Minerals Bentonite Research Articles

Avoiding unrealistic behaviour in coupled reactive-transport simulations of cation exchange and mineral kinetics in clays

AbstractBentonite clay is often included as a buffer, backfill and/or sealing material in designs for deep geological repositories for radioactive wastes. It is expected that bentonite materials may undergo some mineralogical alteration as they interact with in situ groundwaters over long timescales on the order of thousands to millions of years. Long-term modelling of these materials is therefore important in order to demonstrate confidence that the engineered designs will continue to perform as required over their intended lifetimes (required assessment timescales can be up to 1 million years). The key geochemical processes that must be considered in such modelling are mineral dissolution and precipitation and cation exchange. These processes are expected to occur simultaneously and so modelling of their coupled effects and their rates (kinetics) is necessary. Illustrative reactive-transport models of the geochemical alteration of montmorillonite (the primary mineral in bentonite exhibiting cation exchange) are presented which demonstrate that one possible approach to fully coupling cation exchange and clay mineral dissolution kinetics, referred to here as the ‘all-component coupling’ approach, may lead to unrealistic behaviour due to feedback that may occur in the formulation. This feedback can be avoided if a ‘common-component’ conceptual model for the dissolution of exchanger end members is adopted, where only the saturation of the exchanger ‘structural unit’ is considered when evaluating the potential for dissolution of the mineral. Such considerations have been proposed historically in stability analyses for montmorillonite, but have not been explored widely in the modelling literature.

Sorption Ability of Bentonite Rocks from Yogyakarta to Eliminate the Radiocesium Elements in Solution

This activity was to examine the ability of bentonite minerals from Yogyakarta to absorb the radiocesium contained in the solution. The purposes of the experiment were to determine sorption ability of bentonite mineral from Yogyakarta to absorb radiocesium in solution or groundwater and to enrich the Indonesia bentonite capability database to absorb radiocesium. The bentonite material was planned to be used as a buffer material of the engineered barrier system on the radwaste disposal facility in the future. The contact time, the presence of Na and K ions in the solution, as well as the variable of dissolved CsCl concentration were considered as experiment parameters. The value of Kd was also used as the indicator of radiocesium sorption into the bentonite samples. The experiment results shown that the maximum of Kd value was about 6800 mL/g for sample-1, and the presence of dissolved Na and K ions in the solution could reduce the values of Kd which were 800 and 300 mL/g for sample-1, respectively. Determination of isotherm sorption of radiocesium by bentonite from Yogyakarta was approximated by using linear equation or Freundlich law.

An EXAFS study for characterizing the time-dependent adsorption of cesium on bentonite.

Bentonite is considered for use as a buffer material in the final disposal repositories of radioactive waste. Long-lived 135Cs with a half-life of 2.3 × 106 years is a key radionuclide in high-level waste, and lots of 137Cs with a half-life of 30.2 years exists in low-level waste. Therefore, the adsorption of Cs on bentonite is a critical issue in evaluating the long-term safety of radioactive waste disposal. In this study, EXAFS techniques were used to characterize the time-dependent process from the beginning of adsorption to equilibrium. From the results of this study, we found changes including to the Cs adsorption sites, the Cs-O distance between Cs and the oxygen atom, and that the adsorption of Cs ions occurred before the reaction reached equilibrium. The fraction of OS complexes when Cs was adsorbed on bentonite can refer to the CN (Cs-O1st)/CN (Cs-O2nd) ratio of coordination numbers, and this study found that the OS complex was the major adsorption species when Cs adsorbed onto bentonite. In addition to the ratio CN (Cs-O1st)/CN (Cs-O2nd) providing information on the adsorption site, we also discussed the change of Cs-O1st and Cs-O2nd bond distances to identify the adsorption sites at different times. Comparing the XRD patterns of montmorillonite and bentonite, we found that the interlayer collapsed after Cs was adsorbed onto montmorillonite, but it expanded after Cs was adsorbed onto bentonite. From the results of EXAFS fitting, we found that the movement of Cs ions was from regular interlayer sites to expanded interlayer sites, which caused the interatomic distance of Cs-O2nd to decrease with an increase in time. It was revealed that the adsorption of Cs on bentonite occurred in two steps. The first step includes the rapid uptake of Cs by attachment to the oxygen atoms of the H2O molecules at the regular interlayer sites, especially for the OS complexes. The second step includes a slower process where dehydrated Cs ions move from the regular interlayer sites to the expanded interlayer sites. In this study, Cs L3-edge EXAFS spectroscopy was conducted for the Cs adsorbed on bentonite to identify the Cs adsorption sites over time, as this is important in evaluating the mobility of Cs in the environment. These results are beneficial in finding the process of Cs adsorption on bentonite, which could be used for the design of the final disposal of spent nuclear fuel.

Cation exchange capacity of bentonite in a saline environment

Cation exchange capacity (CEC) is one of the basic characteristics of clays and clay minerals. Accessory minerals, such as carbonates, can influence the measured value of the CEC because of their dissolution.In the present study, the CEC of Ca-/Mg-bentonite Calcigel® was studied by the Cu-trien method in the presence of NaCl at various concentrations (0–20 wt%). These conditions simulate the states of bentonite in geotechnical barriers during their hydration with saline solutions, e.g., in underground radioactive waste deposits.First, changes in the pH value, which were induced by Cu-trien and NaCl, were investigated, and the CECs of Calcigel/NaCl mixtures were measured and analyzed. Second, the influence of NaCl on the UV/Vis spectra of Cu-trien was tested. Third, the impacts of Cu-trien (3.33 × 10−3 mol l−1) and NaCl on the solubilities of carbonate and dolomite were analyzed.The change in carbonate solubility, based on variations in the NaCl concentrations as well as the Cu-trien additions, has been identified as the main factor influencing the determination of the CEC of Ca-/Mg-bentonite Calcigel®. With this knowledge of the solubilities of carbonates under controlled conditions and with the knowledge of bentonite mineral compositions, it is possible to correct the determined values of the cation exchange capacity.

Performance Analysis of Local Pekanbaru Bentonite for Reactive Solid Application of Mud Drilling

In oil and gas drilling activities, drilling mud is one of the most important commodities. The main mineral used as a reactive solid that works to suck fresh water and form drilling mud is bentonite. Bentonite which is used as a drilling mud in the market is mostly imported from the United States. In Indonesia there are several areas that have enough potential for bentonite minerals, namely Java, Sumatra, parts of Kalimantan and Sulawesi with reserves estimated to be more than 380 million tons. (Riyanto A, 1994). This study uses bentonite in Kulim area, Tenayan Raya City, Pekanbaru, in hopes of providing useful information input, especially in the use of bentonite minerals in drilling mud. Using local bentonite the price is cheaper and more efficient.
 The object observed was the effect and number of bentonite mixed with fresh water so that the rheological properties of drilling mud such as viscosity, gel strength, mud cake and filtration loss were obtained and would be in accordance with API specification 13A standards. Whereas to find out the composition and structure of local mineral clay, SEM and EDX analyzes were performed to determine the characteristics and composition of these minerals. From these tests add additives NaCO3 and NaOH as ion exchangers and add the element Na to the sludge.
 From SEM and EDX analysis, two samples taken in central Sumatra Sumatra can be categorized as clay Illite fe-rich and Clay Illite Platty. Rheological testing of drilling mud and chemical composition analysis of clay Illite fe-rich minerals and Clay Illite Platty in Riau, Central Sumatra and with the addition of additives NaCO3 and NaOH to local Clay, Rheology in mud based on Clay Illite Platty is obtained with Bentonite. commonly used as a basic material for the manufacture of oil and gas drilling mud with API Spec13 A.

Adsorption of atrazine from aqueous solution using unmodified and modified bentonite clays

Properties of raw bentonite clay of Afuze in Edo state which are abundant and cheap bentonite mineral in Nigeria as adsorbents for the removal of atrazine in aqueous solution were investigated. The bentonite clay-types were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrophotometry and X-ray diffraction (XRD). Batch adsorption experiments were carried out to determine the equilibrium characteristics, thermodynamics and kinetics of the sorption processes. The data obtained were subjected to Langmuir, Freundlich and Temkin isotherm equations, while pseudo-first-order, pseudo-second-order rate equations, intra-particle diffusion and Elovich models were considered for kinetics and mechanism. The results showed that the adsorption processes were described by different isotherm models; they were all spontaneous (∆G ranges from − 938.34 to − 6263.58 kJ/mol) and exothermic (range of ∆H is − 252.73 to − 1057.08 kJ/mol), and with decreased randomness, ∆S (− 3.110 to − 0.581 J.mol/K). Pseudo-second-order kinetics model gave the better fit for all the sorption processes which implies physisorption process as the rate limiting step. Thus, bentonite clay-types can be used to adsorb atrazine.

Sorption of Eu(III) on Fe–montmorillonite relevant to geological disposal of HLW

Abstract Montmorillonite (Mt) is the major clay mineral of bentonite, which is the candidate buffer material in the engineered barrier system for geological disposal of high level waste (HLW). The alteration of Mt due to its interaction with carbon steel (overpack) can produce Fe–Mt. In order to understand the basic properties of Fe–Mt, the sorption studies using Eu(III) are reported here. For this, Fe(III)–Mt was prepared by conventional cation exchange method using FeCl3 with Na–Mt. The obtained Fe(III)–Mt was then reduced to Fe(II)–Mt using ascorbic acid. Both the samples were characterized based on their X-ray diffraction, Fourier transform infrared spectra, cation exchange capacity and specific surface area. The batch sorption studies of Eu(III) were conducted for both Fe(III)–Mt and Fe(II)–Mt as a function of pH (3–10), ionic strength (0.001 M–1 M) and Eu(III) concentration (10−8–10−3 M). The distribution coefficient (Kd) was found to be higher for Fe(III)–Mt compared to Fe(II)–Mt and Na–Mt. The sudden increase in sorption in the pH range 4.5–6 and remaining constant beyond it indicates ion exchange mechanism at pH<4.5, with surface complexation mechanism dominating the sorption at pH>4.5. This is further corroborated by ionic strength dependent sorption data which shows decrease in sorption capacity of Fe–Mt with increasing ionic strength at low pH, but remaining more or less unchanged at higher pH. Eu(III) adsorption isotherm on Fe–Mt increased linearly with [Eu(III)] reaching saturation at 10−5 M and 10−4 M for Fe(III)–Mt and Fe(II)–Mt, respectively. The amount of iron released from Fe–Mt and Fe(II)/Fetotal during sorption were estimated to understand the effect on Eu(III) sorption behaviour by release of interlayer iron in Fe–Mt.

Analysis of the structural changes of a pellet/powder bentonite mixture upon wetting by X-ray computed microtomography

Abstract Pellet/powder bentonite mixture is one of the candidate materials for sealing plugs in deep geological high-level radioactive waste disposal. This note presents an investigation on the structure changes of this mixture occurring during the saturation process by means of X-ray computed micro-tomography. The test was performed in an infiltration column (60 mm in inner diameter and 120 mm in height). Water was supplied to the two ends of the column and the changes of the sample morphology were observed during a period of 100 days of hydration. Digital Volume Correlation (DVC) technique was used to determine the vertical displacement field of the bentonite powder. A pressure transducer was used to measure the axial swelling pressure during the hydration. The results show that the initial distribution of powder in the inter-pellet pores was not homogeneous; the powder filled almost completely the pores in the zones close to the two ends while air-filled inter-pellet voids were observed in the middle of the column specimen. When water started to infiltrate inside the specimen from both ends, the pellets and the powder grains started to swell (because of the swelling properties of smectite, the principal mineral of bentonite) and filled the voids. That induced at the same time increase of swelling pressure and downward movement of powder grains. The results allowed a better understanding on the hydro-mechanical couplings, at the pellet scale, in the pellet/powder bentonite mixture upon wetting.

Effects of minerals on steam distillation during thermal heavy-oil recovery: An experimental investigation

ABSTRACTAn experimental study was carried out to investigate the role of various clay and non-clay minerals present in reservoir formations on steam distillation process. Dead oil samples (100 g) of two heavy oil reservoirs with 30 g of water and 10 g of crushed rock mixed with different clay minerals were kept under steam pressure with 150, 200, and 250°C in a batch autoclave reactor for a period of 40 hours, and the results were compared with respect to the changes in the density, viscosity and chemical composition of remaining heavy oil. Three different clay minerals (bentonite, kaolinite, and sepiolite) were added to the crushed rock to observe their effects. Among these clay minerals, kaolinite had the greatest effect on steam distillation. Kaolinite has an inert surface compared to other clay minerals which can be considered as an catalytic effect to make easier the evaporation of the volatile components of heavy oil during steam distillation. On the other hand, bentonite which has a swelling property in the presence of water may not allow the entrance of oil molecules because of its low permeability has retard/decrease the evaporation of volatile components. In case of kaolinite addition, density and viscosity of remaining oil are the greatest comparing with the two other minerals added. In addition, the asphaltene content of the remaining oil after distillation increased compared to original oil sample for all added clay minerals.

Purification of Aqueous Solutions from Salts and Radionuclides

The paper presents the technology of industrial waste purification based on the use of natural mineral bentonite sorbent with a large specific surface area, achieved by a cavitation crushing method, partially up to nanosize particles. The possibility for the purification of liquid radioactive waste (LRW) is shown by the example of floor drains with a significant content of salts, as well as organic mineral oils and surface-active substances. In addition to sorption of radionuclides, the used nanostructured sorbent has the ability to sorb heavy metals, salts, borates.
 The proposed technology contains several stages: ultrasonic treatment of ozonized LRW with the addition of sorbent; centrifugation or precipitation of the resulting mixture; obtaining a sorption-crystalline precipitate and condensate by evaporation. The final stage of processing — evaporation and vitrification in detail in this paper are not considered.
 The research presents the method of purification of actual LRW solutions for subsequent treatment with sorption-crystalline concentrate for vitrification. Coefficient of activity decrease equals to 103. The cost of technology is negligible, because it is based on the use of cheap bentonite. The proposed method can be used also for cleaning general industrial waste.

Antimicrobial ciclopiroxolamine/clay nanocomposites

The clay minerals are commonly used materials in pharmaceutical field both as inorganic excipients or active agents. We focused on the development of long-acting antimicrobial formula where clay minerals act as inorganic antimicrobial drug carries. Two series of organoclay nanocomposites with increasing amount of active antifungal drug ciclopiroxolamine were successfully synthesized through the intercalation reaction. In the first case clay mineral vermiculite was used as supporting matrix and secondly clay mineral bentonite was used. The structural characteristics of all prepared samples were studied by XRD and FTIR techniques. Furthermore, the content of organic carbon was determined for nanocomposite samples. Antimicrobial activity of nanocomposites was tested against bacterial strains Staphylococcus aureus and Escherichia coli, and against yeast Candida albicans and it was evaluated by finding minimum inhibitory concentration (MIC). Generally, nanocomposites based on clay mineral bentonite possess better antimicrobial activity.

REMOVAL OF LEAD FROM POLLUTED WATER BY USING CLAY MINERALS

Clay minerals or natural materials such as zeolite play an important role in reducing the potential hazards of toxic elements. They cannot completely destroy heavy metals but can only be transformed from a single phase oxidation or organic compound to another. In this study clay minerals used to reduce the hazardous of lead on aqueous solutions. The used minerals were zeolite, bentonite and montmorillonite. Each mineral was applied at the rates of 1, 3 and 5% (W/V) of waste water. The concentrations used of lead were 60, 120 and 180ppm. The results observed that wherever increased the rate of the clay minerals added to the contaminated liquid has increased the amount adsorbed of lead. Therefore, the highest amount adsorbed of lead was obtained with 5% of soil minerals in all cases. The highest amount of lead adsorbed was obtained with zeolite at the rate of 5% (177 ppm) followed by montmorillonite and bentonite (165 and 145 ppm), respectively. There is a positive relationship with both the amount adsorbed of lead and the rate of soil mineral added to the solution of contaminated. On the other hand, the highest lead removal efficiency was found as about 98.7% with the rate of 5% zeolite mineral. Whereas, the lowest lead removal efficiency was found as about 39% with the rate of 1% bentonite mineral. The arrangement of the soil minerals ability to adsorb lead was followed this order: zeolite < montmorillonite < bentonite. This study suggests that using of available natural materials could be an economic and promising alternative solution in contaminated water to minimize hazards of heavy metals. The clay minerals are suitable materials for heavy metal removal from the industrial waste water.

Influence of supercritical CO2 on bentonite properties

Wet bentonite was used to simulate a caprock for geologic CO2 sequestration. Its properties were characterized after reacting with supercritical (SC) CO2 alone and in the presence of salt solutions. High-pressure reaction tests were conducted to investigate the interaction of SC CO2, bentonite, and water. Wet bentonite mixed with 1N NaCl solution and then reacted with SC CO2 resulted in noticeable changes in volume and bentonite mineral components compared with unreacted bentonite, due to SC CO2 induced dehydration. Plagioclase, K-feldspar, montmorillonite, and pyrite were dissolved but Ca-bearing minerals, i.e., calcite, dolomite, and gypsum, and halite were precipitated. In contrast, wet bentonite mixed with the salt solution reacted with SC CO2 in the presence of the salt solution resulted in less distinct changes in volume and mineral components, likely due to the dissolution of SC CO2 in the salt solution. The fewer changes in mineral components in the bentonite reacted with SC CO2 in the presence of the salt solution were attributed to the greater quantity of water, causing CO2 dissolution. These results suggest implicitly that caprock in the immediate vicinity of an injection well may significantly deteriorate due to the interaction between caprock and dry SC CO2, and caprock far from the injection well may deteriorate less because the SC CO2 may react in the presence of large quantities of water.

Coupled THMC models for bentonite in an argillite repository for nuclear waste: Illitization and its effect on swelling stress under high temperature

Subsurface manipulations such as those expected from the disposal of heat-emanating radioactive waste in deep repositories can induce strongly coupled Thermal (T), hydrological (H), mechanical (M) and chemical (C) processes. Adequate coupled THMC models are highly desirable or even indispensable for performance assessment of such repositories, for examples for the analysis of bentonite-based engineered barrier system (EBS) surrounding the emplaced waste. In this study, we present coupled THMC model simulations of a generic nuclear waste repository in an argillite with a bentonite-based buffer. The objective is to evaluate the chemical changes in the EBS bentonite and their effect on mechanical behavior under high temperature, attempting to shed light on whether EBS bentonite can sustain temperatures higher than 100°C without significant impact on barrier's performance.Two scenarios were simulated for comparison: a case in which the temperature near the waste canister peaks at 200°C and a case in which the temperature at the same spot culminate with about 100°C. Simulations for a generic case with Kunigel-VI bentonite as backfill and Opalinus Clay as host rock were conducted for 1000years and reported in the previous study (Zheng et al., 2015). In this paper, simulations for 100,000years have been done for two types of bentonite-based buffer materials: Kunigel-VI and FEBEX bentonite. This enables us to evaluate how different types of bentonite behave in terms of the illitization and its impact on swelling stress and whether we can generalize these results to support decision making. The simulations show the occurrence of illitization in the bentonite buffer and the enhancement of illitization under high temperature. However, FEBEX bentonite undergoes less illitization mainly due to the higher ion concentration in pore water and the lower content of K-feldspar in the bentonite mineral composition. Moreover, the reduction of swelling stress by chemical changes is more pronounced for Kunigel-VI bentonite than for FEBEX bentonite. Overall, the results of our model simulations suggest that an argillite repository with a bentonite-based EBS that is similar to FEBEX bentonite could sustain temperatures much higher than 100°C as far as illitization concerns. Model results also reveal that illitization is stabilized after about 2000years in bentonite near the waste package, but continues in bentonite near the bentonite-argillite interface, which manifests the strong effect of geochemical interaction between EBS bentonite and host rock on long term illitization in bentonite.

Influence of enzymatic lime on clay mineral behavior

Atterberg Limit Tests, unconfined compressive strength tests, and California Bearing Ratio Tests were conducted on the two minerals—kaolinite and bentonite—after subjecting them to stabilization with lime, enzyme, and enzymatic lime. The purpose of the study was to evaluate the effectiveness of enzymatic lime as a stabilizer over lime and enzyme. Results establish that enzymatic lime stabilization is the better stabilizer in terms of strength development. The unconfined compressive strength and California Bearing Ratio values of enzymatic lime stabilized samples have increased up to 5 and 30 times in the case of kaolinite mineral, but to only less than 1.5 times in the case of bentonite mineral. The study thus indicates that enzymatic lime stabilization is predominantly effective for clays containing kaolinite minerals.

Composite Polymer-Clay Hydrogels Based on Bentonite Clay and Acrylates: Synthesis, Characterization and Swelling Capacity

Clay minerals, especially montmorillonite, as well as bentonite minerals with a high content of montmorillonite, have the highest ability to adsorb various organic compounds. In the East Kazakhstan region, the Manyrak deposit has huge deposits of “pink” bentonite clay (BC) with 70% of montmorillonite, extensively studied back in the 70-80-s. Now it is successfully useful in the organo-polymer composition as a mineral filler of polymer composite materials (PCM) and finds the application as domestic sorbents for the group extraction of non-ferrous ions in the purification of industrial sewage and drinking water. This article presents the results of research of creating polymer-clay composite materials based on domestic bentonite clay with improved sorption characteristics. The polymeric matrix of the composites consists of acrylates ‒ polyacrylic and polymethacrylic acids (PAA and PMAA). BC-PAA and BC-PMAA gels were obtained by radical polymerization “in situ” using the intercalation method (and wi thout it). Preliminary intercalation forms more homogeneous and interconnected composite gels. An increase in the content of the clay component and the cross-linking agent in the starting mixture results in a higher cross-linking rate and compaction of the composite gels. The behavior of the swelling of gels under the influence of temperature, pH, ionic strength indicates their polyelectrolyte character with dominant hydrogen bonds and partial hydrophobic interactions (the latter is improved in the case of BC-PMAA). The preparation of composite gels based on local BC and PAA and PMAA expands the range of composite materials and can be used as sorbents for wastewater treatment.

SINTESIS DAN PERBANDINGAN STRUKTUR, TEKSTUR BENTONIT ALAM DAN BENTONIT TERAKTIVASI ASAM

Bentonite is a material that has several layers, which consists of one layer of octahedral and two tetrahedral layers or commonly known as the bentonite mineral that is composed of layers of 2: 1. Bentonite nature in general is less than optimal when used as an adsorbent. This can be overcome by activating the natural bentonite either chemistry or physics. In this study, natural bentonite acid activated. Bentonite activated with HF acid with a variety of 1% -5%. Acid can damage the structure of octahedral layers in the space between the layers. Effect of activation with HF acid cause ion exchange of Al3+, Fe3+, Mg2+ with H+ ions from the acid HF so changes smectite crystalline structures. Activation of bentonite with lead acid cation exchange capacity decreased and significantly increases the specific surface area of 26.893 m2 / g (natural bentonite) to 43.167 m2 / g (activated).

Adsorption Properties of Bentonite with In Situ Immobilized Polyaniline Towards Anionic Forms of Cr(VI), Mo(VI), W(VI), V(V)

A new composite material bentonite-PANI was synthesized by in situ immobilization of polyaniline (PANI) on the surface of natural mineral bentonite. It was established as a result of the modification of bentonite a surface area and an interlayer distance of mineral decrease and particles of bentonite transformed of irregular shape with different porosity on irregularly shaped particles of smaller size. It has been found that the total Cr(VI) ions extraction took place under the acid conditions (pH=1 – 2) and W(VI) ions have been well adsorbed in the pH range from 1 to 8 by the composite bentonite-PANI unlike the initial mineral. Whereas adsorption of oxo anions of V(V) and Mo(VI) made up some 50%. It is proved that the in situ immobilization of bentonite by polyaniline leads to increasing the value of adsorption capacity towards the investigated ions compared with the initial mineral. It was established that the adsorption properties of the synthesized composite with respect to the studied oxo ions were worse than the adsorption properties of composite vermiculite-PANI, similar to the composite Sokyryntsyy clinoptilolite-PANI and better than composites of polyaniline with Podilskyy saponite and Karelian shungite.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.6976

Alteration of compacted GMZ bentonite by infiltration of alkaline solution

AbstractConcepts for geological disposal of high-level radioactive waste usually include bentonite buffer materials. Numerous studies have been performed with most usingWyoming bentonite. Gaomiaozi (GMZ) bentonite has been selected as a potential buffer/backfill material for the deep geological repository of high-level radioactive waste in China. In this context, the highly alkaline environment induced by cementitious materials in the repository is likely to alter montmorillonite, the main clay mineral in GMZ bentonite. This alteration may result in deterioration of the physical and/or chemical properties of the buffer material. To acquire quantitative data which would allow us to assess the dissolution of montmorillonite and changes in the diffusivity of hydroxide ions as well as their effects on the swelling pressure and permeability of the compacted GMZ bentonite, an experimental study was conducted under highly alkaline (NaOH solutions with various pH values were used), simulated groundwater conditions. The GMZ bentonite also contains cristobalite which may also have been dissolved. The microstructure of the compacted bentonite samples after the experiments was determined by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDX) was carried out to identify mineralogical changes. At pH &gt;13, the permeability of specimens increased significantly; the swelling potential decreased with increasing pH. Furthermore, the pore volume and pore size of GMZ bentonite changed when exposed to alkaline solution, resulting in an increase in porosity and permeability. The main alteration mechanisms of compacted GMZ bentonite undergoing infiltration by highly alkaline solution are likely to be dissolution and modifications in terms of the microstructure and mineralogy.

A novel bio-based deflocculant for bentonite drilling mud

The physical and chemical properties of bentonite, a widely utilized drilling fluid additive, in the aqueous phase could potentially change when encountering drilling fluids contaminants. Therefore, prior to encountering an excepted contaminant, it is mandatory that one treat the bentonite mud by an appropriate deflocculant. This study assesses for the first time the performance of Oak seed extract (OSE) as a novel bio-based deflocculant in bentonite drilling mud through some extensive experiments. After being exposed to high temperatures and contaminants, the value of rheological parameters and fluid loss of bentonite mud free from any additives changed remarkably. The OSE kept the stability of bentonite in aqueous phase by restraining the capacity of bentonite to form a flocculated structure, decreasing rheological parameters and fluid loss value. From bentonite inhibition tests, the incapacity of OSE to reduce the magnitude of plastic viscosity was fairly clear. Based on particle size measurements, OSE had a significant impact in reducing particle size of contaminated bentonite muds. According to SEM observations, no remarkable difference was seen between the morphological features of modified bentonite with and without OSE, indicating particle delamination in both cases and no inhibitive property of OSE. The findings verify that OSE can act as a superior deflocculant. The deflocculating performance of OSE was more drastic in the case of cement-contaminated mud owing to its acidic nature (pH=4.58 at 1mass%). Therefore, this study proposes the pre-treat of the bentonite mud with OSE for encountering ultra-high pH condition generated by cement. The deflocculation mechanism is believed to be a neutralization of the positive edges of montmorillonite (Mt, dominant mineral in bentonite) by tannins (dominant constituent in OSE), destroying the ability of Mt layers to link one another. In addition to high performance, environmentally friendliness and cost effectiveness are characteristics which can be considered as other fascinating aspects of OSE.