Structure Of Bentonite Research Articles

The swelling effect of sodium-bentonite as an additive in water-based drilling sludge with different concentration of polyamine inhibition

A highly reactive sludge on drilling progress has become a common problem. The problem will cause swelling clay or high filtration loss. With a risk of swelling appearance and too much filtration loss that may cause, sodium-bentonite is widely used in drilling sludge to give more viscosity and optimal ability to hold and lift the cutting inside the borehole. It contains mostly montmorillonite like particles of sodium that overpower the iolite content inside it. Polyamine as an inhibitor to the clay can infiltrate into the bentonite c-spacing, which is a gap between two layers of bentonite structure. A test has been conducted to measure the effect of polyamine inhibition inside a water-base sludge formulation x that is previously inhibited with sodium-bentonite. These tests were conducted using a number of instruments such as API Filtrate loss, swell meter test, retort oven, and Vann vg meter with API Standard procedure. The result provides a distinctive conclusion about how the rheological elements react toward the polyamine existence with different concentrations (4gr-10,5gr) inside the sludge. This research also reveals that the sludge durability is different between room temperature and high temperature (300°F).

Fe-Cr pillared clay as catalysts for the ethanol to gasoline conversion

Bentonite is a clay mineral type of montmorillonite that can be used as a catalyst. The use of bentonite as a catalyst has weaknesses, namely small surface area, pore volume and low thermal stability, so it is necessary to modify the structure. Modification of bentonite structure carried out in this research used the pillarization method (Pillared Clay or PILC) with the addition of Fe and Cr metals to form Cr/PILC, Fe/PILC, and Fe-Cr/PILC catalysts. The PILC catalysts can be used as a catalyst in the ethanol to gasoline conversion processess for alternative fuels. The XRD result shows that the pillarization process with the addition of Fe and Cr metals was succeeded so it can increase the interlayer spacing by 22,03 Å, 15,79 Å, and 15,85 Å on the Cr/PILC, Fe/PILC, and Fe-Cr/PILC catalysts. The SAA result shows an increase in surface area and pore volume in the Cr/PILC, Fe/PILC, and Fe-Cr/PILC catalysts structure. The presence of Brønsted acid type is indicated through the absorption peaks at 1515-1640 cm−1 and Lewis acid type at 1435-1470 cm−1 from the FTIR result. The TGA result shows an increase in thermal stability on the Cr/PILC, Fe/PILC, and Fe-Cr/PILC catalysts. The Fe-Cr/PILC catalyst shows the best activity results on the ethanol to gasoline conversion process with the acquisition of percent conversion and selectivity by 43.30% and 87.15% respectively.

Magnetically modified bentonite: Characterization and stability

Bentonite – clay rock, which consist mainly of clay mineral montmorillonite, is an excellent sorbent, widely used in wastewater treatment. The aim of the presented work was to evaluate the effect of the microwave radiation on the structure and stability of raw bentonite which is to be applied as a sorbent of ions from water solutions. Water extracts were prepared by batch method using deionized water. The leachate was prepared for 1, 6 and 24 h in different ratios of solid-to-liquid phase from the samples of raw clay and the magnetically modified clay – prepared by interaction with microwave radiation. In the filtrate, pH was determined as well as concentrations of Al, Ca, Fe, K, Mg, Na and Si using Atomic emission spectrometry with inductively coupled plasma. The results imply that microwave treatment of the bentonite changes the pH of the leachates to more acidic compared to the raw bentonite in which the pH increases. Magnetically modified bentonite treated by microwaves contained 2.67 wt% of the iron oxide which is 4 times more than in the raw bentonite. The microwave treatment of bentonite did not cause higher leaching of observed elements in comparison with raw bentonite.

Adsorption of zinc and copper (II) ions from aqueous solution using modified nano bentonite: equilibrium, kinetics, and thermodynamic studies

ABSTRACT In this research, modified Nanobentonite was prepared by calcination of bentonite for adsorption of zinc and copper ions. Nanobentonite particles were characterized by the EDX method, FTIR, and SEM. Adsorption efficiency, thermodynamic properties, and initial concentrations were studied. FTIR result showed sodium chloride affects the bentonite structure. According to the results, the rate of Zn2+adsorption at the chemical adsorption step is higher than the rate of adsorption of Cu2+. The amount of enthalpy and entropy are uniformly reduced when the Cu2+ and Zn2+ ions are adsorbed. The adsorption of Cu2+ ions is two-step and was occurring through an alternating ion-exchange mechanism.

Removal of Synthetic Estrogen from Water by Adsorption on Modified Bentonites

Natural bentonite is an adsorbent that can be easily modified as a low-cost material effective for the removal of persistent pharmaceutical micropollutants from water bodies. In this study, the modification of untreated bentonite by sodium is addressed to obtain Na-bent, which was further modified with L-Tryptophan (L-Trp) as well as with FeCl2.4H2O to produce Trp-Na-bent and Fe-Na-bent, respectively. The nonmodified and modified bentonite samples were tested for the adsorption of the pharmaceutical micropollutant 17α-ethinylestradiol (EE2) present in water bodies, a synthetic estrogen with very high toxicity. The structure of bentonite, before and after modification, was characterized using Fourier transform infrared, X-ray diffraction, Brunauer-Emmett-Teller, and thermal analysis (thermogravimetric analysis and differential scanning calorimetry) techniques. The influence of various experimental parameters on the adsorbent/adsorbate interaction was investigated. Equilibrium and kinetic studies of EE2 micropollutant adsorption were performed varying the initial adsorbate concentration, mass of bentonite, and contact time. The maximum adsorption for an initial concentration of 10 mg/L of EE2 was 4.20 mg/g, reaching the equilibrium after 2 h. The equilibrium data were fitted with Langmuir, Freundlich, and Dual-mode model equations. Adsorption kinetic data were analyzed using the pseudo-first order, pseudo-second order, and intraparticle diffusion models. The pseudo-second order model was the one that better described the kinetic data. The highest value of the equilibrium rate constant was obtained for Trp-Na-bent, followed by Fe-Na-bent. The results obtained show that the Trp-Na-bent complex exhibits a promising performance for the adsorption of EE2.

Quantitative characterization and comparsion of bentonite microstructure by small angle X-ray scattering and nitrogen adsorption

Quantitative characterization of the pore structure of typical bentonite in China is beneficial to nuclear waste treatment and sludge solidification modeling. A new small angle X-ray scattering (SAXS) method and conventional method low-temperature nitrogen adsorption and desorption (LTNAD) were combined to investigate the pore structure of four Chinese typical bentonites. The pore size and pore size distribution measured by the novel SAXS and conventional LTNAD methods were compared. The results suggested that Gaomiaozi bentonite exhibited Porod positive deviation effect. The GMZ01 had better sortability than GMZ07, and the pore size was concentrated. The average pore size of GMZ01 and GMZ07 calculated by the maximum entropy method were close. LTNAD experiment indicated that the specific surface area (SSA) of bentonite depended on the pore volume of mesopores and micropores and the types of exchangeable cations between layers. The SSA was positively correlated with the adsorption capacity. SAXS revealed that pore size estimated by maximum entropy method was larger than that evaluated by Guinier method. The log-normal distribution method in SAXS model was more suitable for characterizing small pores than maximum entropy method. Compared with maximum entropy method, The LTNAD method was more compatible with the SAXS lognormal distribution method. Compared with LTNAD, the SAXS has a wider detection range. These findings fill a gap in SAXS research on Gaomiaozi bentonite (GMZ01, GMZ07, CaGMZ).

Effect of F, V and Mn co-doping on the catalytic performance of TiO2-pillared bentonite in the photocatalytic denitration

F, V and Mn co-doped TiO2-pillared bentonite was prepared by the sol-gel method and characterized by XRD, nitrogen sorption, UV-vis spectroscopy, SEM, etc.; its performance in the photocatalytic denitration of NO was investigated under visible light irradiation at room temperature. The results indicate that the photocatalytic denitration efficiency of F-V-Mn co-doped TiO2-pillared bentonite for NO at a concentration of 661 μg/m3 is approximately 100%; when the concentration of NO increases to 1657 μg/m3, the photocatalytic efficiency decreases to 81.9%, which is however 33.8% higher than that over the unpillared F-V-Mn co-doped TiO2. The reaction rate constant over the F-V-Mn co-doped TiO2-pillared bentonite is twice as high as that over the V-Mn co-doped TiO2 pillared bentonite; moreover, the F-V-Mn co-doped TiO2-pillared bentonite also displays improved resistance against water and SO2 poisoning. TiO2 pillars can not only retain the flaky crystal structure of bentonite, but also increase the distance between bentonite layers from 0.667 to 0.710 nm and enhance the adsorption capacity. Meanwhile, the doping elements can inhibit the growth of TiO2 rutile and reduce the band gap of TiO2, which is effective in improving the response to visible light, prolonging the service life, and broadening the application range of TiO2 for the photocatalytic denitration.

Synthesis, characterization and properties of organically compounded bentonite by molecular intercalation process

A new process for manufacturing organically compounded bentonite was developed successfully based on the organic intercalation and layered structure of bentonite. The main steps in the proposed process included wet sodium activation of bentonite ore, organic compounding and high-pressure roll grinding. The optimum procedure is recommended as follows: 5 mass% of sodium carbonate powder and 30 wt.% water are added to activate the bentonite ore for 24 h to prepare activated bentonite; 0.5 wt.% of organic molecules are added into the activated bentonite for organic compounding for 12 h; then, the high-pressure roll grinding is followed to treat the organically compounded bentonite; and finally, drying and fine grinding are performed for preparing the final organically compounded bentonite product with 10 wt.% moisture and 98% passing 0.074 mm. The obtained organically compounded bentonite was characterized using an X-ray diffractometer, a scanning electron microscope and an X-ray photoelectron spectrometer. To confirm the effect of organically compounded bentonite on green balls, the pelletizing tests were carried out. The results showed that high-pressure roll grinding can not only enhance the ability of the crystal layer to hold the combined water, but also strengthen the intercalation compounding of the organic additive, which is beneficial for the formation of a fiber-interlaced structure of the organically compounded bentonite and improves the quality index of the bentonite itself. Also, the organically compounded bentonite is helpful to improve the indexes of green balls.

Sensitivity of bentonite swelling to pore water activity

The deformability of bentonites is strongly conditioned by their salinity conditions. Consequently, the chemomechanical coupling must be taken into account to characterise correctly the deformational behaviour of these materials. Some models have been developed that account for this coupling. These models, which usually assume a double-porosity approach to characterise the structure of compacted bentonite, idealise the geochemical system, commonly using a simplified definition of the activity of the species dissolved in the aqueous solutions present in the bentonite pores. In this paper, the significance of the formulation used to calculate the activities is analysed. As a sensitivity exercise, the extended Debye–Hückel model is applied to estimate the activity coefficients of the species in the macrostructure. The exercise is conducted by simulating vertical free-swelling tests under different salinity conditions. It is shown that when the salinity conditions are not negligible, the results are improved using this illustrative model compared with the case in which the activity of the species was assumed equal to their concentration. Although the formulation of the activity coefficients could be improved for higher-salinity conditions, this study highlights the sensitivity of the bentonite mechanical behaviour to the activity definition.

Synthesis and characterization of acid-activated bentonite from Aceh Tamiang

Bentonite is new class of microporous materials with high surface areas which have been extensively studied as interesting material in catalyst application and adsorbents. The characterization of bentonite were performed using Infrared spectrophotometer, X-ray Diffraction, and Transmission Electron Microscopy (TEM) instruments. The results showed that the characteristic of natural bentonite and acid-activated bentonite does not give significant different results. XRD pattern of natural bentonite and acid-activated bentonite indicates those bentonites have the main content such as montmorillonite, quartz and alumina. The TEM profile showed the basal spacing in layered structure of acid-activated bentonite was increasing compared to the natural bentonite. The natural bentonite showed the characteristic absorption peaks such as Si-O, Al-O, Si-O-Si which is observed at wave numbers 1149,57 cm−1, 945,12 cm−1, 640 cm−1, and 459 cm−1 but the acid-activated bentonite only showed the characteristic absorption peaks such as Si-O and Al-O which is observed at wave numbers 1018,41 cm−1and 493,78 cm−1. The absorption intensity of streching – OH peak on acid-activated bentonite higher than natural bentonite. It indicates that the bentonite after activation is more pure compared to bentonite before activated.

Adsorption equilibrium, isotherm, kinetics, and thermodynamic of modified bentonite for removing Rhodamine B

Anionic and cationic surfactant modified sodium bentonite (Na-Bt) has been prepared by the cationic surfactant cetyltrimethyl ammonium bromide (CTAB) and the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) to sodium bentonite, respectively. The properties of the modified samples are characterized by XRD, SEM, BET and FT-IR. The results of characterization shown that the cationic surfactant had changed the structure and properties of natural sodium bentonite, which proved that surfactants had been successfully implanted into sodium bentonite. But anionic surfactant had no change, this manifested SDBS didn’t insert the layers of bentonite. In addition, adsorption experiments of Rhodamine B (RhB) proved that the modified sodium bentonite adsorption performance is greatly improved. The adsorption experiments also indicated that CTAB-bentonite had the largest adsorption capacity compared with SDBS-bentonite due to the formation of a highly effective partition medium by cationic surfactant micelle. The adsorption data of RhB is analyzed with the isothermal model, thermodynamics and kinetics. Overall, this study provided high-efficiency method for the removal RhB by the surfactant modified bentonite.

Acid activation of bentonite clay for recycled automotive oil purification

The search for inexpensive and environmentally friendly alternatives for used motor oil (UMO) purification has become a topic of research. In this study, the use of bentonite clay modified by acid activation is proposed. Sulfuric acid, acetic acid (v-acid/w-clay ratio=20, 40 and 60%) and sulfuric/acetic mixtures (1:1 ratio) were used in the bentonite clay activation. The activated clays were used in the UMO treatment in a ratio of 1:4 w/v, using batch adsorption processes (contact time=12 min). To determine the structural and morphological modifications produced by the acid activation process, the clays were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The oil clarification efficiency was quantified by UV-Vis spectroscopy, acidity, alkalinity and viscosity index. It was determined that sulfuric acid and the sulfuric/acetic activations presented a similar bentonite structure transformation, which appears in the cations leaching of intermediate layer. The treated oil with the highest clarifications (with respect to UMO) were the ones treated using bentonite activated with sulfuric acid 40 v/w% and sulfuric/acetic acid (1:1 ratio) with clarifications of 70 and 68%, respectively. The oil treated with clay activated with sulfuric acid (40%) reduced its viscosity, acidity and alkalinity by 23%, 80% and 29%, respectively.

Fractal characteristics of pore structure of compacted bentonite studied by ESEM and MIP methods

In this paper, we aim to clarify microstructure of bentonite from Cerny vrch deposit in the Czech Republic. We adopt results of ESEM and MIP experiments performed at various suctions along wetting and drying paths on bentonite samples compacted from powder to two different initial dry densities. The data were used for quantification of fractal dimension characteristics of pores of different sizes. Two different methods of calculating fractal dimension were used for MIP data, and one method was used for evaluation of ESEM images. Fractal dimensions obtained from MIP data, combined with the measured pore size density functions, allowed us to identify two different pore families: micropores and macropores. Macropores can be further subdivided into fine macropores and coarse macropores based on fractal analysis. The pore systems were further distinguished by different responses to suction changes and to compaction effort. In general, we observed slight increase in fractal dimension with increasing suction and with increasing dry density.

Адсорбция тетрациклина на композите магнетит-бентонит

In this research, magnetite-bentonite composites were synthesized as a unique sorbent for the delivery of tetracycline. The introduction of magnetite particles into bentonite structure is based on X-ray phase analysis. Adsorption of tetracycline on bentonite surface and magnetite-bentonite composite was studied. It is shown that maximum adsorption of tetracycline on the surface of bentonite and composite magnetite-bentonite is 84.2 and 71.1 mg/g, respectively. The dependence of adsorption on pH and time was established. The increase in the adsorption value on the surface of the composite magnetite-bentonite with increasing pH is due to the dissociation in alkaline medium of bentonite silicate groups in the composite content. Electrostatic interaction occurs between the amino acids of tetracycline and negatively charged silicate groups in bentonite, oxygen atoms and OH groups form hydrogen bonds with SiOH groups of bentonite and Fe-O groups of magnetite. Electrostatic interactions and H-bonds were determined as the main forces providing adsorption.

The influence of acid modification on the structure of montmorillonites and surface properties of bentonites

Bentonites are often used as components of engineered barrier systems (EBS) for the radioactive waste disposal and isolation of hazardous nuclear facilities. In this paper, we consider possible transformations of the composition, structure and properties of bentonites when they are used as EBS components during the decommissioning of open pools with liquid radioactive waste (LRW). Operating conditions were modeled by the treatment with nitric acid at different durations (from 1 to 6 h), concentrations (from 1 to 8 M) and temperatures (20and 90°C). Nitric acid was chosen because it is used in the preparation procedure of LRW for isolation. To assess the intensity of transformations, bentonites with a high content of Al- and Fe-rich montmorillonites were selected. The work revealed effects of interlayer modification, leaching of octahedral cations, changes of the grain size distribution, specific surface area and weakening of surface basicity. It was also shown that temperature has a stronger effect on the structural transformation of montmorillonite than acid concentration and treatment duration. Formation of Al hydroxy-interlayered (HI) layers was observed due to the treatment with the nitric acid of lower concentration (1 M). The effect of a higher concentration at the same treatment duration and temperature leads to a more intensive leaching of Al from the octahedral sheets and protonation of the interlayer, which prevents the formation of Al hydroxy-interlayered (HI) layers. CO2 desorption after the nitric acid treatment decreases significantly, maintaining a relatively high value only when the conditions allow the interlayer to be protonated. Modification of structural and adsorption characteristics due to the acid treatment can be used to simulate modification of the engineered barriers' properties for a long-term operation in the disposal of radioactive and toxic wastes.

Cell viability and bacterial reduction activity of Ag-modified bentonite

Abstract The interest on the potential biomedical applications of clay materials are recently growing. Among the clay minerals, it was found that the smectite group clays are the most suitable for adsorption processes. This group includes bentonite in which the structure is composed of octahedral and tetrahedral layers of silica. In this study, bentonite clays from SAILE Industries, Inc. in Mangatarem, Pangasinan, Philippines were characterized and fabricated as Ag-bentonite composites to determine the potential of the mineral for biomedical applications. Bentonite clay powder was mixed with silver nitrate solution via ion-exchange process. The synthesized powders were filtered using centrifugation and washed with deionized water to remove any excess silver ions. Drying followed at 60°C and stored in a dark container prior to characterization. XRD and XRF was used to evaluate the phase composition and chemical analysis of the Ag-bentonite composite, respectively. The biological tests were also done to investigate the antibacterial and cell viability of the sample.XRD result showed that the sample is composed of the montmorrilonite, hectorite and mordenite phases. Chemical analysis revealed the presence of Ag in the bentonite structure with a content of about 14.24±0.13%. Antibacterial activity of the sample was evaluated using plate reduction method where about 99% reduction of S. Aureus was observed after 24 h. Moreover, approximately 89±4.37% live cells was detected after the 24-h incubation of the sample using lymphocyte culture. With these results, the synthesized AgB samples may find suitable future biomedical use due to its stable structure, antibacterial and biocompatibility properties

Effects of a simulated gap on anisotropic swelling pressure of compacted GMZ bentonite

Gaomiaozi (GMZ) bentonite is a promising buffer material for Chinese high-level radioactive waste (HLW) disposal, and will be either compacted in situ or used as dense prefabricated material when constructing engineered barriers. Uniaxial compaction can induce anisotropy of the bentonite structure, resulting in anisotropic swelling. In this work, a series of swelling pressure tests were performed on compacted GMZ bentonite to investigate the anisotropy of its property and highlight the dry density effect. Two kinds of technological gaps were simulated to analyze the change in anisotropy of properties with limited swelling deformation. The relationship between swelling pressure and dry density was found to be logarithmic, and axial pressure increased more rapidly than radial pressure with dry density. The ratio of radial to axial pressure decreased significantly in the dry density range 1.395 Mg/m3–1.706 Mg/m3; beyond this, it remained at about 0.76. For the swelling volume ratio of less than 16.7%, the stable swelling pressure was controlled by the final dry density. For a larger swelling volume ratio, the axial gap induced a smaller swelling pressure compared with the case of no gap at the same final dry density.

Catalytic pyrolysis of crude glycerol over shaped ZSM-5/bentonite catalysts for bio-BTX synthesis

Ex-situ catalytic pyrolysis of crude glycerol for the synthesis of bio-based benzene, toluene and xylenes (bio-BTX) was performed in a tandem micro-reactor (TMR), a batch gram scale reactor and a continuous integrated bench scale unit using ZSM-5/bentonite extrudates. A bio-BTX yield of 8.1 wt.% (14.6% carbon yield) based on crude glycerol was obtained over the fresh catalysts (Cat-F) in the bench scale unit (crude glycerol feed rate of 200 g h−1, pyrolysis temperature of 520 °C and catalytic upgrading temperature of 536 °C). Catalyst activity was shown to be a function of the time on stream (TOS) and after 4.7 h the activity dropped with about 8%. After an oxidative regeneration step to remove coke, the activity of the regenerated catalysts (Cat-R1) was recovered to 95% of the original catalyst activity. After 11 reaction-regeneration cycles, the bio-BTX yield decreased to 5.4 wt.% (9.7% carbon yield) over Cat-R11. The fresh, deactivated and regenerated ZSM-5/bentonite catalysts were characterized in detail using nitrogen physisorption, XRD, ICP-AES, EA, TEM-EDX, TGA, NH3-TPD, pyridine-IR and solid MAS NMR. Coke (10.5 wt.% over Cat-D) was mostly deposited on ZSM-5 planes, and not only decreased the number of Lewis and Brönsted acid sites, but also blocked the pores, resulting in catalyst deactivation. Coke removal was effectively performed using an oxidative treatment. However, exchange of cations (e.g., Na) of the bentonite and possibly also from the crude glycerol feed with protons of ZSM-5 was observed, leading to irreversible deactivation. Furthermore, the layered structure of bentonite collapsed due to the removal of interlamellar water and dehydroxylation.

Anisotropic Shape Memory Behaviors of Polylactic Acid/Citric Acid–Bentonite Composite with a Gradient Filler Concentration in Thickness Direction

To date, polylactic acid (PLA) composites with a uniform dispersion of fillers have been extensively studied. However, there is little research about the shape memory (SM) behavior of a PLA composite in which the nanoclays have a nonuniform dispersion. In this paper, the alkaline calcium bentonite (ACBT) was first modified by citric acid (CA) to improve the compatibility between bentonite (BT) and PLA. The structure of CA-modified bentonite (CABT) was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Then the CABT/PLA composite with gradient concentration of CABT in thickness direction was fabricated. Because of the good affinity between the grafted CA and the ester groups, the CABT imposed powerful restrictions on the PLA chains, which contributed to the anisotropic driving force for shape recovery. The relationship between the structure and the properties and the mechanism of anisotropic SM...

Mechanism of ammonium adsorption from wastewater by modified bentonite and optimization by response surface

ABSTRACTThree modified bentonites, dry alkali modification, thermal modification, and acid modification, were prepared and characterized by XRD and FTIR. Batch experiments were performed to evaluate their efficiency as adsorbent for ammonium removal. Multi-variables interaction effects were evaluated by Response Surface Methodology. The results showed that the adsorption efficiency of ammonium by dry alkali modification bentonite was the best in three modified methods; the next was that of thermal modification. The crystalline structure of bentonite was significantly changed with dry alkali modification. Na2SiO3 and Na2AlSi3O8(OH) were achieved by bentonite with powder NaOH modification. The increase in the mole ratio of exchangeable cations indicated that the adsorption efficiency of ammonium increased; while the layer spacing of bentonite expanded with the amount of the adsorbed water and hydrated water increased by thermal modification. In multi-variables interaction effects (holding time, calcination temperature, pH, dosage), the most significant factors were calcination temperature and dosage.