Structure Of Bentonite Research Articles

Molecular dynamics simulation of modified bentonite and barrier mechanism of phenol pollution in groundwater

In this paper, phenol was used as the target pollutant, and the cutoff walls were prepared with modified bentonite, cement, and sand. Density functional theory (DFT) was used to simulate the modification mechanism of 3-amino-propyl triethoxy silane (APTES) and bentonite. The charge and energy of APTES were discussed, and the graft morphology was simulated. The structure of bentonite was characterized using Scanning electron microscope (SEM) and X-ray Diffraction (XRD) after modification. The spacing of the bentonite layer increased, and the surface of bentonite was folded and stacked, indicating that APTES had been grafted onto the surface of the bentonite. Adsorption kinetics and isothermal tests indicated that modified bentonite's adsorption reaction to phenol aligns more with the pseudo-second-order kinetic model and Langmuir model. According to Computed Tomography (CT) scanning, three-dimensional reconstruction, and Finite element method (FEM) calculations revealed that the effective porosity of the modified bentonite cutoff wall increased significantly, while its permeability coefficient decreased. Through column tests and centrifugal tests, the seepage velocity of phenol solution with different concentrations in the cutoff walls was 10-9m/s. The migration of phenol at a contaminated site was simulated for over 4000 days using Visual ModFlow. The results indicated that the implementation of cutoff wall successfully controlled the migration of phenol.

Evaluation of the Nitrogen Release Properties of Chitosan-Bentonite Beads

In this study, chitosan-bentonite beads were prepared by using bentonite and chitosan as fertilizer carrier materials and urea as fertilizer components. The prepared samples were named BUC0.2, BUC0.4 and BUC0.6 based on the bentonite ratios of 0.2%, 0.4% and 0.6% (weight/volume). In the FT-IR and XRD results, it was seen that the characteristic peaks of the bentonite structure became evident in the BUC0.6 sample, while chitosan peaks were dominant in the BUC0.2 sample, as expected. As the amount of bentonite increased, the swelling ratio generally increased from 31.6% to 48.6. In the nitrogen release experiments, a very rapid nitrogen release occurred in the first hours of release. It was thought to be due to the rapid dissolution of urea in water. The cumulative release percentage showed a slightly decreasing trend in the days following the release experiment. When nitrogen release profiles of the samples containing different amounts of bentonite were compared, it was observed that the nitrogen release curves were quite close to each other due to the lower bentonite ratio. Release percentages of the samples containing different amounts of bentonite were obtained between 61.2-67.7. Observations supported the efficient degradation of fertilizers in the soil environment. As a result, it was evaluated that the prepared materials were promising as environmentally friendly nitrogen fertilizer.

Adsorption characteristics and mechanism analysis of heavy metal Zn2+by cement-soil and alkali activated slag-bentonite-soil

With the increasing emphasis on low-carbon environmental protection, alkali activated cementitious materials are gradually being used as a substitute for cement in vertical cutoff walls for polluted sites. The composition of barrier materials significantly impacts the adsorption of heavy metals, thereby affecting the service life of cutoff walls. However, the adsorption characteristics and mechanisms of traditional cement-soil (CS) and alkali activated slag-soil (AASS) for heavy metals are still unclear. This study investigates the adsorption characteristics of Zn2+ using different mix ratios of barrier materials. Various mix proportions were designed, and qualitative and quantitative analyses were conducted using X-ray diffraction and thermogravimetric tests, respectively. The research results indicate that the adsorption of Zn2+ by barrier materials prepared from CS and slag-bentonite-soil (AASBS) is mainly chemical adsorption. The adsorption rate of heavy metals can be enhanced by increasing the cement content in the CS mix ratio. This is primarily because an increase in OH- in the hydration products encourages the formation of heavy metal precipitation. The generation of C-S-H and ettringite in the hydration products and ion exchange of heavy metals improve the adsorption of heavy metals. Increasing slag and alkali activator dosage, along with decreasing alkali activator modulus, promotes C-A-S-H generation and increases OH-, enhancing heavy metal precipitation. Increasing the content of bentonite in the AASBS mixture promotes the generation of C-A-S-H, and the interlayer structure of bentonite promotes the ion exchange of heavy metals. The findings of the study may offer a theoretical foundation for the installation of AASBS vertical cutoff walls in contaminated areas.

Preparation and Characterization of Chitosan-Modified Bentonite Hydrogels and Application for Tetracycline Adsorption from Aqueous Solution.

The "sol-gel method" was used to prepare spherical chitosan-modified bentonite (SCB) hydrogels in this study. The SCB hydrogels were characterized and used as sorbents to remove tetracycline (TC) from aqueous solutions. The adsorbents were characterized by SEM, XRD, FTIR, TG, and BET techniques. Various characterization results showed that the SCB adsorbent had fewer surface pores and a specific surface area that was 96.6% lower than the powder, but the layered mesoporous structure of bentonite remained unchanged. The adsorption process fit to both the Freundlich model and the pseudo-second-order kinetic model showed that it was a non-monolayer chemical adsorption process affected by intra-particle diffusion. The maximum monolayer adsorption capacity determined by the Langmuir model was 39.49 mg/g. Thermodynamic parameters indicated that adsorption was a spontaneous, endothermic, and entropy-increasing process. In addition, solid-liquid separation was easy with the SCB adsorbent, providing important reference information for the synthesis of SCB as a novel and promising adsorbent for the removal of antibiotics from wastewater at the industrial level.

Predicting anion diffusion in bentonite using hybrid machine learning model and correlation of physical quantities

Radionuclide diffusion will be influenced by numerous factors. Establishing a model that can elucidate the internal correlation between mesoscopic diffusion and the microscopic structure of bentonite can enhance the comprehension of radionuclide diffusion mechanisms. In this study, a light gradient boosting machine (LightGBM) was employed to predict the effective diffusion coefficients of HCrO4−, I−, and CoEDTA2− in bentonite. The model's hyperparameters were optimized using the particle swarm optimization (PSO) algorithm. Several correlated physical quantities, such as mesoscopic parameters (total porosity, rock capacity factor, and ion molar conductivity) and microscopic parameters (ionic radius and montmorillonite stacking number) were incorporated to develop a machine learning model that incorporated micro- and meso-scale features. The predictive performance of PSO-LightGBM was verified using diffusion experiments, which investigated the diffusion of HCrO4−, I−, and CoEDTA2− at compacted dry densities of 1200–1800 kg/m3 using a through-diffusion method. Spearman correlation and Shapley additive explanation analyses revealed that the compacted dry density, ionic diffusion coefficient in water, ionic radius, and total porosity were the top-four influencing factors among the 16 input features. Partial dependence plot analysis elucidated the relationship between the effective diffusion coefficient and each input feature. The analysis results were consistent with the experimental findings, demonstrating the reliability of machine learning. Due to the incorporation of multi-scale features, the PSO-LightGBM model demonstrated enhanced predictive accuracy, linking the microstructure of bentonite to radionuclide diffusion, and providing a comprehensive interpretation of the diffusion mechanism.

INFLUENCE OF рН AND Ca<sup>2+</sup> IONS ON CHEMICAL COMPOSITION AND SORPTION OF <sup>137</sup>Cs BY CHERKASY BENTONITES (UKRAINE)

The safety of near-surface and deep radioactive waste storage facilities is based on a system of engineered and natural barriers. Significant degradation of the engineered barrier system composed of cemented waste matrixes covered by cement mixture, concrete compartments, and structures at the basement of the storage facility may cause radionuclide transfer from the facility to groundwater. Mixing of the cement and concrete with water leads to the formation of several various hydration products with subsequent leaching of Ca2+ ions and formation of hydroxyl ions (OH-), which affects the alkalinity of the water environment and the sorption properties of bentonite, as a component of the engineered barrier at the basement of near-surface facilities. The article presents the results of an experimental study of the influence of Ca2+ ion concentration and pH of the model solution (similar to groundwater composition at Vector Site in Chornobyl Exclusion Zone) on the elemental composition and sorption properties of natural (NB) and Na-modified (PBA-20) bentonites from the Cherkasy deposit concerning 137Cs at the Solid : Solution ratio of 1 : 100. Geochemical modeling suggests that addition of CaCl2 to test solution and resulting alkaline pH leads to precipitation of solids, mainly oxides, hydroxides, Fe oxyhydroxides (hematite, goethite, limonite), and Ca carbonates (calcite, aragonite, dolomite). Their role in Cs adsorption was evaluated. The concentration of structural elements (Si, Al) in bentonites practically does not change with Ca2+ ion concentration increase in the model solution, demonstrating the bentonite structure’s stability under these conditions. At the same time, an increase in the Ca concentration and a decrease in the Na concentration was found in the ion exchange complex of the bentonites if compared to the initial natural bentonite. This results in the transformation of Na-modified bentonite from Na, Ca-form to Ca, Na-form. The total sorption capacity of NB and PBA-20 bentonite concerning Cs+ ions at increased concentrations of Ca2+ ions and pH of the solution slightly decreases, though retaining high values of the degree of absorption (> 90 %). The total adsorption of Cs+ ions on NB and PBA-20 bentonites from model groundwater with the addition of CaCl2 from 16 to 960 mg/dm3 and increase of рН from 7.4 to 11.8 decreases with the increase in ionic strength, in particular, due to competition with Са2+ and Na+ ions. NB and PBA-20 bentonites of the Cherkasy deposit remain a reliable component of the liner at the repository basement owing to their main functional property – high absorption capacity for 137Cs, which is an important dose-forming radionuclide of short-lived low- and medium-level waste.

Effect of cations on monochlorobenzene adsorption onto bentonite at the coexistence of Tween 80

The effect of several prevalent cations (including Na+, K+, Mg2+, Ca2+, Al3+, and Fe3+) on the adsorption of monochlorobenzene (MCB) onto bentonite was investigated at the coexistence of nonionic surfactant Tween 80 (T80) in surfactant-enhanced remediation (SER). They are all favorable for MCB and T80 adsorption, especially Mg2+ and Ca2+. Adsorption of MCB is strongly depended on T80 micelles. When its concentration exceeds the solubility, MCB is easier to bind with T80 micelles and be adsorbed by bentonite. Acidic environment can facilitate MCB and T80 adsorption, but the effect of cations on the adsorption is most significant under alkaline conditions. Adsorption capacity of MCB increases first followed by a slight decrease with increasing cations concentrations. The maximum adsorption rate of MCB determined is about 68.4% in a solution containing Mg2+ in the isothermal adsorption of MCB, while it is only 6.8% in a cation-free solution. Various characterizations showed that cations mainly changed the repulsion between bentonite particles and T80 micelles and the agglomeration and structure of bentonite, thus affecting the adsorption of MCB and T80 micelles. Our research demonstrated the nonnegligible promotion of MCB adsorption on bentonite by cations and acidic environment, which will adversely affect SER efficiency.

Structure and properties of ZnO‐organobentonite‐filled natural rubber composites

AbstractThis study involved the preparation of composites consisting of zinc oxide (ZnO) nanoparticles deposited within the structure of organophilic bentonite. These composites were subsequently utilized as fillers in natural rubber (NR). The organobentonites were initially prepared via a cation exchange reaction using alkylammonium ions with different chain lengths (C8N−C18N) and later deposited by ZnO nanoparticles. The identification of the ZnO‐organobentonites was conducted using various techniques, including powder X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV‐Vis spectroscopy, etc. The findings demonstrate the successful deposition of ZnO nanoparticles within the organobentonite's structure. The basal space between the silicate layers increased with the increasing chain length of alkylammonium ions. When added to NR, the ZnO‐organoclays mutually acted as a cure activator and filler. As expected, the ZnO‐organoclay modified by octadecylammonium ions (C18N) showed the greatest reinforcement due to its highest capability to enlarge the basal space between the silicate layers.

Dietary incorporation of magnetic bentonite nanocomposite: impacts on in vitro fermentation pattern, nutrient digestibility, and growth performance of Baluchi male lambs.

Incorporation of bentonite into the diets of ruminants can be helpful to maximize their performance. Modifying the structure of bentonite to nano and nanocomposite has improved their chemical stability and physicochemical properties, enhancing adsorption, absorption, and cation exchange capacity. Aims: This study aimed to assess the effect of magnetic bentonite nanocomposite (MBNC) on in vivo and in vitro fermentation process patterns, nutrient digestibility, and growth performance of Baluchi male lambs. Effects of control (basal diet), natural bentonite (NB) (10 g/kg dry matter (DM)), processed bentonite (PB) (5 and 10 g/kg DM basal diet), and MBNC (5 and 10 g/kg DM basal diet) on gas production (GP), and the fermentation process were determined using in vitro GP technique. For the in vivo experiment, 20 Baluchi male lambs were used with 4 experimental treatments: control, NB (5 g/kg DM), PB (5 g/kg DM), and MBNC (5 g/kg DM) and 5 replications in a completely randomized design for 60 consecutive days. The potential for GP and its fractional rates were significantly decreased and increased in MBNC, respectively (P<0.01). The lowest cumulative GP, and CH4 yield were observed in MBNC (P<0.05). In vitro, DM and organic matter (OM) digestibility and all fermentation parameters increased with the addition of two levels of MBNC to the culture medium (P<0.01). Except for feed conversion ratio (FCR), other growth performance parameters increased with the addition of MBNC to the diet (P<0.01). The ruminal pH, total volatile fatty acids (TVFA), acetate, and propionate significantly increased when MBNC incorporated to the diet (P<0.01). The NH3-N (P<0.001) was significantly decreased in MBNC. The bentonite supplementation decreased acetate to propionate (P=0.001) compared to the control. Adding MBNC at the 5 g/kg diet DM level can be used as a useful supplement to optimize rumen fermentation pattern, reduce methane production, and increase lamb performance.

Unlocking the potential of V/Ti-AAC: a promising eco-friendly catalyst for cyclohexene epoxidation

Abstract Bentonite is an abundant natural resource in the Maghnia region of Algeria that may have potential value in catalysis, but heretofore has been considered of low value for this purpose due to its low acidity and low catalytic activity. Low cost is one of the main criteria for choosing a suitable material for catalysis. Because bentonite is abundant and low-cost, its use as a starting material for the preparation of catalysts deserves reconsideration. The present study was undertaken, therefore, to optimize the performance of bentonite as a catalyst in one of the most promising reactions in organic synthesis, namely, cyclohexene epoxidation. The bentonite was subjected to adjustment of its structure by means of a number of laboratory treatments based on its large cation exchange capacity. These modifications aimed to achieve an environmentally friendly catalytic process by incorporating transition metals, specifically titanium and vanadium, into the modified bentonite structure through acid activation. Redox properties were enhanced and Lewis and Brønsted acidities were introduced. The vanadium oxide, supported on titania-pillared, acid-activated bentonite (5V/Ti-AAC), was characterized comprehensively using various techniques, including diffuse-reflectance UV-visible spectroscopy (DR UV-Vis), Fourier-transform infrared spectroscopy (FTIR) for surface acidity analysis, X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray elemental analysis (EDX). The catalytic activity was investigated in response to certain variables, such as catalyst mass, nature of the solvent, amount of oxidant, and reaction temperature. A kinetic study was conducted to understand the reaction behavior. The experimental results demonstrated intriguing catalytic activity, achieving a 42% conversion rate with ~68% selectivity toward the epoxide product when employing tert-butyl hydroperoxide (TBHP) as the oxidant and heptane as the solvent. This study highlights the potential of 5V/Ti-AAC as an environmentally friendly catalyst applied in the epoxidation of cyclohexene.

Temperature-dependent microbial reactions by indigenous microbes in bentonite under Fe(III)- and sulfate-reducing conditions

Bentonite is a promising buffer material for constructing spent nuclear fuel (SNF) repositories. However, indigenous microbes in bentonite can be introduced to the repository and subsequent sealing of the repository develops anoxic conditions over time which may stimulate fermentation and anaerobic respiration, possibly affecting bentonite structure and SNF repository stability. Moreover, the microbial activity in the bentonite can be impacted by the heat generated from radionuclides decay. Therefore, to investigate the temperature effect on microbial activities in bentonite, we created microcosms with WRK bentonil (a commercial bentonite) using lactate as the electron donor, and sulfate and/or ferrihydrite (Fe(III)) as electron acceptors with incubation at 18 ℃ and 50 ℃. Indigenous WRK microbes reduced sulfate and Fe(III) at both temperatures but with different rates and extents. Lactate was metabolized to acetate at both temperatures, but only to propionate at 18 ℃ during early-stage microbial fermentation. More Fe(III)-reduction at 18 ℃ but more sulfate-reduction at 50 ℃ was observed. Thermophilic and/or metabolically flexible microbes were involved in both fermentation and Fe(III)/sulfate reduction. Our findings illustrate the necessity of considering the influence of temperature on microbial activities when employing bentonite as an engineered buffer material in construction of SNF repository barriers.

Determination of Sulfide Consumption by Fe-bearing Components of Bentonites

Geologic repositories for spent nuclear fuel use bentonite as a buffer to protect the metallic containers confining the radioactive material. Sulfate-reducing bacteria, which may be present in groundwater, at the bentonite–host rock interface or eventually within the bentonite may produce sulfide, representing a potential threat for the metallic canisters, particularly copper. Bentonites can act as potential sulfide scavengers. Little is yet known, however, regarding the underlying mechanisms, the maximum extent of sulfide consumption, and the potential impacts on bentonite structure under repository conditions. In the current study, concentrated (4–150 mM) sulfide solutions were reacted in batch experiments with six natural Fe-bearing bentonites, with various purified Fe-bearing components of bentonite (a series of purified montmorillonites and three iron (oxyhydr)oxides), and with one synthetic mixture, for up to 1.5 months at pH values ranging from 7 to 13. The solutions were analyzed by colorimetry to determine sulfide and polysulfide concentrations and the solids were analyzed by 57Fe Mössbauer spectrometry to determine iron speciation. Important sulfide consumption coupled with a reduction of structural Fe in the clay samples was observed. Not all clay structural Fe was reactive toward sulfide; the proportion of active structural Fe depended on the clay structure and pH. In the presence of excess sulfide in solution regarding Fe in the solid sample, the clay structural Fe was found to be the main reactant while the reaction with iron (oxyhydr)oxides was largely inhibited. Three bentonite groups were distinguished, based on the sulfide oxidation capacity of their main clayey component.

Effects of iron corrosion products on the degradation of bentonite structure and properties

Bentonite is a key material for engineering barriers to prevent groundwater and nuclide migration in the multi-barrier system of high-level radioactive waste (HLW) geological disposal. However, its barrier property will be degraded under the action of iron corrosion products of steel disposal containers. In this paper, the effects of iron corrosion products on the degradation of bentonite structure and properties were investigated in the simulated environments for HLW geological disposal. The results showed that Fe2+/Fe3+ dissolved from iron powder could enter montmorillonite (Mt) interlayer and substituted part of Na+, which caused the decrease of the volume and interlayer spacing of Mt, and the structural integrity of Mt was destroyed. Macroscopically, the water absorption and swelling property of bentonite were significantly decreased. The degradation mechanism of Mt structure was mainly that Fe2+/Fe3+ generated by iron corrosion entered the interlayer domain of Mt to compensate for the interlayer charge deficit.

Material characteristics and pollutant diffusion simulation of cutoff walls made of alkali activated slag/bentonite

To prevent heavy metal pollution, vertical cut-off walls made of cement soil are often used as barriers. This article developed a cementitious material with a “low-carbon footprint” (alkali activated slag) to replace cement. The performance of alkali activated slag soil and cement soil was comprehensively explored through unconfined compressive strength, hydraulic conductivity, Zn2+ adsorption, and chloride ion diffusion tests. And the micro pore structure and micro morphology characteristics of the cutoff wall were explored through nuclear magnetic resonance testing and scanning electron microscopy testing. Finally, considering the normal distribution of pollutants, the diffusion process of pollutants in the transition layer, cut-off wall and aquifer is simulated by using the COMSOL Multiphysics 5.6. Research has found that alkali activated slag soil meets the requirement of low permeability in the early stage of maintenance, making up for the shortcomings of cement soil maintenance in the early stage. After adding bentonite to alkali activated slag soil, it was found that the hydraulic conductivity and effective diffusion coefficient showed a decreasing trend, while the adsorption rate of Zn2+ was significantly increased. Due to the double layered structure of bentonite and the hinge of C-A-S-H generated by alkali activated slag, it promotes an increase in the proportion of small pores and the generation of free water with poor fluidity, thereby improving the blocking effect of the cut-off wall on pollutants. Through simulation results, it was found that the breakthrough time of alkali activated slag soil as a cutoff wall is 3.07 times that of cement soil. After adding 6% and 12% bentonite to the alkali activated slag soil, the breakthrough time of the cut-off wall increased by 1.74 times and 4.25 times, respectively.

Metallurgical Properties of Iron Ore Pellet when Using Bentonite Modified by Soda

The study reported the ability to use soda-modified bentonite applied to the pelletization of iron ore and its effect on metallurgical properties such as green pellet strength, compressive strength and degree of reduction. The properties of the pellets were used in different binders for comparison as bentonite, soda-modified bentonite (1, 2 % per weight of bentonite), and soda. Green pellets were tested for drop numbers. After drying and atmosphere firing, pellets were reduced at 900, 1000 and 1100 ºC for 30, 60 and 120 minutes. The obtained results show that when using 1 % soda-modified bentonite as a binder in the pelletization process gives the highest degree of reduction, appropriated green pellet strength and compressive strength. In addition, modifying bentonite by using soda not only increases the adhesion of bentonite without affecting the structure of bentonite but also helps increase the degree of reducibility of iron ore pellets. This modified bentonite by soda can be applied in pellet manufacturing to reduce the bentonite as the binder in pelletization process.

Research Progress on the Influence of Thermo-Chemical Effects on the Swelling Pressure of Bentonite

The swelling pressure of bentonite changes dramatically due to diffused nuclear radiation heat and underground osmosis, causing the failure of the buffer isolation layer in deep geological repositories for the disposal of high-level radioactive waste. A detailed overview of the relevant research results on the swelling pressure variation of bentonite under thermo-chemical effects is presented in this paper. The results showed that the values of the swelling pressure obtained by different test methods are dissimilar. The swelling pressure of bentonite decreased with the increasing pore solution concentration; nevertheless, the effect of temperature on the swelling pressure is still controversial. At the micro-level, crystal layer swelling and double- layer swelling are generally considered to be the main factors affecting the swelling pressure; the pore structure and water distribution of bentonite will change owing to thermo-chemical effects. At the macro-level, involving intergranular stress, a mechanical parameter was proposed to explain the mechanism of the changes in the swelling pressure of bentonite. Finally, future research directions for the study of the evolution of bentonite swelling properties under thermo-chemical effects are proposed, based on the current research results.

Conversion of crude palm oil to biofuels via catalytic hydrocracking over NiN-supported natural bentonite

&lt;abstract&gt; &lt;p&gt;Nickel nitride supported on natural bentonite was prepared and tested for hydrocracking Crude Palm Oil (CPO). The catalyst was prepared using the wet impregnation method and various nickel nitride loading. Subsequently, the nickel nitrate-bentonite was calcined and nitrided under H&lt;sub&gt;2&lt;/sub&gt; steam. The surface acidity of as-synthesized NiN-bentonite was evaluated using the gravimetric pyridine gas. Meanwhile, the physiochemical features of the catalyst were assessed using XRD, FT-IR and SEM-EDX. The results showed that the NiN species was finely dispersed without affecting the bentonite's structure. Furthermore, the co-existence of Ni and N species on EDX analysis suggested the NiN was successfully supported onto the bentonite, while the surface acidity features of raw bentonite were increased to 1.713 mmol pyridine/g at 8 mEq/g of nickel nitride loading. The catalytic activity towards the CPO hydrocracking demonstrated that the surface acidity features affect the CPO conversion, with the highest conversion achieved (84.21%) using NiN-bentonite 8 mEq/g loading. At all nickel nitride loading, the NiN-bentonite could generate up to 81.98–83.47% of bio-kerosene fraction, followed by the bio-gasoline ranging from 13.12–13.9%, and fuel oil ranging from 2.89–4.57%.&lt;/p&gt; &lt;/abstract&gt;

Nickel Nanoparticles Anchored on Bentonite Clay for Methane Decomposition with Ordered Carbon as a Product

Catalysts were synthesized with Ni and bentonite clay, without previous treatment, through wet impregnation with 5, 10 and 20% of Ni (m/m). They were characterized by energy dispersive X-ray fluorescence spectrometry (EDX), X-ray diffraction (XRD), temperature-programmed reduction (TPR), thermogravimetric analysis (TGA), adsorption and desorption of N2 at 77 K, and transmission electron microscopy (TEM). The catalytic activity in relation to the methane conversion reaction was evaluated at 500 °C for 0.5 h. The addition of 10 and 20% of nickel to the clay led to a disordered bentonite structure, characterized by the disappearance of the 001 reflection on the X-ray diffractograms, with a consequent increase in the interaction between nickel oxide and clay (TPR). All catalysts synthesized showed catalytic activity in relation to the conversion of methane to form ordered carbon. The catalyst with 20% of nickel had the highest activity, with 74% of methane conversion.

Transformation of the structure and adsorption properties of bentonite during physical and chemical treatment

The paper presents the results of studies of the effect of electromagnetic, ultrasonic and acid treatments on the structure and the adsorption index of alkaline-earth bentonite modified with nanoparticles of silicon oxide and aluminum. Studies have shown that electromagnetic, ultrasonic and acid treatments contribute to an increase in the adsorption capacity of bentonite modified with nanoparticles of silicon oxide by 5, 10, and 25%, respectively. Modification of bentonite with stabilized nanodispersed hydrosols of amorphous silicon oxide (6-10.5 nm) and crystalline boehmite (3.5-4 nm) of 0.1-0.5 wt. % with subsequent ultrasonic and microwave treatments allows to increase its adsorption index for methylene blue and the cation exchange capacity up to 40%. And during the combining with preliminary activation in suspension with sodium carbonate it allows to increase up to 80%. The increase in the adsorption properties of bentonite is due to a double increase in the homogeneity of the structure, dispersion and specific surface area of aluminosilicate particles and transformations of the phase composition. As a result, through the use of advances in the field of nanotechnology, a combining of physical and chemical effects, the technology of modifying natural aluminosilicates based on bentonite has been improved, which makes it possible to significantly increase the adsorption characteristics of materials based on it.

Dual-functional anti-corrosion coatings with surface hydrophobicity and internal smart-releasing Ce3+ loaded in bentonite on carbon steel

Water-based coatings are gradually replacing traditional oil-based coatings for environmentally friendly applications, which creates a new paradigm in corrosion control of metallic components. In this work, water-based ZrO2–SiO2 sol-gel coatings were prepared for corrosion protection of carbon steel. The effects of the sol-gel ZrO2 to SiO2 ratio, coating thickness, corrosion inhibitor content and surface hydrophobicity on the coating physicochemical and anti-corrosion properties were investigated. The results showed that, compared to the pure silica coating, coating with 1/9 wt% ZrO2 in SiO2 matrix and coating thickness of 25 μm provided about 7 times higher corrosion resistance (impedance modulus 1.38 × 108 Ω cm2). A smart-releasing corrosion inhibitor containing Ce3+ ions (0.91 wt%) loaded into the layered structure of bentonite showed ability to delay the corrosion of substrate by 9 orders of magnitude by trapping Cl− ions from the environment and releasing Ce3+ ions at the cracked substrate surface. By applying a hydrophobic top layer, the water contact angle increased from 89° to 115°, which further increased the impedance modulus of the coating from 2.42 × 109 to 3.60 × 109 Ω cm2. The optimized coating passed salt spray standard corrosion test for 720 h (on scribed coating) due to the cathodic protection by corrosion inhibitor and shielding effects of a top hydrophobic layer. This work provides an enhanced strategy of dual-functional anti-corrosion coatings with surface water repellency and internal smart-releasing corrosion inhibitor for steel against environmental corrosion and damages with efficient self-healing functionality.