Showing papers on "Clay minerals published in 2020"
TL;DR: In this article, a review of studies involving the use of clay minerals for the remediation of soils and water contaminated with heavy metals is presented, highlighting the properties of clay materials which make them good adsorbents and the processes necessary for adsorption to take place.
Abstract: Clay minerals are affordable, abundant, naturally occurring minerals found in many parts of the world that have been used effectively for remediation of many contaminants. This review article is aimed at studies involving the use of clay minerals for the remediation of soils and water contaminated with heavy metals. All relevant scientific literature using science direct online database from the year 2000 till 2019 were evaluated. The review highlighted the properties of clay minerals which make them good adsorbents and the processes necessary for adsorption to take place. It revealed that clay minerals are quite effective for remediation purposes, confirmed that clay minerals are very affordable, reliable, and environmentally friendly remediation materials for heavy metal contaminated media. Also, several methods are available for the modification of clay minerals in order to increase their adsorption capacity. However, in order to establish the use of clay minerals as heavy metal remediation materials compared to other established methods, more investigations are required, to determine the best modification type for clay minerals as well as the standard dosage of clay minerals required for the adsorption of heavy metals.
166 citations
TL;DR: In this article, the authors present an approach for processing and activating 1:1 (kaolinite, halloysite) and 2: 1 (montmorillonite, illite) clay minerals.
158 citations
TL;DR: In this article, the main characteristics of clays and clay minerals in nitrate uptake are evaluated and the known shortcomings of their application discussed, leading to suggestions for further research, and a review aims to assemble the available literature research on the application of Clays and Clay minerals as well as the mechanisms that lead to successful removal of nitrate from water.
130 citations
TL;DR: In this article, a detailed characterization of the alkaline lake is presented, including evidence for a pH of > 9.0 indicated by δ15N data (average 18.4) and the presence of alkali minerals such as trona and shortite; globular bacteria-like fossils; low contents of clay minerals; organic and inorganic geochemistry indicating high salinity, strongly reducing conditions, and hydrothermal activity.
118 citations
TL;DR: In this article, the adsorption of dissolved cadmium, Cd(II), under seawater-like conditions to the marine cyanobacterium Synechococcus sp.
108 citations
TL;DR: This study compares the mineralogy and speciation of REE in economic weathering profiles from China to prospective regoliths developed on peralkaline rocks from Madagascar and shows that REE are truly adsorbed as easily leachable 8- to 9-coordinated outer-sphere hydrated complexes, dominantly onto kaolinite.
Abstract: Global resources of heavy Rare Earth Elements (REE) are dominantly sourced from Chinese regolith-hosted ion-adsorption deposits in which the REE are inferred to be weakly adsorbed onto clay minerals. Similar deposits elsewhere might provide alternative supply for these high-tech metals, but the adsorption mechanisms remain unclear and the adsorbed state of REE to clays has never been demonstrated in situ. This study compares the mineralogy and speciation of REE in economic weathering profiles from China to prospective regoliths developed on peralkaline rocks from Madagascar. We use synchrotron X-ray absorption spectroscopy to study the distribution and local bonding environment of Y and Nd, as proxies for heavy and light REE, in the deposits. Our results show that REE are truly adsorbed as easily leachable 8- to 9-coordinated outer-sphere hydrated complexes, dominantly onto kaolinite. Hence, at the atomic level, the Malagasy clays are genuine mineralogical analogues to those currently exploited in China.
104 citations
TL;DR: In this paper, a series of T2 and T1-T2 NMR experiments were performed on oil-bearing shale and its components (clay minerals and kerogen) to obtain the T 1 -T 2 fluid typing chart and analyze the adsorbed and free oil in shale.
76 citations
TL;DR: In this article, high-resolution scanning electron microscopy (SEM) and TEM images provided direct evidence of parallel aligned clay-organic nanocomposites with an approximate thickness of each organic and clay nanolayer and the positive correlations between their morphology, occurrence and relative content.
74 citations
TL;DR: A systematic review of published results on the wettability of six different clay minerals is provided here, spanning from experimental studies to molecular dynamics simulations, and a range of conclusions are clearly established and a future outlook is given.
67 citations
TL;DR: In this article, chemical weathering and porosity profiles from catchments developed on marine shale located in Pennsylvania, USA, SSHCZO, California, USA (Eel River Critical Zone Observatory, ERCZO); and Taiwan (Fushan Experimental Forest).
66 citations
TL;DR: In this paper, the authors investigated the role of halloysite-abundant clay assemblages in heavy rare earth element (REE) mining in the Zudong mine in South China.
Abstract: Abstract Rare earth elements (REEs) have become increasingly important to our modern society due to their strategical significance and numerous high technological applications. Regolith-hosted heavy rare earth element (HREE) deposits in South China are currently the main source of the HREEs, but the ore-forming processes are poorly understood. In these deposits, the REEs are postulated to accumulate in regolith through adsorption on clay minerals. In the Zudong deposit, the world’s largest regolith-hosted HREE deposit, clay minerals are dominated by short, stubby, nanometer-scale halloysite tubes (either 10 or 7 Å) and microcrystalline kaolinite in the saprolite and lower pedolith and micrometer-sized vermicular kaolinite in the humic layer and upper pedolith. A critical transformation of the clay minerals in the upper pedolith is coalescence and unrolling of halloysite to form vermicular kaolinite. Microcrystalline kaolinite also transformed to large, well-crystalline vermicular kaolinite. This transformation could result in significant changes in different physicochemical properties of the clay assemblages. Halloysite-abundant clay assemblages in the deep regolith have specific surface area and porosity significantly higher than the kaolinite-dominant clay assemblages in the shallow soils. The crystallinity of clay minerals also increased, exemplified by decrease in Fe contents of the kaolinite group minerals (from ~1.2 wt% in the lower saprolite to ~0.35 wt% in the upper pedolith), thereby indicative of less availability of various types of adsorption sites. Hence, halloysite-abundant clay minerals of high adsorption capacity in deep regolith could efficiently retain the REEs released from weathering of the parent granite. Reduction in adsorption capacity during the clay transformation in shallow depth partially leads to REE desorption, and the released REEs would be subsequently transported to and adsorbed at deeper part of the soil profile. Hence, the clay-adsorbed REE concentration in the lower pedolith and saprolite (~2500 ppm on average) is much higher than the uppermost soils (~400 ppm on average). Therefore, weathering environments that favor the release of the REEs in the shallow soils but preservation of halloysite in the deep regolith can continuously adsorb REEs in the clay minerals to form economically valuable deposits.
TL;DR: A review of the interactions of clay minerals with microorganisms at different levels of complexity, starting from organic molecules, individual and aggregated microbial cells, fungal and bacterial symbioses with photosynthetic organisms, pedosphere, up to environmental and biotechnological implications is presented in this article.
Abstract: Clay minerals are very common in nature and highly reactive minerals which are typical products of the weathering of the most abundant silicate minerals on the planet. Over recent decades there has been growing appreciation that the prime involvement of clay minerals in the geochemical cycling of elements and pedosphere genesis should take into account the biogeochemical activity of microorganisms. Microbial intimate interaction with clay minerals, that has taken place on Earth’s surface in a geological time-scale, represents a complex co-evolving system which is challenging to comprehend because of fragmented information and requires coordinated efforts from both clay scientists and microbiologists. This review covers some important aspects of the interactions of clay minerals with microorganisms at the different levels of complexity, starting from organic molecules, individual and aggregated microbial cells, fungal and bacterial symbioses with photosynthetic organisms, pedosphere, up to environmental and biotechnological implications. The review attempts to systematize our current general understanding of the processes of biogeochemical transformation of clay minerals by microorganisms. This paper also highlights some microbiological and biotechnological perspectives of the practical application of clay minerals–microbes interactions not only in microbial bioremediation and biodegradation of pollutants but also in areas related to agronomy and human and animal health.
TL;DR: In this paper, the authors investigated the relationship of clay minerals, pore throat structure and reservoir properties of the Permian tight sandstones in the Hangjinqi area, in the north Ordos Basin, China.
TL;DR: In this paper, the authors analyzed the porosity of Ordovician Wufeng and Silurian Longmaxi groups in the Sichuan Basin by using the field emission-scanning electron microscopy, helium pycnometry, and low-pressure gas adsorption experiments.
TL;DR: In this paper, the results from earlier laboratory and field experiments were interrogated for the possibilities of sequestration, or long-term accumulation, of carbon from excess greenhouse gases in the atmosphere.
Abstract: Results from earlier laboratory and field experiments were interrogated for the possibilities of sequestration, or long-term accumulation, of carbon from excess greenhouse gases in the atmosphere. In the laboratory study, samples of three (top) soils dominated by kaolinite and illite (together), smectite, and allophane were examined for the adsorption and desorption of dissolved organic carbon (DOC). Adsorption and desorption of DOC were carried out on clay fractions extracted physically and after first native organic matter and then iron oxides were removed chemically. Labeled organic material was added to the soils to assess the priming effect of organic carbon (OC). In the field, changes in OC were measured in sandy soils that had been amended by additions of clay for between 3 and 17 years, both through incorporation of exogenous clay and delving of in situ clay. The laboratory experiments demonstrated that a portion of DOC was held strongly in all soils. The amount of DOC adsorbed depended on clay mineral types, including Fe oxides. Much adsorbed DOC was lost by desorption in water and a substantial amount of native OC was lost on priming with new OC. Addition of clay to soils led to increased OC. Therefore, addition of clay to soil may enhance net sequestration of C. Organic carbon close to mineral surfaces or within microaggregates is held most strongly. Carbon sequestration may occur in subsoils with unsaturated mineral surfaces. However, incorporation of carbon into macroaggregates from enhanced plant growth might be most effective in removing excess carbon from the atmosphere, albeit over the short-term.
TL;DR: In this paper, the results indicated that advised conditions were as follows: 5 min was the contact time of dye-clay; the better adsorbent masses were 0.25 g and 0.5 g per 100 ml solution for raw (ANb) and purified clays (ANp), respectively; the initial dye concentrations were 1 gL−1 for raw clay and 50 mgL− 1 for purified clay; pH solution had any effect on the yield of dye removal only when raw clay was used only when it was used; however, acid environment was advised when
Abstract: Clay minerals have large surface areas that contribute to their high adsorption capacity. Pure clays were often used. However, their prices remain expensive. However, the natural clay minerals that are locally available can have economic and environmental benefits for textile wastewater treatment. The tested natural clays had given low removal yields. Therefore, we wanted to test particular rich organic matter clay for adsorbing azo dye, which is a very toxic molecule. In order to make the use of this clay type have a better efficiency for removal of this dye from the polluted waters, the optimal conditions had been specified. The results indicated that advised conditions were as follows: 5 min was the contact time of dye-clay; the better adsorbent masses were 0.25 g and 0.5 g per 100 ml solution for raw (ANb) and purified clays (ANp), respectively; the initial dye concentrations were 1 gL−1 for raw clay and 50 mgL−1 for purified clay; pH solution had any effect on the yield of dye removal only when raw clay was used; however, acid environment was advised when purified clay was the adsorbent and for the two tested clays about 20–30°C was the better solution temperature. X-Ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) analysis confirmed that functional groups of clay adsorbed the dye. Langmuir maximum adsorption capacities of ANb and ANp were found to be 397 mgg−1 and 132.3 mgg−1 at pH 7 and 5, respectively. Raw and chemically activated samples gave similar results. Adsorption of ANb and ANp data showed better agreement with the pseudo-second-order kinetic model. Thermodynamic parameters of the two adsorbents confirmed that the adsorption was endothermic (ΔH > 0) and spontaneous (ΔG0 < 0). Energy level was high when purified clay was used; however, it was significantly lower when the adsorbent was raw clay. Therefore, it was likely that adsorption by carbonates and organic matter involved small energy amounts. Comparing between these and other previous results, Jebel Louka natural clay type is better recommended for MR removal from textile wastewater, since the removal yield was about 98%. Hence, this tested clay type could provide an alternative low-cost material that could be used in treatment of the textile wastewater rich in MR and the obtained adsorption model and desorption tests provided a background for pilot and industrial scale applications.
TL;DR: The results showed that 512, 51262, 51263, and 51264 were formed away from the clay mineral surface, indicating that the arrangement of H2O molecules resulted in a more optimal tetrahedral structure for CH4 hydrate formation than that near the negatively charged-layer surface.
Abstract: Molecular dynamics simulations were used to investigate the effects of the external surface of a 2:1 clay mineral with different charge amounts and charge locations on CH4 hydrate formation. The results showed that 512, 51262, 51263, and 51264 were formed away from the clay mineral surface. The surface of the clay mineral with high- and low-charge layers was occupied by Na+ to form various distributions of outer- and inner-sphere hydration structures, respectively. The adsorbed Na+ on the high-charge layer surface reduced the H2O activity by disturbing the hydrogen bond network, resulting in low tetrahedral arrangement of H2O molecules near the layer surface, which inhibited CH4 hydrate formation. However, more CH4 molecules were adsorbed onto the vacancy in the Si-O rings of a neutral-charge layer to form semicage structures. Thus, the order parameter of H2O molecules near this surface indicated that the arrangement of H2O molecules resulted in a more optimal tetrahedral structure for CH4 hydrate formation than that near the negatively charged layer surface. Different nucleation mechanisms of the CH4 hydrate on external surfaces of clay mineral models were observed. For clay minerals with negatively charged layers (i.e., high and low charge), the homogeneous nucleation of the CH4 hydrate occurred away from the surface. For a clay mineral with a neutral-charge layer, the CH4 hydrate could nucleate either in the bulk-like solution homogeneously or at the clay mineral-H2O interface heterogeneously.
TL;DR: The direction and magnitude of magnesium isotope fractionation attendant to the formation of clay minerals is fundamental to decipher the biogeochemical cycling of Mg in the critical zone and for the oceanic Mg budget as discussed by the authors.
TL;DR: The dominance of OM-associated U provides a framework to understand U mobility in the shallow subsurface, and, in particular, emphasizes roles for desorption and colloid formation in its mobilization.
Abstract: Uranium contamination threatens the availability of safe and clean drinking water globally. This toxic element occurs both naturally and as a result of mining and ore-processing in alluvial sediments, where it accumulates as tetravalent U [U(IV)], a form once considered largely immobile. Changing hydrologic and geochemical conditions cause U to be released into groundwater. Knowledge of the chemical form(s) of U(IV) is essential to understand the release mechanism, yet the relevant U(IV) species are poorly characterized. There is growing belief that natural organic matter (OM) binds U(IV) and mediates its fate in the subsurface. In this work, we combined nanoscale imaging (nano secondary ion mass spectrometry and scanning transmission X-ray microscopy) with a density-based fractionation approach to physically and microscopically isolate organic and mineral matter from alluvial sediments contaminated with uranium. We identified two populations of U (dominantly +IV) in anoxic sediments. Uranium was retained on OM and adsorbed to particulate organic carbon, comprising both microbial and plant material. Surprisingly, U was also adsorbed to clay minerals and OM-coated clay minerals. The dominance of OM-associated U provides a framework to understand U mobility in the shallow subsurface, and, in particular, emphasizes roles for desorption and colloid formation in its mobilization.
TL;DR: In this article, the role of rigid matrix minerals, particularly biogenically-sourced microcrystalline quartz, on organic porosity and pore size evolution was investigated in the Upper Devonian Duvernay Formation of western Canada.
TL;DR: The occurrence of pharmaceutical products (PPs) within environmental compartments challenges the scientific community and water treatment operators to find suitable and practicable removal solution as mentioned in this paper, which is a challenge for all of us.
Abstract: The occurrence of pharmaceutical products (PPs) within environmental compartments challenges the scientific community and water treatment operators to find suitable and practicable removal solution...
TL;DR: In this article, the characteristics of pore structures and the relationships between shale's physical properties and pore structure in the complex tectonic area were analyzed using X-ray diffraction (XRD), optical microscopic composition analysis, focused ion beam-scanning electron microscopy (FIB-SEM), vitrinite reflectivity and nitrogen adsorption experiments.
TL;DR: In this article, the authors used the time scale of a drill hole to measure the preservation potential and the stability of phyllosilicates, which is also some kind of a yardstick to measure preservation potential.
TL;DR: In this article, a hybrid stochastic modeling algorithm, called DEM-QSGSA, was proposed to generate a dozen digital shale models with different mineral components containing quartz, feldspar, calcite, clay minerals, pyrite, and organic matter.
TL;DR: Nanoarchitecture of hybrids materials based on clay minerals as nano building blocks for the environmental remediation is summarized with the emphasis on the utilization of layered clay minerals, especially smectite group of clay minerals for designing functional nanostructures for the adsorption of molecular contaminants from the environments.
TL;DR: In this paper, the authors studied the sorption and speciation of Tl in 36 geogenically Tl-rich topsoil materials from the Swiss Jura Mountains by combining chemical extractions, isotope exchange experiments, adsorption experiments, X-ray absorption spectroscopy (XAS), and sorption modelling.
TL;DR: In this paper, the effects of clay content and composition on organic carbon stabilization in soil, and the mechanisms involved were determined by studying the decomposition of alfalfa residues in artificial soils made from quartz sand and kaolinite with and without additions of the non-layered colloids (NLCs) goethite, manganese oxide or imogolite.
Abstract: Mineralization of soil organic carbon and CO2 emission from the soil is slowed by interactions between organic matter and minerals. The main minerals involved are clay minerals and oxides but there is limited understanding of their effects when combined, as occurs in soil. We aimed to determine the effects of clay content and composition on organic carbon stabilization in soil, and the mechanisms involved. This was achieved by studying the decomposition of alfalfa residues in artificial soils made from quartz sand and kaolinite with and without additions of the non-layered colloids (NLCs) goethite, manganese oxide or imogolite. The artificial soils were inoculated with microbes from natural soil and incubated at 23 °C in the dark at 60% of water holding capacity for 180 days. With increasing contents of clay and NLCs, organic carbon mineralization decreased, whereas carbohydrate and microbial biomass carbon contents increased. Of the NLCs, goethite had the least effect and imogolite the greatest effect on carbohydrate content. The effects of the treatments on mineralization and carbohydrate content were explained mostly by specific surface area (> 83% of variation), presumably due to the effects on sorption. The effects of the treatments on microbial biomass were related to the volume of habitat (water-filled pore space) and availability of substrate (influenced by sorption). These results showed that clay content and composition influenced the stabilization of soil organic carbon mostly through the supply of surfaces for sorption reactions rather than via interactions unique to particular colloids.
TL;DR: In this paper, a case study of continental palaeo-weathering recorded in late Neoproterozoic sequences of the Adelaide Geosyncline, South Australia is presented.
TL;DR: In this article, the pore structure of clay minerals has been widely studied, and the characteristic of the characteristic pore structures has also been investigated for gas adsorption in shale.
Abstract: Clay minerals contain a massive amount of nanopores and play a significant role in gas adsorption in shale. Although the pore structure of clay minerals has been widely studied, the characteristic ...
TL;DR: In this paper, the use of amidocyanogen silanol (ANS-1), a newly developed oligomer with an amino siloxane structure, as a potential shale inhibitor was reported.