For the acid-leaching process of halloysite nanotubes (HNTs), the structure and energetic evolution is crucial for the basic understanding and further modification of HNTs. The specific surface area, pore volume, and bond distribution of HNTs at different Al leaching percentages were studied by molecular dynamics simulation. With the increase of the Al leaching percentage, the inner diameter of the halloysite nanotubes is gradually enlarged, forming some nanoporous (1–20 nm) interlayer spaces inside the tube wall of HNTs due to the strong bondings between the adjacent layers, and the specific surface area and pore volume of HNTs increased in a complex way at each transition stages. For the transition structures, the interlayer nanopores greatly increase the specific surface area and pore volume of HNTs, which is more obvious after 50% Al leaching. The free water molecules inside lumen structure of HNTs would have an impact on the thermodynamics and the structure evolution of HNTs. Although the transition structures with extremely large loading capacity may not be naturally most stable, they might be stabilized or achieved by some fast transient regulation methods.

The detection of mixed-layered clays is well known on Mars and evidences the presence of water on the planet. To understand the processes related to the formation of these mixed-layered clays on Mars, we performed a set of hydrothermal syntheses on basaltic ash of Stromboli volcano (Southern Italy), selected for its composition similar to Martian rocks. Syntheses were carried out by opportunely modulating the experimental conditions. Trials were performed at constant pH = 5, with pressure of 0.1–50 Mpa and temperatures ranging from 150 °C to 350 °C, and runs lasting from 5 to 31 days. In specific conditions described herein, corrensite crystals (mixed-layered clays) were produced. Optical microscope (OM), Powder X-Ray Diffraction (PXRD) and Scanning and Transmission Electron Microscopy, both combined with Energy Dispersive Spectroscopy (SEM/EDS; TEM/EDS), wavelength-dispersive electron probe microanalysis (WDS/EPMA), X-ray fluorescence (XRF), thermogravimetric and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FTIR/ATR) and micro-Raman spectroscopy (μR) were used for a detailed mineralogical, chemical and morphological characterization before and after hydrothermal alteration. The findings that emerge point out that corrensite formed on Mars probably originated from the alteration of the basaltic rocks at a low grade of hydrothermal metamorphism in a Fe(II) enriched environment.

This study investigates the conversion of biotite, a subgroup of clay minerals, into photocatalysts through heat treatment with CaCl2. The resulting reaction products were analyzed in terms of their composition, structure, optical properties, and photocatalytic activity against CrVI and salicylic acid (SA). Biotite and CaCl2 mixtures could be heated to 600 °C while retaining the biotite crystal structure, whereas heating to 700 °C resulted in transformation to octahedral wadalite crystals. The band gap of the wadalite obtained after heat treatment was approximately 3.10 eV. The photocatalytic reduction rate per unit surface area increased markedly with increasing heat-treatment temperature, and the CrVI reduction and SA degradation rates of the sample calcined at 800 °C were approximately 18 and 9 times greater, respectively, than those of the sample calcined at 500 °C. Leaching tests of the reaction products revealed that the elution of Ca2+ and Cl− was particularly significant. Even the samples that retained the biotite structure after heat treatment displayed some photocatalytic activity, indicating that this method may be applicable to preparing photocatalysts from mica and related minerals with similar structures.

Halloysite surface was modified with tetrabutylammonium iodide, and then the obtained nanomaterial was used as support for ZnO nanoparticles. After characterization, the nanomaterial was used as a catalyst for fatty acid methyl esters (FAMEs) production. The recyclability of the nanomaterial was also investigated, and the optimization of reaction conditions by the design of experiments approach was performed as well. In addition, the synthesized nanomaterial was tested as a catalyst for FAME production from a series of waste lipids affording biodiesel in moderate to good yields (35–95%), depending on the matrix. To fully exploit the feasibility of clay minerals as catalysts in biodiesel formation, a screening of different clays and clay minerals with different morphologies and compositions, such as sepiolite, palygorskite, bentonite, and hectorite was also performed in the esterification of FFAs (a mixture of 1:1 palmitic and stearic acids). Finally, hectorite, chosen as a model of 2:1 clay minerals, was covalently modified, and tested as a catalyst in the esterification of FFAs.

The assessment of the long-term performance of the engineered barrier systems of high-level radioactive waste (HLW) repositories requires the use of reactive transport models. Here a non-isothermal reactive transport model of the long-term geochemical evolution of a HLW disposal cell in a granitic host rock is presented. The model includes the vitrified waste (40 cm in diameter), the carbon-steel canister (5 cm thick), the saturated FEBEX bentonite buffer (75 cm thick) and the reference granitic rock. The model accounts for the thermal transient stage and assumes generalized steel corrosion under anaerobic conditions with a corrosion rate equal to 1.41 m/y. Canister failure is assumed to occur when the remaining canister thickness is equal to 3.5 cm at t = 25,000 years. Canister corrosion caused an increase in pH. The computed pH in the canister just before canister failure (t = 25,000 years) was equal to 9.25 and ranged from 7.82 to 9.25 in the bentonite. Magnetite, the main corrosion product, precipitated in the bentonite and especially in the canister. The thickness of magnetite precipitation band in the bentonite was ≈ 1 cm. Siderite precipitated at both sides of the canister/bentonite interface. The precipitation front penetrated >1 cm into the bentonite. Nuclear glass started dissolving after canister failure (t > 25,000 years). The concentration of dissolved silica increased in the inner part of the glass until t = 30,000 years and decreased in the outer part of the glass due to the out diffusion of dissolved silica into the canister and the bentonite. This diffusive flux caused the precipitation of greenalite at the glass/canister and canister/bentonite interfaces. The pH at the end of the simulation (t = 50,000 years) ranged from 7.93 to 7.89 in the glass, from 7.89 to 8.66 in the canister and from 7.87 to 8.6 in the bentonite. Magnetite precipitated in the canister while there was carbon steel to corrode. Once the canister was fully corroded, magnetite redissolved near the glass/canister interface. Greenalite precipitated in the canister and the bentonite, especially at the glass/canister interface and siderite precipitated at the canister/bentonite interface. The simulation results should be useful for the performance assessment of engineered barriers of radioactive waste repositories in granitic host rocks.

In the present study, Ag nanoparticles modified Fe3O4 anchored on roughened halloysite nanotubes nanocomposites (Ag@Fe3O4/RHNT) with high peroxidase-like activity and good magnetism was fabricated, and accordingly, an efficient and sensitive colorimetric sensing platform was established for the detection of H2O2. Firstly, halloysite nanotubes was pre-treated and then Fe3O4 nanoparticles were uniformly deposited on the external surface of RHNTs. Finally, Ag nanoparticles were grown onto Fe3O4/RHNT by in-situ reduction method. All characterization results confirmed the successful synthesis of Ag@Fe3O4/RHNT. The resultant Ag-Fe3O4 RNHTs exhibited satisfied catalytic activity to the oxidation of TMB (4,4’-Diamino-3,3′, 5,5′-tetramethylbiphenyl) in the presence of H2O2, and the catalytic process is accompanied with the color changed from colorless to bule. Thus, a sensitive colorimetric sensor for detection of H2O2 was developed based on Ag@Fe3O4/RHNT nanocomposites. And the optimal reaction temperature and pH were determined to be 55 °C and 4, respectively. H2O2 can be detected in the range of 10–100 μM with the detection limit of 0.7 μM. In conclusion, we established an efficient colorimetric sensing system for H2O2, and applied it to detect H2O2 in milk and serum.

The overuse or abuse of antibacterial drugs has led to serious health problems. At present, among various antimicrobial materials (natural, organic, inorganic, etc.), inorganic antimicrobial materials, especially ZnO, have received widespread attention. However, an important factor that influences the function of nanoparticles is agglomeration. The agglomeration-sensitive nature of ZnO compromises its antibacterial properties. Here, talc is used as a substrate to control the size and dispersion of ZnO, forming composite minerals with excellent antibacterial properties against both Escherichia coli and Staphylococcus aureus. According to transmission electron microscopy, ZnO/talc is easily adhered to bacterial cells, whereas atomic force microscopy reveals that antibacterial effects are caused by non-covalent interactions between ZnO/talc and bacterial membranes. The comprehensive investigation of antibacterial performance and interfacial interaction is conducive to our understanding of the antibacterial mechanism of inorganic compounds, and also provides new perspectives on the biological effects of inorganic nanomaterials.

The Li-bearing claystone and carbonate are sedimentary rocks deposited in the lacustrine environment hosting the Bigadiç borate deposits in western Anatolia. The purpose of this paper is to explain the mineralogical, geochemical, stable isotope characterizations and formation of Li-rich claystone (hectorite, saponite), and have strategic, technological, and economic importance for the country's economy, which have not been sufficiently studied previously. In the rhyolitic and dacitic tuffs, sanidine and plagioclase crystals were altered, biotite and hornblende, Fe-oxidized, locally opaque, and chloritized in a sericitized, Fe-oxidized, argillized, calcified, and zeolitized glassy matrix. The claystone consists mainly of smectite and minor illite, volcanogenic quartz, feldspar, mica, hornblende, and occasionally calcite, aragonite, dolomite, and gypsum/anhydrite. Hectorite and saponite were determined based on the expansion of their basal peaks following heating at 500 °C and solvation with ethylen-glycol; additionally, hectorite expanded, and saponite was not affected after glycerine-saturated Cs-smectite and heating at 100 °C for 20 h. Smectite shows webby to crenulated forms, and coexist with feldspar, volcanic glass, rhomboidal calcite, blocky gypsum/anhydrite, and Fe-oxide phases. The Li values increase up to 2650 ppm in the smectite-rich claystone and marl, and up to 449 ppm in the volcanic rocks. The positive correlation of REE with each of SiO2, Al2O3, and K2O; positive correlation of MgO vs. Li, and increase of MgO + CaO, Sr, Li, LREE relative to MREE and HREE; negative Eu anomaly and high values of As and S suggest that the feldspar, mica, and hornblende alteration originating from the Miocene volcanic and pyroclastic materials and presence of gypsum/anhydrite during the hydrothermal alteration activities were the sources for the smectite formation. The high negative δ18O values of calcite, the δD and δ18O values of smectite and δ34S‰ and δ18O‰ values of gypsum, and the 87Sr/86Sr isotope ratios range of calcite and gypsum suggest the contribution of mixing meteoric and hydrothermal environmental conditions during the depositional and diagenetic process(es) in the playa lake environment.

The application of nanotechnology in the field of agrochemicals release is an effective way to reduce the use of fertilizers and improve their utilization. Here, different ratios of urea were successfully intercalated into halloysite (Hal) by solid-phase milling method, and the maximum loading of urea was calculated as 14.99 ± 1.33 wt%. X-ray powder diffraction (XRD) demonstrated the distance of the Hal (001) plane increased from 0.7 to 1.0 nm by the urea intercalation. Subsequently, urea-Hal‑sodium alginate (SA) hydrogel beads (UHS) were fabricated by Ca2+ crosslinking method. SA and Hal content has a significant influence on the morphology and surface properties of the hydrogel. The optimal ratio of UHS was found as 2 wt% CaCl2, 2 wt% SA, and 2 wt% Hal. UHS had good water retention and slow release properties, and the water retention rate of UHS was increased by 13% compared with that of raw soil. The release curve showed that the release time of urea in UHS was 60 times longer compared to pure urea. Furthermore, using wheat as a plant model, UHS can provide slow-release nitrogen nutrients to promote the growth of wheat. In virtue of good swelling and slow-release properties, low cost, simple preparation process and environmental friendliness, UHS has a promising future in slow-release fertilizers for modern agriculture technology.

This article investigates the intercalation of carbamide within globular glauconite involving the chemical activation of glauconite with carbamide solution-gel at varying concentrations of total nitrogen (N). Mineral nanocomposites were prepared with a multitude of novel functions. As the N concentration of the initial solution increased, the proportion of intercalated N enhanced to 8%. A 20% of N concentration in carbamide solution maximizes intercalation. Intercalation occurs in the interlayer of smectite layers (micropores) in glauconite. In nanocomposites, the decrease in specific surface space, total volume pores, and average pore size reflect the absorption of carbamide in meso- and macropores of glauconite globules. Glauconite nanocomposites retain a spherical particle morphology and a distinct microlayer close to the surface. The increased proportion of nitrogen in the microlayers close to the surface indicates a high filtration capacity of the globules. The near-surface microlayer serves as a diffusion channel for the glauconite interior, where new substances are absorbed in the micro- (interlayer) and macropores. The stepwise kinetics of nutrient release, which supports the various forms of carbamide absorption in glauconite, distinguishes the nanocomposites. In addition to N-compounds, glauconite nanocomposites are mineral sources of the available potassium (K) in soils. As a result, chemically manufactured glauconite nanocomposites have some following advantages: the micro-granular mineral form, a permeable inner near-surface microlayer, incubated in micro-, meso-, and macropores N-compounds, and the available K.

A series of TiO2 pillared sericite nanocomposites were prepared by the sol-gel method followed by thermal treatment. Two factors, namely sericite dosage, and calcination temperature were researched to see their effects on the structure and properties of TiO2 pillared sericite nanocomposite. X-ray diffraction and nitrogen adsorption-desorption isotherms were used to analyze the changes of crystal phase, grain size and pore structure information of the generated TiO2 nanoparticles in the composite. Among all the samples, the TiO2 pillared sericite composite calcined at 800 °C has the best photocatalytic properties. Trapping experiment proved that the main active species are ·O2−, h+ and ·OH in order of participation during the photodegradation of methyl orange by the prepared composite. Sericite has a synergistic role in enhancing the photocatalytic activity of TiO2 pillared sericite nanocomposite. Good photocatalytic activity, together with its availability and good recyclability, makes sericite a promising substrate in the field of photocatalysis.

This work reports on the development of various nanostructured materials based on the assembly of SiO2, TiO2 and ZnO nanoparticles to sepiolite fibers (Sep) and their incorporation as a filler of Nafion to improve their performance as proton exchange membrane for fuel cells applications. Various nanoarchitectures, SiO2-Sep, TiO2-SiO2-Sep and ZnO@SiO2-Sep, were prepared following a colloidal route based on the controlled hydrolysis of alkoxide precursos (tetramethoxysilane and titanium tetraisopropoxide) in the presence of hexadecyltrimethylammonium-sepiolite. The SiO2 and TiO2 nanoparticles were consolidated after a thermal treatment that also removes the surfactant and assures their assembly to the clay. In the case of the ZnO@SiO2-Sep nanostructured material, previously formed ZnO nanoparticles were assembled to the intermediated produced after the hydrolysis-polycondensation of tetramethoxysilane on the organoclay, followed by a thermal treatment that consolidates the nanoarchitecture. The resulting nanoarchitectures were characterized by XRD, FTIR, SEM, TEM and N2 adsorption-desorption isotherms, confirming the formation of the nanoparticles and their assembly through silanol groups at the external surface of the clay. Nafion-based composite membranes were prepared using as nanofiller the produced SiO2-Sep, TiO2-SiO2-Sep and ZnO@SiO2-Sep nanoarchitectures. Thermal properties, water uptake and proton conductivity of the resulting composite membranes were evaluated in comparison to those of a neat Nafion membrane to ascertain their potential usefulness for applications in PEMFC.

Nanoparticles often-called proto-imogolites have been identified as an intermediate in the formation process of imogolite nanotubes as early as 1979. Their composition and structure are now well documented in the case of synthetic imogolite. One specific characteristic of proto-imogolite is that they have a curved shape with a local structure close to the one of imogolite. During a growth stage, they evolve toward nanocrystals (allophane, imogolite). Their thorough characterization has so far been difficult. Using synchrotron Small Angle X-ray Scattering coupled with Raman spectroscopy, we observe that proto-imogolites form during the initial stage of the co-precipitation of aluminum and silicon molecular precursors thanks to a reorganization process. The shape of the initial proto-imogolites, before the growth stage, depends on the synthesis conditions and controls the characteristics of the final product. We show using cryo-TEM images that, at the end of the growth stage, non-tubular nanostructures continue to coexist with nanotubes. Protocols to quantify remaining non-tubular nano-objects and purify the samples are discussed.

Innovative hemodialysis membranes are essential for hemodialysis process, the vital clinical treatment for patients with kidney failure. In the present study, for the first time halloysite nanotubes (Hal) were applied to adsorb creatinine through molecular sieve mechanism. Firstly, calcination process performed to improve the affinity of Hal for creatinine. Afterwards, eight different composite polyacrylonitrile (PAN) nanofibrous membranes containing two types of Hal including raw Hal (RHAL) and calcined Hal (CHAL) were developed via an electrospinning device (10, 20, 30 and 40 wt%). Morphological analysis revealed that, with low contents of Hal (10 and 20 wt%), the structural integrity of nanofibers was maintained. However, with the high contents of Hal (30 and 40 wt%), structural integrity of nanofibers was affected and conical beads were formed. The mechanical properties and hydrophilicities of the composite PAN based membranes were higher than pure PAN based membrane and improved by increasing Hal contents up to 20 wt% and then reduced. Therefore, among the composite PAN based membranes, the membranes loaded with 10 and 20 wt% of Hal were selected for further evaluations. Adsorption studies showed that the composite PAN based membrane loaded with 20 wt% of CHAL had best performance with >70% of creatinine removal. The MTT assay also presented; the highest cell viability about 90% for the same membrane. Blood compatibility of the membranes for both bovine serum albumin (BSA) surface adsorption and platelet adhesion revealed that the composite PAN membranes were significantly more blood compatible than the polyethersulfone (PES) commercial and pure PAN based membranes. As a result, composite PAN based membrane loaded with 20 wt% of CHAL which combines adsorption and traditional mechanism, seems promising for hemodialysis membranes.

Machine learning was used to predict the effective diffusion coefficient of radionuclides in compacted bentonites to reduce the cost of experimental methods. Through-diffusion experiments were conducted to determine the effective diffusion coefficient of Re(VII), which was used as a surrogate for 99Tc(VII), in compacted Anji bentonite. Five parameters (the external surface area, the ionic strength, the mass ratio of montmorillonite, the compacted dry density, and the accessible porosity) that affect the effective diffusion coefficient were calculated by a multi-porosity model to generate data for the analysis of the machine learning models to overcome the limited experimental data. The effective diffusion coefficient was predicted using two popular machine learning models, the Light Gradient Boosting Machine and Artificial Neural Network models, where the former exhibited higher sensitivity and accuracy in the prediction than the latter. The performance of the machine learning models was validated by comparing the experimental effective diffusion coefficients between this study and previous studies. The present work revealed that the machine learning method can be a powerful tool and may offer a new means of studying the effective diffusion coefficient.

Estimation of the swelling strain or swelling pressure is important for predicting the behavior of compacted bentonite barriers. In this study, the electrical conductivity of compacted bentonite was measured under free-swell and confined conditions to investigate the predictability of swelling strain or swelling pressure from the measured electrical conductivity. The evolution of electrical conductivity by water penetration was qualitatively consistent with that of swelling strain or swelling pressure, implying that monitoring electrical conductivity could be used to detect the initiation and termination of swelling process or any internal changes in compacted bentonite. The relationships between normalized swelling strain and normalized electrical conductivity, and between normalized swelling pressure and normalized electrical conductivity were developed based on the results of Ca-bentonite hydrated with NaCl solution, and those were verified using the results of Ca-bentonite hydrated with KCl and CaCl2 solutions, and Na-bentonite hydrated with NaCl solution. Finally, the limitations and possibilities of using electrical conductivity in estimating swelling parameters and monitoring swelling process were discussed in this study.

An unprecedented approach allowed correlating the pesticide fate in clay-containing media under air exposure with their ecotoxicity. This constitutes the novelty of this work and involves the study of the toxicity of ozonized pesticide-containing waters towards an aquatic plant, Lemna minor. The behavior of diazinon (DAZ) and atrazine (ATR) in natural clay-containing media was simulated in plant growth media fulfilling the Swedish Institute for Standards (SIS) containing Na+ and Fe2+-exchanged montmorillonite (Mt). The exchangeable cation was found to influence the pesticide ozonation and toxicity towards Lemna minor. Pesticide interactions appear to promote high catalytic surface through a compromise between low pH and high Mt dispersion. These results provide valuable findings for predicting pesticide ecotoxicity according to their natural oxidative degradation in the host clay suspension.

In this research, a halloysite-based nitrogen-phosphorous fire retardant epoxy system was evaluated. The synthesized melamine phosphate in combination with pentaerythritol as an intumescent fire retardant which was effective in previous studies was introduced. To achieve a strong and thermally stable char residue a tubular high aspect ratio halloysite nanotube to make bridgeable network and reducing flame spread as a promising reinforcing nanoclay was proposed. The present study focuses on investigating the fire retardant capabilities of partially cured melamine formaldehyde resin that has been used to cover fire retardant additives. The synthesized fire retardant additives were characterized by spectroscopic, microscopic analysis, etc. The synthesized fire retardant additives had an excellent effect on fire retardancy of epoxy resin and the strength of residual char. Thermogravimetric analysis data showed that suitable amount of halloysite had positive effect on the char residue to protect the substrate at high temperatures. Cone calorimetery test showed that the epoxy based fire retardant sample was successful to release heat slowly, and slow down the burning process by the formation of an efficient char on the surface of the substrate. The total smoke released by epoxy based fire retardant sample was 1469.1 m2/m2 while that of neat epoxy was 5589.6 m2/m2.

Benzene poses a severe threat to human health due to its prevalence and carcinogenicity. The adsorption behavior of benzene on clay mineral surfaces is significant to its migration and retention in soils. Therefore, it is crucial to understand the mechanism of benzene adsorption behavior under different environmental conditions. In this study, a series of Grand Monte Carlo (GCMC) simulations were performed to obtain benzene isotherms on clay under various temperatures and air humidity. The adsorption mechanisms were investigated via analysis of the distribution of interaction energy, density, and orientation of adsorbed benzene and water. Results show that benzene form multiple layers on mineral surfaces, and surfaces have a great impact on the first layer of adsorbed benzene. The impedance effect of temperature on benzene adsorption is attributed to the temperature-dependent chemical potential of benzene, but not the interaction between benzene and surfaces, which is slightly temperature-reliant. Humidity shows different inhibition effects on benzene adsorption due to different surface hydration behavior and competitive adsorption between water and benzene. Benzene tends to be adsorbed on hollow sites on kaolinite surfaces, which is the same as water. The surface cations on montmorillonite and mica are significant to benzene and water adsorption, and their density distribution causes different competitive adsorption behavior.

The processing of porous architectures based on Layered Double Hydroxides (LDH) is reviewed. Especially, a focus was put on porosity in nm and μm ranges that can be prepared via various post-treatments and templating techniques for the enhancement of the original properties. A challenge toward the desired porosity is control of structural ordering as well as crystal growth of LDH. The present review paper is mainly dedicated to summarizing the synthetic approaches to access the porous LDH that have found a wide range of applications such as adsorption/environment purification, catalysis, energy storage & production and bio-applications.