Bentonite Clay Suspensions Research Articles

Fractional modelling of salinity/temperature-dependent shear rheological behavior including stress overshoot for bentonite clay suspensions

Based on the experimental studies of thixotropic behavior of bentonite clay suspensions at different salinities and temperatures, a complex nonlinear rheological phenomenon was firstly discovered in our previous work [Yin et al., Eng. Geol, 295(2021): 106,435], which exhibits multi-stage stress responses including stress overshoot and power-law flow behaviors. Motivated from this observation, in this work, a variable-order viscoelastic element and a novel viscoplastic element are combined to simultaneously characterize the complex multi-stage stress response of suspensions, where the former is used to describe stress overshoot and the latter is applied to characterize power-law flow behavior. The model is further employed to describe salinity/temperature-dependent rheological behavior of suspensions, where the criteria for model parameters are established. The results indicate that fractional order can be regarded as an index to identify the flow behavior where the order evolution exhibits three stages corresponding to the multi-stage flow behavior of bentonite suspensions. Applications of the proposed fractional model at different salinities and temperatures further validate the predictability and efficiency.

Elastoviscoplasticity, hyperaging, and time-age-time-temperature superposition in aqueous dispersions of bentonite clay.

Clay slurries are both ubiquitous and essential in the oil exploration industry, and are most commonly employed as drilling fluids. Due to its natural abundance, bentonite clay is often the de facto choice for these materials. Understanding and predicting the mechanical response of these fluids is critical for safe and efficient drilling operations. However, rheological modeling of bentonite clay suspensions is complicated by the fact that thermally-driven microscopic arrangements of particle aggregates lead to a continual evolution of the viscoelastic properties and the yield stress of the suspension with time. Ergodic relations fundamental to linear viscoelastic theory, such as the Boltzmann superposition principle, do not hold in this scenario of 'rheological aging'. We present an approach for modeling the linear viscoelastic response of aging bentonite suspensions across a range of temperatures that is based on the transformation from laboratory time to an effective 'material time' domain in which time-translation invariance holds, and the typical relations of non-aging linear viscoelastic theory apply. In particular, we model the constitutive relationship between stress and strain-rate in the bentonite suspensions as fractional Maxwell gels with constant relaxation dynamics in the material time domain, in parallel with a non-aging Newtonian viscous contribution to the total stress. This approach is supported by experimental measurements of the stress relaxation and rapid time-resolved measurements of the linear viscoelastic properties performed using optimized exponential chirps. This data is then reduced to master curves in the material domain using time-age-time superposition to obtain best fits of the model parameters over a range of operating temperatures.

Structure formation in suspensions and biocidal properties of copolymer of 2-acrylamido-2-methylpropanesulfonic acid and allylamine

Bentonite is a type of montmorillonite caly that used in many places in the industry. It has been widely used for drilling fluid for many decades. Reducing the friction and lubricating the drilling the bentonite fluid has to be smooth and viscos. In this work, the structure-formation of bentonite clay suspensions in the presence of the 2-acrylamido-2-methylpropanesulfonic acid – allylamine (AMPS-AA) copolymer was studied. The static shear stress (SSS) of the bentonite suspension was investigated at different polymer concentration and monomer molar ratio. The antimicrobial activity of the copolymer AMPS-AA against sulfate-reducing bacteria (SRB) with different molar composition was studied. Based on the research results AMPS-AA copolymer was suggested to be a structuring and antibacterial agent for bentonite clay.

Bentonite clay suspension -coagulation process and identification of properties

The main aim of the research presented in this paper is study of volume coagulation of bentonite suspension. Investigation of physical properties included measurement of particle size distribution, chemical and phase analysis of prepared suspension, as well as preparation of sedimentation test graph and determination of dependence between concentration of the suspension and turbidity of the suspension. Relationship between coagulant dose and concentration was also determined during this analysis. This research could help in determination of critical coagulation concentration duringanalysis of coagulation process. Also it could be used duringsimulations of distribution of suspension in high - performance sedimentation settling tanks for suspension of similar origin in water treatment process.

In situ upgrading of pyrolysis biofuels by bentonite clay with simultaneous production of heterogeneous adsorbents for water treatment

The ability to in situ upgrade pyrolysis biofuels, together with the production of a value-added byproduct from the solid biomass residue, would reduce the economic and environmental costs of the integrated biorefinery. In the present work, biomass samples (mango pits and pineapple plants) were immersed in Fuller’s Earth (bentonite clay) suspensions. Pyrolysis at low temperatures (290–350°C) showed that the incorporation of Fuller’s Earth into both biomasses increases the amount of H2, CH4, C2H2, C2H4, and C2H6 evolved as compared to raw biomass. The biomasses’ behavior diverges in terms of bio-oil and biochar quality. For mango pit, pretreatment with Fuller’s Earth increased desirable compounds such as furans and hexanes, whereas for pineapple plant oxygenated and high molecular weight compounds increased with pretreatment. While surface areas of both biomasses increased with incorporation of bentonite clay, the mango pit saw a significant increase in adsorption capacity and rate of methylene blue removal from water, whereas the pineapple plant adsorption rate decreased with pretreatment; capacity increased at low pyrolysis temperature and decreased at high temperature. While incorporation of Fuller’s Earth increased the thermal energy required to heat the impregnated mixtures to pyrolysis temperature, a distributed activation energy model analysis shows that activation energy of pyrolysis was virtually the same for impregnated and raw biomass samples, suggesting that this may be either a thermally catalytic or chemically catalytic effect. Thus, incorporation of bentonite into some biomasses may represent positive benefits in terms of in situ upgrading bio-fuels and hybrid biochars produced at lower pyrolysis temperatures.

Cationic xylan–METAC copolymer as a flocculant for clay suspensions

The work presented herein focused on the flocculation of kaolin and bentonite clay suspensions using cationic copolymerized xylan under controlled conditions.

Synthesis and flocculation characteristics of a novel biodegradable flocculating agent amylopectin-g-poly(acrylamide-co-N-methylacrylamide)

Abstract Amylopectin-g-poly(acrylamide-co- N -methylacrlymide) [AP-g-poly(AM-co-NMA)] was prepared in presence of potassium persulfate (K 2 S 2 O 8 ) as the initiator by solution polymerization technique. The synthesised graft copolymer was characterized by various characterization techniques like FTIR, 1 H NMR and 13 C NMR spectroscopy, thermal analysis and SEM. Biodegradation of the graft copolymers was carried out by enzyme hydrolysis. Flocculation performance of the graft copolymer was evaluated in 1.0 wt% coal, 1.0 wt% silica, 1.0 wt% kaolin, 0.25 wt% iron ore and 1.0 wt% bentonite clay suspensions. The flocculation efficiency of the graft copolymer was also evaluated by the colour removal capacity from aqueous solution of a synthetic dye, malachite green. A comparative study of the flocculation performance AP-g-poly(AM-co-NMA) was also made with another laboratory synthesised graft copolymer namely amylopectin-g-polyacrylamide (AP-g-PAM) and some commercially available flocculants in the same suspensions and also in the malachite green solution. The results showed that the graft copolymer AP-g-poly(AM-co-NMA) showed better flocculation performance than that of AP-g-PAM as well as to some of the commercial flocculating agents.

Methane Hydrate Formation and Dissociation in the presence of Bentonite Clay Suspension

AbstractThe present work reports the effect of bentonite clay on methane hydrate formation and dissociation in synthetic seawater of salinity 3.55 % of total dissolved salts. Extensive observations of pressure‐temperature equilibrium during formation and decomposition of methane hydrate under different conditions have been made. It is observed that phase equilibrium conditions of hydrate are affected on changing the concentration of bentonite clay in synthetic seawater. Induction time for hydrate nucleation has been measured under different concentrations of clay and subcooling conditions. The presence of bentonite clay in synthetic seawater reduces the induction time of hydrate formation. Enthalpy of hydrate dissociation is calculated by Clausius‐Clapeyron equation using measured phase equilibrium data. The amount of gas consumed during hydrate formation has been calculated using real gas equation. It is found that a larger amount of gas is consumed upon addition of bentonite clay in synthetic seawater.

The molecular aggregation of pyronin Y in natural bentonite clay suspension

The molecular aggregation and spectroscopic properties of Pyronin Y (PyY) in the suspension containing natural bentonite clay were studied using molecular absorption, steady-state and time-resolved fluorescence spectroscopy techniques. Interaction between the clay particles and the cationic dye compounds in aqueous solution resulted in significant changes in spectral properties of PyY compared to its molecular behavior in deionized water at the same concentration. These changes were due to the formation of dimer and aggregate of PyY in the clay suspension as well as the presence of the dye monomer. The H-type aggregates of PyY in the clay suspension were identified by the observation of a blue-shifted absorption band of the dye compared to that of its monomer. In spite of diluted dye concentrations, the H-aggregate of PyY in the clay suspension was formed. The intensive aggregation in the clay suspension attributed to the localized high dye concentration on the negatively charged clay surfaces. Adsorption sites of PyY on the clay particles were discussed by deconvulated absorption and excitation spectra. Fluorescence spectroscopy studies revealed that the fluorescence intensity of PyY in the clay suspension is decreased by H-aggregates drastically. Moreover, the presence of H-aggregates in the clay suspension resulted in the decrease of fluorescence lifetime and quantum yield of PyY compared to those in deionized water.

Rheological and thixotropic properties of aqueous bentonite clay suspension preliminarily subjected to electrohydrodynamic treatment

The flow behavior of a thixotropic aqueous bentonite clay dispersion subjected to an electrohydrodynamic treatment is considered. The treatment results in the dispersion of particles and their aggregates, as well as in the activation of their surface. Kinetic dependences are determined for the destruction of the dispersion structure and its thixotropic restoration in a shear flow and under the effect of vibration.

Effect of cationic surfactant adsorption on the rheological and surface properties of bentonite dispersions

In this study, the adsorption, bridging, and intercalation effects of a cationic surfactant, benzyldimethyltetradecyl ammonium chloride (BDTDACl), on bentonite clay suspensions was investigated. The adsorption, rheological behaviors, and colloidal properties of the clay dispersions were determined as a function surfactant concentration. Adsorption isotherms were obtained using the batch-equilibrium technique. The rheological behavior of the clay suspensions was obtained by shear stress-shear rate measurements within 0–350 s−1 shear rates. The structure of the composite particles was analyzed by using X-ray diffraction analysis and it was found that the expansions of basal d-spacings are less than 16.80 Å, suggesting a monolayer structure.

Drag and relaxation in a bentonite clay suspension

We measure the drag force on a sphere moving slowly through a 6% by weight suspension of bentonite clay particles in water. The steady state drag force depends only weakly of the speed of the sphere, indicating that yield stress effects dominate the drag in the range of pulling speeds studied. The drag force increases as a function of time as the suspension gels. The yield stress of the suspension as a function of suspension age is determined from the zero-velocity intercept of our force-pulling speed data. Both the initial transient build-up of the force and its relaxation when the motion stops are described by two exponential time constants, each of which shows an inverse power law dependence on pulling speed. We also determine the yield stress from the force remaining after the relaxation; it is significantly smaller than that determined from the steady-state force data due to the disruption of the structure of the suspension by the motion of the sphere.

Influence of Cationic Polymers on the Rheological Behavior of Bentonite Clay Suspensions

Influence of Cationic Polymers on the Rheological Behavior of Bentonite Clay Suspensions

Static filtration of purified sodium bentonite clay suspensions. Effect of clay content

The effect of clay content on the static filtration properties of purified Na-montmorillonite suspensions was studied at two different pressures. The results of filtering parameters are as expected. When the clay percentage increases, the thickness ( e) of the obtained cake increases, leading to the decrease of water loss (WL), and consequently, to the decrease of permeability ( k). These decreases of WL and k are more important for the low applied pressure than for the high one. The differences between values of the different experimental parameters (WL and e) obtained at applied pressures of 5.7×10 5 and 1.5×10 5 Pa, as a function of clay content in the initial samples, show some singular points. At the clay content corresponding to the sol–gel transition (SGT), already determined by rheological measurements, ΔWL presents a change in concavity and Δ e shows a maximum. Localisation of this maximum seems to be a simple way to detect the SGT by performing static filtration experiments of two series' of clay suspensions at two different pressures. According to the water contents obtained at the two pressures, all the cakes were localised in region (2), defined by Norrish (1954) as the “macroscopic” swelling paste of Na-montmorillonite. At low applied pressure, the texture of the cakes is identified by transmission electron microscopy (TEM). Generally, at low magnification, all samples are globally homogeneous. However, they present some regions more dense than others. At high magnification, the number of layers per particle seems to depend on SGT. Indeed, in the cake corresponding to 1% w/w of clay in the initial suspension, isolated layers are most frequent and particles with two to four layers per particle are scarce. In the cake obtained from the gel (3% w/w of clay) the most frequent stacking is about three layers per particle, and isolated layers almost disappear. In the cake obtained from gel, at the SGT (5.5% w/w of clay) which is the less oriented sample, the most frequent stacking is statistically also around three layers per particle but with a greater number of particles, some isolated layers appear again. After the sol–gel transition, in the cake obtained from the 7% sample (which is the most oriented sample), the number of particles increases but the number of layers in each particle decreases (two layers per particle most frequently occurs), and the number of isolated layers again rises. The frequent distances between the aggregates and particles were estimated on the TEM images of the cakes obtained at 1.5×10 5 Pa. The distances between the particles of the cakes obtained under 5.7×10 5 Pa was identified by X-ray diffraction (XRD). All these distances measured by the two techniques are compared with a linear extrapolation of Norrish's (1954) experimental data. At SGT, the cakes obtained at the two pressures correspond to aggregates connected with several distance configurations. However, the cakes obtained from the 3% initial clay content always show two distances (19 and 39 Å) at high pressure. At low pressure, one distance is about 300 Å, and the other is about 65 Å. This last distance disappears in the cake obtained from the more diluted suspension (1%) and only the higher distance persists. The 3% initial clay suspension seems to correspond to a “local osmotic transition”, which occurs between aggregated particles (or small aggregates) in the semi-diluted suspensions and isolated particles and/or layers in the more diluted suspensions.

MEMBRANE SURFACE MODIFICATION AND BACKPULSING FOR WASTEWATER TREATMENT

Using a novel photoinduced grafting method, hydrophobic polypropylene (PP) membranes were rendered hydrophilic by grafting monomers of poly(ethylene glycol 200) monomethacrylate (PEG200MA), dimethyl aminoethyl methacrylate (DMAEMA), or acrylic acid (AA), to produce a neutral, positive, or negative charge, respectively, on the membrane surface. Using both unmodified and modified PP membranes, as well as a hydrophilic cellulose acetate (CA) membrane, the effects of backpulsing and surface chemistries on membrane fouling were investigated for crossflow microfiltration of bentonite clay suspensions and crude oil emulsions. Without backpulsing, the permeate volumes collected over 60 min were not strongly dependent on membrane surface chemistry and morphology for the filtration of either clay or oil. With backpulsing, however, 5-fold and 6-fold permeate enhancements were obtained by backpulsing alone and by a combination of backpulsing and surface modification, respectively, for clay filtration. The recovered water fluxes after backwashing the PP membranes fouled without backpulsing were approximately 80% of the initial water flux, showing that bentonite fouling is primarily nonadhesive. However, the recovered fluxes with backpulsing were slightly less than those without backpulsing, due to internal fouling after each backpulse. For the filtration of crude oil, 1.3-fold and 2.7-fold permeate volume enhancements were obtained by backpulsing alone and by a combination of backpulsing and surface modification, respectively. More than a 3-fold permeate volume enhancement was obtained upon adding an anionic or cationic surfactant to the oil mixture when the modified membrane was similarly charged. The recovered flux after backwashing the unmodified PP membrane fouled without backpulsing or surfactant was only about 30% of the initial water flux, indicating adhesive primarily fouled by oil, but the recovered flux doubled when the membranes were rendered hydrophilic by surface modification.

Shear and compressive yield in the filtration of a bentonite suspension

A suspension of compressive yield stress P 0 will not be filtered unless the differential filtration pressure P exceeds P 0. Measurements showing this pressure threshold are reported for a bentonite clay suspension. The cumulative filtrate volume for the suspension is found to vary as P 0.215 − P 0.215 0, from which P 0 is obtained. The shear yield stress τ 0 of the suspension is obtained from analyses of conventional shear rheological data. A friction angle α for bentonite, given by arcsin (τ 0/ P 0), is closely similar in magnitude to literature data for similar clays in plastic deformation. Interpreted as an elastic property, τ 0/ P 0 gives a Poisson ratio for the floc network which is numerically close to that of an elastic polymeric network.

The influence of dilute clay suspensions on sea scallop ( Placopecten magellanicus) feeding activity and tissue growth

Long and short-term laboratory experiments were conducted to examine biological responses of sea scallops ( Placopecten magellanicus) to relatively dilute bentonite clay suspensions. The effect of bentonite addition (0, 2 and 10 mg·dm −3 treatments) to a natural diet of phytoplankton and organic detritus (seston) on somatic and reproductive tissue growth was examined over 68 days during the period of gametogenesis. Filtration, ingestion and pseudofaeces production rates and particle retention efficiency were measured for scallops which were fed mixtures of algae (dried Tetraselmis suecica) or natural seston and bentonite (0 to 15 mg·dm −3). Pre-ingestive particle-selection capabilities were examined through chlorophyll a, organic content and carbon and nitrogen analyses of suspended particles and pseudofaeces. The results indicate a low tolerance to suspended bentonite. Extensive chronic mortalities and significant impacts on somatic and reproductive tissue growth were exhibited at 10 mg·dm −3. Despite an inability to effectively retain clay-size particles, sea scallop feeding activity was altered by dilute bentonite suspensions. Animals fed natural seston without added bentonite displayed filtration rates twice as high as when 2 mg bentonite per dm 3 was added, but tissue growth in both groups was similar. When provided with a diet of Tetraselmis, a similar reduction in filtration rate required bentonite concentrations exceeding 6 mg·dm −3; levels lower than 1.0 mg·dm −3 enhanced filtration rates. Sea scallops displayed two feeding mechanisms for actively enhancing the quality of ingested matter when exposed to elevated levels of suspended clay. Scallops were less efficient at retaining bentonite particles at concentrations exceeding 2 mg·dm −3 than at lower levels. This shift in retention efficiency did not require a period of acclimation. Above a threshold bentonite concentration of 2 mg·dm −3, scallops produced pseudofaeces and selectively ingested seston or Tetraselmis over clay particles. Selection efficiencies, determined from relative chlorophyll a, AFDW, POC and the PN-concentration of retained particles and pseudofaeces, were low compared with values published for other suspension-feeding bivalves.

Vane rheometry of bentonite gels

We describe the use of a four-bladed vane to measure the yield stress τ 0 of a series of aqueous bentonite clay suspensions. An extension of the vane technique is given, showing how the shear modulus G and the yield strain γ y can also be obtained. These techniques are validated by comparing the results with those obtained from conventional concentric cylinder rheometry at low clay concentrations where wall-slip is absent. A study of the clay concentration dependence is made for volume fractions (φ) up to 0.1. The magnitudes of τ 0, G and γ y are found to scale closely as aφ x over the volume fraction range 0.01–0.1, with x approximating to 3 for τ 0, to 4 for G and to −1 for γ y. Whereas x is largely time-independent, a increases with time for both τ 0 and G as the dispersions spontaneously gel.

Specific deposit and models of horizontal counter-current filtration

Horizontal filtration with counter-current principle has got distinct advantages over conventional rapid sand filters (RSF), in terms of longer duration of filter run and better utilization of the entire media depth and overcomes most of the shortcomings of RSF, such as mud ball formation, development of negative pressure inside the filter media at relatively shallow operating depths of water over the filter media, etc. Even direct filtration may be feasible without secondary sedimentation. The present study was carried out in the laboratory on various models of horizontal filters with counter-current flow under varying discharge conditions with constant head, using sand and gravel as filter media and bentonite clay suspension in water as turbidity. In the coarsest media, incremental head losses were found to increase with time whereas in the finest media, it was found to be reversed. In the intermediate layers, incremental head losses increased at the initial filter run but decreased later on. The increase in specific deposit resulted in incremental head loss whereas decrease in permeability caused a decrease in approach velocity and hence decrease in incremental head loss. Coarsest media layer attracts maximum deposit and leads to more head loss increase as compared to other layers. Exponential decrease in effluent discharge in three distinct stages was observed during the filter run. Such a variation is modelled. Specific deposit is maximum in coarsest media but decreases sharply along the depth of media. Such a variation is also modelled. The depth of the media is increased in order to maintain throughout quality requirements. A model is presented to relate depth of media with duration for a discharge of more than 100 litres per minute per metre square (1 min −1 m −2). It was observed that due to small magnitudes of specific deposit in the sand and gravel media, the exponential constants y and z in the Ives' model of efficiency are not important. The exponential constant x is however found to play a significant role. Methodology of evaluation of the exponential constant x in Ives' model is presented. This constant x is shown to remain around 1.7.

Increased Walleye Egg Hatch and Larval Survival after Protease Treatment of Eggs

Abstract Various techniques for eliminating the clumping of newly spawned walleye eggs (Stizostedion vitreum) were evaluated by measuring hatch, growth, and survival. Percent hatch was highest (83%) in egg groups water hardened in 0.01% protease solution. Other water-hardening techniques tested were: (1) continuous stirring; (2) 250 mg/L tannic acid solution; and (3) bentonite clay suspension. Low hatching percentages for eggs continuously stirred or treated with bentonite were attributed to fungus. Fungus was minimal on eggs treated with protease or tannic acid. Fish hatched from each egg treatment group were intensively cultured for 21 d in one of four rearing environments: (1) well water; (2) well water receiving 1% sea salt for the initial 3 d; (3) well water receiving a 6-mL daily addition of antifoam emulsion for the initial 9 d; or (4) well water receiving both the 1% sea salt and antifoam treatments. There was slightly higher survival in larval fish hatched from eggs treated with protease or tannic acid and reared in well water containing 1% sea salt. We observed no differences in average fish length among the test groups.