Acid mine drainage(AMD)leachate is a global pollutant issue that impacts groundwater environment quality.This study investigated the feasibility of a composite biopolymer-amended bentonite as a geosynthetic clay liner...Acid mine drainage(AMD)leachate is a global pollutant issue that impacts groundwater environment quality.This study investigated the feasibility of a composite biopolymer-amended bentonite as a geosynthetic clay liner core material to contain AMD leachate.The real AMD leachate with a pH of 3.1,sourced from an acidic pyrite tailings site,was employed as a specific test leachate used in this study.The composite biopolymer was composed of welan gum(WG)and xanthan gum(XG)at different dry weight-based ratios.Modified fluid loss(MFL)tests were conducted to evaluate hydraulic conductivity(k)of bentonites to optimize WG:XG ratio.Rheological properties of biopolymer solutions were measured,serving as indicative parameters of biopolymer elution.The results indicated biopolymer-amended bentonites with the WG:XG ratio of 8:2 possessed lowest k(1.5×10^(−11)m/s to 7.2×10^(−11)m/s),lower than unamended bentonite(1.2×10^(−10)m/s to 8.6×10^(−10)m/s)in the AMD leachate condition.In addition,biopolymer solutions with WG:XG ratio of 8:2 exhibited highest viscosity.Thermogravimetric analysis,ultraviolet–visible spectroscopy,and Fourier transform infrared spectroscopy were conducted on the composite biopolymer,revealing that WG and XG interacted via physical cross-linking.Additionally,scanning electron microscopy and atomic force microscopy images indicated that a physical cross-linking and dense network structure conformation was developed in the composite biopolymer hydrogel at the WG:XG ratio of 8:2.The results demonstrate that the composite biopolymer is a promising low-carbon amendment material for enhancing containment performance of bentonite used in geosynthetic clay liners to contain AMD leachate.展开更多
Polymer-modified bentonite(PMB)is much more effective at containing chemically aggressive liquids than conventional bentonite.The PMB manufacturing process typically utilizes natural,high-quality sodium bentonite(NaB)...Polymer-modified bentonite(PMB)is much more effective at containing chemically aggressive liquids than conventional bentonite.The PMB manufacturing process typically utilizes natural,high-quality sodium bentonite(NaB)owing to its excellent hydrophilicity and swelling capacity.However,calcium bentonite(CaB),which is much more abundant worldwide,is rarely used for containment applications owing to its poor hydrophilicity.This study proposed a polymerization method that transforms sodium-activated calcium bentonite(NCB)into PMB to achieve low hydraulic conductivity(k)to aggressive liquids.The mechanism for its low k was revealed through characterization techniques and analyses(e.g.X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),and Brunauer-Emmett-Teller(BET)).The results showed that the PMB had a small amount of polymer elution(indicating better interface stability)and thus exhibited excellent barrier properties under chemically aggressive conditions,with the k of<10^(-11) m/s for 0.6 mol/L NaCl solution,which is four orders of magnitude lower than that of the NCB(k=3×10^(-7) m/s).Various microscopic analyses indicated that the selected monomers were successfully polymerized,and intercalated into and grafted onto the montmorillonite layers of bentonite.The formed polymer network increased the swelling capability of PMB granules,decreased the pore size,and created narrow and tortuous flow pathways leading to a very low k to aggressive liquids.展开更多
Bentonite is a necessary binder in producing pellets.Its excessive use reduces the iron grade of pellets and increases production costs.Minimizing bentonite dosage is essential for producing high-quality iron ore pell...Bentonite is a necessary binder in producing pellets.Its excessive use reduces the iron grade of pellets and increases production costs.Minimizing bentonite dosage is essential for producing high-quality iron ore pellets.Addressing the gap in the application of organically-intercalated modified bentonite in the pelletizing field,this study introduces an innovative modification process for bentonite that employs the synergistic effect of mechanical force and dimethyl sulfoxide to enhance the intercalation of organic compounds within bentonite,thus significantly enhancing its binding performance.The colloid value and swell capacity of modified bentonite(98.5 m L/3g and 55.0 m L/g)were much higher than the original bentonite(90.5 m L/3g and 17.5 m L/g).With the decrease of bentonite dosage from1.5wt%to 1.0wt%,the drop number of green pellets from a height of 0.5 m and the compressive strengths of roasted pellets using the modified bentonite(6.0 times and 2916 N per pellet)were significantly higher than those of the original bentonite(4.0 times and 2739 N per pellet).This study provides a comprehensive analysis of the intercalation modification mechanism of bentonite,offering crucial technical insights for the development of high-performance modified bentonite as iron ore pellet binders.展开更多
The objective of this work is to determine changes of surface properties of a bentonite after acid activation, using hydrochloric acid solutions (HCl) at room temperature. XRD, FX, FTIR, MEB, and BET analyses of the s...The objective of this work is to determine changes of surface properties of a bentonite after acid activation, using hydrochloric acid solutions (HCl) at room temperature. XRD, FX, FTIR, MEB, and BET analyses of the samples have been carried out to examine the structure of bentonite before and after acid activation. It is found that the raw bentonite is composed of dioctahedral montmorillonite with predominant quantity and certain amounts of quartz, albite and illite, etc. It has an cation exchange capacity (CEC) of 74.32 meq/g which allows it to be characterized as typical sodium bentonite. The changes, at low acid concentrations, are the result from from cation exchange (exchangeable cations with H+ ions). Differences of surface area at high acid concentrations (0.25 - 0.4 M) were caused by structural changes and partial decomposition of the samples. Data of surface area measurements have showed that with increase of concentration of hydrochloric acid, the surface area increased. The maximum value (837.11 m2/g) was reached by the sample activated with 0.4 M HCl. By against, activation with higher concentration (0.6 M) caused a decrease in the surface area.展开更多
Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of th...Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of the areas of the City of Diwaniyah,in a house covered with green netting,with a shade rate of 25%,to study the effect of bentonite and humic acid on the growth and flowering of a Catharanthus roseus L.plant in sandy soil.The experiment included two factors:the first factor was bentonite clay,and the second factor was humic acid.Using a randomized complete block design(R.C.B.D)with three replications,data were analyzed using the analysis of variance(ANOVA)method,and comparison was made according to the least significant difference(L.S.D)test at a probability level of 0.05.The experiment consisted of adding bentonite clay at 0,2,6,and 8 g L-1,humic acid at 0,0.5,1,and 10 g L-1.The results showed that adding bentonite clay and humic acid to sandy soil can have a significant positive effect on the growth and flowering of the Catharanthus roseus plant grown in poor sandy soil conditions.Bentonite,clay and humic acid were added at concentrations of 8 and 10 g L-1,which led to an increase in plant height and number of leaves and leaf area.They reached 30.07,23.84 cm2,76.62,63.42 cm2 for leaf-1 and 24.73,20.22 cm2 for leaf-1,respectively.The results also showed an increase in the content of nitrogen(N),phosphorus(P),and potassium(K)in leaves by 2.27,1.92,1.99%and 1.51,1.22,1.77%.This also led to an increase in chlorophyll pigment and anthocyanin at the highest concentration and gave the highest value.Therefore,adding bentonite and humic acid together gave the highest values in vegetative and chemical characteristics,compared to treatments without addition.展开更多
The corrosion of waste canisters in the deep geological disposal facilities(GDFs)for high-level radioactive waste(HLRW)can generate gas,which escapes from the engineered barrier system through the interfaces between t...The corrosion of waste canisters in the deep geological disposal facilities(GDFs)for high-level radioactive waste(HLRW)can generate gas,which escapes from the engineered barrier system through the interfaces between the bentonite buffer blocks and the host rock and those between the bentonite blocks.In this study,a series of water infiltration and gas breakthrough experiments were conducted on granite and on granite-bentonite specimens with smooth and grooved interfaces.On this basis,this study presents new insights and a quantitative assessment of the impact of the interface between clay and host rock on gas transport.As the results show,the water permeability values from water infiltration tests on granite and granite-bentonite samples(10−19-10−20m^(2))are found to be slightly higher than that of bentonite.The gas permeability of the mock-up samples with smooth interfaces is one order of magnitude larger than that of the mock-up with grooved interfaces.The gas results of breakthrough pressures for the granite and the granite-bentonite mock-up samples are significantly lower than that of bentonite.The results highlight the potential existence of preferential gas migration channels between the rock and bentonite buffer that require further considerations in safety assessment.展开更多
The equilibrium and kinetic of hydrate in sediments can be affected by the presence of external components like bentonite with a relatively large surface area.To investigate the hydrate formation and decomposition beh...The equilibrium and kinetic of hydrate in sediments can be affected by the presence of external components like bentonite with a relatively large surface area.To investigate the hydrate formation and decomposition behaviors in bentonite clay,the experiments of methane hydrate formation and decomposition using the multi-step decomposition method in bentonite with different water contents of 20%,40%and 60%(mass)were carried out.The contents of bound,capillary and gravity water in bentonite clay and their roles during hydrate formation and decomposition were analyzed.In bentonite with water content of 20%(mass),the hydrate formation rate keeps fast during the whole formation process,and the final gas consumption under different initial formation pressures is similar.In bentonite with the water contents of 40%and 60%(mass),the hydrate formation rate declines significantly at the later stage of the hydrate formation.The final gas consumption of bentonite with the water contents of 40%and 60%(mass)is significantly higher than that with the water content of 20%(mass).During the decomposition process,the stable pressure increases with the decrease of the water content.Hydrate mainly forms in free water in bentonite clay.In bentonite clay with the water contents of 20%and 40%(mass),the hydrate forms in capillary water.In bentonite clay with the water content of 60%(mass),the hydrate forms both in capillary water and gravity water.The bound water of dry bentonite clay is about 3.93%(mass)and the content of capillary water ranges from 42.37%to 48.21%(mass)of the dry bentonite clay.展开更多
The capacities of natural and modified Brazilian bentonite samples as adsorbents to remove hexavalent metal chromium were investigated under several conditions in batch and column methods. The raw material, Ca-bentoni...The capacities of natural and modified Brazilian bentonite samples as adsorbents to remove hexavalent metal chromium were investigated under several conditions in batch and column methods. The raw material, Ca-bentonite, was modified by anchorament of 3-aminopropyltrietoxisilane （APS） and 3,2- aminoethylaminopropyltrimetoxisilane （AEAPS） in the surface of bentonite sample： This type of new occurrence of bentonite is suitable as a raw material for adsorption process. Adsorption behavior of three bentonite types was strongly depending on pH of adsorbate solution, contact time adsorbent/adsorbate, and initial concentration of Cr（VI）. The results were confirmed by column method and reveals that the adsorption process of materials accorded by the Redlich-Peterson, Sips, Dubinin-Radushkevich, and tang- muir isotherm models. The exothermic entbalpic values reflected a favorable energetic process for chro- mium ions anchored in the material surfaces. The negative Gibbs free energy results supported the spontaneity of three adsorption reactions with Cr（VI） ions.展开更多
In the French deep geological disposal for radioactive wastes,compacted bentonite/claystone mixtures have been considered as possible sealing materials.After emplacement in place,such mixtures are hydrated by the site...In the French deep geological disposal for radioactive wastes,compacted bentonite/claystone mixtures have been considered as possible sealing materials.After emplacement in place,such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete.In this study,the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites(MX80 Na-bentonite and Sardinia Cabentonite)were investigated by carrying out a series of swelling pressure,hydraulic conductivity and mercury intrusion porosimetry(MIP)tests.It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution,the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges.For the Sardinia bentonite/claystone mixture,the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions,suggesting insignificant cation exchanges.Additionally,the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures.The large-pore volume increased consequently and enhanced water flow.In the cement solution,the hydroxide could also dissolve the montmorillonite,reducing the swelling pressure,and increase the large-pore volume,facilitating the water flow.Furthermore,the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.展开更多
As a potential engineered barrier material for disposal of radioactive waste in clay formations,claystone aggregate excavated from the Opalinus clay(OPA),its mixture with bentonite MX80 in a mass ratio of 7/3,and pure...As a potential engineered barrier material for disposal of radioactive waste in clay formations,claystone aggregate excavated from the Opalinus clay(OPA),its mixture with bentonite MX80 in a mass ratio of 7/3,and pure bentonite were extensively investigated with respect to the hydro-mechanical properties and performances.With these materials,a series of parallel experiments was performed under sequentially applied conditions of hydration with synthetic porewater of the clay formation,consolidation and water flow under increased stresses,and gas injection into the water-saturated and compacted materials under loading.Significant responses of the clay mixtures were observed.Main findings include:(1)the hydration and induced swelling of the mixtures are mainly dominated by bentonite content and dry density;(2)the consolidation decreases the porosity and water permeability exponentially by 2-3 orders of magnitude to low values of 10^(-18)-10^(-20) m^(2) at stresses of 2-5 MPa,depending upon bentonite content;and(3)the gas penetration in the water-saturated and compacted bentonite is characterised by a cyclic pressure rising/dropping process limited in between the upper breakthrough and lower shut-off boundaries,whereas the compacted claystone and claystone/bentonite mixture allow for gas release at low and moderate pressures.The results are helpful for design of the engineered barriers for safe isolation of radioactive waste in repositories.展开更多
Globally bentoite clay has been proposed as an engineered barrier material for safe underground disposal of high-level nuclear waste.Clay has many favorable properties such as high liquid limit,and plastic limit along...Globally bentoite clay has been proposed as an engineered barrier material for safe underground disposal of high-level nuclear waste.Clay has many favorable properties such as high liquid limit,and plastic limit along with other properties which make it the most suitable for this application.In the present study,an attempt has been made to study the behavior of Barmer bentonite under the influence of high temperatures up to 120℃.Properties of barmer bentonite namely,liquid limit,plastic limit,and maximum dry density have been determined after thermal treatment at 25℃,60℃,80℃,100℃ and 120℃.The extensive experimental results indicate that liquid limit and plastic limit show a decreasing trend while maximum dry density increases with an increase in temperature.Liquid limit and plastic limit decrease up to 12%and 11%respectively when the temperature reaches up to 120℃.Maximum dry density increases by 10%due to thermal treatment and optimum water content decreases by up to 4%.Statistical analysis has been carried out to obtain the correlation between temperature and physical properties of Barmer bentonite such as liquid limit,plastic limit,maximum dry density,and optimum water content.The XRD analysis of Barmer bentonite at room temperature and 120℃ shows very small variation in mineralogical composition.Whereas,interlayer distance has been measured and found to be decreasing with an increase in temperature.Further,a comparative analysis shows that the measured properties of studied Barmer bentonite lie in the range of previously measured values of other types of bentonite across the globe.展开更多
In the deep geological disposal repository of high-level radioactive waste,buffer/backfill materials typically consist of compacted bentonite block and granular bentonite.As these materials undergo a long-term hydrati...In the deep geological disposal repository of high-level radioactive waste,buffer/backfill materials typically consist of compacted bentonite block and granular bentonite.As these materials undergo a long-term hydration,it is anticipated that the two forms of bentonite materials(i.e.compacted bentonite powder(CBP)and granular bentonite(GB))are expected to exhibit differing hydro-mechanical behaviors due to the differences in their structures.This work aims to investigate the differences in swelling pressure and compressibility through a series of swelling pressure tests,compression tests and mercury intrusion porosimetry(MIP)tests.The experimental results demonstrated that swelling pressure curves of the CBP specimens showed higher first peak values and more pronounced collapse than those of the GB specimens at a given dry density,regardless of vapor-water hydration or liquid-water hydration.The final swelling pressures of the two materials were similar at the same dry density,suggesting an independent correlation between swelling pressure and dry density.At the high suction range,the compression curves exhibited an obvious bi-linear pattern for the CBP specimens and a significant nonlinearity for the GB specimens.Meanwhile,the CBP specimens presented higher pre-consolidation pressures and larger compression indices than the GB specimens at a given suction.As suction decreased,the compression curves of the two materials gradually approached each other and their differences were reduced accordingly.After reaching saturation,a good consistency between them was observed whether for final swelling pressure or compressibility.Pore structure analysis revealed that the two materials both presented an initially double structure,and their differences were primarily manifested at the macrostructural level.Eventually,the differences in swelling pressure or compression curves of the two materials were well interpreted by combining microstructural evolutions.展开更多
Understanding the mechanisms of gas transport and the resulting preferential pathways formation through bentonite-based barriers is essential for their performance evaluation.In this experimental study,gas migration w...Understanding the mechanisms of gas transport and the resulting preferential pathways formation through bentonite-based barriers is essential for their performance evaluation.In this experimental study,gas migration within a heterogenous mixture of MX80 bentonite pellets and powder with a ratio of 80/20 in dry mass was investigated.A novel X-ray transparent constant volume cell has been developed to assess the effect of gas pressure,material heterogeneities,and water vapor gas saturation on breakthrough pressure and gas pathways.The new cell allows to perform high-resolution X-ray computed micro-tomography(X-ray μCT)scans to track microstructural changes during different phases of saturation and gas injection.Experimental results showed that the gas breakthrough occurred when the pressure was raised to 3 MPa.This is slightly higher than the expected swelling pressure(2.9 MPa)of the bentonite sample.Each gas injection was followed by a long resaturation phase restoring material homogeneity at μCT resolution scale(16 mm).However,the elapsed time needed for gas to breakthrough at 3 MPa diminished at each subsequent injection test.X-ray μCT results also revealed the opening of the specimen/cell wall interface during gas passage.This opening expanded as the injection pressure increased.The gas flow along the interface was associated with the development of dilatant pathways inside the sample,although they did not reach the outlet surface.It was observed that the water vapor gas saturation had no effect on the breakthrough pressure.These findings enhance the understanding of the complex mechanisms underlying microstructural evolution and gas pathway development within the highly heterogeneous mixture.The experimental outcomes highlight the effectiveness of X-ray μCT to improve quality protocols for engineering design and safety assessments of engineered barriers.展开更多
Clay minerals are one of the potential good adsorbent alternatives to activated carbon because of their large surface area and high cation exchange capacity. In this work the adsorptive properties of natural bentonite...Clay minerals are one of the potential good adsorbent alternatives to activated carbon because of their large surface area and high cation exchange capacity. In this work the adsorptive properties of natural bentonite and kaolin clay minerals in the removal of zinc (Zn2+) from aqueous solution have been studied by laboratory batch adsorption kinetic and equi- librium experiments. The result shows that the amount of adsorption of zinc metal ion increases with initial metal ion concentration, contact time, but decreases with the amount of adsorbent and temperature of the system for both the ad- sorbents. Kinetic experiments clearly indicate that adsorption of zinc metal ion (Zn2+) on bentonite and kaolin is a two-step process: a very rapid adsorption of zinc metal ion to the external surface is followed by possible slow decreas- ing intraparticle diffusion in the interior of the adsorbent. This has also been confirmed by an intraparticle diffusion model. The equilibrium adsorption results are fitted better with the Langmuir isotherm compared to the Freundlich model. The value of separation factor, RL from Langmuir equation give an indication of favourable adsorption. Finally from thermodynamic studies, it has been found that the adsorption process is exothermic due to negative ?H0 accompa- nied by decrease in entropy change and Gibbs free energy change (?G0). Overall bentonite is a better adsorbent than kaolin in the the removal of Zn2+ from its aqueous solution.展开更多
Flexible wearable electronic devices based on hydrogels have immense potential in a wide range of applications.However,many existing strain sensors suffer from significant limitations including poor mechanical propert...Flexible wearable electronic devices based on hydrogels have immense potential in a wide range of applications.However,many existing strain sensors suffer from significant limitations including poor mechanical properties,low adhesion,and insufficient conductivity.To address these challenges,this study successfully developed an organic-inorganic double-network conductive hydrogel using acrylic-modified bentonite (AABT) as a key component.The incorporation of AABT significantly enhanced the mechanical properties of the ATHG@LiCl hydrogel,achieving an impressive stretchability of 4000% and tensile strength of 250 kPa.Moreover,it improved the electrical conductivity of the hydrogel to a maximum of 1.53 mS/cm.The catechol structure of tannic acid (TA) further augmented the adhesive properties of the ATHG@LiCl hydrogel toward various substrates such as copper,iron,glass,plastic,wood,and pigskin.The addition of lithium chloride (LiCl) and dimethyl sulfoxide(DMSO) endowed the hydrogel with exceptional freezing resistance and flexibility,even at low temperatures of-20℃.Remarkably,the hydrogel maintained a conductivity of 0.53 mS/cm under these conditions,surpassing the performance of many other reported hydrogels.Furthermore,the ATHG@LiCl hydrogel demonstrated outstanding characteristics,such as high sensitivity (gauge factor GF=4.50),excellent transparency (90%),and reliable strain-sensing capabilities,indicating that the ATHG@LiCl hydrogel is a highly promising candidate for flexible wearable soft materials,offering significant advancements in both functionality and performance.展开更多
Predicting the gas diffusion coefficient of water-saturated Na-bentonite is crucial for the overall performance of the geological repository for isolating high-level radioactive waste(HLW).In this study,a conceptual m...Predicting the gas diffusion coefficient of water-saturated Na-bentonite is crucial for the overall performance of the geological repository for isolating high-level radioactive waste(HLW).In this study,a conceptual model that incorporates a multi-porosity system was proposed,dividing the pore space into free water pores,interlayer water pores,and diffuse double layer(DDL)water pores,to describe the molecular diffusion behaviour of the dissolved gas in saturated bentonite.In this model,gas diffusion in these three porosities is considered as independent and parallel processes.The apparent gas diffusion coefficient is quantified by applying weighted approximations that consider the specific porosity,tortuosity factor,and constrictivity factor within each porosity domain.For verification,experimental data from gas diffusion tests on saturated MX-80 and Kunipia-F bentonite specimens across a wide range of dry densities were utilized.The proposed model could successfully capture the overall trend of the apparent gas diffusion coefficient for bentonite materials across the partial dry density of montmorillonite ranging from 900 kg/m^(3)to 1820 kg/m^(3),by employing only one fitting parameter of the scaling factor.When the partial dry density of montmorillonite decreased to 800 kg/m^(3),the proposed model shows an underestimation of the apparent gas diffusion coefficient due to possible changes of the tortuosity factor.Model predictions indicate that gas diffusion in saturated bentonite is primarily controlled by the free pore domain,with minimal contributions from DDL pores.Despite being the dominant pore type,interlayer pores contribute limitedly to total Da/Dw values due to significant constrictivity effects.展开更多
Understanding the effects of temperature on the hydro-mechanical behavior of compacted bentonite is important for performance assessments of bentonitebased buffer,backfill,and sealing systems in deep geological dispos...Understanding the effects of temperature on the hydro-mechanical behavior of compacted bentonite is important for performance assessments of bentonitebased buffer,backfill,and sealing systems in deep geological disposal of high-level radioactive wastes.Motivated by such applications,most past experimental studies were focused on highly compacted and high-quality bentonite.Such degrees of dry densities may not be economically or technically feasible for other emerging applications,including as an alternative material to cement in plugging and abandonment of wells.A bespoke high-pressure high-temperature constant rate of strain(CRS)apparatus was developed for the work reported here to conduct a series of tests for evaluating the hydro-mechanical response of compacted bentonite to elevated temperatures.Experiments were performed with bentonite specimens with high impurity contents at a range of dry densities(1.1,1.4,and 1.7 Mg/m^(3))and temperatures between 20 and 80℃.The results show that temperature increase leads to the decrease of swelling pressure for all studied densities.Larger reductions of swelling pressure were observed with increasing dry densities,suggesting the possibility of a larger exchange of pore water in the microstructure system of the clay.The transfer of water from micropores to macropores at elevated temperatures is shown to be a key controlling process at high-density compacted bentonite by which temperature affects the swelling pressure and hydraulic conductivity.展开更多
Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic s...Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic shower experiments to comprehensively investigate the influence of bentonite colloids on Sr^(2+)migration in granite,considering adsorption capacity.Bentonite colloids have a considerably greater adsorption capacity than both bentonite and granite,with a maximum adsorption of 30.303 mg/g.The adsorption behavior of bentonite colloids on Sr^(2+)is well described by the Langmuir isotherm and pseudo-second-order kinetic models,indicating that a single-layer chemical adsorption process is controlled by the site activation energy.The adsorbed Sr^(2+)is unevenly distributed on the colloids,and the adsorption mechanism may involve ion exchange with Ca.Bentonite colloids exhibit superior adsorption in neutral environments.The cations in groundwater inhibit Sr^(2+)adsorption,and the inhibition efficacy decreases in the order Fe^(3+)>Ca^(2+)>Mg^(2+)>K^(+).The presence of bentonite colloids in a granite column slightly influences the retention of Sr^(2+)in the column while markedly reducing the Sr^(2+)penetration time from 70 h to 18 h.However,the coexistence of Co^(2+),Ni^(2+),and Cs^(+)in a multinuclide system weakens the ability of the colloids to promote Sr^(2+)migration.In comigration of colloid and multinuclide systems,the adsorption of nuclides by bentonite colloids causes the nuclide migration speed to decrease in the order Sr^(2+)>Cs^(+)>Ni^(2+)>Co^(2+).This study provides insights into Sr^(2+)migration in cave repositories for low-and medium-level radioactive waste.展开更多
Bioceramic material of the quaternary system;SiO2- CaO-Na2O-P2O5 that has composition similar to Bio- glass? 45S5 was prepared by the sol-gel method from locally obtained bentonite clay (BTC). The monolith obtained wa...Bioceramic material of the quaternary system;SiO2- CaO-Na2O-P2O5 that has composition similar to Bio- glass? 45S5 was prepared by the sol-gel method from locally obtained bentonite clay (BTC). The monolith obtained was sintered at 1000?C for 2 h to facilitate densification and phase transformation. X-ray diffraction (XRD) analysis revealed the presence of sodium calcium silicate, Na2Ca2Si3O9 as major crystal phase, and another secondary orthorhombic phase, NaCaPO4. Fourier transform infrared (FTIR) spectroscopic investigation confirmed the presence of Si-O-Si bonds and a crystalline phosphate in the glass network. Scanning electron microscopy (SEM) revealed a network of micropores and interconnected macropores. Overall, the material displays features amenable for possible utilization in tissue engineering scaffolds.展开更多
Wet flue gas desulfurization(WFGD)could effectively reduce sulfur dioxide emission.However,magnesium sulfite(MgSO_(3)),a by-product of desulfurization,was easy to result in secondary pollution.In this study,the solid ...Wet flue gas desulfurization(WFGD)could effectively reduce sulfur dioxide emission.However,magnesium sulfite(MgSO_(3)),a by-product of desulfurization,was easy to result in secondary pollution.In this study,the solid catalyst Co-Bent(bentonite supported cobalt)was prepared by blending method for MgSO_(3) oxidation with bentonite as the carrier and cobalt as the active component.At the calcination temperature of 550℃ and the Co loading level of 3 wt.%,the catalyst showed excellent catalytic performance for the oxidation of high concentration MgSO_(3) slurry,and the oxidation rate of MgSO_(3) was 0.13 mol/(L·h).The research indicated that the active component was uniformly distributed within porous structure of the catalyst as Co_(3)O_(4),which facilitated the oxidation of SO_(3)^(2-) catalyzed by Co_(3)O_(4).Kinetic researches indicated the oxidation rate of MgSO_(3) was influenced by the catalyst dosage,the reaction temperature,the solution pH,the airflow rate,and the SO_(3)^(2-) concentration.Additionally,after recycling experiments,the regenerated catalyst retained its high catalytic performance for the MgSO_(3) oxidation.The reaction mechanism for the catalytic oxidation of MgSO_(3) by Co-Bent catalyst was also proposed.The generation of active free radicals(OH·,SO_(4)^(-)·,SO_(3)^(-)·,SO_(5)^(-)·)accelerated the MgSO_(3) oxidation.These results provide theoretical support for the treatment of MgSO_(3) and the development of durable catalyst.展开更多
基金funding support from the National Natural Science Foundation of China(Grant No.42477178)the National Key Research and Development Program of China(Grant No.2023YFC3709600)the Primary Research and Development Plan of Anhui Province(Grant No.2023t07020018).
文摘Acid mine drainage(AMD)leachate is a global pollutant issue that impacts groundwater environment quality.This study investigated the feasibility of a composite biopolymer-amended bentonite as a geosynthetic clay liner core material to contain AMD leachate.The real AMD leachate with a pH of 3.1,sourced from an acidic pyrite tailings site,was employed as a specific test leachate used in this study.The composite biopolymer was composed of welan gum(WG)and xanthan gum(XG)at different dry weight-based ratios.Modified fluid loss(MFL)tests were conducted to evaluate hydraulic conductivity(k)of bentonites to optimize WG:XG ratio.Rheological properties of biopolymer solutions were measured,serving as indicative parameters of biopolymer elution.The results indicated biopolymer-amended bentonites with the WG:XG ratio of 8:2 possessed lowest k(1.5×10^(−11)m/s to 7.2×10^(−11)m/s),lower than unamended bentonite(1.2×10^(−10)m/s to 8.6×10^(−10)m/s)in the AMD leachate condition.In addition,biopolymer solutions with WG:XG ratio of 8:2 exhibited highest viscosity.Thermogravimetric analysis,ultraviolet–visible spectroscopy,and Fourier transform infrared spectroscopy were conducted on the composite biopolymer,revealing that WG and XG interacted via physical cross-linking.Additionally,scanning electron microscopy and atomic force microscopy images indicated that a physical cross-linking and dense network structure conformation was developed in the composite biopolymer hydrogel at the WG:XG ratio of 8:2.The results demonstrate that the composite biopolymer is a promising low-carbon amendment material for enhancing containment performance of bentonite used in geosynthetic clay liners to contain AMD leachate.
基金supported by the National Natural Science Foundation of China(Grant Nos.52478351,52208329)the Shenzhen Science and Technology Innovation Commission(Grant No.JCYJ20240813143306009)support is gratefully acknowledged.
文摘Polymer-modified bentonite(PMB)is much more effective at containing chemically aggressive liquids than conventional bentonite.The PMB manufacturing process typically utilizes natural,high-quality sodium bentonite(NaB)owing to its excellent hydrophilicity and swelling capacity.However,calcium bentonite(CaB),which is much more abundant worldwide,is rarely used for containment applications owing to its poor hydrophilicity.This study proposed a polymerization method that transforms sodium-activated calcium bentonite(NCB)into PMB to achieve low hydraulic conductivity(k)to aggressive liquids.The mechanism for its low k was revealed through characterization techniques and analyses(e.g.X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),and Brunauer-Emmett-Teller(BET)).The results showed that the PMB had a small amount of polymer elution(indicating better interface stability)and thus exhibited excellent barrier properties under chemically aggressive conditions,with the k of<10^(-11) m/s for 0.6 mol/L NaCl solution,which is four orders of magnitude lower than that of the NCB(k=3×10^(-7) m/s).Various microscopic analyses indicated that the selected monomers were successfully polymerized,and intercalated into and grafted onto the montmorillonite layers of bentonite.The formed polymer network increased the swelling capability of PMB granules,decreased the pore size,and created narrow and tortuous flow pathways leading to a very low k to aggressive liquids.
基金financial support by the National Key Research and Development Program of China(No.2023YFC2907801)the Hunan Provincial Natural Science Foundation of China(No.2023JJ40760)the Scientific and Technological Project of Yunnan Precious Metals Laboratory,China(No.YPML-2023050276)。
文摘Bentonite is a necessary binder in producing pellets.Its excessive use reduces the iron grade of pellets and increases production costs.Minimizing bentonite dosage is essential for producing high-quality iron ore pellets.Addressing the gap in the application of organically-intercalated modified bentonite in the pelletizing field,this study introduces an innovative modification process for bentonite that employs the synergistic effect of mechanical force and dimethyl sulfoxide to enhance the intercalation of organic compounds within bentonite,thus significantly enhancing its binding performance.The colloid value and swell capacity of modified bentonite(98.5 m L/3g and 55.0 m L/g)were much higher than the original bentonite(90.5 m L/3g and 17.5 m L/g).With the decrease of bentonite dosage from1.5wt%to 1.0wt%,the drop number of green pellets from a height of 0.5 m and the compressive strengths of roasted pellets using the modified bentonite(6.0 times and 2916 N per pellet)were significantly higher than those of the original bentonite(4.0 times and 2739 N per pellet).This study provides a comprehensive analysis of the intercalation modification mechanism of bentonite,offering crucial technical insights for the development of high-performance modified bentonite as iron ore pellet binders.
文摘The objective of this work is to determine changes of surface properties of a bentonite after acid activation, using hydrochloric acid solutions (HCl) at room temperature. XRD, FX, FTIR, MEB, and BET analyses of the samples have been carried out to examine the structure of bentonite before and after acid activation. It is found that the raw bentonite is composed of dioctahedral montmorillonite with predominant quantity and certain amounts of quartz, albite and illite, etc. It has an cation exchange capacity (CEC) of 74.32 meq/g which allows it to be characterized as typical sodium bentonite. The changes, at low acid concentrations, are the result from from cation exchange (exchangeable cations with H+ ions). Differences of surface area at high acid concentrations (0.25 - 0.4 M) were caused by structural changes and partial decomposition of the samples. Data of surface area measurements have showed that with increase of concentration of hydrochloric acid, the surface area increased. The maximum value (837.11 m2/g) was reached by the sample activated with 0.4 M HCl. By against, activation with higher concentration (0.6 M) caused a decrease in the surface area.
文摘Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of the areas of the City of Diwaniyah,in a house covered with green netting,with a shade rate of 25%,to study the effect of bentonite and humic acid on the growth and flowering of a Catharanthus roseus L.plant in sandy soil.The experiment included two factors:the first factor was bentonite clay,and the second factor was humic acid.Using a randomized complete block design(R.C.B.D)with three replications,data were analyzed using the analysis of variance(ANOVA)method,and comparison was made according to the least significant difference(L.S.D)test at a probability level of 0.05.The experiment consisted of adding bentonite clay at 0,2,6,and 8 g L-1,humic acid at 0,0.5,1,and 10 g L-1.The results showed that adding bentonite clay and humic acid to sandy soil can have a significant positive effect on the growth and flowering of the Catharanthus roseus plant grown in poor sandy soil conditions.Bentonite,clay and humic acid were added at concentrations of 8 and 10 g L-1,which led to an increase in plant height and number of leaves and leaf area.They reached 30.07,23.84 cm2,76.62,63.42 cm2 for leaf-1 and 24.73,20.22 cm2 for leaf-1,respectively.The results also showed an increase in the content of nitrogen(N),phosphorus(P),and potassium(K)in leaves by 2.27,1.92,1.99%and 1.51,1.22,1.77%.This also led to an increase in chlorophyll pigment and anthocyanin at the highest concentration and gave the highest value.Therefore,adding bentonite and humic acid together gave the highest values in vegetative and chemical characteristics,compared to treatments without addition.
基金The Royal Society,UK,Grant/Award Number:IEC\NSFC\211366Fundamental Research Funds for the Central Universities(China University of Mining and Technology),Grant/Award Number:2023ZDPY11National Natural Science Foundation of China,Grant/Award Numbers:51809263,52174133。
文摘The corrosion of waste canisters in the deep geological disposal facilities(GDFs)for high-level radioactive waste(HLRW)can generate gas,which escapes from the engineered barrier system through the interfaces between the bentonite buffer blocks and the host rock and those between the bentonite blocks.In this study,a series of water infiltration and gas breakthrough experiments were conducted on granite and on granite-bentonite specimens with smooth and grooved interfaces.On this basis,this study presents new insights and a quantitative assessment of the impact of the interface between clay and host rock on gas transport.As the results show,the water permeability values from water infiltration tests on granite and granite-bentonite samples(10−19-10−20m^(2))are found to be slightly higher than that of bentonite.The gas permeability of the mock-up samples with smooth interfaces is one order of magnitude larger than that of the mock-up with grooved interfaces.The gas results of breakthrough pressures for the granite and the granite-bentonite mock-up samples are significantly lower than that of bentonite.The results highlight the potential existence of preferential gas migration channels between the rock and bentonite buffer that require further considerations in safety assessment.
基金supported by the National Natural Science Foundation of China(52076208,51736009)the Guangdong Special Support Program(2019BT02L278)+2 种基金the Special project for marine economy development of Guangdong Province(GDME2020D044)the Science and Technology Program of Guangzhou(20202102080159)Guangdong Basic and Applied Basic Research Foundation(2022A1515010835)。
文摘The equilibrium and kinetic of hydrate in sediments can be affected by the presence of external components like bentonite with a relatively large surface area.To investigate the hydrate formation and decomposition behaviors in bentonite clay,the experiments of methane hydrate formation and decomposition using the multi-step decomposition method in bentonite with different water contents of 20%,40%and 60%(mass)were carried out.The contents of bound,capillary and gravity water in bentonite clay and their roles during hydrate formation and decomposition were analyzed.In bentonite with water content of 20%(mass),the hydrate formation rate keeps fast during the whole formation process,and the final gas consumption under different initial formation pressures is similar.In bentonite with the water contents of 40%and 60%(mass),the hydrate formation rate declines significantly at the later stage of the hydrate formation.The final gas consumption of bentonite with the water contents of 40%and 60%(mass)is significantly higher than that with the water content of 20%(mass).During the decomposition process,the stable pressure increases with the decrease of the water content.Hydrate mainly forms in free water in bentonite clay.In bentonite clay with the water contents of 20%and 40%(mass),the hydrate forms in capillary water.In bentonite clay with the water content of 60%(mass),the hydrate forms both in capillary water and gravity water.The bound water of dry bentonite clay is about 3.93%(mass)and the content of capillary water ranges from 42.37%to 48.21%(mass)of the dry bentonite clay.
基金MCT, CNPq, and CAPES for financial supports and fellowships
文摘The capacities of natural and modified Brazilian bentonite samples as adsorbents to remove hexavalent metal chromium were investigated under several conditions in batch and column methods. The raw material, Ca-bentonite, was modified by anchorament of 3-aminopropyltrietoxisilane （APS） and 3,2- aminoethylaminopropyltrimetoxisilane （AEAPS） in the surface of bentonite sample： This type of new occurrence of bentonite is suitable as a raw material for adsorption process. Adsorption behavior of three bentonite types was strongly depending on pH of adsorbate solution, contact time adsorbent/adsorbate, and initial concentration of Cr（VI）. The results were confirmed by column method and reveals that the adsorption process of materials accorded by the Redlich-Peterson, Sips, Dubinin-Radushkevich, and tang- muir isotherm models. The exothermic entbalpic values reflected a favorable energetic process for chro- mium ions anchored in the material surfaces. The negative Gibbs free energy results supported the spontaneity of three adsorption reactions with Cr（VI） ions.
基金supported by Ecole des Ponts Paris Tech and the French National Radioactive Waste Management Agency(Andra)China Scholarship Council for the grant scholarship。
文摘In the French deep geological disposal for radioactive wastes,compacted bentonite/claystone mixtures have been considered as possible sealing materials.After emplacement in place,such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete.In this study,the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites(MX80 Na-bentonite and Sardinia Cabentonite)were investigated by carrying out a series of swelling pressure,hydraulic conductivity and mercury intrusion porosimetry(MIP)tests.It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution,the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges.For the Sardinia bentonite/claystone mixture,the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions,suggesting insignificant cation exchanges.Additionally,the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures.The large-pore volume increased consequently and enhanced water flow.In the cement solution,the hydroxide could also dissolve the montmorillonite,reducing the swelling pressure,and increase the large-pore volume,facilitating the water flow.Furthermore,the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.
基金funded by the German Federal Ministry for Economic Affairs and Energy(BMWi)under contract number 02E11627。
文摘As a potential engineered barrier material for disposal of radioactive waste in clay formations,claystone aggregate excavated from the Opalinus clay(OPA),its mixture with bentonite MX80 in a mass ratio of 7/3,and pure bentonite were extensively investigated with respect to the hydro-mechanical properties and performances.With these materials,a series of parallel experiments was performed under sequentially applied conditions of hydration with synthetic porewater of the clay formation,consolidation and water flow under increased stresses,and gas injection into the water-saturated and compacted materials under loading.Significant responses of the clay mixtures were observed.Main findings include:(1)the hydration and induced swelling of the mixtures are mainly dominated by bentonite content and dry density;(2)the consolidation decreases the porosity and water permeability exponentially by 2-3 orders of magnitude to low values of 10^(-18)-10^(-20) m^(2) at stresses of 2-5 MPa,depending upon bentonite content;and(3)the gas penetration in the water-saturated and compacted bentonite is characterised by a cyclic pressure rising/dropping process limited in between the upper breakthrough and lower shut-off boundaries,whereas the compacted claystone and claystone/bentonite mixture allow for gas release at low and moderate pressures.The results are helpful for design of the engineered barriers for safe isolation of radioactive waste in repositories.
文摘Globally bentoite clay has been proposed as an engineered barrier material for safe underground disposal of high-level nuclear waste.Clay has many favorable properties such as high liquid limit,and plastic limit along with other properties which make it the most suitable for this application.In the present study,an attempt has been made to study the behavior of Barmer bentonite under the influence of high temperatures up to 120℃.Properties of barmer bentonite namely,liquid limit,plastic limit,and maximum dry density have been determined after thermal treatment at 25℃,60℃,80℃,100℃ and 120℃.The extensive experimental results indicate that liquid limit and plastic limit show a decreasing trend while maximum dry density increases with an increase in temperature.Liquid limit and plastic limit decrease up to 12%and 11%respectively when the temperature reaches up to 120℃.Maximum dry density increases by 10%due to thermal treatment and optimum water content decreases by up to 4%.Statistical analysis has been carried out to obtain the correlation between temperature and physical properties of Barmer bentonite such as liquid limit,plastic limit,maximum dry density,and optimum water content.The XRD analysis of Barmer bentonite at room temperature and 120℃ shows very small variation in mineralogical composition.Whereas,interlayer distance has been measured and found to be decreasing with an increase in temperature.Further,a comparative analysis shows that the measured properties of studied Barmer bentonite lie in the range of previously measured values of other types of bentonite across the globe.
基金funded by the National Natural Science Foundation of China(Grant Nos.42207227)the Natural Science Foundation of Hunan Province,China(Grant No.2022JJ40586)The authors also thank the China Postdoctoral Science Foundation(Grant Nos.2022M722428).
文摘In the deep geological disposal repository of high-level radioactive waste,buffer/backfill materials typically consist of compacted bentonite block and granular bentonite.As these materials undergo a long-term hydration,it is anticipated that the two forms of bentonite materials(i.e.compacted bentonite powder(CBP)and granular bentonite(GB))are expected to exhibit differing hydro-mechanical behaviors due to the differences in their structures.This work aims to investigate the differences in swelling pressure and compressibility through a series of swelling pressure tests,compression tests and mercury intrusion porosimetry(MIP)tests.The experimental results demonstrated that swelling pressure curves of the CBP specimens showed higher first peak values and more pronounced collapse than those of the GB specimens at a given dry density,regardless of vapor-water hydration or liquid-water hydration.The final swelling pressures of the two materials were similar at the same dry density,suggesting an independent correlation between swelling pressure and dry density.At the high suction range,the compression curves exhibited an obvious bi-linear pattern for the CBP specimens and a significant nonlinearity for the GB specimens.Meanwhile,the CBP specimens presented higher pre-consolidation pressures and larger compression indices than the GB specimens at a given suction.As suction decreased,the compression curves of the two materials gradually approached each other and their differences were reduced accordingly.After reaching saturation,a good consistency between them was observed whether for final swelling pressure or compressibility.Pore structure analysis revealed that the two materials both presented an initially double structure,and their differences were primarily manifested at the macrostructural level.Eventually,the differences in swelling pressure or compression curves of the two materials were well interpreted by combining microstructural evolutions.
基金funding from the European Union's Horizon 2020 research and innovation program European Joint Program on RadioactiveWaste Management(EURAD)(2019e2024)WP-Gas‘Mechanistic understanding of gas transport in clay materials’under Grant agreement No.847593.
文摘Understanding the mechanisms of gas transport and the resulting preferential pathways formation through bentonite-based barriers is essential for their performance evaluation.In this experimental study,gas migration within a heterogenous mixture of MX80 bentonite pellets and powder with a ratio of 80/20 in dry mass was investigated.A novel X-ray transparent constant volume cell has been developed to assess the effect of gas pressure,material heterogeneities,and water vapor gas saturation on breakthrough pressure and gas pathways.The new cell allows to perform high-resolution X-ray computed micro-tomography(X-ray μCT)scans to track microstructural changes during different phases of saturation and gas injection.Experimental results showed that the gas breakthrough occurred when the pressure was raised to 3 MPa.This is slightly higher than the expected swelling pressure(2.9 MPa)of the bentonite sample.Each gas injection was followed by a long resaturation phase restoring material homogeneity at μCT resolution scale(16 mm).However,the elapsed time needed for gas to breakthrough at 3 MPa diminished at each subsequent injection test.X-ray μCT results also revealed the opening of the specimen/cell wall interface during gas passage.This opening expanded as the injection pressure increased.The gas flow along the interface was associated with the development of dilatant pathways inside the sample,although they did not reach the outlet surface.It was observed that the water vapor gas saturation had no effect on the breakthrough pressure.These findings enhance the understanding of the complex mechanisms underlying microstructural evolution and gas pathway development within the highly heterogeneous mixture.The experimental outcomes highlight the effectiveness of X-ray μCT to improve quality protocols for engineering design and safety assessments of engineered barriers.
文摘Clay minerals are one of the potential good adsorbent alternatives to activated carbon because of their large surface area and high cation exchange capacity. In this work the adsorptive properties of natural bentonite and kaolin clay minerals in the removal of zinc (Zn2+) from aqueous solution have been studied by laboratory batch adsorption kinetic and equi- librium experiments. The result shows that the amount of adsorption of zinc metal ion increases with initial metal ion concentration, contact time, but decreases with the amount of adsorbent and temperature of the system for both the ad- sorbents. Kinetic experiments clearly indicate that adsorption of zinc metal ion (Zn2+) on bentonite and kaolin is a two-step process: a very rapid adsorption of zinc metal ion to the external surface is followed by possible slow decreas- ing intraparticle diffusion in the interior of the adsorbent. This has also been confirmed by an intraparticle diffusion model. The equilibrium adsorption results are fitted better with the Langmuir isotherm compared to the Freundlich model. The value of separation factor, RL from Langmuir equation give an indication of favourable adsorption. Finally from thermodynamic studies, it has been found that the adsorption process is exothermic due to negative ?H0 accompa- nied by decrease in entropy change and Gibbs free energy change (?G0). Overall bentonite is a better adsorbent than kaolin in the the removal of Zn2+ from its aqueous solution.
基金supported by the National Natural Science Foundation of China(No,22271074)Natural Science Foundation of Hebei Province(Nos.B2023208042,B2022208032,B2021208066,E2024208084 , E2024208088)+2 种基金Science Research Project of Hebei Education Department(No.JZX2024013)Special Fund for Local Scientific and Technological Development under the Guidance of the Central Government(No.236Z3704G)Hebei Province High Level Talent Funding(No.A202001010).
文摘Flexible wearable electronic devices based on hydrogels have immense potential in a wide range of applications.However,many existing strain sensors suffer from significant limitations including poor mechanical properties,low adhesion,and insufficient conductivity.To address these challenges,this study successfully developed an organic-inorganic double-network conductive hydrogel using acrylic-modified bentonite (AABT) as a key component.The incorporation of AABT significantly enhanced the mechanical properties of the ATHG@LiCl hydrogel,achieving an impressive stretchability of 4000% and tensile strength of 250 kPa.Moreover,it improved the electrical conductivity of the hydrogel to a maximum of 1.53 mS/cm.The catechol structure of tannic acid (TA) further augmented the adhesive properties of the ATHG@LiCl hydrogel toward various substrates such as copper,iron,glass,plastic,wood,and pigskin.The addition of lithium chloride (LiCl) and dimethyl sulfoxide(DMSO) endowed the hydrogel with exceptional freezing resistance and flexibility,even at low temperatures of-20℃.Remarkably,the hydrogel maintained a conductivity of 0.53 mS/cm under these conditions,surpassing the performance of many other reported hydrogels.Furthermore,the ATHG@LiCl hydrogel demonstrated outstanding characteristics,such as high sensitivity (gauge factor GF=4.50),excellent transparency (90%),and reliable strain-sensing capabilities,indicating that the ATHG@LiCl hydrogel is a highly promising candidate for flexible wearable soft materials,offering significant advancements in both functionality and performance.
基金financial support from the National Natural Science Foundation of China(Grant No.42202304)is greatly acknowledged.
文摘Predicting the gas diffusion coefficient of water-saturated Na-bentonite is crucial for the overall performance of the geological repository for isolating high-level radioactive waste(HLW).In this study,a conceptual model that incorporates a multi-porosity system was proposed,dividing the pore space into free water pores,interlayer water pores,and diffuse double layer(DDL)water pores,to describe the molecular diffusion behaviour of the dissolved gas in saturated bentonite.In this model,gas diffusion in these three porosities is considered as independent and parallel processes.The apparent gas diffusion coefficient is quantified by applying weighted approximations that consider the specific porosity,tortuosity factor,and constrictivity factor within each porosity domain.For verification,experimental data from gas diffusion tests on saturated MX-80 and Kunipia-F bentonite specimens across a wide range of dry densities were utilized.The proposed model could successfully capture the overall trend of the apparent gas diffusion coefficient for bentonite materials across the partial dry density of montmorillonite ranging from 900 kg/m^(3)to 1820 kg/m^(3),by employing only one fitting parameter of the scaling factor.When the partial dry density of montmorillonite decreased to 800 kg/m^(3),the proposed model shows an underestimation of the apparent gas diffusion coefficient due to possible changes of the tortuosity factor.Model predictions indicate that gas diffusion in saturated bentonite is primarily controlled by the free pore domain,with minimal contributions from DDL pores.Despite being the dominant pore type,interlayer pores contribute limitedly to total Da/Dw values due to significant constrictivity effects.
基金University of Manchester and the China Scholarship Council,Royal Society,UK,Grant/Award Number:IECNSFC211366National Natural Science Foundation of China,Grant/Award Numbers:5247415,52174133Natural Science Foundation of Jiangsu Province of China,Grant/Award Number:BK20240107。
文摘Understanding the effects of temperature on the hydro-mechanical behavior of compacted bentonite is important for performance assessments of bentonitebased buffer,backfill,and sealing systems in deep geological disposal of high-level radioactive wastes.Motivated by such applications,most past experimental studies were focused on highly compacted and high-quality bentonite.Such degrees of dry densities may not be economically or technically feasible for other emerging applications,including as an alternative material to cement in plugging and abandonment of wells.A bespoke high-pressure high-temperature constant rate of strain(CRS)apparatus was developed for the work reported here to conduct a series of tests for evaluating the hydro-mechanical response of compacted bentonite to elevated temperatures.Experiments were performed with bentonite specimens with high impurity contents at a range of dry densities(1.1,1.4,and 1.7 Mg/m^(3))and temperatures between 20 and 80℃.The results show that temperature increase leads to the decrease of swelling pressure for all studied densities.Larger reductions of swelling pressure were observed with increasing dry densities,suggesting the possibility of a larger exchange of pore water in the microstructure system of the clay.The transfer of water from micropores to macropores at elevated temperatures is shown to be a key controlling process at high-density compacted bentonite by which temperature affects the swelling pressure and hydraulic conductivity.
基金supported by the General Project of the National Natural Science Foundation of China(No.42377413).
文摘Colloids are prevalent in nuclear waste repositories,with bentonite colloids posing an uncontrollable risk factor for nuclide migration processes.In this study,static adsorption experiments were coupled with dynamic shower experiments to comprehensively investigate the influence of bentonite colloids on Sr^(2+)migration in granite,considering adsorption capacity.Bentonite colloids have a considerably greater adsorption capacity than both bentonite and granite,with a maximum adsorption of 30.303 mg/g.The adsorption behavior of bentonite colloids on Sr^(2+)is well described by the Langmuir isotherm and pseudo-second-order kinetic models,indicating that a single-layer chemical adsorption process is controlled by the site activation energy.The adsorbed Sr^(2+)is unevenly distributed on the colloids,and the adsorption mechanism may involve ion exchange with Ca.Bentonite colloids exhibit superior adsorption in neutral environments.The cations in groundwater inhibit Sr^(2+)adsorption,and the inhibition efficacy decreases in the order Fe^(3+)>Ca^(2+)>Mg^(2+)>K^(+).The presence of bentonite colloids in a granite column slightly influences the retention of Sr^(2+)in the column while markedly reducing the Sr^(2+)penetration time from 70 h to 18 h.However,the coexistence of Co^(2+),Ni^(2+),and Cs^(+)in a multinuclide system weakens the ability of the colloids to promote Sr^(2+)migration.In comigration of colloid and multinuclide systems,the adsorption of nuclides by bentonite colloids causes the nuclide migration speed to decrease in the order Sr^(2+)>Cs^(+)>Ni^(2+)>Co^(2+).This study provides insights into Sr^(2+)migration in cave repositories for low-and medium-level radioactive waste.
文摘Bioceramic material of the quaternary system;SiO2- CaO-Na2O-P2O5 that has composition similar to Bio- glass? 45S5 was prepared by the sol-gel method from locally obtained bentonite clay (BTC). The monolith obtained was sintered at 1000?C for 2 h to facilitate densification and phase transformation. X-ray diffraction (XRD) analysis revealed the presence of sodium calcium silicate, Na2Ca2Si3O9 as major crystal phase, and another secondary orthorhombic phase, NaCaPO4. Fourier transform infrared (FTIR) spectroscopic investigation confirmed the presence of Si-O-Si bonds and a crystalline phosphate in the glass network. Scanning electron microscopy (SEM) revealed a network of micropores and interconnected macropores. Overall, the material displays features amenable for possible utilization in tissue engineering scaffolds.
基金supported by the State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology (No. 2022TS10)the Taishan Industrial Experts Programthe Natural Science Foundation of Shandong Province of China (No. ZR2023ME212).
文摘Wet flue gas desulfurization(WFGD)could effectively reduce sulfur dioxide emission.However,magnesium sulfite(MgSO_(3)),a by-product of desulfurization,was easy to result in secondary pollution.In this study,the solid catalyst Co-Bent(bentonite supported cobalt)was prepared by blending method for MgSO_(3) oxidation with bentonite as the carrier and cobalt as the active component.At the calcination temperature of 550℃ and the Co loading level of 3 wt.%,the catalyst showed excellent catalytic performance for the oxidation of high concentration MgSO_(3) slurry,and the oxidation rate of MgSO_(3) was 0.13 mol/(L·h).The research indicated that the active component was uniformly distributed within porous structure of the catalyst as Co_(3)O_(4),which facilitated the oxidation of SO_(3)^(2-) catalyzed by Co_(3)O_(4).Kinetic researches indicated the oxidation rate of MgSO_(3) was influenced by the catalyst dosage,the reaction temperature,the solution pH,the airflow rate,and the SO_(3)^(2-) concentration.Additionally,after recycling experiments,the regenerated catalyst retained its high catalytic performance for the MgSO_(3) oxidation.The reaction mechanism for the catalytic oxidation of MgSO_(3) by Co-Bent catalyst was also proposed.The generation of active free radicals(OH·,SO_(4)^(-)·,SO_(3)^(-)·,SO_(5)^(-)·)accelerated the MgSO_(3) oxidation.These results provide theoretical support for the treatment of MgSO_(3) and the development of durable catalyst.
