Bentonite Platelets Research Articles

Effective crack-prevention strategy with composite of two clays of different sized particles

Crack formation and its possible prevention or remedy is an important branch of material science, closely related to study of granular materials and soft matter physics. This work reports a study on cracking behaviour in composites of bentonite and Laponite® in varying proportions. Both components are clays of the montmorillonite group. Our experiments demonstrate that for the particular composition - Laponite® : bentonite ∼1:1, cracks are totally absent. If either component exceeds the other, cracks develop. This is demonstrated over a range of film thickness. Scanning Electron Microscope (SEM) images of the films at different compositions indicate that at this particular ratio, the much smaller particles of Laponite®, pack into the spaces between the bentonite platelets perfectly, to form a defect-free smooth film.

Infiltration behaviour and microstructure of filter cake from sand-modified bentonite slurry

This study uses a setup involving a scanning electron microscopy (SEM) to examine the infiltration behaviour and mechanism of the formation of filter cake from sand-modified bentonite slurry. We began by determining whether a filter cake can be formed by using water–bentonite slurry in samples of the fine, medium, and coarse sand (Series 1). Water–bentonite–sand slurries with different mass ratios of bentonite and fine sand (B:S) were subsequently tested using the medium and coarse sand (Series 2). The results show that for Series 1, a thin filter cake (<0.1 mm after drying) with extremely low permeability (∼10−8 m/s) was formed only when the fine sand was used. The filter cake consisted of layers of dense bentonite platelets arranged perpendicular to the infiltration direction. Similar results were obtained for Series 2 between the medium and coarse sand. Within the range of 1:1.5 ≤ B:S ≤ 1:0.5, the low permeable filter cake was formed on the deposited layer of fine sand and bentonite platelet. Contrary to expectations, adding more sand (B:S = 1:2) did not complete the formation of filter cake, and instead led to continuous deposition of fine sand and bentonite platelet, which may cause inadequate effective face support during slurry shield tunneling.

Preparation and action mechanism of temperature sensitive N-isopropylacrylamide/nanosilica hybrid as rheological modifier for water-based drilling fluid

A temperature-sensitive silica nanohybrid with a temperature response at 35 °C was prepared by copolymerization of temperature-sensitive monomer N-isopropylacrylamide (NIPAM) with reactive nanosilica (RNS-D).The rheological properties of the as-prepared NIPAM/nano-SiO2 nanohybrid as the rheological modifier of water-based drilling fluid were tested. Findings demonstrate that NIPAM/nano-SiO2 nanohybrid contributes to increasing the viscosity of the drilling fluid upon elevating temperature, and the drilling fluid fits to the Herschel-Bulkley model. The drilling fluid containing 1.0% (mass fraction) of NIPAM/nano-SiO2 nanohybrid exhibits significant thermally thickening performance at the critical association temperature (Tass) of NIPAM (Tass; 35 °C). In terms of the action mechanism of NIPAM/nano-SiO2 nanohybrid in drilling fluid, the amide group of NIPAM/nano-SiO2 nanohybrid can form hydrogen bond with bentonite, thereby being well adsorbed on the surface and edge of bentonite platelets or even entrapped into the interlay of the bentonite platelets. The resultant cross-linked structure can function to prevent the flocculation of bentonite platelets and increase the viscosity of the drilling fluid. After heating to Tass, the temperature-sensitive polymer molecular chains undergo hydrophilic to hydrophobic transformation and hydrophobic association to form cross-linked three-dimensional network structure and increase the viscosity of the drilling fluid. More importantly, the water-based drilling fluid with 1.0% NIPAM/nano-SiO2 nanohybrid still retains thermally thickening behavior and flat rheology even after being aged at 150 °C. Therefore, the temperature-sensitive NIPAM/nano-SiO2 nanohybrid could be a potential rheological modifier for flat rheology water-based drilling fluid.

Effect of calcium ions on bentonite network structure

In this study, the network structure of bentonite was characterized systematically in deionized water and salt water containing calcium ions. It was found that the stability of bentonite network structure firstly increased and then gradually decreased, as the concentration of calcium ions increased from 0 to 1.0 mol/L. Cryo-SEM observed that bentonite platelets formed in three-dimensional E-F mode in deionized water, which were developed into E-E association and then much denser and more compact aggregates, with increasing the concentration of calcium ions. Meanwhile, the size of the bentonite network structure increased firstly and then slightly decreased. Based on these characterizations, the evolution modes of bentonite network structure with increasing the concentration of Ca2+ was proposed, which could be selected and used as a guideline to control clay minerals in flotation.

Cationic starch modified bentonite-alginate nanocomposites for highly controlled diffusion release of pesticides

To promote the controlled release efficacy of nanocomposites based on alginate and bentonite, (3-chloro-2-hydroxypropyl)trimethyl ammonium grafted starch was prepared and used as modifying agent of the clay. The nanocomposites were characterized by FTIR, XRD, SEM and TG analysis, to reveal the structural effects on the swelling property of the matrix and the release of alachlor, the model compound. Thermodynamics study indicated that the adsorption of alachlor on the bentonite was dominated by hydrophobic interaction with the siloxane surface of the clay and enhanced by the binding of the cationic starch. The electrostatic attraction between alginate and cationic starch bound on the surface also decreased the aggregation of bentonite platelets, leading to a more compact structure of the nanocomposites. The higher adsorption capability and lower permeability of the matrix resulted in a slower release of alachlor, which was dominated by Fickian diffusion mechanism. The release of alachlor first decreased and then increased with increasing content of bentonite and cationic starch modified bentonite in the nanocomposites, reaching a minimum around weight percentage 10%, at which the time taken for 50% of active ingredient to be released were 4.4 and 7.3 times that for the release from pure alginate hydrogel.

Co-Modification of Bentonite by CTAB and Silane and its Performance in Oil-Based Drilling Mud

AbstractThe stability, dispersion, and rheological properties of clay suspensions are important in the process of drilling. Organic clays were obtained traditionally by cation exchange, which is thermally unstable due to weak electrostatic interaction between the cationic surfactant and clay minerals. The purpose of the present study was to yield a stable and well dispersed organic bentonite (OBent) as a rheological additive for oil-based drilling mud. The co-modified method was used to modify bentonite by a cationic surfactant (cetyltrimethoxyammonium bromide: CTAB) and a silane coupling agent (hexadecyltrimethoxysilane: HDTMS). Firstly, the basal spacing of bentonite was enlarged by intercalation of CTAB, and the thermal stability of bentonite was improved by covalent bonds of HDTMS onto the bentonite platelets. The as-prepared OBent was characterized by infrared analysis, X-ray diffraction analysis, thermogravimetric analysis, and scanning electron microscopy. The hydrophobicity, solubility, viscosity, and tribological performance of the OBent were also recorded. The test results showed that the hydrophobicity of the co-modified bentonite was improved significantly, and was greater than that of bentonite modified with single surfactant CTAB or HDTMS. The bentonite modified by the surfactant together with the silane coupling agent had stable rheology and a lower coefficient of friction than the single surfactant-modified bentonite because more HDTMS entered into the interlayer spaces and formed chemical bonds at the inner surface of platelets.

Rheology of magnetic colloids containing clusters of particle platelets and polymer nanofibres.

Magnetic hydrogels (ferrogels) are soft materials with a wide range of applications, especially in biomedicine because (i) they can be provided with the required biocompatibility; (ii) their heterogeneous structure allows their use as scaffolds for tissue engineering; (iii) their mechanical properties can be modified by changing different design parameters or by the action of magnetic fields. These characteristics confer them unique properties for acting as patterns that mimic the architecture of biological systems. In addition, and (iv) given their high porosity and aqueous content, ferrogels can be loaded with drugs and guided towards specific targets for local (non-systemic) pharmaceutical treatments. The ferrogels prepared in this work contain magnetic particles obtained by precipitation of magnetite nanoparticles onto the porous surface of bentonite platelets. Then, the particles were functionalized by adsorption of alginate molecules and dispersed in an aqueous solution of sodium alginate. Finally, the gelation was promoted by cross-linking the alginate molecules with Ca2+ ions. The viscoelastic properties of the ferrogels were measured in the absence/presence of external magnetic fields, showing that these ferrogels exhibited a strong enough magnetorheological effect. This behaviour is explained considering the field-induced strengthening of the heterogeneous (particle-polymer) network generated inside the ferrogel. This article is part of the theme issue 'Patterns in soft and biological matters'.

Application of Tea Polyphenols as a Biodegradable Fluid Loss Additive and Study of the Filtration Mechanism.

Drilling fluids with poor filtration property are disadvantageous for well drilling, easily causing wellbore instability and formation collapse. This work reports the novel utilization of tea polyphenols (TPs) as a fluid loss additive in the bentonite–water-based drilling fluids (BT-WDFs). The influence of TP concentration and temperature on the filtration property of the fluids was described. The results showed that an increase in the TP concentration contributed to a decrease in fluid loss. Especially BT-WDFs added with 3.0 wt % TP exhibited a low fluid loss (less than or approximately 10 mL) at room temperature and high temperatures (∼150 °C), displaying better filtration property and temperature resistance than common fluid loss agents. Through the investigations on the viscosity, the particle size of TP/BT-WDFs, and micromorphology of filter cakes, the dispersion effect of TP was considered as the dominant factor for the filtration property of TP/BT-WDFs. TP molecules, containing many functional groups, could attach to the surface of bentonite platelets, improve the hydration of bentonite particles, and promote the dispersion of bentonite particles. At room temperature, TP facilitated the dispersion of hydrated bentonite. The existing “house-of-cards” structure was weakened, decreasing the particle size and viscosity of TP/BT-WDFs. At high temperature, bentonite dehydrated and aggregated, thereby increasing the particle size of bentonite particles, decreasing the viscosity of bentonite dispersion, and resulting in a high fluid loss. The addition of TP dispersed bentonite from face-to-face (FF) attraction to edge-to-face (EF) attraction, recovered the house-of-cards structure, and increased the viscosity of TP/BT-WDFs. Under the dispersion effect of TP, an appropriate grain composition of bentonite particles was formed and the pore throats were plugged to prevent the penetration of water. Finally, a compact and thin filter cake was built and the fluid loss was greatly reduced. The TP/BT-WDFs exhibited good filtration property. TP is a prospective candidate to be a high-performance and biodegradable fluid loss additive in well-drilling applications.

Space-confined growth of layered basic zinc acetate nanosheets and their orderly fragmented ZnO nanoparticles on clay platelets.

Here, hierarchical nanostructures of clay-based hybrids were synthesized via a space-confined growth of layered basic zinc acetate (LBZA) nanosheets standing upright on both sides of bentonite clay platelets. These thermally instable LBZA nanosheets were thermally decomposed and fragmented into ZnO nanoparticles well-dispersed on bentonite platelets. The morphology and structure of LBZA/bentonite and ZnO/bentonite was characterized by SEM, TEM, XRD, TG-DSC, and FTIR. Surface density of LBZA nanosheets on bentonite platelets was simply controlled by tuning the amount of zinc acetate. LBZA/bentonite and ZnO/bentonite was used for the adsorption of Congo red (CR) and photodegradation of methyl orange (MO), respectively. Results showed that LBZA/bentonite exhibited higher adsorption capacity for Congo red (CR) than original bentonite. In addition, bentonite-supported ZnO nanoparticles efficiently promoted the photodegradation of MO under UV light irradiation.

Surface-Chemistry-Tuned Cellulose Nanocrystals in a Bentonite Suspension for Water-Based Drilling Fluids

A bentonite (BT) suspension is extensively used as a water-based drilling fluid (WDF) for well excavation; however, it suffers from insufficient rheology and poor filtration performance at low solid content. Cellulose nanocrystals (CNCs) with nanoscale dimensions, large surface area, high stiffness, and reactive functional groups are promising candidates to improve the rheology and filtration performance of BT-WDFs through surface interactions. Consequently, a fundamental understanding of the surface interaction between CNCs and BT platelets becomes critical. This work aims to reveal the crucial role of surface characteristics of CNCs on their interaction with BT platelets as well as the rheological and filtration performance of CNC/BT-WDFs. Two types of CNCs with distinctive surface characteristics [i.e., carboxylated CNCs (cCNCs) and cationic CNCs (caCNCs)] were rationally prepared and applied as modifiers in BT-WDFs. The cCNCs were shown to attach to the edge surface of BT platelets and acted as “bridg...

Enhancing the properties of water based drilling fluid using bismuth ferrite nanoparticles

Drilling fluids are characterized by rheological and filtration characteristics and control of these properties is critical to the success of drilling operation. Among the popular additives for the control of these properties, nanoparticles are emerging to be one of the best additives for drilling fluids. For water based muds, rheology and filtration loss is generally controlled by polymers and it can also be improved by addition of small amounts of nanoparticles. In this paper, we have synthesized a BiFeO3 (BFO) nanoparticle by non-aqueous wet chemical techniques and used as additive for water based mud along with bentonite and other polymeric additives. BFO nanoparticles showed good compatibility with clay resulting in improved mud properties. Interaction of nanoparticles with clay and polymers resulted in enhanced apparent viscosity (AV), plastic viscosity (PV), yield point (YP), and API fluid loss. It was found that increasing the nanoparticle concentration from zero to 0.30 w/v% resulted in 25% increase in AV, PV and YP whereas a 35% decrease in API filtrate loss was observed at 20 °C before hot rolling. Even after hot rolling at 110 °C, these properties were not degraded significantly as was the case with mud without nanoparticles. Nanoparticles combined with bentonite platelets imparted good thermal stability to the drilling fluid.

Effect of thermal aging and electrolyte on bentonite dispersions: Rheology and morphological properties

In this work, the effect of thermal aging and electrolyte on the rheological and morphological properties of bentonite dispersion was studied. Previous studies reported the effect of electrolyte concentration and thermal aging on bentonite rheological properties but detailed morphological studies of the effect of electrolyte and thermal aging of bentonite dispersion have never done before. Dynamic and steady shear rheological experiments were performed at 25 °C and data were fitted to two different models (Herschel-Bulkley and Cross models) to study the rheological behavior of thermally aged and electrolyte treated bentonite dispersions. The bentonite dispersion was thermally aged at 120 °C in the rolling oven for 24 h prior to rheological measurements. The electrolyte treated bentonite dispersion was formulated by mixing 0.1 M NaCl in bentonite dispersion with constant stirring for 24 h. It was noticed that electrolyte treated bentonite dispersions have low rheological properties (viscosity, yield stress, and gel strength) compared to the base bentonite dispersion. Thermal aging of bentonite dispersion resulted in the immense increase in rheological properties of bentonite dispersion compared to the base dispersion. XRF, XRD, and TGA were used to study the chemical composition and thermal stability of the bentonite. Scanning electron microscope (SEM) analysis and transmission electron microscope (TEM) analysis were performed to understand the effect of electrolyte and thermal aging on the morphology of bentonite dispersions. The d-spacing of bentonite platelets were calculated from XRD analysis and compared with the interlayer distance measured with TEM analysis. The morphology of electrolyte treated bentonite dispersion showed the aggregation of bentonite platelets while thermal aging resulted in flocculation of the bentonite platelets. This work will help to understand the effect of electrolyte and thermal aging on rheology and morphological properties of bentonite-based drilling fluids. The comparative study of the effect of electrolyte and thermal aging on bentonite morphological properties using SEM, XRD and TEM analysis has never studied before in the literature.

Thermal properties of Bentonite Modified with 3-aminopropyltrimethoxysilane

Chemical modifications of Bentonite (BNT) clay have been carried out by using 3-aminoprophyltrimethoxysilane (APS) in various solvent media. The degradation properties of products (BNTAPS) were characterized by thermogravimetric analysis (TGA). Samples were heated at 30 to 700°C with a heating rate 10 deg/min, and the total silane-grafted amount was determined by calculating the weight loss at 200 – 600°C. The thermogram of TGA showed that there were three main decomposition regions which are attributed to the elimination of physically adsorbed water, decomposition of silane and dehydroxylation of Bentonite. High weight loss attributed to the thermal decomposition of silane was observed between 200 to 550°C. Quantitative analysis of grafted silane results high silane loaded using a solvent with high surface energy, which indicates the type of solvent affected interaction and adsorption of APS in BNT platelets.

Intercalation of ionic liquids into bentonite: Swelling and rheological behaviors

In this study, direct intercalation of three different green ionic liquids (ILs) having different salt and cation sizes into bentonite interlayer is investigated. The ILs covered in this study are: 1-hexyl-3-methylimidazolium chloride [IL-1], 1-butyl-3-methylimidazolium octyl-sulfate [IL-2], and 1-butyl-3-methylimidazolium bromide [IL-3]. The aim of this IL modification of bentonite is to enhance both rheological and thermal stability of the modified bentonite. This objective is achieved by increasing the swelling of the bentonite interlayer, which is essential for many applications. The basal d-spacing of the ILs intercalated bentonite in comparison with dried bentonite powder as detected by XRD results showed that the cations of the three ILs are successfully intercalated into the interlayer of the bentonite platelets by a cation exchange mechanism and the swelling is likely influenced by the cation size, type and concentration of the ILs. The measurements of the equilibrium concentrations of the ILs in the solution suggested that adsorption is taking place on the external surfaces. This assumption is validated by Zeta potential measurements. The results from particle sizes and Zeta potential measurements have shown that bentonite intercalated with IL-1 and IL-2 are the most effective in decreasing the overall repulsive forces and increasing the attractive forces on the bentonite surface. Consequently, larger bentonite aggregates are produced by the chloride based IL intercalated bentonite rather than those intercalated with the bromide based IL or pure bentonite. In a similar manner, rheological measurements showed that the bentonite intercalated with IL-1 and IL-2 produced strong bentonite aggregates with higher G′, G″, τc and η* than those intercalated with IL-3 and the untreated bentonite samples. Rheological, Zeta Potential and XRD measurements have confirmed that green ionic liquids can be used in different applications to enhance bentonite swelling.

Settling of Bentonite Particles in Gelatin Solutions for Stickwater Treatment

The settling of calcium and sodium bentonite coated with adsorbed protein from gelatin solutions was investigated across pH 3 to 9. The particle settling or sedimentation was achieved at acidic environment regardless of the amount of protein adsorbed by the particles. The settling is attributed to the formation of “house of cards” structure by bentonite platelets and it is strongly influenced by solution pH. The collapse of this formation resulted in floc formation or particle suspension where no settling can be observed. Few possible settling mechanisms were proposed based on the charge balance and interactions between bentonite platelets and protein molecules in the system. The findings are intended for treatment of gelatin-rich stickwater (meat rendering waste water) using bentonite as low-cost adsorbent. Integrating adsorption and settling into one unit operation has multiple benefits; reducing BOD by removing the proteins and bentonite is directly modified with organics and can be recovered via gravity settling for composite additive application.

The effect of sea water on copper and gold flotation in the presence of bentonite

In this study, the flotation of a copper–gold ore in the presence of 10% bentonite in tap water and sea water was investigated. It was found that bentonite had a deleterious effect on copper and gold flotation in tap water, but this deleterious effect was mitigated in sea water. Rheology measurements, settling tests and Cryo-SEM analyses were conducted to understand the underpinning mechanism. It appears that the high viscosity produced by bentonite due to its swelling capacity and cross-linked network structures negatively affected flotation hydrodynamics and therefore copper and gold flotation in tap water. It is interesting that sea water reduced the swelling capacity of bentonite and modified the association modes of bentonite platelets in flotation pulp, resulting in the breakup of links between the structures with relatively large pores, which contributed to the improvement of copper and gold flotation.

Kompozycje poliuretanowe do szybkiego prototypowania zawierajace bentonity modyfikowane silseskwioksanami

Cast polyurethane resins (PUR) filled with bentonites modified with silsesquioxanes (POSS) were prepared. The effect of amount and type of modified bentonites as well as the type of resin used on mechanical and processing properties of composites containing 1,5—4,5 wt. % nanofiller was studied. The addition of modified bentonites to the polyurethane resin resulted in the increase of tensile strength by 40 % and Charpy impact resistance by 70 %, however, the decrease in Rockwell hardness by 18 % was found. The structure of the composites resembled that of typical aluminosilicate clay/polymer nanocomposites with fine platelets morphology of brittle fractures observed by scanning electron microscopy (SEM) and the disappearance of the peak corresponding to the distance between bentonite platelets in WAXS diffractogram.

A Polarized Fourier Transform Infrared Spectrometry Attenuated Total Reflection Study of Bentonite Settled onto Magnetite

Sodium bentonite in aqueous suspension was allowed to settle onto a layer of magnetite, and the orientation of the bentonite platelets was monitored using the Fourier transform infrared spectrometry-attenuated total reflection technique. This study is the first reported use of polarized IR to study the in situ settling of delaminated bentonite platelets onto a thin layer of magnetite nanoparticles. The experiment was performed at a pH value (pH 5.6) close to the point of zero charge for the edge surfaces of the bentonite platelets in order to possibly enhance the probability for the (001) surface of bentonite to adhere to the positively charged magnetite particles. The order parameter (S) of the platelets was calculated both for the dry film and the film formed during water evaporation. These results were compared with the orientation of bentonite platelets on the internal reflection element (ZnSe) without magnetite particles, a system where the three layer model is valid. During settling of the bentonite, the tilt angle of the normal to the (001) surface of the platelets decreases and reaches a minimum value for the dry film. When the film is still covered by a layer of water, the tilt angles indicate the film to be at least partly built up of so-called card-house structures, implying that the edge surfaces of the platelets are at least partly adhering to the basal (001) surfaces.

Kompozyty zywicy epoksydowej zawierajace modyfikowane bentonity

The subject of the paper is organophilization of bentonites (Table 1) with quaternary ammonium salt (QAS): alkylbenzyldimethylammonium chloride, and investigation of the product application as a filler for epoxy resins (EP). The effectiveness of such modification of a clay (degree of bentonite platelets' intercalation) was evaluated using X-ray diffraction method (Fig. 2). Liquid EP compositions with modified bentonites showed high thixotropy coefficient. Limited sedimentation of the filler during the storage was the additional advantage of them (Fig. 3, Table 2). It was found that the addition of modified bentonite (in an amount up to 5.0 wt. %) to the commercial epoxy resin caused significant improvement in tensile strength, unit elongation at break, Brinell hardness and especially unnotched impact strength (sometimes even threefold). A clear effect of homogenization temperature of the resin filled on the tested mechanical properties of the composites was also observed (Table 3-6, Fig. 4-11). The composites of EP with modified bentonites showed the features of nano-composites: improved stiffness, strength, transparency and fine-platelets morphology of fractures, characterized by scanning electron microscopy (Fig. 12-15).

Mechanism of Smectic Arrangement of Montmorillonite and Bentonite Clay Platelets Incorporated in Gels of Poly(Acrylamide) Induced by the Interaction with Cationic Surfactants

Structure transitions, induced by the interaction with the cationic surfactant cetylpyridinium chloride in nanocomposite gels of poly(acrylamide) with incorporated suspensions of the two closely related layered clays bentonite and montmorillonite, were studied. Unexpectedly, different behaviors were revealed. X-ray diffraction measurements confirm that, due to the interaction with the surfactant, initially disordered bentonite platelets arrange into highly ordered structures incorporating alternating clay platelets and surfactant bilayers. The formation of these smectic structures also in the cross-linked polymer gels, upon addition of the surfactant, is explained by the existence of preformed, poorly ordered aggregates of the clay platelets in the suspensions before the gel formation. In the case of montmorillonite, smectic ordering of the disordered platelets in the presence of the surfactant is observed only after drying the suspensions and the clay-gel composites. Rheology studies of aqueous suspensions of the two clays, in the absence of both surfactant and gel, evidence a much higher viscosity for bentonite than for montmorillonite, suggesting smaller clay-aggregate size in the latter case. Qualitatively consistent results are obtained from optical micrographs.