicalIF":1.5,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43077934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Olga V. Nestroinaia, Irina G. Ryltsova, Maksim N. Yaprintsev, Evgeniya Yu. Nakisko, Evgeniy S. Seliverstov, Olga E. Lebedeva
Abstract The sorption properties of two layered minerals of the hydrotalcite supergroup – hydrotalcite and stichtite – were investigated with the aim of determining their kinetic parameters of sorption and their adsorption isotherm type. Pristine hydrotalcite and stichtite were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive Х-ray analysis and laser diffraction analysis of the particle-size distribution. The ‘memory effect’ of the sorbents was examined after calcination at 650°C. Slight indications of reconstructed hydrotalcite were observed, while the stichtite dehydration–rehydration cycle was irreversible. The hydrotalcite and stichtite were used to remove Congo Red from the aqueous solution. The pseudo-second order kinetic model described the process adequately. Mixed external and internal diffusion was confirmed for both minerals. The sorption of Congo Red on stichtite fits the Langmuir model. Stichtite demonstrated a maximum adsorption capacity of 2.5 mmol g–1 at 35°C. Increasing temperature increased the adsorption rate of Congo Red on stichtite but did not affect the adsorption rate constant for hydrotalcite.
{"title":"Sorption of Congo Red anionic dye on natural hydrotalcite and stichtite: kinetics and equilibrium","authors":"Olga V. Nestroinaia, Irina G. Ryltsova, Maksim N. Yaprintsev, Evgeniya Yu. Nakisko, Evgeniy S. Seliverstov, Olga E. Lebedeva","doi":"10.1180/clm.2022.26","DOIUrl":"https://doi.org/10.1180/clm.2022.26","url":null,"abstract":"Abstract The sorption properties of two layered minerals of the hydrotalcite supergroup – hydrotalcite and stichtite – were investigated with the aim of determining their kinetic parameters of sorption and their adsorption isotherm type. Pristine hydrotalcite and stichtite were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive Х-ray analysis and laser diffraction analysis of the particle-size distribution. The ‘memory effect’ of the sorbents was examined after calcination at 650°C. Slight indications of reconstructed hydrotalcite were observed, while the stichtite dehydration–rehydration cycle was irreversible. The hydrotalcite and stichtite were used to remove Congo Red from the aqueous solution. The pseudo-second order kinetic model described the process adequately. Mixed external and internal diffusion was confirmed for both minerals. The sorption of Congo Red on stichtite fits the Langmuir model. Stichtite demonstrated a maximum adsorption capacity of 2.5 mmol g–1 at 35°C. Increasing temperature increased the adsorption rate of Congo Red on stichtite but did not affect the adsorption rate constant for hydrotalcite.","PeriodicalId":10311,"journal":{"name":"Clay Minerals","volume":"57 1","pages":"105 - 113"},"PeriodicalIF":1.5,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47705187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Exploring reliable hydrogenation catalysts to remove trace olefins in aromatic hydrocarbons through hydrogenation is an important topic. In this paper, a bimetallic Cu–Ru/montmorillonite (Cu–Ru/M) catalyst was prepared using a step-by-step impregnation method, and the effects of bimetallic catalysts on removing olefins were assessed. The catalysts were characterized using X-ray diffraction, Brunauer–Emmett–Teller specific surface area, inductively coupled plasma atomic emission spectrometry, high-resolution transmission electron microscopy and temperature-programmed reduction of H2. The results show that there is a strong interaction between Cu and Ru on the Cu–Ru/M catalyst, which improves the dispersion of the metals on the surface of the support M. The hydrogen spillover phenomenon of Cu–Ru/M enhances its activity and adsorption capacity for hydrogen species. The catalytic performance test confirmed that the bimetallic catalyst has significantly greater activity and stability. The optimal loadings are 5% copper and 1% ruthenium, and the performance of this catalyst is comparable to those of noble-metal Pt/M catalysts.
{"title":"Application of supported Cu–Ru catalysts for the removal of trace olefins in aromatics","authors":"Xiao Liang, Naiwang Liu, Li Shi, Xuan Meng","doi":"10.1180/clm.2022.23","DOIUrl":"https://doi.org/10.1180/clm.2022.23","url":null,"abstract":"Abstract Exploring reliable hydrogenation catalysts to remove trace olefins in aromatic hydrocarbons through hydrogenation is an important topic. In this paper, a bimetallic Cu–Ru/montmorillonite (Cu–Ru/M) catalyst was prepared using a step-by-step impregnation method, and the effects of bimetallic catalysts on removing olefins were assessed. The catalysts were characterized using X-ray diffraction, Brunauer–Emmett–Teller specific surface area, inductively coupled plasma atomic emission spectrometry, high-resolution transmission electron microscopy and temperature-programmed reduction of H2. The results show that there is a strong interaction between Cu and Ru on the Cu–Ru/M catalyst, which improves the dispersion of the metals on the surface of the support M. The hydrogen spillover phenomenon of Cu–Ru/M enhances its activity and adsorption capacity for hydrogen species. The catalytic performance test confirmed that the bimetallic catalyst has significantly greater activity and stability. The optimal loadings are 5% copper and 1% ruthenium, and the performance of this catalyst is comparable to those of noble-metal Pt/M catalysts.","PeriodicalId":10311,"journal":{"name":"Clay Minerals","volume":"57 1","pages":"77 - 86"},"PeriodicalIF":1.5,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42386446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Weijuan Zhao, D. Zhao, Bo Wu, Bo Li, Baohua Zhou, Jianfeng Cui, Qinlong Chen
Abstract The Nanjing Bao'ensi site is the largest and highest-ranking royal temple from the Ming Dynasty, and it is famous for its full-body glass pagoda. In this study, the glazed tiles excavated from the southern area of the Bao'ensi site were selected and analysed using X-ray diffraction, thermal dilation and energy-dispersive X-ray fluorescence to determine their phase composition, firing temperature and chemical composition. The glazed tile bodies of the Bao'ensi site consist mainly of quartz and mullite, although some samples contain trace amounts of other minerals. All of the body samples were fired to the same temperature range (i.e. 1000–1100°C). The firing temperature combined with the phase composition indicate that the raw materials and firing process of the glazed tile body samples have similarities, but there are certain differences. The source of the raw materials for a portion of the glazed tile bodies is Dangtu, Anhui, whilst the source of the raw materials for the remaining materials remains to be discovered.
{"title":"Characteristics of the raw materials of glazed tile bodies in the southern area of the Bao'ensi site, Nanjing, China","authors":"Weijuan Zhao, D. Zhao, Bo Wu, Bo Li, Baohua Zhou, Jianfeng Cui, Qinlong Chen","doi":"10.1180/clm.2022.28","DOIUrl":"https://doi.org/10.1180/clm.2022.28","url":null,"abstract":"Abstract The Nanjing Bao'ensi site is the largest and highest-ranking royal temple from the Ming Dynasty, and it is famous for its full-body glass pagoda. In this study, the glazed tiles excavated from the southern area of the Bao'ensi site were selected and analysed using X-ray diffraction, thermal dilation and energy-dispersive X-ray fluorescence to determine their phase composition, firing temperature and chemical composition. The glazed tile bodies of the Bao'ensi site consist mainly of quartz and mullite, although some samples contain trace amounts of other minerals. All of the body samples were fired to the same temperature range (i.e. 1000–1100°C). The firing temperature combined with the phase composition indicate that the raw materials and firing process of the glazed tile body samples have similarities, but there are certain differences. The source of the raw materials for a portion of the glazed tile bodies is Dangtu, Anhui, whilst the source of the raw materials for the remaining materials remains to be discovered.","PeriodicalId":10311,"journal":{"name":"Clay Minerals","volume":"57 1","pages":"114 - 119"},"PeriodicalIF":1.5,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41456204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We read with interest the article by Crundwell et al 1 about 2 patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome who manifested clinically with bilateral sensorineural hearing impairment after speech development and significantly profited from unilateral implantation of a2 cochlea implant. 1 In patient 1 (53-year-old male), MELAS was found to be due to the variant m.3243A > G in MT-TL1 and in patient 2 (47-year-old male), the genetic cause of MELAS was unknown. 1 The study is appealing but has some limitations that raise concerns which need to be discussed. We disagree with the statement in the abstract that MELAS is the most common mitochondrial disorder (MID). 1 There are only few data available on the epidemiology of MIDs. 2 However, the few data reported in the literature and our own experiences suggest that non-syndromic MIDs prevail when compared with syndromic MIDs, such as MELAS. Furthermore, we do not agree with the statement in the introduction that MELAS is characterized by myelopathy and respiratory insufficiency. 1 Myelopathy is not a typical phenotypic feature of MELAS and has been only rarely reported in these patients. 3 Myelopathy is more common in leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL), a syndromic MID, in which myelopathy is a pathognomonic feature of the disease. 4 Respiratory insufficiency may develop in MELAS only in the case of affection of the respiratory muscles, the brainstem, or the lungs. It is contradictory to state that the diagnosis of MELAS was genetically confirmed and to state, at the same time, that the causative mtDNA variant
{"title":"Impaired Hearing in MELAS.","authors":"Josef Finsterer","doi":"10.5152/iao.2022.22750","DOIUrl":"10.5152/iao.2022.22750","url":null,"abstract":"We read with interest the article by Crundwell et al 1 about 2 patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome who manifested clinically with bilateral sensorineural hearing impairment after speech development and significantly profited from unilateral implantation of a2 cochlea implant. 1 In patient 1 (53-year-old male), MELAS was found to be due to the variant m.3243A > G in MT-TL1 and in patient 2 (47-year-old male), the genetic cause of MELAS was unknown. 1 The study is appealing but has some limitations that raise concerns which need to be discussed. We disagree with the statement in the abstract that MELAS is the most common mitochondrial disorder (MID). 1 There are only few data available on the epidemiology of MIDs. 2 However, the few data reported in the literature and our own experiences suggest that non-syndromic MIDs prevail when compared with syndromic MIDs, such as MELAS. Furthermore, we do not agree with the statement in the introduction that MELAS is characterized by myelopathy and respiratory insufficiency. 1 Myelopathy is not a typical phenotypic feature of MELAS and has been only rarely reported in these patients. 3 Myelopathy is more common in leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL), a syndromic MID, in which myelopathy is a pathognomonic feature of the disease. 4 Respiratory insufficiency may develop in MELAS only in the case of affection of the respiratory muscles, the brainstem, or the lungs. It is contradictory to state that the diagnosis of MELAS was genetically confirmed and to state, at the same time, that the causative mtDNA variant","PeriodicalId":10311,"journal":{"name":"Clay Minerals","volume":"29 1","pages":"276-277"},"PeriodicalIF":0.0,"publicationDate":"2022-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10682798/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88223886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The treatment of water containing heavy metals has attracted increasing attention because the ingestion of such water poses risks to human health. Due to their relatively large specific surface areas and surface charges, clay minerals play a significant role in the adsorption of heavy metals in water. However, the major factors that influence the adsorption rates of clay minerals are not well understood, and thus methods to predict the sorption of heavy metals by clay minerals are lacking. A method that can identify the most appropriate clay minerals for removal of a given heavy metal, based on the predicted sorption of the clay minerals, is required. This paper presents a widely applicable deep learning neural network approach that yielded excellent predictions of the influence of the sorption ratio on the adsorption of heavy metals by clay minerals. The neural network model was based on datasets of heavy-metal parameters that are available generally. It yielded highly accurate predictions of the adsorption rate based on training data from the dataset and was able to account for a wide range of input parameters. A Pearson sensitivity analysis was used to determine the contributions of individual input parameters to the adsorption rates predicted by the neural network. This newly developed method can predict the major factors influencing heavy-metal adsorption rates. The model described here could be applied in a wide range of scenarios.
{"title":"A deep learning neural network approach for predicting the factors influencing heavy-metal adsorption by clay minerals","authors":"R. Liu, Lei Zuo, Jiajia Zhao, D. Tao","doi":"10.1180/clm.2022.20","DOIUrl":"https://doi.org/10.1180/clm.2022.20","url":null,"abstract":"Abstract The treatment of water containing heavy metals has attracted increasing attention because the ingestion of such water poses risks to human health. Due to their relatively large specific surface areas and surface charges, clay minerals play a significant role in the adsorption of heavy metals in water. However, the major factors that influence the adsorption rates of clay minerals are not well understood, and thus methods to predict the sorption of heavy metals by clay minerals are lacking. A method that can identify the most appropriate clay minerals for removal of a given heavy metal, based on the predicted sorption of the clay minerals, is required. This paper presents a widely applicable deep learning neural network approach that yielded excellent predictions of the influence of the sorption ratio on the adsorption of heavy metals by clay minerals. The neural network model was based on datasets of heavy-metal parameters that are available generally. It yielded highly accurate predictions of the adsorption rate based on training data from the dataset and was able to account for a wide range of input parameters. A Pearson sensitivity analysis was used to determine the contributions of individual input parameters to the adsorption rates predicted by the neural network. This newly developed method can predict the major factors influencing heavy-metal adsorption rates. The model described here could be applied in a wide range of scenarios.","PeriodicalId":10311,"journal":{"name":"Clay Minerals","volume":"57 1","pages":"70 - 76"},"PeriodicalIF":1.5,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42785919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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