Calcium Bentonite Research Articles

Gel Formation at the Front of Expanding Calcium Bentonites

The removal of potentially harmful radioactive waste from the anthroposphere will require disposal in geological repositories, the designs of which often favour the inclusion of a clay backfill or engineered barrier around the waste. Bentonite is often proposed as this engineered barrier and understanding its long-term performance and behaviour is vital in establishing the safety case for its usage. There are many different compositions of bentonite that exist and much research has focussed on the properties and behaviour of both sodium (Na) and calcium (Ca) bentonites. This study focusses on the results of a swelling test on Bulgarian Ca bentonite that showed an unusual gel formation at the expanding front, unobserved in previous tests of this type using the sodium bentonite MX80. The Bulgarian Ca bentonite was able to swell to completely fill an internal void space over the duration of the test, with a thin gel layer present on one end of the sample. The properties of the gel, along with the rest of the bulk sample, have been investigated using ESEM, EXDA and XRD analyses and the formation mechanism has been attributed to the migration of nanoparticulate smectite through a more silica-rich matrix of the bentonite substrate. The migration of smectite clay out of the bulk of the sample has important implications for bentonite erosion where this engineered barrier interacts with flowing groundwater in repository host rocks.

Dietary addition of Calcium Bentonite enhances conditions of livestock hygiene and Droppings Characteristics and Health of Broilers Chicks

This experiment was conducted to study the effects of the addition of calcium bentonite (CaB) supplementation on growth performance, hygienic con-ditions of livestock buildings, dropping characteristics and health of broiler chicks. One hundred and fifty 1 day-old male Hubbard ISA broilers were allo-cated to 3 groups, reared for 50 days, designated as follows: soy-corn based diet without addition of bentonite (control), 2% CaB and 5% CaB. At 50th day, body weight was about 13% (P<0.05) higher in broilers groups feeding bentonite than in the control group. The CaB 5% diet decreased significantly (P<0.05) the moisture proportion of dropping characteristics. Thereby, the results of microbiological analysis (total germs, yeast and mould, total coliform, fecal coliform, Staphylococcus aureus, fecal streptococci) showed that the microbial load is reduced in the groups receiving bentonite compared to the control group. The HDL cholesterol was higher 0.64 g/l (P<0.05) in the groups receiving bentonite compared with the LDL cholesterol which was higher in the control group. Erythrocytes, leucocytes and thrombocytes cell count, and hematocrit percentage were significantly (P<0.05) lower in CaB2% group of broilers, but these levels increased (P<0.05) in CaB5% group. Microscopic observations made on histological sections of groups CaB2% and CaB5% show more scar tissue in the foci of lymphoid necrosis in the Fabricius bursa than the control group. The results from this experiment suggest that the addition of calcium bentonite in broiler diets has the beneficial effects by improving the hygienic conditions of livestock buildings and the health of animals.

Impact of In Situ Soil in Soil-Bentonite Cutoff Wall Backfill on Compressibility and Hydraulic Conductivity

Soil-bentonite cutoff walls, consisting of excavated in situ soil and bentonite as backfills, are used extensively as vertical barriers for groundwater pollution control. Sand mixed with high-quality natural sodium bentonite (NaB) is commonly used as a research object to investigate the hydraulic and compression properties of soil-bentonite backfills. However, pure sand could rarely be found in real conditions, and natural NaB may not be available readily in some countries such as China, India, and Turkey. This paper presents a comprehensive laboratory investigation on the compressibility and hydraulic conductivity (k) of soil-bentonite backfills created by simulated in situ soil and low-quality sodium activated calcium bentonite (SACaB). The simulated in situ soils are prepared using sand-natural clay mixtures with sand to natural clay mass ratios ranging from 0.5 to 6.0, and the bentonite content (BC) in the base mixture ranges from 0 to 15%. The result indicates that BC dominates the compression index (Cc) of the backfill, and a unique relationship between void ratio at effective vertical compression stress of 1 kPa and compression index is proposed for various types of soil-bentonite backfills. An increase in either BC or clay size fraction (CF) in simulated in situ contributes to reducing k, but the impact of CF in simulated in situ soil on k tends to be insignificant for backfill with BC higher than 6%. A new characteristic parameter based on the concept of void ratio of bentonite (eb), named apparent void ratio of clay size fraction (eC), is developed for predicting soil-bentonite backfills created by in situ soils and bentonites with various contents.

Compressive strength and durability performance of mortar containing palm oil boiler clinker aggregate, rice husk ash, and calcium bentonite

The utilization of local waste by-products as a building material has attracted great attention for an environmental sustainability and become a fundamental part of sustainable construction. In this experimental research, the local palm oil industrial waste and agricultural waste are utilized for the green mortar production. To examine the compressive strength and the durability performance of the green mortar mixtures, Palm oil boiler clinker (POBC) was used as a substitution material for natural fine aggregate. An ordinary Portland cement was partially replaced by rice husk ash (RHA) and calcium bentonite (CB) in the proportion of 10%, 20%, and 30% by weight of cement. The compressive strength, water absorption, porosity, durability against sulphuric acid and sodium sulphate attacks, and microstructures of the POBC mortar mixtures were evaluated at the curing age of 7, 28, and 56 days. The experimental results revealed that the compressive strength, water absorption, porosity, and durability characteristics of POBC mortar incorporating RHA and CB were improved by long-term curing. Particularly, the 56-day POBC mortar incorporating up to 30% of RHA and 10% of CB yielded the superior durability against sulphuric acid and sodium sulphate attacks.

Experimental design and modeling of removal of organic matter and nutrients in the OMW by calcium bentonite

The present work reports the application to reduction of the organic matter and nutrients in oil mill liquid waste (OMW), using the natural calcium bentonite from Morocco as adsorbent. The margine is characterized by a high concentration of low biodegradable and highly toxic organic matter. In order to evaluated the reduction capacity of bentonite to remove organic matter and nutrients, characterization mineralogical, chemical and also morphological of adsorbent were conducted. During the experiment and in the scenarios studied, all the total of parameters adsorbed was strongly depend on the percentage of bentonite. While, the percentage of pH of OMW was gradually decreased from 4.03 to 8. 04. The COD concentrations were decreased from 172.72 to 29.71 g/l, and also the phosphorus concentrations were decreased from 1.16 to 0.29 g/l. The electrical conductivity decrease in this work from 16.93 to 0.17 mS/cm. This present work proves that calcium bentonite is an effective adsorbent for the elimination the nutrients and organic compound.

Application of a blast furnace slag carrier catalyst in flue gas denitration and sulfur resistance.

It is an urgent need to develop a new catalyst with high efficiency and low cost. In the present study, we successfully prepared bimetallic-supported denitration catalysts using the blast furnace slag as the main material and calcium bentonite as the binder. The as-prepared catalyst was characterized via X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Besides, the mechanism of denitration was further determined with the help of the denitration and sulfur resistance of the catalyst. The results indicated that when the Mn load was 5%, and the second metal reactive component was loaded at 3%, Mn–Cu/GGBS (catalyst prepared by loading Mn and Cu on the blast furnace slag) had the best effects on low temperature denitration. Moreover, the conversion rate of NO was up to 97%, and it possessed the capability of specific sulfur resistance; when the third metal reactive component, Ce, was introduced with 1% load, the sulfur resistance of the Mn–Cu–Ce/GGBS (catalyst prepared by loading Mn, Cu, and Ce on the blast furnace slag) catalyst was further improved compared with that of the Mn–Cu/GGBS catalyst.

Evolution of Pore Characteristics for Bentonite Modified by an Ionic Soil Stabilizer during Hydration Processes

An ionic soil stabilizer (ISS) is used to reinforce clay soils because the ISS can regulate the hydration processes and microstructures of clays. To evaluate the regulation of ISS, natural bentonite was modified by ISS at different concentrations in this research. Water vapour adsorption and X-ray diffraction (XRD) were carried out to interpret the hydration mechanism of bentonite. Meanwhile, an associated analysis between hydration pore structures and hydration mechanisms was implemented through variation of pore characteristic tests at different relative humidities (RHs) to distinguish multiscale pore adsorption of water during the corresponding hydration process. In addition, the pore characteristics were studied via XRD, nitrogen adsorption, and mercury injection tests. Finally, the origins that adsorbed water and pore structures changed by adding ISS were discussed. The results showed that for calcium bentonite, the cations hydrated first in the range of [Formula: see text], accompanied by the expansion of micropores. Then, adsorption occurred on the basal surface of the crystal layer in the range of [Formula: see text], with water mainly adsorbed into the mesopores. With further hydration when [Formula: see text], diffused double layer (DDL) water ceaselessly entered the macropores. Both adsorbed water and multiscale pore size decreased when ISS was added to bentonite. The origins of the reduction were the regulation of ISS to exchangeable cations and the basal surface of the crystal layer.

Behavior of compacted Ca-bentonite subjected to HMC loading: observations and interpretation

This study presents result of HMC experimental test and discussions of chemical effort in Cabentonite. SWCC test, swelling pressure test and unconfined compression test as hydro-mechanical-chemical (HMC) test were applied to Cabentonite-sand mixture. Na-type bentonite has been studied to predict safety and confidence for artificial barrier layer consist of bentonite that many experimental research reports are represented, and can offer technology advanced comprehensive performance due to mathematical simulation models associated to physical parameters on thermal-hydration-mechanical-chemical properties. This study proposed a significant property for calcium bentonite to relate evaluating safety in radioactive waste disposal system, which emphasised much influence of suction and salinity chloride to hydration-mechanical behaviour for Calcium bentonite.

In vitro Detoxification of Aflatoxin B1 by Calcium Bentonite Clay Supplementation in Aflatoxigenic Mould Contaminated Feeds for Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758)

Aflatoxins are toxic, carcinogenic secondary metabolites mainly produced by Aspergillus flavus fungi that is often detected in food and agricultural commodities. Calcium bentonite clay has been used historically as an anti-caking agent and a feed binder and demonstrated the ability to bind aflatoxins. Feed samples were prepared for Nile tilapia to determineaflatoxin detoxification properties of calcium bentonite clay. 0.5%, 1%, 1.5% and 2% of this clay was incorporated into Aspergillus flavus contaminated feed and labeled as TF1, TF2, TF3, TF4, and TF5 respectively. The determination and quantification of aflatoxins produced by the fungus in the feed samples were carried out by HPTLC method. The RF values of all the feed samples were confirmed to be the presence of aflatoxin B1 and AFB2, G1 and G2 toxins were not found in any of the samples. Results from this study revealed that the calcium bentonite clay at 2% effectively reduced AFB1 toxin by its adsorption properties. Moreover, calcium bentonite clay improved water stability, water absorption rate with minimal disintegration and nutrients leaching of feed samples in water.

Development of bentonite-gelatin nanocomposite hybrid hydrogels for tissue engineering

Clay nanocomposite hydrogels show great potential in tissue engineering applications due to their large layer space, cationic exchange capability, antimicrobial activity and advances in cell attachment and cell proliferation. Bentonite is a natural clay composed of a multi-layered structure with calcium and sodium cations between the tetrahedral and the octahedral layers. This article presents the development of a nanocomposite hydrogel from bentonite nanoparticles and gelatin methacryloyl (GelMA) for tissue engineering applications by investigating its mechanical, morphological and biocompatibility properties. In this research, two chemical treatment methods were studied on bentonite to manipulate it's drying density and its moisture content as an aim to enhance the mechanical stiffness of bentonite. Compression test was used to compare the mechanical properties of calcium and sodium bentonite-GelMA. It is clear that sodium bentonite enhances the mechanical properties of pure GelMA two times, while calcium bentonite showed no effect. The microstructure analysis showed a difference in the pore size when the concentrations of bentonite were varied. The 3D cell encapsulation experiment showed a maintenance of high cell viability over 5 days. The content covered in this paper will be an introduction for bentonite-GelMA nanocomposite hydrogels for further research studies in tissue engineering.

Studies on Hydration Swelling and Bound Water Type of Sodium- and Polymer-Modified Calcium Bentonite

Modified calcium bentonite (Ca-bentonite) is extensively used in engineered barrier systems (EBSs) for municipal and industrial disposal sites due to its high swelling potential and low hydraulic conductivity. However, few studies have focused on the micromechanism of hydration and swelling under the effect of inorganic chemical solution. In this study, free swell index (FSI) and the type and content of modified Ca-bentonite bound water under the inorganic chemical solution were quantitatively studied by using the free swell test and nuclear magnetic resonance (NMR). According to the results, modification of sodium and polymer significantly increases the FSI of Ca-bentonite, bringing it close to that of natural sodium bentonite. In addition, the chemical stability of polymer-modified bentonite is significantly higher than that of sodium-modified bentonite but less than that of natural Na-bentonite. The FSI of modified Ca-bentonite decreases with the increase of cation valence and ionic strength. T2 distribution curves of the two types of modified bentonite are three-peak curves. With the increase of ionic strength, the content of total water and permeated hydrated water (accounting for 69%–95%) in bentonite decreases gradually, whereas the surface hydration water (accounting for 2%–31%) and free water content (accounting for 0–15%) increase. A uniform linear relationship exists between the FSI and corresponding total peak area of NMR (independent of ion valence, concentration, and bentonite type). Furthermore, a linear relationship exists between the FSI of the same type of bentonite and the T2 relaxation time. Research results can provide data and theoretical basis for quantitative analysis and mechanism of the hydration swelling of bentonite.

A New Measure for Active Clay in Green Sand

An alternative approach to measure active clay in green sand has been developed. While active clay determination using methylene blue adsorption is a comparison of the cation exchange capacity (CEC) of greensand to the CEC of a reference bentonite, the new technique allows direct CEC measurement by adsorption of highly selective Cu(II)-triethylenetetramine dye and subsequent quantification in a spectrophotometer. The difference in concentration of the dye before and after reaction to the greensand allows to calculate the number of adsorption sites in the molding sand, which are predominately attributed to present smectite clay minerals. The result obtained is the CEC of the molding sand, which can be used to calculate the active clay content or number of smectite clay minerals, respectively, by literature data or the CEC of a reference sample. The test procedure can discriminate among various levels of active clay content, regardless if sodium or calcium bentonite is available in silica sand. Results in this study with the new approach show repeatability with acceptable test-to-test variability when measuring green sand samples from 6 to 12% active clay. Increasing sample weight allows to discriminate active clay levels even below 4 weight-%. The new proposed method eliminates systematic errors of the methylene blue test and offers advantages in usability and accuracy.

The effects of lime, bentonite and nano-clay on erosion characteristics of clay soils

Erosion, both surficial and internal, presents risks to performance and stability of earth dams, dikes, and water barriers. The consequences and severity of erosion incidents are amenable to soil erodibility. This study investigates the efficiency of additives/stabilizers in modifying soil erosion characteristics. Erosion parameters, namely coefficient of soil erosion, critical shear stress, and erosion rate index, for five very fine, highly erodible clay/silt soils treated with additives, that is sodium bentonite, calcium bentonite, hydrated lime, silica fume and a Nano clay, are determined via the Hole Erosion Test (HET). Also, alterations in plasticity index and compaction properties for treated soils are examined. Experimental findings suggest that hydrated lime, which delivers an ample amount of Ca2+, reduces erodibility mainly be increasing critical shear stress, while calcium bentonite which encompasses structural Ca cations, enhances erosion resistance by decreasing the coefficient of soil erosion. Besides, sodium bentonite does not improve the erosion resistance. From a practical viewpoint soil treatment with hydrated lime and calcium bentonite lowers the likelihood of concentrated leak erosion initiation and decelerates the progression of piping.

The Interaction between Cations in Saline Water and Calcium Bentonite in Copper Flotation

In this study, the effect of cations, Na+ and Mg2+, in saline water on copper flotation in the presence of calcium bentonite was investigated. It was found that as the concentration of NaCl was increased, the copper recovery initially decreased and then increased to above 99%, while the copper grade initially increased and then decreased. In contrast, as the concentration of MgCl2 was increased, the copper recovery continuously increased, while the copper grade continuously decreased. The variation of copper recovery and grade was mainly attributed to the synergistic effect of pulp rheology and flotation solution chemistry. The underpinning mechanisms are the compressing electrical double layer and ion-exchange interaction between saline water and bentonite, which occur at the same time. Using saline water slightly affected the pulp rheology with a decrease in copper recovery at low NaCl concentration. Increasing the concentration of cations in saline water might even facilitate the flowing out of exchangeable cations, especially divalent cations, from the interlayer space of bentonite to the solution, resulting in the decrease of copper grade at high salt concentration.

Characteristic of Permeability with the Sand, Calcium Bentonite and Solidifier Mixtures according to Selective Reaction of TCE

Characteristic of Permeability with the Sand, Calcium Bentonite and Solidifier Mixtures according to Selective Reaction of TCE

Adsorption of Anionic Dye on the Acid-Functionalized Bentonite.

The efficiency of acid treatment on natural calcium bentonite (natural bentonite) for anionic dye adsorption was investigated using methyl orange (MO) as a probe. Additionally, adsorption experiments were accomplished between the natural bentonite, acidified bentonite, and a cationic dye (methylene blue, MB). Acid functionalization in natural bentonite (RF) was carried out with HCl and H2SO4 acids (RF1 and RF2, respectively). The samples were characterized by chemical analysis, mineralogy, particle size, and thermal behavior with the associated mass losses. The adsorption efficiency of MO and MB dyes was investigated by the effects of the initial concentration of adsorbate () and the contact time (). The acid treatment was efficient for increasing the adsorption capacity of the anionic dye, and the values measured were 2.2 mg/g, 67.4 mg/g e 47.8 mg/g to RF, RF1 e RF2, respectively. On the other hand, the acid functionalization of bentonite did not significantly modify the MB dye adsorption. The Sips equation was the best fit for the adsorption isotherms. Thus, we found that the acid-functionalized bentonite increases the anionic dye adsorption by up to 8000%. The increased adsorptive capacity of acidified bentonite was explained in terms of electrostatic attraction between the clay surface and the dye molecule.

Preparation of Modified Calcium Bentonite for the Prevention of Heavy Metal Ion Transport in Groundwater

Vertical engineered barriers are often used to prevent the transport of heavy metal ions in groundwater, and barrier layers are the key to pollution control. In this study, modified calcium-based bentonite (CB) was prepared via the modification of CB with sodium carboxymethyl cellulose (CMC) and sodium hexametaphosphate (SHMP) for the prevention of heavy metal ions transport. CMC-SHMP@CB composites were prepared by pulping, drying and grinding. Structural characterization was performed by using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The swelling, permeability and adsorption properties of the CMC-SHMP@CB composites were further evaluated. The results show that these CMC-SHMP@CB composites have a hybrid microstructure from the intercalation and exfoliation action during modification. The swell index in deionized water of the CMC-SHMP@CB composites is 24.4 mL/2 g, which is 4.8 times that of the original CB index. Modification of CB with CMC and SHMP significantly improves its anti-permeation performance. In the presence of Cd2+ and Ni2+ ions, the hydraulic conductivity of the CMC-SHMP@CB composites still reaches ~ 3 × 10-11 m/s, which is much lower than the value of untreated CB. The adsorption capacity values of CMC-SHMP@CB for Ni2+ and Cd2+ were 11.01 mg/g and 13.82 mg/g, which are 5.6 times and 7.2 times the values before modification. CMC-SHMP@CB composites have great potential for use as the barrier layers for the prevention of heavy metal ions transport in groundwater.

Thermodynamic Interpretation on the Rheology of Aqueous Bentonite Suspensions

Since their exceptional rheological behavior, bentonite suspensions are widely used in engineering, industrial, agricultural, and drilling applications. So, the aim of the present study is to investigate the rheological properties of three types aqueous suspensions prepared with calcium bentonite (CaB), sodium bentonite (NaB) obtained from that by Na2CO3 activation, and NaB with the excess soda. The CaB taken from Giresun/Turkey region contains calcium smectite (CaxS) as clay mineral and opal CT (SiO2.nH2O) as impurity which is paracrystalline silica. Soda content by the activation and bentonite content in the suspension were changed in the interval of 2.5-15.0% and 5-20% by mass, respectively. CaxS completely converted to sodium smectite (Na2xS) by the activation with the soda content of 2.5% and then Na2xS+Na2CO3 mixtures formed. Rheological properties of these aqueous suspensions were measured using a Fann Viscometer. These properties reached their maxima by the most thixotropic Na2xS suspensions and greatly increased with the increasing of smectite content. Rheological plots drawn of the shear rate vs. shear stress in the interval of 170-1020 s-1 showed that the suspensions flow as a Bingham Plastic. Change in rheological properties depending on the smectite type and content as well as excess soda content was explained thermodynamically based on the chemical potential gradient between interlayer and dispenser waters.

Influence of Bentonite Nanoclay on the State of the Rat Intestine Protective Barrier in the Experiment

Bentonite nanoclays are widely used in the food industry as technological aids, that is, adsorbents in the purification of vegetable oils and in the production of beverages. Permitted food additives include sodium, potassium and calcium aluminosilicates (E554–E556), bentonite (E558), and kaolin (E559). The data on the oral toxicity of nanoclays (NCs) are few and contradictory. It is known that in vitro native and organomodified NCs exhibit cytotoxicity against both normal and transformed animal and human cells. Due to high ion-exchange and adsorption capacity, NCs can interfere with the absorption of trace elements in the gastrointestinal tract, in particular zinc. Nanoclays can affect the composition and activity of intestinal microbiocenosis. In an experiment on the subacute 92-day oral toxicity of bentonite NCs for Wistar rats it was shown that NCs at a dose of 100 mg/kg bw (body weight) prevent the permeation of chicken ovalbumin macromolecules through the intestinal barrier, which were not detected in the blood of all tested rats 3 h after its intragastric administration at a dose of 2000 mg/kg bw. In the same animals, a significant increase in absolute body weight was noted. The results of microscopic examination of the mucous membrane of the small intestine showed an increase in the secretion of the intestinal mucus with the formation of a dense mucous barrier at an NC dose of 10 mg/kg bw or more. The formation of this barrier already occurred with the localization over the brush border of enterocytes with an increase in the number of goblet cells at a dose of 10 mg/kg bw. At a dose of 100 mg/kg bw, together with a sharp increase in the number of these cells, a merged layer of the dense mucus was formed, sticking together the villi in the apical part. At the lowest of the studied NC doses (1 mg/kg bw), an increase in the desquamation of enterocytes in the apical part of the villi was observed. Morphometric analysis of the villus length and crypt depth showed that the villus/crypt ratio decreased under NC consumption within 32–34% compared with the control regardless of the dose of the nanomaterial. NC consumption in the entire range of the studied doses had a negative effect on the morphofunctional state of the villi and crypts of the rat ileum, while excessive mucus secretion at an NC dose of 100 mg/kg bw can disrupt parietal digestion and affect the barrier and immunoregulatory functions of the intestine.

Effect of pH Variations on the Yield Stress of Calcium Bentonite Slurry Treated with pH-Responsive Polymer

The pH-responsive polymers, such as polyacrylamide (PAM), show distinct conformational states according to the pH of their environmental groundwater. Therefore, the interactions between clay–polymer and polymer–water molecules, which determine the yield stress of bentonite–polymer composites, can be affected by the pH of groundwater. This study aims to evaluate the effect of pH variation on the yield stress of calcium bentonite treated with PAM. The yield stresses (τy) of untreated and PAM treated clays were measured with varying volume fractions of solid (VF = 10–23%) and under varying pH conditions (pH = 7.6–9.6). In addition, the zeta potential was measured for both untreated and treated clays to figure out the change in the surface charge of the mineral surface due to PAM treatment. The results of this study demonstrate that τy for treated clay is higher than that for untreated clay at a given VF, because van der Walls attraction dominates electrostatic repulsion in the case of treated clay. Due to the change in conformational states of PAM and the consequent change in surface charge that comes with varying pH, the pH-dependent change in τy of treated clay is significantly different from that of untreated clay.