Showing papers on "Vermiculite published in 2022"

Precise Cation Recognition in Two-Dimensional Nanofluidic Channels of Clay Membranes Imparted from Intrinsic Selectivity of Clays.

Abstract: Various kinds of clays occur naturally and are accompanied by particular cations in their interlayer domains. Here we report the reassembled membranes with nanofluidic channel arrays by using the natural clays montmorillonite, mica, and vermiculite, which were imparted with the natural selectivity for realizing precise recognition and directional regulation of the naturally occurring interlayer cations. A typical surface-governed ionic transport behavior was observed in the clay nanofluidic channels. Through asymmetric structural modification, cationic current rectification was realized in montmorillonite channels that performed as a nanofluidic diode. Interestingly, in the mica nanofluidic channel, the K+ that was naturally occurring in the interlayer domain of mica showed a reciprocating motion and resulted in a periodically fluctuating current. Electrodialysis demonstrated that such a fluctuating current reflects a directional selectivity for K+, achieving at least a 6000 times permeation rate difference with Li+ ions. The specific selectivity for Li+/Mg2+ on vermiculite reached up to 856 times with similar cations by the current technique. As-obtained clay membranes possess application prospects in energy conversion, brine resource development, etc. Such a strategy can achieve the designed selectivity through systematic screening of the building blocks, thus imparting them with the inherent characteristics of natural clays, which provides an alternative solution to the present manufacture of selective membranes.

Effect of Clay Mineralogy and Soil Organic Carbon in Aggregates under Straw Incorporation

Abstract: The interaction between soil organic carbon (SOC) and clay minerals is a critical mechanism for retaining SOC and protecting soil fertility and long-term agricultural sustainability. The SOC composition and minerals speciation in clay fractions (<2 μm) within soil aggregates under straw removed (T) and straw incorporation (TS) conditions were analyzed by X-ray diffraction, Fourier transform infrared spectra and X-ray photoelectron spectroscopy. The TS treatment promoted enrichment of clay in aggregates. The TS increased the contents of SOC (27.0–86.6%), poorly crystalline Fe oxide (Feo), and activity of Fe oxides (Feo/Fed); whereas, it reduced the concentrations of free Fe oxide (Fed) in the clay fractions within aggregates. Straw incorporation promoted the accumulation of aromatic-C and carboxylic-C in the clay fraction within aggregates. The relative amount of hydroxy-interlayered vermiculite, aliphatic-C, and alcohol-C in the clay fractions within the macroaggregates was higher than that microaggregates, whereas the relative amounts of illite, kaolinite, Fe(III), and aromatic-C had a reverse tendency. The hydroxy-interlayered vermiculite in clay fractions showed positive correlation with the amounts of C–C(H) (r = 0.93) and C–O (r = 0.96 *, p < 0.05). The concentration of Feo and Feo/Fed ratio was positively correlated with the amounts of C=C and C(O)O content in clay within aggregates. Long-term straw incorporation induced transformation of clay minerals and Fe oxide, which was selectively stabilized straw-derived organic compounds in clay fractions within soil aggregates.

Investigation of vermiculite infiltration effect on microstructural properties of thermal barrier coatings (TBCs) produced by electron beam physical vapor deposition method (EB-PVD)

Abstract: Thermal barrier coatings (TBCs) are protective coating systems that are mostly utilized to improve the thermal insulation and functional performance of gas turbine engines and other aircraft components that are both stable and movable. These coatings protect materials operating in harsh conditions from structural damage caused by corrosion, oxidation, the CaO-MgO-Al 2 O 3 -SiO 2 effect (CMAS), thermal shock , volcanic ash, and vermiculite deposits at high temperatures. In this study, CoNiCrAIY metallic bond coatings were coated on Inconel 718 super alloy using a high velocity oxygen-fuel (HVOF) deposition technique. Then, single YSZ, Gd 2 Zr 2 O 7 (GZ), and double YSZ/GZ based ceramic topcoats were applied to the bond coats by using the electron beam physical vapor deposition (EB-PVD) method. The produced TBC samples and the uncoated Inconel 718 superalloy substrate were subjected to vermiculite (VM) deposition at 1250 °C for 4 h, and then the coatings were characterized. To determine the phase structures, microstructural and mechanical properties of the TBCs, X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer elemental mapping analysis (EDS), stereo microscopy analyses, porosity, and hardness measurements were used. The obtained results were comparatively evaluated with the recent related studies in the literature. • The aim of this study is to investigate the VM behavior of innovative single- and double-layer TBC systems. • The VM infiltration has occurred through the surface of the Inconel 718 superalloy substrate and all other TBC systems. • HVOF-bond coating and EB-PVD GZ coating were used for deposition of the TBCs. • On the Inconel 718 super alloy surface, YSZ, Gd 2 Zr 2 O 7 , and YSZ/Gd 2 Zr 2 O 7 coatings were deposited. • The TBC systems' initial porosity percentages decreased, but the top coating hardnesses increased. • The TGO structure formed at the interface with the effect of high temperature.

In-Depth Analysis of Physicochemical Properties of Particulate Matter (PM10, PM2.5 and PM1) and Its Characterization through FTIR, XRD and SEM–EDX Techniques in the Foothills of the Hindu Kush Region of Northern Pakistan

Abstract: The current study investigates the variation and physicochemical properties of ambient particulate matter (PM) in the very important location which lies in the foothills of the Hindu Kush ranges in northern Pakistan. This work investigates the mass concentration, mineral content, elemental composition and morphology of PM in three size fractions, i.e., PM1, PM2.5 and PM10, during the year of 2019. The collected samples were characterized by microscopic and spectroscopic techniques like Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX) spectroscopy. During the study period, the average temperature, relative humidity, rainfall and wind speed were found to be 17.9 °C, 65.83%, 73.75 mm and 0.23 m/s, respectively. The results showed that the 24 h average mass concentration of PM10, PM2.5 and PM1 were 64 µgm−3, 43.9 µgm−3 and 22.4 µgm−3, respectively. The 24 h concentration of both PM10 and PM2.5 were 1.42 and 2.92 times greater, respectively, than the WHO limits. This study confirms the presence of minerals such as wollastonite, ammonium sulphate, wustite, illite, kaolinite, augite, crocidolite, calcite, calcium aluminosilicate, hematite, copper sulphate, dolomite, quartz, vaterite, calcium iron oxide, muscovite, gypsum and vermiculite. On the basis of FESEM-EDX analysis, 14 elements (O, C, Al, Si, Mg, Na, K, Ca, Fe, N, Mo, B, S and Cl) and six groups of PM (carbonaceous (45%), sulfate (13%), bioaerosols (8%), aluminosilicates (19%), quartz (10%) and nitrate (3%)) were identified.

Composite adsorbent materials for desalination and cooling applications: A state of the art

Abstract: Adsorption technology is very attractive for producing desalinated water and cooling with no harmful impact on the environment. The performance of adsorption water applications (desalination and cooling) depends on the adsorption characteristics. Many adsorption systems designs were investigated worldwide, employing different adsorbent materials to develop a cost‐effective and high‐performance system. This review presents and summarizes the studies in adsorption and the corresponding applications in desalination and cooling and compares the adsorption properties of composite adsorbents. The review focuses on the composite materials and how they were synthesized while comparing them in terms of the amount of adsorption. The reviewed materials have been classified according to the basic host, such as silica gel, zeolite, carbon, metal‐organic frameworks (MOF), and vermiculite. The review contains more than 70 composites. The maximum reached water vapor uptake is 1.92 kg/kg of PHTS/CaCl2‐20 wt% composite at 0.9 P/Ps. The highest available desorption amount is 1.48 kg/kg of MOF composite for desalination applications and 0.87 kg/kg of vermiculite composite for cooling applications.

A Two-Dimensional Lamellar Vermiculite Membrane for Precise Molecular Separation and Ion Sieving

Abstract: Lamellar membranes constructed from two-dimensional (2D) nanosheets have exhibited exceptional permselective characteristics. However, their complex and contaminative nanosheet synthesis, low structural stability, and low chemical resistance severely limit industrial-scale production and practical applications. Herein, the stability, molecular separation, ion-sieving properties, and broad applicability were evaluated to demonstrate the application potential of 2D vermiculite (VMT) nanomaterials in high-performance membrane development. First, the large-scale 2D VMT nanosheets with average lateral sizes of ∼12 μm were prepared from the widely occurring natural clay via a facile procedure, and the 2D lamellar VMT membrane showed excellent long-term stability in harsh environments, even in an ultrasonic bath. Furthermore, the VMT membrane showed fast solvent permeance with a favorable retention rate of dye molecules and a surface charge-governed ionic transport behavior because of the negatively charged nanochannel, indicating the potential in both molecule separation and ion sieving. Moreover, the broad applicability of the VMT membrane was also confirmed using a simple intercalation optimizing strategy developed for other 2D membranes. Building on these findings, our work shows a possible route to the development of advanced membranes for energy and environmental applications.

Efficacy of biological agents and fillers seed coating in improving drought stress in anise

Abstract: Many plants, including anise, have tiny, non-uniform seeds with low and light nutrient reserves. The seeds also show a weak establishment, especially under stressful conditions where their accurate planting in the soil and optimal yield are tough. This study sought to improve anise seeds’ physical and physiological characteristics under drought stress. To this end, two factorial experiments under laboratory and greenhouse conditions were performed in a completely randomized design with 4 and 3 replications, respectively. Five levels of seed inoculation (inoculation with T36 and T43 of Trichoderma harzianum, and CHA0 and B52 of Pseudomonas fluorescent, and non-inoculation which means that control seeds were not treated with microbial inoculant), three levels of coating (K10P20, K10P10V5, and non-coating), and three levels of drought stress (0, –3, and –6 bars) were considered as the factorial experiment [vermiculite (V), kaolin (K), and perlite (P) numbers refer to the amount of material used in grams]. The laboratory experiment revealed that the combined treatments of bio-agents with coating increased the physical and germination characteristics of anise seeds compared to the control treatment. The greenhouse experiment showed that drought stress reduced the initial growth indices. Still, the combination treatments of biological agents and coating (fillers) could alleviate the destructive effects of drought stress to some extent and improve these indices. The best treatment was provided by T36 and K10P20 in both experiments, which significantly increased morphological indices.

Clay mineralogy fingerprinting of loess-mantled soils on different underlying substrates in the south-western Poland

Abstract: Loess may be integrated into slope deposits at different soil depths and may influence related physical, chemical and mineralogical soil properties. Therefore, tracking the border between deposited loess and underlying materials and estimating the depth of loess penetration is a challenge. Five soils from the Lower Silesia province in south-western Poland having different types of geologic substrate and being covered by loess deposits of various thicknesses were chosen to: 1) trace the origin of phyllosilicates in these heterogeneous soils (loess vs. underlying bedrock); 2) determine the influence of the geologic substrate and the loess mantle on clay mineral transformation in the soil; and 3) relate clay mineralogical traits to soil morphology. The loess consisted of long-distance and local aeolian sources as shown by the Ti/Zr ratios and heavy mineral composition. Geochemical and mineralogical traces of loess were easily detected in the mixed zone and in part also in the basal layer. The loess deposits are characterised by mica, chlorite, kaolinite, interstratified mica-vermiculite or hydroxy-interlayered vermiculite, vermiculite and a minor amount of smectite. Aeolian silt admixture was an important source of chlorite at all sites. The vertical distribution of mica indicated two types of sources — loess input and substrate. Smectite, however, has mostly been inherited from the underlying bedrock (serpentinite, glacio-fluvial deposits and basalt slope sediment) or was formed in the soils from mica or chlorite. Where present in the loess, smectite was only found in small amounts. The presence of kaolinite, HIV and mixed layered mica-vermiculite could be derived either from aeolian input or neoformation and thus actively occurring mineral (trans)formation reactions. Similar to mica, vermiculite was derived from both aeolian input and the geological substrate. The widespread loess deposits in this region rejuvenated the soil formation process, as evidenced by their mineralogical and chemical composition.

Thallium adsorption onto phyllosilicate minerals

Abstract: The adsorption of thallium (Tl) onto phyllosilicate minerals plays a critical role in the retention of Tl in soils and sediments and the potential transfer of Tl into plants and groundwater. Especially micaceous minerals are thought to strongly bind monovalent Tl(i), in analogy to their strong binding of Cs. To advance the understanding of Tl(i) adsorption onto phyllosilicate minerals, we studied the adsorption of Tl(i) onto Na- and K-saturated illite and Na-saturated smectite, two muscovites, two vermiculites and a naturally Tl-enriched soil clay mineral fraction. Macroscopic adsorption isotherms were combined with the characterization of the adsorbed Tl by X-ray absorption spectroscopy (XAS). In combination, the results suggest that the adsorption of Tl(i) onto phyllosilicate minerals can be interpreted in terms of three major uptake paths: (i) highest-affinity inner-sphere adsorption of dehydrated Tl+ on a very low number of adsorption sites at the wedge of frayed particle edges of illite and around collapsed zones in vermiculite interlayers through complexation between two siloxane cavities, (ii) intermediate-affinity inner-sphere adsorption of partially dehydrated Tl+ on the planar surfaces of illite and muscovite through complexation onto siloxane cavities, (iii) low-affinity adsorption of hydrated Tl+, especially in the hydrated interlayers of smectite and expanded vermiculite. At the frayed edges of illite particles and in the vermiculite interlayer, Tl uptake can lead to the formation of new wedge sites that enable further adsorption of dehydrated Tl+. On the soil clay fraction, a shift in Tl(i) uptake from frayed edge sites (on illite) to planar sites (on illite and muscovite) was observed with increasing Tl(i) loading. The results from this study show that the adsorption of Tl(i) onto phyllosilicate minerals follows the same trends as reported for Cs and Rb and thus suggests that concepts to describe the retention of (radio)cesium by different types of phyllosilicate minerals in soils, sediments and rocks are also applicable to Tl(i).