Showing papers on "Vermiculite published in 2020"

Cation-controlled wetting properties of vermiculite membranes and its promise for fouling resistant oil-water separation.

Abstract: Manipulating the surface energy, and thereby the wetting properties of solids, has promise for various physical, chemical, biological and industrial processes. Typically, this is achieved by either chemical modification or by controlling the hierarchical structures of surfaces. Here we report a phenomenon whereby the wetting properties of vermiculite laminates are controlled by the hydrated cations on the surface and in the interlamellar space. We find that vermiculite laminates can be tuned from superhydrophilic to hydrophobic simply by exchanging the cations; hydrophilicity decreases with increasing cation hydration free energy, except for lithium. The lithium-exchanged vermiculite laminate is found to provide a superhydrophilic surface due to its anomalous hydrated structure at the vermiculite surface. Building on these findings, we demonstrate the potential application of superhydrophilic lithium exchanged vermiculite as a thin coating layer on microfiltration membranes to resist fouling, and thus, we address a major challenge for oil–water separation technology. Manipulation of surface energy and wetting properties of solids may impact a variety of processes, including membrane fouling. Here the authors tune properties of vermiculite laminates from superhydrophilic to hydrophobic by cation exchange, and demonstrate potential for fouling resistant oil–water separation.

Cation controlled wetting properties of vermiculite membranes and its potential for fouling resistant oil-water separation

Abstract: The surface free energy is one of the most fundamental properties of solids, hence, manipulating the surface energy and thereby the wetting properties of solids, has tremendous potential for various physical, chemical, biological as well as industrial processes. Typically, this is achieved by either chemical modification or by controlling the hierarchical structures of surfaces. Here we report a phenomenon whereby the wetting properties of vermiculite laminates are controlled by the hydrated cations on the surface and in the interlamellar space. We find that by exploiting this mechanism, vermiculite laminates can be tuned from superhydrophillic to hydrophobic simply by exchanging the cations; hydrophilicity decreases with increasing cation hydration free energy, except for lithium. Lithium, which has a higher hydration free energy than potassium, is found to provide a superhydrophilic surface due to its anomalous hydrated structure at the vermiculite surface. Building on these findings, we demonstrate the potential application of superhydrophilic lithium exchanged vermiculite as a thin coating layer on microfiltration membranes to resist fouling, and thus, we address a major challenge for oil-water separation technology.

The possibility of vermiculite, sunflower stalk and wheat stalk using for thermal insulation material production

Abstract: In order to reduce heating costs in winter and cooling costs in summer, buildings are thermally insulated. In Turkey, large amounts of sunflower and wheat are produced every year. After production, sunflower and wheat stalks , create a serious storage problem. When these waste materials are used in houses for heating purposes, they cause environmental pollution. On the other hand, a large amount of vermiculite mineral is obtained during the natural wear of mica in Malatya and Sivas mines in Turkey. This mineral is capable to expand at high temperatures. A new insulation material produced by using vermiculite, sunflower stalk, wheat stalk and gypsum was investigated in this study as an alternative to non-renewable plastic-based synthetic insulation materials. The physical, mechanical and engineering properties of the samples were determined and the values were compared with the products on the market. The proposed compressed insulation material including vermiculite, sunflower stalk, wheat stalk and gypsum has a great potential as an insulating construction material with a thermal conductivity coefficient of 0.063–0.334 W/mK, a compressive strength of about 0.363 MPa and a density of 0.166–0.302 g/cm3.

Enhancement and mechanism of vermiculite thermal expansion modified by sodium ions

Abstract: Aimed at improving vermiculite's thermal expansibility, a novel method of Na+ modification has been proposed. The modification effects were characterized via X-ray fluorescence spectroscopy, X-ray diffraction, and thermogravimetric-differential thermal analysis. The result indicated that sodium ions entered vermiculite interlayers through the exchange of interlamellar calcium ions. The effects of the heating time on the expansion ratio of Raw-V and Na-V samples were investigated at the temperature range of 400–700 °C. The result indicated that the maximum increment in the expansion ratio could reach up to 26.5% after Na+ modification. The influencing mechanism of Na+ modification on the thermal expansibility of vermiculite was explored via molecular dynamics simulation and the binding energy and dehydration enthalpy change calculation. The simulation and calculation results showed a good agreement with the expansion experiment result. This study provides a novel method for the preparation of high-performance expanded vermiculite.

Ability of micaceous minerals to adsorb and desorb caesium ions: Effects of mineral type and degree of weathering

Abstract: To evaluate the effects of type of micaceous mineral and degree of weathering on the ability to adsorb and desorb radiocaesium (RCs) ions, various levels of weathering were induced (K‐depletion) in three types of micaceous minerals: biotite, muscovite and illite. The ability to adsorb RCs was represented by RCs interception potential (RIP) and a desorption ratio was determined by the amount of ¹³⁷Cs desorbed from the minerals by 1 M ammonium acetate (¹³⁷Cs desorption ratio). The RIP values were in the order of illite > biotite > muscovite. The RIP values for biotite gradually increased with the release of up to ~50% of the K⁺ from interlayer sites but then decreased with the further release of K⁺, up to ~100%, which was associated with the formation of a fully expanded interlayer: vermiculite. The change from increasing to decreasing RIP due to the weathering of the biotite strongly indicated that the selective adsorption sites for RCs are not located in an expanded interlayer but in intermediate sites between non‐expanded and expanded interlayers: frayed edge sites (FES). In contrast, for both the muscovite and illite, the RIP only increased. The ¹³⁷Cs desorption ratio, <7% for all the samples, tended to decrease with increasing degrees of weathering and did not differ greatly by mineral type. These results contribute to a more accurate prediction of the risk of RCs transfer from soils to crops and the understanding of the weathering processes of micaceous minerals in soils. HIGHLIGHTS: Radiocaesium adsorption and desorption was investigated for gradually K‐removed biotite, muscovite and illite. Vermiculitization of biotite via K removal firstly increased then decreased the frayed edge sites (FES). Adsorption was influenced by di/trioctahedral character and charge localization, and desorption by degree of weathering. These results lead to better understanding of the weathering processes of micaceous minerals and fate of RCs in soils.

Comparative study of the effect of structural arrangement of clays in the thermal activation: Evaluation of their adsorption capacity to remove Cd(II)

Abstract: In this work, comparison of the effect of thermal activation on the physicochemical properties of laminar clays bentonite and vermiculite and sepiolite as fibrous clay and their adsorption capacity of Cd(II) from aqueous solution, were studied. The physicochemical characterization demonstrated that the elimination of superficial, interlaminar and crystalline water resulted in materials with reduced specific surface area, increased negative superficial charges and cation exchange capacity depends of crystalline structure. With an increase in the activation temperatures of 100–300 °C, 300–600 °C, and 600–900 °C, the Cd(II) adsorption capacity of bentonite was reduced by 32, 30, and 55 %, respectively. Increasing the thermal activation temperature of sepiolite from 300 to 800 °C, encourage the capacity of sepiolite to adsorb metallic ions by 40 %. Raw vermiculite always presented a better capacity to adsorb Cd(II) than thermally activated vermiculite; sample activated at 300 °C adsorbed 50 % less than natural vermiculite. The relation between the chemical and textural properties of the activated clays and their capacity to adsorb Cd(II) demonstrated that the adsorption capacity of the thermally activated clays was strongly dependent on the quantity of negative charge surface and their cation exchange capacity, inferred that the main mechanisms was due to two mechanism, electrostatic interactions of attractive forces between negative superficial charge and cationic specie of Cd(II) and cation exchange between interlaminar cations, OH− in silanols and aluminols groups with Cd(II).

Characterization of Ethylene–propylene Composites Filled with Perlite and Vermiculite Minerals: Mechanical, Barrier, and Flammability Properties

Abstract: Perlite and vermiculite are naturally occurring minerals, commonly used by industry to obtain highly thermoisolative and/or non-flammable materials. However, there has been little research into the preparation and application of rubber compounds containing these inexpensive mineral fillers. Here, we show the benefits of perlite and vermiculite minerals as fillers for ethylene-propylene rubber (EPM) composites. To obtain more uniform dispersion and improved compatibility between the minerals and the elastomer matrix, 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (AMIMTFSI) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIMTFSI) imidazolium ionic liquids (ILs) were added. The mineral fillers were found to be attractive semi-reinforcing fillers, which also act as flame retardants in the elastomer composites. Furthermore, a higher content of vermiculite mineral significantly reduced the air permeability of the composites. The incorporation of ionic liquids into the EPM-filled systems had a considerable effect on the torque increment, crosslink density, and more importantly the flammability of the studied compounds. The application of 2.5 parts per hundred parts of rubber (phr) BMIMTFSI, in particular, reduced the flammability of the EPM composite, as the maximum heat release rate (HRRmax) decreased from 189.7 kW/m2 to 170.2 kW/m2.

Grain Size Distribution and Clay Mineral Distinction of Rare Earth Ore through Different Methods

Abstract: Although clay mineral content in ion-absorbed rare earth ores is crucial for migrating and releasing rare earth elements, the formation, distribution, and migration of clay minerals in supergene rare earth ores have not been fully understood. Therefore, this study analyzes the characteristics of clay mineral type and content, soil particle size, pH value, leaching solution concentration, and leaching rate. This analysis was performed using different methods, such as regional rare earth mine soil surveys, in situ leaching profile monitoring, and indoor simulated leaching. The results showed that the grain size and volume curve of rare earth ore have unimodal and bimodal shapes, respectively. X-ray diffraction showed the differences in clay mineral types formed by different weathered bedrocks. The principal clay minerals were kaolinite, illite, chlorite, and vermiculite, with their relative abundance varying with parent rock lithology (granite and low-grade metamorphic rocks). In the Ganxian granite weathering profile, the kaolinite content increased from top to bottom. The decomposition of feldspar minerals to kaolinite was enhanced with an increase in the SiO2 content during weathering. The in situ leaching profile analysis showed that the kaolinite content increased initially and then decreased, whereas the illite/mica content exhibited the opposite trend. Under stable leaching solution concentration and leaching rate, clay mineral formation is favored by lower pH. Low pH, low leaching rate, and highly-concentrated leaching solution (12 wt%) resulted in a slow increase in kaolinite content in the upper part of the profile (30 cm). A lower concentration of the leaching solution (4 wt%) resulted in rapid enrichment of kaolinite after 15 days. Low pH, leaching solution concentration, and leaching rate promoted the formation of distinct kaolinite horizons. We suggest that by disregarding other control factors, rare earth recovery of over 90% can be achieved through leach mining with solutions of 8 wt% and a pH of 5 at a leaching rate of 5 mL/min.

Mineral sorbents for ammonium recycling from industry to agriculture

Abstract: In tropical environments, nutrient-poor soils are commonly found, leading to high fertilizers application rates to support agricultural activities. In contrast, anthropogenic activities generate large amounts of effluents containing nitrogen. In this study, two minerals (natural zeolite and vermiculite) were tested to remove NH4+ from an industrial effluent with high pH and contents in Na+ and K+. Afterwards, they were tested as an alternative slow-release fertilizer in the soil. To verify the best conditions to adsorb NH4+, batch tests were conducted using synthetic solutions and an industrial effluent. In general, the efficiency of both minerals in removing NH4+ was high (85% for zeolite and almost 70% for vermiculite) as well as the ability to decrease the industrial effluent pH. In this process, more NH4+ and K+ ions were removed in comparison with Na+, which remained in solution. These minerals were tested as slow-release fertilizers by leaching with distilled water (both minerals releasing 2 mg L−1 NH4+) and with an acid solution (releasing 10 mg L−1 NH4+ from zeolite and 50 mg L−1 NH4+ from vermiculite—corresponding only to 12% of total NH4+ retained by zeolite and 29% by vermiculite). During the test of soil incubation with zeolite-NH4+, the NH4+ ions of the exchangeable sites were retained for a longer period, minimizing their loss by leaching and biological nitrification. Consequently, soil acidification was prevented. Therefore, both minerals showed high efficiency in removing NH4+ from solution which can then be slowly released as a nutrient in the soil.

Photo-oxidative degradation of organo-functionalized vermiculite clay-reinforced polyimide composites

Abstract: Herein, accelerated photo-oxidation under UV light of polyimide (PI) films filled with functionalized vermiculite (VMT) clay (i.e., 1–7 wt %.) were examined from 0 to 600 h. Thick films (⁓ 60 µm) were fabricated and exposed to accelerated UV light (λ > 295 nm). The as-synthesized PI-reinforced clay nanocomposites were examined by Fourier transform infrared (FT-IR), scanning surface micrograph (SEM), yellowing index, and thermogravimetric analysis (TGA), respectively. The surface morphology examined by SEM exhibits well exfoliation of VMT clay in the PI matrix. The change in internal chemistry on a higher temperature and clay composition is found to be the result of the aggregation of clay. The yellowing index determined by UV–Vis spectroscopy followed a similar tendency as the carbonyl index. TGA analysis revealed good heat resistance in clay-based PI due to the lower thermal expansion of clay reinforcement. Overall, the data clearly showed a better photo-stability of the developed clay/PI composites over the pristine polymer. It is concluded that clay-based PI could be a better alternative in applications requiring harsh conditions, as clay has improved the oxidative, thermal, and insulation properties of the PI matrix.

Extent of zeolite synthesis via alkaline fusion from tailings dam sediments

Abstract: Zeolite was synthesized via alkaline fusion from the tailings dam sediments of a sand mine in southern Brazil. The sediments are composed of a mixture of illite, kaolinite, vermiculite, quartz and K-feldspar yielding a silty-loam texture. The extent of zeolite synthesis was tested under varied NaOH:sediment ratio, temperature and fusion time. At the NaOH:sediment ratio of 8:5 and fusion temperature of 600 °C, all minerals were dissolved and converted in faujasite, except a quartz residue of less than 5 wt%. The synthetic faujasite shows intergrown octahedral habit, grain size < 2 µm, specific surface area of 760 m2 g−1 and cation exchange capacity of 4.6 cmol kg−1. Experiments at lower NaOH:sediment ratio produced lower amounts of zeolite from 6:5 to 5:5 and 4:5, faujasite fraction declined from 73 to 50 wt%. At an NaOH:sediment ratio of 3:5, the faujasite fraction dropped to 0.7 wt%, below which no faujasite was formed. By decreasing temperature from 550 to 250 °C, a smooth decrease in faujasite formation was observed, from 64 to 29 wt%. A synthetic analogous of ferrierite appeared in the runs at 300 and 250 °C. Experiments using prolonged heating (up to 12 h) at low temperatures (300, 200 °C) and low NaOH:sediment ratio (3:5) did not enhance zeolite formation. Kaolinite and vermiculite were dissolved in all runs, while residual illite was ubiquitous and residual quartz was present in all experiments.

Evaluation of vermiculite application rates on growth and yield of brassica napus (rape)

Abstract: Production of leaf vegetables requires intensive soil nutrients management. A 3-year field experiment was carried out to assess effects of vermiculite application rates on the growth and yield of Brassica napus. The experiment was conducted during the 2016/17, 2017/18 and 2018/19 summer seasons at the Marondera University of Agricultural Sciences and Technology (MUAST) farm, Mashonaland East Province, Zimbabwe. Vermiculite was applied at five levels of 0 (control), 1, 2, 5 and 10 t ha-1 in a completely randomised block design (RCBD) with 3 replicates. Basal and top-dressing fertilizers were applied using the recommended rates in the study area. The B. napus leaf width, leaf length, fresh and dry matter yield, leaf nutrient concentration and N and P uptake were measured. Analysis of variance (ANOVA) at p = 0.05 was done to compare the effects of vermiculite application rates on growth and yield of B. napus. Growth parameters and yield of B. napus significantly (P <0.05) differed among the five levels of vermiculite. Application rates of 5 t ha-1 and 10 t ha-1 improved leaf width and length, fresh and dry matter yield of B. napus. Farmers may therefore apply 5 -10 t ha-1 of vermiculite in order to increase rape leaf yields. However, there is need for further researches to determine the optimum application rates of vermiculite are essential.

Quantification of Mixed-Layer Clays in Multiple Saturation States Using NEWMOD2: Implications for the Potassium Uplift Hypothesis in the SE United States

Abstract: Quantification of mineral assemblages in near-surface Earth materials is a challenge because of the often abundant and highly variable crystalline and chemical nature of discrete clay minerals. Further adding to this challenge is the occurrence of mixed-layer clay minerals, which is complicated because of the numerous possible combinations of clay layer types, as defined by their relative proportions and the ordering schemes. The problem of ensuring accurate quantification is important to understanding landscape evolution because mineral abundances have a large influence on ecosystem function. X-ray diffraction analysis of the variable cation-saturated clay fraction in soil and regolith from the Calhoun Critical Zone observatory near Clinton, South Carolina, USA, was coupled with modeling using NEWMOD2 to show that mixed-layer clays are often dominant components in the mineral assemblages. Deep samples in the profile (>6.5 m) contain mixed-layer kaolinite/smectite, kaolinite/illite-like, kaolinite-vermiculite, illite-like/biotite, and illite-like/vermiculite species (with ‘illite-like’ defined herein as Fe-oxidized 2:1 layer structure with a negative layer charge of ~0.75 per unit formula, i.e. weathered biotite). The 2:1 layers in the mixed-layer structures are proposed to serve as exchange sites for K+, which is known to cycle seasonally between plant biomass and subsurface weathering horizons. Forested landscapes have a greater number of 2:1 layer types than cultivated landscapes. Of two nearby cultivated sites, the one higher in landscape position has fewer 2:1 layer types. Bulk potassium concentrations for the forested and two cultivated sites show the greatest abundances in the surface forested site and lowest abundance in the surface upland cultivated site. These observations suggest that landscape use and landscape position are factors controlling the mixed-layer mineral assemblages in Kanhapludults typical of the S.E. United States Piedmont. These mixed-layer clays are key components of the proposed mechanism for K+ uplift concepts, whereby subsurface cation storage may occur in the interlayer sites (with increased negative 2:1 layer charge) during wetter reduced conditions of the winter season and as biomass decay releases cation nutrients. Cation release from the mixed-layer clays (by decreased 2:1 layer charge) occurs under drier oxidized conditions during the growing seasons as biota utilize cation nutrients. The types and abundances of mixed layers also reflect long-term geologic factors including dissolution/alteration of primary feldspar and biotite and the subsequent transformation and dissolution/precipitation reactions that operate within the soil horizons. Thus, the resulting mixed-layer clay mineral assemblages are often complex and heterogeneous at every depth within a profile and across landscapes. X-ray diffraction (XRD) assessment, using multiple cation saturation state and modeling, is essential for quantifying the clay mineral assemblage and pools for cation nutrients, such as potassium, in the critical zone.