Search Results (681)

Ca²⁺-rich brines strongly destabilize bentonite-based drilling fluids by weakening hydration and increasing filter-cake permeability. In this work, raw sodium bentonite (Na-Bt) and a series of cation-exchanged bentonites (Li-, Mg-, Ca-, and K-Bt) were comparatively investigated to clarify how cation-dependent hydration characteristics and interlayer structure govern filtration behavior under saline conditions. XRD, zeta potential, TG–DTG, BET, and SEM were employed to correlate basal spacing, surface electrostatic properties, thermal/water-loss behavior, surface area and pore-structure characteristics, and filter-cake microstructure with API fluid loss. Among the examined 2 wt% brines, CaCl₂ produced the most severe deterioration and was therefore selected as the representative screening condition. Under 2 wt% CaCl₂, Li-Bt exhibited the lowest FL_API (141 mL), which was substantially lower than that of Na-Bt (265 mL), indicating the most favorable intrinsic resistance to Ca²⁺-dominated salinity. The cation-exchange analysis further showed that Li-Bt and Mg-Bt had relatively higher calculated exchange degrees than Ca-Bt and K-Bt under the present preparation conditions. Based on the 2 wt% CaCl₂ dataset, a descriptor-based relation between FL_API, hydrated ionic radius (r_h), and basal spacing (d₀₀₁) was established, and an Al-modified bentonite provided an out-of-sample verification with close agreement between predicted and measured filtration loss. Additional tests in 1–3 wt% CaCl₂ showed that although absolute fluid loss increased with brine severity, the relative ranking of the cation-exchanged bentonites remained broadly unchanged. TG–DTG, BET, and SEM results further provided complementary evidence for the structural and microstructural differences among the samples. Overall, the results demonstrate that hydration-related response, interlayer structure, and surface/pore characteristics jointly govern the filtration behavior of cation-exchanged bentonites, providing a useful basis for screening salt-tolerant clay materials for Ca²⁺-rich brines. Full article

Polyethylene terephthalate is a prominent polymer known for its mechanical properties, chemical resistance, and recyclability, and it is widely utilized across various industries. Enhancing the properties of polyethylene terephthalate (PET) through nanocomposite technology, particularly with the inclusion of nanoscale fillers, has garnered significant attention. This study investigates synthetic layered double hydroxides (LDHs), specifically MgAl LDH modified with calcium dodecylbenzene sulphonate in n-butyl alcohol (CDS) organic surfactant, as an alternative to natural clays for PET nanocomposites. Additionally, modified LDH serves a dual role as both a catalyst and a dispersive agent, promoting effective exfoliation within the PET matrix. A polymerization process was employed to ensure proportional and effective dispersion of the nanofillers, addressing the critical challenge of achieving uniform distribution. The resulting nanocomposites demonstrated superior mechanical strength, thermal stability, and barrier properties compared to traditional intercalated counterparts. Moreover, synthetic LDHs present a more sustainable solution, reducing the environmental footprint associated with natural clay mining, which includes land degradation, water pollution, energy consumption, and biodiversity loss. This research provides a promising pathway for developing high-performance, environmentally friendly PET nanocomposites, with significant implications for various industrial applications, from packaging to automotive and electronics. The findings highlight the potential of synthetic LDHs to advance material science while aligning sustainable development goals. Full article

Fine migration is widely recognized as a primary cause of production decline in unconsolidated sandstone reservoirs. Migrated fines may accumulate within pore throats and obstruct flow channels, or they may be transported into the wellbore with the produced fluids, leading to operational issues such as wellbore plugging, pump sticking, and equipment abrasion. Despite extensive studies on fine migration, the role of particle wettability has received limited attention. In this study, the mineralogical composition of formation particles was first characterized using X-ray diffraction (XRD) and quantitative clay analysis. Surface modification experiments were then conducted to investigate the effect of hexadecylamine (HDA) on particle wettability and to determine the optimal reaction conditions. Surface characterization techniques were employed to elucidate the modification mechanism. Subsequently, sand-packed tube displacement experiments were performed to evaluate the influence of wettability alteration on fine migration behavior. The underlying mechanisms were further interpreted through interfacial thermodynamic analysis. Two potential field application schemes are proposed to facilitate practical implementation in oilfield operations. The results indicate that the water contact angle of formation particles increased from 0° to 150° when treated with 0.8 wt% HDA for 24 h. Surface characterization confirms that HDA molecules were physically adsorbed onto the particle surfaces. Displacement experiments demonstrate that the permeability reduction rate decreases significantly with increasing particle hydrophobicity. Thermodynamic analysis suggests that the work of adhesion on the modified particle surface was reduced by 93.3%, thereby weakening fluid–particle interfacial coupling and suppressing fine mobilization. This study provides a wettability-based approach for mitigating permeability damage caused by fine migration in unconsolidated sandstone reservoirs. Full article

This review provides a comprehensive analysis of organically grafted clay minerals modified with organo-alkoxides, silanes, and amine-based compounds for water treatment applications. Emphasis is placed on per- and polyfluoroalkyl substances (PFAS) as representative emerging contaminants due to their persistence and environmental relevance. The review systematically examines synthesis strategies, surface functionalization mechanisms, and structure–performance relationships governing adsorption behavior. The analysis demonstrates that adsorption performance is controlled by the interplay between grafting chemistry, surface accessibility, and environmental conditions rather than adsorption capacity alone. While ion-exchange organoclays exhibit high adsorption capacities under controlled conditions, covalently grafted and polymer-modified systems provide superior stability and resistance to leaching. However, discrepancies in experimental conditions across studies limit direct comparison of reported adsorption capacities. The review identifies key challenges related to regeneration efficiency, environmental safety, and scalability, and highlights that long-term stability and compatibility with realistic water matrices are decisive factors for practical implementation. Future research should focus on standardized testing protocols, pilot-scale validation, and comprehensive environmental risk assessment. Full article

During the installation of prefabricated vertical drains (PVDs) in soft soil foundations, the smear effect induced by mandrel shoe penetration can severely damage the soil structure and reduce permeability, thereby becoming a key factor restricting foundation consolidation efficiency. Previous studies have generally neglected the smear disturbance caused by the geometry of the mandrel shoe. Although existing studies have conducted numerical and theoretical analyses on the smear effect induced by PVD installation, most of them are still based on equivalent circular simplifications and are therefore unable to characterize the anisotropic disturbance induced by a triangular mandrel shoe. To address this limitation, a three-dimensional CEL penetration model considering the real triangular geometry was established, and the traditional cavity expansion theory was directionally modified. The effects of penetration rate, geometric angular structure, and soil type of the triangular mandrel shoe on the smear zone were systematically investigated. The results show that, with increasing penetration rate, the near-field peak stress and far-field displacement increase simultaneously; from slow penetration to fast penetration, the near-field peak stress increases by approximately 42%. By quantitatively defining the critical threshold corresponding to a sharp 50% attenuation in radial displacement as the boundary of the strong smear zone, it was found that increasing the size of the mandrel shoe significantly amplifies the geometric corner effect, and the near-field disturbance range increases by about 21% compared with that of the small-sized case. The larger the size, the more pronounced the anisotropic disturbance characteristics become: the stress concentration effect and displacement splitting in the vertex direction are further enhanced, causing the disturbance range in that direction to far exceed that in the side direction. Soil properties are the key medium parameters controlling the smear zone. Owing to its relatively high stiffness index and skeleton strength, Clayey Silt shows the largest displacement range, whereas Common Clay exhibits the smallest smear zone because of its stronger structural constraint. The modified theoretical model agrees well with the CEL numerical simulation results, verifying its effectiveness under conditions that consider the geometric characteristics of the mandrel shoe. This study provides a theoretical basis and numerical support for the structural design of mandrel shoes in soft-ground PVD construction. Full article

The stabilization of soft, organic-rich soils with cement is often hindered by retarded hydration and poor long-term performance under cyclic loads. While nano-silica or sand are known modifiers, their individual efficacy in high-organic environments remains limited, and a systematic comparison of their composite effect across different soil types is lacking. This study investigates the synergistic enhancement of cement-stabilized soils using a combined nano-SiO₂ and sand composite, comparing its effectiveness in high-organic soft soil and low-organic clay. Laboratory tests, including unconfined compressive strength (UCS), cyclic loading, scanning electron microscopy (SEM), and X-ray diffraction (XRD), were conducted. Results showed a stark contrast in 28-day UCS between unmodified soft soil cement (0.13 MPa) and clay cement (1.04 MPa). The optimal composite of 3.5% nano-SiO₂ and 40% sand increased the 28-day UCS to 1.39 MPa for soft soil (a 969% improvement) and 5.51 MPa for clay (a 430% improvement), respectively. Notably, under a cyclic stress ratio (CSR) of 0.7~0.8, unmodified specimens failed after fewer than 120 load cycles, whereas the composite-modified soils withstood 20,000 cycles without failure, demonstrating exceptional fatigue resistance independent of static strength gain. Microstructural analysis revealed that the composite effectively promoted the formation of cementitious hydration products, counteracting the inhibitory effect of organic matter. This research demonstrates that the nano-silica sand composite provides a superior and more broadly applicable improvement for cement-stabilized soils across the tested organic content range (3.3–7.7% LOI) compared to single-additive approaches, significantly enhancing both mechanical strength and long-term durability. Full article

The catalytic upgrading of vacuum residue (VR) is constrained by the high cost, diffusional limitations, and rapid deactivation of conventional zeolite-based catalysts due to severe coking. Addressing this, we developed novel, low-cost, and coke-resistant catalysts utilizing naturally abundant Iraqi kaolin. A composite support comprising 80 wt.% Iraqi red kaolin and 20 wt.% white kaolin was synthesized via thermal activation at 800 °C and acid leaching. This support was subsequently impregnated with transition and rare-earth metals (Ni, Co, Ce) at 3–40 wt.% loadings, and comprehensively characterized using XRD, BET, SEM-EDX, and XPS. Catalytic performance was evaluated during VR upgrading in a fixed-bed batch reactor at 450 °C. Among the formulations, the 20 wt.% Ce-loaded catalyst (MKRW-800A@Ce20%) exhibited superior efficiency, achieving 80.15% VR conversion, 61.04% liquid yield, and minimal coke formation (3.81 g) compared to Ni and Co counterparts. This enhanced activity is attributed to synergistic effects of improved surface acidity, textural accessibility, and the Ce³⁺/Ce⁴⁺ redox couple, which promotes selective cracking while suppressing coke precursors. These findings provide new insights into the rational design of natural clay-based catalysts, establishing Ce-modified metakaolin as a viable, sustainable alternative to zeolites for industrial heavy-oil processing. Full article

The building-integrated photovoltaic (BIPV) system has advantages in construction and energy, but due to the use of flammable polymer packaging materials, it introduces complex fire safety-related challenges. Although polymer backboards are traditionally considered to be the main combustible components in photovoltaic modules, recent studies have shown that ethylene–vinyl acetate (EVA) packaging materials play a key role in the development of fires. This study investigated the fire behavior, optical properties and system-level fire effects of montmorillonite (MMT) nano-clay-modified EVA packaging materials. Through the 50 kW/m² conical calorimeter test, optical transmittance measurement and the accelerated aging test, pure EVA and EVA containing 3% MMT were evaluated, and the measured fire parameters were further incorporated into the simplified BIPV cavity fire model. The results show that MMT modification reduces the peak heat release rate of EVA by about 30%, delays the ignition time, and increases the formation of carbides, while maintaining the optical transmittance of more than 88%. At the system level, the reduction in heat release leads to a decrease in the cavity temperature and delays the ignition of adjacent insulation materials. These findings establish a direct link between material-level fire behavior and the fire performance of BIPV systems, indicating that nano-clay-modified EVA is a feasible strategy that can improve the fire safety of BIPV systems integrated into the facade without compromising optical or durability requirements. Full article

By examining a novel nanomaterial that has been modified for use in sustainable construction, this study primarily responds to the growing need for environmentally acceptable materials. The primary goal was to improve the functional and aesthetic qualities of building materials by synthesizing and characterizing environmentally friendly clay-based nanomaterials doped with cobalt pyrophosphate (Co₂P₂O₄). The authors employed contemporary experimental methods, such as scanning electron microscopy (SEM) for morphological characterisation, Fourier transform infrared spectroscopy (FT-IR) for molecular bonding assessment, and X-ray diffraction (XRD) for crystal structure research. The published findings show the doped nanomaterials’ potential durability as well as their structural integrity. An economic assessment is part of the investigation. The study is noteworthy for emphasizing the potential of cobalt-doped pyrophosphate nanoparticles as eco-friendly colour pigments for construction materials made of clay. Full article

As global oil and gas exploration extends to deep and ultra-deep formations, high-temperature and high-salt environments have become major challenges for drilling fluid viscosifiers. In this study, a hydrophobic associative polymer viscosifier, HATA, was synthesized via free-radical copolymerization using acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), sodium styrene sulfonate (SSS), and stearyl methacrylate (SMA) as monomers, and its structure was systematically characterized, while its performance and action mechanism in a 4 wt% bentonite base slurry were evaluated. The results show that the base slurry modified with 3 wt% HATA maintains an apparent viscosity retention ratio of 69.20% following 16 h of hot rolling at 180 °C, with an API filtration loss of only 7.2 mL, and its HTHP filtration loss is 73.72% lower than that of the blank bentonite slurry system; this viscosifier sustains effective viscosity and yield point of the drilling fluid system at 200 °C and in 36 wt% NaCl brine. HATA achieves viscosity enhancement and filtration control by regulating surface charges of bentonite particles, constructing stable three-dimensional networks, and stabilizing clay hydration layers, thus presenting a high-performance viscosifier formulation for high-temperature and high-salinity water-based drilling fluids with important theoretical and engineering application values. Full article

Among the naturally abundant clays in the Earth’s crust, montmorillonite (MMT), a member of the smectite group, stands out for its versatility. Its interesting properties can be further improved by chemical processing with inorganic acids and reaction temperatures close to boiling. In this study, a Brazilian polycationic MMT was treated with a low-concentration (2M) aqueous solution of hydrochloric acid at 60 and 70 °C for 5 h. The resulting modified clay was then employed in the purification of post-consumption oil (PCO), specifically soybean oil. The effect of the modification variables of the clay and also the purification parameters (time and temperature) were investigated, comparing the adsorptive and purification capacities of the modified MMT with those of the natural and a commercial clay sample. The characterization of the MMT (raw and modified) was carried out by bulk density, moisture content, plasticity limit, BET, SEM/EDS, XRD, and FTIR, whereas the characterization of the PCO, as-received and after purification, involved the analyses of apparent density, relative flow time, UV-Vis spectrophotometry, and acid value. The results show that light acid activation, especially at 70 °C, promoted a significant increase in the surface area up to 96% and the adsorption capacity of the clay. The oil purification showed good results in all tests, with the best condition being 70 °C for 24 h with the C70 clay. Thus, the satisfactory results represent an economy of time and energy. Full article

This study explores the use of bentonite to enhance biological biogas upgrading in a bubble reactor (BR) operated under mesophilic conditions (39 ± 1 °C). The experimental setup consisted of a 2 L vertically oriented BR (height-to-diameter ratio 16:1) fed with a synthetic gas mixture (60% H₂, 15% CO₂, 25% CH₄, v/v) at a gas recirculation rate of 4 L L_R⁻¹ h⁻¹. The aim was to overcome hydrogen’s low gas–liquid mass transfer rate while avoiding the operational challenges typically associated with trickle-bed reactors (TBR). Bentonite increases the density and hydrostatic pressure of the liquid medium and likely alters its rheology, thereby extending the gas–liquid contact time without requiring elevated pressures or intensive gas recirculation. Additionally, bentonite is expected to provide microstructural support that promotes the formation of biofilm-like communities, creating favorable microenvironments for hydrogenotrophic methanogens. As a clay-based additive, bentonite may also contribute to improved process stability through adsorption of inhibitory compounds, enhanced biomass retention, and pH buffering. Under mesophilic conditions, the bentonite-modified BR achieved a methane production rate of 2.17 ± 0.06 LCH₄ L_R⁻¹ d⁻¹ at a gas retention time of 1.49 h, with methane purity reaching 96.25%. In comparison, a previously reported mesophilic BR operated under an identical reactor configuration and operating conditions but without bentonite exhibited substantially lower methane production rates, supporting the beneficial role of bentonite in biological methanation. The findings highlight bentonite’s potential dual role (physical and biological) in improving process efficiency and stability in biological methanation. Full article

This study presents an analytical investigation of the dynamic behavior of concrete beams reinforced with different types of nano-clay (NC) particles and resting on a Winkler–Pasternak elastic foundation. The equivalent elastic properties of the nanocomposite were determined using an Eshelby-based homogenization model. An improved quasi-three-dimensional beam theory was applied to formulate the governing equations of motion, which were subsequently then analytically solved using Navier’s method. The analysis shows that NC reinforcement systematically elevates the natural frequencies of the beam, with the magnitude of improvement varying by particle type and concentration. Increasing the NC volume fraction to 30% leads to a significant rise in the fundamental frequency, reaching about 30% for hectorite (SHca-1) compared with the unreinforced beam, whereas montmorillonite (SWy-1) produces a more moderate increase of approximately 13%. This reinforcing effect remains consistent across different span-to-depth ratios, indicating that the influence of nano-clay content on the dynamic response is largely independent of beam slenderness. Furthermore, increasing the Winkler foundation stiffness results in an almost linear rise in frequency of approximately 18–22%, whereas the Pasternak shear parameter produces a stronger effect, reaching around 25% enhancement depending on the reinforcement type. These results indicate that incorporating nano-clay platelets can be an effective strategy for enhancing the vibrational stiffness of concrete beams and improving their dynamic performance when interacting with supporting soil media. Full article

The advancement of sustainable construction requires the development of earthen materials compatible with 3D printing (additive manufacturing), along with specified engineering standards. Many existing studies improve workability and early strength using chemical stabilizers such as cement; however, these additives increase embodied carbon and undermine sustainability objectives. Challenges remain in the formulation of an earthen mixture that satisfies both printability and structural requirements for large-scale construction. Previous earth-based mixes have reported excessive shrinkage and inadequate compressive strength. This study presents the systematic optimization of a low-carbon, 3D-printable earthen mixture using locally sourced clay-loam soil from Belén, New Mexico (NM). The soil was modified with graded concrete sand and rice hull fiber to improve printing parameters such as buildability, extrudability, and printability while meeting the NM Earthen Building Code requirements for compressive and flexural strength. Soil characterization tests (particle size distribution, consistency, optimal water content) guided iterative refinement to enhance dimensional stability and mechanical performance. A baseline 2:1 soil-to-sand ratio (max aggregate size No. 4) was established. Incorporating $2\%$ rice hull fiber and reducing max aggregate size to No. 16 (S67F2) early-age shrinkage was reduced from $12.33\%$ to $3.48\%$ ($72\%$ reduction) while maintaining a 28-day compressive strength exceeding 660 psi, more than twice the code minimum. The optimized mixture supported 24 printed layers without deformation, achieved 189 psi flexural strength (three times the code minimum), and produced a stable 2-ft-diameter dome with minimal cracking. Full article

Naturally occurring halloysite nanotubes (HNTs), a clay mineral characterized by a unique dual-charge architecture, offer a promising strategy for enhancing the performance of composite polymer electrolyte (CPE). In this work, HNTs are introduced as a low-cost, functional filler to simultaneously address two key limitations of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based CPE: low ionic conductivity and inadequate lithium-ion transference number. The negatively charged outer surface of HNTs facilitates Li⁺ transport, while the positively charged inner lumen confines anions such as TFSI⁻. Controlled acid etching (6 M HCl, 12 h) further optimizes this structure by removing surface impurities and enlarging the lumen, thereby enhancing both charge-directed ion transport pathways. The resulting HNT-modified CPE achieves a high ionic conductivity of 6.1 × 10⁻⁴ S⋅cm⁻¹ and a Li⁺ transference number of 0.73. When assembled into Li||CPE||LiFePO₄ cells, the electrolyte enables stable cycling over 300 cycles at 0.2C, retains 119.2 mAh/g at 2C, and delivers 85.7 mAh/g even at 5C, demonstrating excellent cycling stability and rate capability. This study reveals the potential of mineral-derived nanomaterials, with their inherent structural and physicochemical properties, to serve as key functional components in high-performance batteries. Full article