Interlayer Water Research Articles

Fabrication and Analysis of an Effective Composite Desiccant for the Rapid Dehydration of Shield Waste Slurry

Massive shield waste slurry generated in shield tunnel construction is difficult to deal with because of its high water content (WC). Only when the WC of waste slurry is reduced to 40%–60% it can be further disposed and reutilized. Three inorganic materials including attapulgite (AT), montmorillonite (MT) and water-washed kaolin (WK) were utilized to dehydrate the shield waste slurry and found that the WC of shield waste slurry dropped to 48.3%, 48.2% and 49.6% with 12.5% AT, 10% MT, and 12.5% WK as the desiccant, respectively. To enhance the dehydration efficiency, a composite desiccant was prepared with AT, MT and WK for the rapid dehydration of waste slurry. The optimized ratio of composite desiccant for AT: MT: WK was decided as 3.23%: 3.50%: 3.40% by response surface methodology based on Box-Behnken design, corresponding with the predicted WC as 44.9%. The WC of shield waste slurry can be decreased to 44.1% after the waste slurry has been dehydrated with the optimal composite desiccant after 6 days. The pH value of solidified shield waste slurry cured with the optimal composite desiccant was approximately 10.5, benefiting the further disposal and resource reutilization of shield waste slurry. The shield waste slurry was characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The results revealed that hydration products came into being during the hydration reaction when the shield waste slurry was cured with desiccant. The hydration products refabricated the microscopic lamellar structure of the waste slurry, squeezed the interlayer gap and drove the interlayer water away, leading to the depression of the WC of waste slurry.

Effects of Ammonium Salts on Rare Earth Leaching Process of Weathered Crust Elution-Deposited Rare Earth Ores

In order to reveal the influence of ammonium salts on the rare earth leaching process of weathered crust elution-deposited rare earth ores, ammonium acetate, ammonium chloride, and ammonium sulfate were used as leaching agents. The effects of the leaching agent on the rare earth leaching efficiency and the expansion, dissolution, and transformation behavior of clay minerals in the rare earth leaching process were studied. The results showed that rare earth leaching efficiency followed the order ammonium acetate > ammonium chloride > ammonium sulfate, with values of 90.60%, 85.96%, and 84.12%, respectively. The swelling ratio of clay mineral followed the order ammonium acetate < ammonium chloride < ammonium sulfate; the clay mineral swelling ratio was 2.09% when ammonium acetate was the leaching agent. Thermogravimetric analysis showed that the interlayer water content was the lowest when ammonium acetate was used as the leaching agent. Under the conditions of different leaching agents, the clay mineral contents changed from illite and halloysite to smectite and kaolinite. When ammonium acetate was used as the leaching agent, the relative conversion of illite was 1.49%, and that of smectite was only 0.17%. SEM analysis showed that the clay minerals expanded and dissolved obviously when ammonium chloride and ammonium sulfate were used as the leaching agents. Meanwhile, the clay mineral layered structure was relatively complete when ammonium acetate was used as the leaching agent. Therefore, when ammonium acetate was used as the leaching agent, it had the least effect on the swelling, dissolution, and transformation of clay minerals. This can provide a theoretical basis for the safe production of weathered crust elution-deposited rare earth ore, and for the screening of green and efficient leaching agents.

Influence of inorganic and organic salts on the hydration mechanism of montmorillonite based on molecular simulation

The molecular dynamics method is used to further reveal, from the molecular point of view, the mechanisms of salt inhibiting the hydration of Na-MMT. The interaction between water molecules, salt molecules, and montmorillonite are calculated by establishing the adsorption models. According to the simulation results, the adsorption conformation, interlayer concentration distribution, self-diffusion coefficient, ion hydration parameters, and other data are compared and analyzed. The simulation results show that the volume and basal spacing increase in a stepwise manner with the increase of water content, and water molecules have different hydration mechanisms. The addition of salt will enhance the hydration properties of compensating cations of montmorillonite and affect the mobility of particles. The addition of inorganic salts mainly reduces the adsorption tightness between water molecules and crystal surfaces, thereby reducing the thickness of water molecules layer, while the organic salts can better inhibit migration by controlling interlayer water molecules. The results of molecular dynamics simulations reveal the microscopic distribution of particles and the influence mechanism when the swelling properties of montmorillonite are modified by chemical reagents.

Insights into the influence mechanism of different interlayer cations on the hydration activity of montmorillonite surface: A DFT calculation

Montmorillonite is one of the main components of mudstones. Physical changes in the microstructure of montmorillonite after water absorption are the root cause of softening and disintegration of mudstone and the deterioration of bearing properties. In this study, the adsorption behavior and hydration mechanism of water molecules on the surface of four cationic forms of montmorillonites (LiMt, NaMt, KMt, and CaMt) were investigated by density functional theory (DFT). The results indicated that water molecules were adsorbed mainly through electrostatic attractive force with interlayer cations. The electrostatic attraction decreased in the following order: Ca-Mt > Li-Mt > Na-Mt > K-Mt; and CaMt demonstrated the strongest adsorption capacity. When adsorption occurred, there was a large charge transfer between the atom of a water molecule (Ow) and interlayer cations, and the hybridization of Ow 2p orbitals with Li 1 s, Na 3 s, K 4 s, and Ca 4 s orbitals formed bonds with certain ionic characteristic. This work directly explained the interaction mechanism of water molecules with montmorillonite at the atomic and electronic levels, which provided a new perspective to understand the adsorption process of water molecules on clay mineral surfaces.

Crystallization kinetics and crystallization process of pseudoboehmite from ammonium aluminum sulfate solution

In this work, the crystallization kinetics of pseudoboehmite was studied by intermittent crystallization method. The kinetic model of pseudoboehmite process was established based on particle number equilibrium. The results show that the nucleation is mainly caused by crystal collision, the main speed control step is diffusion process, and the enlargement of crystals mainly originates from the growth. Reducing the temperature of system can obtain pseudoboehmite crystals which have larger particle size and more uniform particle size distribution. Two parallel octahedral units connected by hydroxyl groups are preferentially stacked along the (020) crystal plane. Excessive interlayer water molecules between (020) crystal planes lead to an increase in the interlayer distance. The increased distance between (020) layers will weaken the hydrogen bond between layers, as well as the electrostatic forces and van der Waals forces, resulting in the formation of folded layers with holes. Finally, the irregularly sheets of pseudoboehmite are stacked to form porous spherical structures.

Ecological and geochemical aspects of interlayer water use for potable water supply of urban population: a case study in the Dnieper–Donetsk aquifer system, Ukraine

Ecological and geochemical aspects of interlayer water use for potable water supply of urban population: a case study in the Dnieper–Donetsk aquifer system, Ukraine

Decoration of layered double hydroxide-fullerene hybrid and its application for improving the thermal stability and antioxidant ability of high-density polyethylene

Layered double hydroxide-fullerene hybrid (LDH-C60) was facilely obtained via a co-precipitation method. Transmission electron micrographs (TEM), scanning electron micrographs (SEM), and X-ray photoelectron spectroscopy (XPS) all provided evidence that C60 was bound to LDH layers, resulting in a reduction in the size and thickness of the layer. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) findings indicated that LDH-C60 may greatly increase the thermal stability of PE. With the addition of LDH, the initial decomposition temperature (Tonset) of PE in N2 was lowered from 463 °C to 451 °C. The thermal stability of PE composites was increased with the addition of LDH-C60, though. For PE/LDH-C60 in N2 and air, the Tonset may be increased by 7 °C and 60 °C, respectively. Due to the interlayer water and anions' poor antioxygen capacity, the OIT for PE/LDH was also noticeably shorter than for PE. Furthermore, the OIT for PE/LDH-C60 was significantly delayed to 12.9 min. LDH-C60 shown a good synergistic impact in enhancing the thermal stability and anti‑oxygen capacity of polyethylene by combining the benefits of LDH and C60.

Green desorption combined with peptization technology for disposing of Cr(VI)-V(V)-containing hazardous aluminum waste to prepare high-valued pseudo-boehmite

Cr(VI)-containing aluminum residues are inevitable industrial hazardous waste in the chromate industry. To reduce and utilize these residues, a combined desorption and peptization technology for disposing of Cr(VI)-V(V)-containing boehmite hazardous waste (γ-AlOOH-Cr-V) with NaOH solutions was proposed, which realized the removal of V(V) and Cr(VI) effectively and the improvement of peptization index (PI) of obtained pseudo-boehmite (PB) synergistically. The results showed that PB with high PI (98.1%) and low content of V(V) (0.0656%) and Cr(VI) (0.0018%) could be achieved by desorbing the γ-AlOOH-Cr-V, while the surface area and pore volume would be decreased during desorption with the increase of NaOH concentration. Besides the leaching toxicity of Cr(VI) of obtained PB of 0.09 mg/L was extremely lower than that of the standard of hazardous waste. It was noted that the evolution of structural hydroxyl groups governed the improvement of peptization performance. DFT results showed that proper interlayer water content was beneficial to the adsorption of hydroxyl ions on the structural hydroxyl groups of PB. This work not only reduced the emission of Cr(VI)-V(V)containing hazardous waste, but also paved the way for the high-valued utilization of co-associated aluminum and vanadium resources in chromite.

Improving the adsorption capacity of amino-modified Mg-Al LDH using a combined DFT and experiment

The adsorption of CO2 using layered double hydroxides (LDHs) such as Mg-Al LDH is both technically feasible and economical. Although some approaches to the modification of LDHs have proved fruitful, there is still a need for further improvement in the adsorption capacity of modified LDHs. Here, a new optimization direction for amino-modified Mg-Al-LDHs is proposed based on using DFT and AIMD simulations to elucidate the mechanism of CO2 diffusion. The proposed approach was then evaluated experimentally. Theoretical calculations showed that the adsorption energy of ordinary amino-modified LDHs was low, at − 0.56 eV. DFT simulations showed that the number of interlayer water molecules affects the CO2 adsorption energy, with the optimum adsorption energy of − 0.78 eV obtained in the presence one interlayer water molecule. Experimental analysis showed that the drying time affects the amount of interlayer water and thus the CO2 adsorption capacity, with the maximum adsorption capacity of 1.7424 mmol/g obtained after drying for 5 h. This study provides useful insights towards the development of materials such as Mg-Al LDHs for efficient CO2 adsorption and highlights the critical role of interlayer-bound water on the adsorption performance.

Enhanced H+ Storage of a MnO2 Cathode via a MnO2 Nanolayer Interphase Transformed from Manganese Phosphate.

The MnO2 cathode has attracted extensive attention in aqueous zinc ion battery research due to its environmental benignity, low cost, and high capacity. However, sluggish kinetics of hydrated zinc ion and manganese dissolution lead to insufficient rate and cycle performances. In this study, a manganese phosphate nanolayer synthesized in situ on a MnO2 cathode can be transformed into a δ-MnO2 nanolayer interphase after activation upon cycling, endowing the interphase with abundant interlayer water. As a result, the δ-MnO2 nanolayer interphase with the function of H+ topochemistry significantly enhances H+ (de)insertion in the MnO2 cathode, which leads to a kinetics conversion from Zn2+-dominated (de)insertion to H+-dominated (de)insertion, thus endowing the MnO2 cathode with superior rate and cycle performances (85.9% capacity retention after 1000 cycles at 10 A g-1). This strategy can be highly scalable for other manganese-based cathodes and provides an insight for developing high-performance aqueous zinc ion batteries.

Research on irrecoverable creep of the hardened cement paste under different relative humidity

Relative humidity (RH) has an important influence on the creep performance of cement-based materials. In this paper, the creep and creep recovery experiments of hardened cement paste (HCP) were carried on under four humidity balance. The low-field 1H nuclear magnetic resonance (NMR) test was performed on the HCP after the creep recovery test to obtain the internal water distribution characteristics of HCP. The creep properties and volume ratio of different micro phases in HCP were acquired by nanoindentation test, backscattered electron (BSE) test, and thermogravimetric (TG) test. Subsequently, the structure features of C–S–H were acquired by the 29Si NMR test and the nitrogen adsorption-desorption test. The results showed that the raise of RH significantly increased the interlayer water content in HCP. The creep properties of C–S–H reduced significantly with the increase of RH. The volume fraction of low-density (LD) C–S–H elevated with raising RH, while the trend of high-density (HD) C–S–H was opposite to the former. When RH increased, the mean chain length of the gel raised, and the gel pores became more numerous, among which the magnitude of change of LD C–S–H pores was more significant.

Thermal stability assessment of calcium monosulfoaluminate 12-hydrate by applying the in-situ X-ray diffraction method at 25–1250 °C

In this study, the stability of synthetic calcium monosulfoaluminate and the reaction mechanism of its conversion into ye`elimite during the thermal treatment were examined. The monosulfoaluminate was produced referring to ye`elimite stoichiometry by applying the mechanochemical treatment (dry grinding at 900 rpm with 3 on–off cycles of 10 min) followed by the hydrothermal synthesis (for 8 h at 110 °C). The data indicated that the prepared sample consists of Ms12 (~ 54.8%), CaCO3 (~ 1.9%), Ms10.5/Hc (~ 0.7%) and amorphous content (~ 42.6%). Meanwhile, the thermal stability assessment by in-situ XRD analysis reveals that the dehydration of monosulfoaluminate interlayer water proceeds at 25–370 °C, where four different hydration states of monosulfoaluminate are identified. Additionally, the results suggest that the removal of water molecules from the main (octahedral) layers begins at ~ 200 °C. Finally, at 700–1250 °C, the solid-state reactions between CŜ, CA and CaO are observed, generating the formation of ye`elimite.

Influence of pseudoboehmite on the performance of shaped mordenite catalyst for dimethyl ether carbonylation

As a key step of indirect production of ethanol from syngas, the carbonylation of dimethyl ether (DME) has attracted much attention. It is of great importance to develop shaped catalyst with high efficiency and strong mechanical properties to promote the process industrialization. Extruded mordenite (MOR) has been used as the catalyst for industrial DME carbonylation. In this work, the effect of properties and content of pseudoboehmite as a binder on mechanical strength and catalytic performance of the extruded MOR were systematically studied. Combining TG, XRD, N2 adsorption, and rheological property analysis etc., we found that the interlayer water content of pseudoboehmite affect peptization process, which leads to the difference in mechanical strength and pore structure. Then, the DME carbonylation performance of the extruded MOR was discussed based on textural parameters and acidic properties. Further, DME diffusion experiments were conducted and analyzed by using standard and the time-fractional diffusion models respectively. As a result, the influence of pseudoboehmite on mass transfer performance was quantitatively analyzed. The results will provide important guidance for the development of shaped zeolite catalysts in industry.

Tensile and compressive behavior of Na-, K-, Ca-Montmorillonite and temperature effects

Molecular dynamics (MD) method was applied to simulate the nano mechanical behavior of Na-, K-, Ca-montmorillonite (MMT) under uniaxial tension and compression, and to explore the effects of the loading direction and temperature. The relation between nano mechanical properties of Na-, K-, Ca-MMT and the hydration was investigated, a comparison was made considering the bulk modulus, shear modulus, elastic modulus and Poisson’s ratio. There are significant differences for the nano mechanical behavior of montmorillonite in different directions, the in-plane tensile and compressive elastic modulus and strength are greater than those in perpendicular to the crystal plane. The nano mechanical properties of Na-MMT have a negative relation with temperature. The nano mechanical properties were found to decrease with the increasing hydration for the montmorillonite. The stiffness coefficients are also influenced by the hydration and interlayer cations. The tensile strength of Ca-MMT is smallest among three types of montmorillonite. The bulk modulus, shear modulus, and Young’s modulus of polycrystal Na-, K-, Ca-MMT are also decreasing with the hydration water layers, while Poisson’s ratio remains unchanged with the increasing hydration. By observing the nano structure change, the tension failure is caused by a slip plane due to bond breaks and the compression failure caused by the local buckling of the crystal sheet in x- and y- direction, while in z- direction, the failure is due to the separation of the interlayer water molecules in tension and bond breaks to form a shear band in compression.

Investigation of the Mechanism and Effect of Citric Acid-Based Deep Eutectic Solvents Inhibiting Hydration and Expansion of Gas Shale Clay Minerals

This study developed a shale hydration inhibitor using a citric acid-based deep eutectic solvent (Cit-DES) and hexadecylammonium bromide (cetyltrimethylammonium bromide) to aid wellbore instability and collapse caused by drilling of shale gas wells with water-based drilling fluids. Soaking and linear expansion experiments were conducted with Na-bent and Longmaxi formation shale, respectively. The changes in illite interlayer spacing, wettability, and water absorption capacity of shale samples before and after soaking in an inhibitor solution were evaluated, which indicated that the inhibitor reduced shale hydration. The results showed that the inhibitor effectively inhibits the osmotic and surface hydration of the shale. Due to the Cit-DES hydrogen bond, the inhibitor is firmly adsorbed on the shale pore wall and inserted between clay minerals, reducing the shale surface energy, hydrophilicity, and surface potential. The swelling expansion rate of shale inhibitors is only 38.9% compared to a 3% KCl solution. The amount of shale imbibition per unit mass in distilled water is 0.011 g/g. In the inhibitor, the imbibition mass per unit of shale is 0.002 g/g, which is only 23.68% of that in distilled water. The inhibitor is environment-friendly and has a broad application prospect for maintaining shale wellbore stability and preventing wellbore collapse during horizontal shale drilling operations.

Theoretical Study on the Swelling Mechanism and Structural Stability of Ni3Al-LDH Based on Molecular Dynamics.

layered double hydroxide (LDH) as a kind of 2D layer material has a swelling phenomenon. Because swelling significantly affects the adsorption, catalysis, energy storage, and other application properties of LDHs, it is essential to study the interlayer spacing, structural stability, and ion diffusion after swelling. In this paper, a periodic computational model of Ni3Al-LDH is constructed, and the supramolecular structure, swelling law, stability, and anion diffusion properties of Ni3Al-LDH are investigated by molecular dynamics theory calculations. The results show that the interlayer water molecules of Ni3Al-LDH present a regular layered arrangement, combining with the interlayer anions by hydrogen bonds. As the number of water molecules increases, the hydrogen bond between the anion and the basal layer gradually weakens and disappears when the number of water molecules exceeds 32. The hydrogen bond between the anion and the water molecule gradually increases, reaching an extreme value when the number of water molecules is 16. The interlayer spacing of Ni3Al-LDH is not linear with the number of water molecules. The interlayer spacing increases slowly when the number of water molecules is more than 24. The maximum layer spacing is stable at around 19 Å. The interlayer spacing, binding energy, and hydration energy show an upper limit for swelling: the number of water molecules is 32. When the number of interlayer water molecules is 16, the water molecules' layer structure and LDH interlayer spacing are suitable for anions to obtain the maximum diffusion rate, 10.97 × 10-8 cm2·s-1.

Liquid Phase Exfoliation of Chemically Prelithiated Bilayered Vanadium Oxide in Aqueous Media for Li-Ion Batteries

Bilayered vanadium oxides are attractive for energy storage due to their high initial specific capacities, which could be stabilized by integrating the bilayers with conductive nanoflakes often produced in a form of aqueous dispersions. Therefore, exfoliation of the bilayered vanadium oxides in water with high yield is desirable. This work introduces the first aqueous exfoliation of chemically prelithiated bilayered vanadium oxide (i.e., δ-LixV2O5·nH2O or LVO) followed by vacuum filtration to produce a free-standing film, exhibiting a lamellar stacking of the bilayered vanadium oxide nanoflakes as evidenced by scanning electron microscopy. Due to the hydrated nature of bilayered vanadium oxides, the relationship between interlayer water content and the vacuum drying temperature (105 °C vs 200 °C) was studied using X-ray diffraction, thermogravimetric analysis, and Raman spectroscopy. It was found that vacuum drying the LVO nanoflakes at 200 °C enabled more efficient removal of crystallographic water than drying at 105 °C, and did not induce a phase transformation. Scanning transmission electron microscopy confirmed the layered structure of the samples, which was more well-ordered in the 200 °C case and had no clear boundaries between flakes at the atomic scale. Furthermore, electrochemical testing in nonaqueous Li-ion cells revealed that vacuum drying at 200 °C led to improvements in ion storage capacity and electrochemical stability. Improvements in electrochemical charge storage properties of the electrodes obtained via LVO exfoliation and free-standing film assembly in water dried at 200 °C reveal that conventional battery electrode drying protocols need to be revised as new electrochemically active materials are synthesized, such as hydrated layered oxides with expanded interlayer regions. The remaining capacity fading can be attributed to the structural LVO degradation, dissolution of vanadium oxide in electrolyte, and parasitic effects of the remaining interlayer water molecules. Our results establish an environmentally friendly and safe approach to obtain two-dimensional (2D) bilayered vanadium oxide nanoflakes and create a pathway to constructing novel 2D heterostructures for improved performance in energy storage applications.

New insights into coal slime water in backfill materials: A fundamental study of pretreatment methods to enhance curing time

Treatment of coal slime water (CSW) faces a major challenge: an increased difficulty due to higher ash content and finer particle size with the improvement of mechanization, which could cause environmental pollution and resource waste. CSW prepared for backfilling material can avoid existing disadvantages in procedures for treating CSW. As a backfilling material, the curing rate is extremely important for preventing bleeding and supporting roofs effectively, which can be achieved by pretreatments. However, there are no reports involving CSW-based backfill materials. Therefore, pretreatment methods, including NaOH treatment (A), combined ultrasonic-NaOH (C-A), and plasma electrolysis (P), were carried out to explore the effect on curing time. The results show that: (1) pretreatments can accelerate the curing time of the backfill slurry and significantly shorten the initial curing time by half; (2) a new composite of calcium silicate and calcium metaaluminate was generated from A and C-A pretreatments, thus promoting hydration and cementation performance; (3) improved hydrophobicity of coal slime can be obtained after A and C-A, which can speed up the curing rate; and (4) active species in plasma thin coal flakes and increased interlayer spacing lead to the ability to absorb water interlayers being enhanced and the initial curing time being shortened. The results showed that the pretreatments can effectively improve the curing rate of CSW slurries due to changes in the functional groups, microstructure and chemical composition, providing technical support for the rapid and efficient preparation of backfilling materials with CSWs.

Interlayer doping of pseudocapacitive hydrated vanadium oxide via Mn2+ for high-performance aqueous zinc-ion battery

Zinc-ion batteries suffer from the structural collapse of cathode materials during charge-discharge cycling, making it difficult to achieve long-cycle performance. Interlayer doping of pseudocapacitive vanadium oxide can effectively prevent the structural collapse of cathodes. Herein, an intercalated V-based oxide Mn0.2V8O20·1.12H2O (MnVO) with interlayer water and Mn2+ is synthesized via a hydrothermal method. Mn2+ combines with oxygen in VO6 octahedron of V-based oxides layers to form the solid pillars, so that the V-based oxides provide a large interlayer spacing and prevent the structural collapse of cathode material during charge-discharge processes. This enables the Zn//MnVO battery to output a specific capacity of 306.4 mAh g−1 at 0.1 A g−1. Good cycling stability is achieved with the capacity retention rate of 86.4% after 1000 cycles at 2.0 A g−1. For comparison, the V-based oxide without Mn-doping can only maintain 70.6% after 1000 cycles. The high specific capacity and good cycle stability of MnVO cathode indicate that the Zn//MnVO battery have broad application prospects in the field of energy storage.

Water sorption isotherms and hysteresis of cement paste at moderately high temperature, up to 80 °C

The constitutive models of concrete often consider water desorption isotherms to be near-equilibrium and significantly affected by moderately high temperature, 40–80°C, typically through microstructural changes. However literature data suggest that adsorption, not desorption, is near-equilibrium and moderate temperatures do not cause microstructural changes. This work supports the latter theory, through dynamic vapor sorption experiments on cement paste at 20–80°C. Samples were pre-conditioned at 60% relative humidity and 20°C, and isotherms were measured for several humidity ranges and testing rates. The results, corroborated by classical DFT simulations, indicate that adsorption is near-equilibrium and mostly unaffected by temperature, whereas desorption is out-of-equilibrium due to the ink-bottle effect at high humidity, and interlayer water at low humidity. Starting from the second cycle, desorption at higher temperatures features a shift of the cavitation pressure and overall a smaller hysteresis. A conceptual model of pore-specific temperature-dependent hysteresis is proposed to qualitatively explain the results.