Search Results (950)

Magnesium phosphate cement (MPC) is a type of rapid-hardening inorganic cementitious material, which has important application value in rapid road repair, solidification of hazardous and radioactive waste, and other fields. However, it suffers from excessively fast setting and hardening and a short working time retention, which severely restrict its engineering application. Therefore, the development of high-efficiency set retarders is of great significance for optimizing MPC performance, enhancing its construction workability, and expanding its application scope. In this study, the effect of sodium polyacrylate (PAAS) on the setting and hardening of magnesium potassium phosphate cement (MKPC) was investigated by testing the setting time and fluidity at a low water-to-solid ratio (W/S = 0.18). Through pH and electrical conductivity measurements, combined with XRD, TG/DTG, and FTIR characterizations, we elucidated the retarding mechanism of PAAS on MKPC using a high water-to-solid ratio (W/S = 10). The results indicate that the setting time of MKPC is positively correlated with the PAAS dosage, whereas the fluidity and compressive strength exhibited a negative correlation with the PAAS dosage. Additionally, PAAS reduces the total heat release and the heat release rate of MKPC. The addition of PAAS increased the pH of the suspension, thereby reducing the solubility of MgO, but did not inhibit the dissolution of KH₂PO₄  The carboxylate groups in PAAS chemically reacted with Mg²⁺ on the surface of MgO to form magnesium carboxylate complexes (Mg-PAA), which remained as precipitates in the MKPC suspension system, thus reducing the amount of available Mg²⁺ participating in the hydration reaction. Furthermore, PAAS had no effect on the final precipitate composition at the end of hydration, which was composed of MgKPO₄·6H₂O  and Mg₃(PO₄)₂·22H₂O  in all cases. Full article

In this study, a novel layered WO₃@Co₃O₄ composite electrode was synthesized via a controlled electrodeposition method employing different surfactants to finely tune its nanostructure. The incorporation of polyacrylic acid (PAA) surfactant yielded an optimized P-W@Co electrode with a hierarchical porous morphology and reduced crystallite size, markedly enhancing electroactive site exposure and electron transport. Structural analyses confirmed the amorphous nature of WO₃ and crystalline spinel Co₃O₄ phases forming an integrated composite architecture. Electrochemical characterizations in a three-electrode system revealed that the P-W@Co electrode exhibited superior pseudocapacitive behavior, with an areal capacitance of 11.70 F/cm² at 20 mA/cm² and excellent rate capability, retaining 80% capacitance at 40 mA/cm². Kinetic studies demonstrated enhanced diffusion-controlled charge storage attributed to improved ion accessibility and charge transfer kinetics. To evaluate practical feasibility, asymmetric supercapacitor devices incorporating P-W@Co as the positive electrode coupled with activated carbon as the negative electrode were fabricated. This device showcased a widened operational voltage (1.5 V), outstanding areal capacitance (211 mF/cm²), and energy density (0.066 mWh/cm²). Importantly, the device exhibited exceptional cycling stability, retaining 81.8% capacitance after 7000 cycles. This work signifies a major advancement in surfactant-mediated design of WO₃@Co₃O₄ layered electrodes for scalable, high-performance supercapacitor applications, combining structural stability, enhanced conductivity, and multifaceted charge storage mechanisms. Full article

Poor aqueous solubility remains a major limitation for the oral delivery of many active pharmaceutical ingredients (APIs). Deep eutectic solvents (DESs) exhibit remarkable drug-solubilization capacity, yet rapid precipitation upon aqueous dilution can compromise their ability to sustain supersaturation. This study investigates polymer-embedded DES (PEDES) systems as liquid supersaturating drug delivery platforms in which hydration and polymer chemistry jointly govern thermodynamic solubilization and kinetic stabilization. A choline chloride/DL-malic acid DES was prepared with 5% or 15% (w/w) water and combined with polyvinylpyrrolidone (PVP) or polyacrylic acid (PAA). Griseofulvin (GRF) was used as a precipitation-prone model drug. Structural characterization (ATR-FTIR, ¹H-NMR), equilibrium solubility measurements, storage stability studies, and non-sink dissolution testing were conducted to elucidate formulation behavior. The DES systems enhanced GRF solubility by up to ~59-fold relative to phosphate buffer (PBS, pH 6.8). Polymer incorporation produced hydration- and concentration-dependent effects. These results suggest the presence of competitive or cooperative interaction regimes. At 5% water, PEDES formulations failed to prevent recrystallization and showed limited supersaturation maintenance. In contrast, PEDES systems containing 15% water exhibited improved stability, with the formulation containing 4% PAA sustaining elevated drug concentrations for 120 min under non-sink conditions. Low-frequency solution-state ¹H-NMR confirmed stronger GRF–PAA interactions relative to PVP, supporting the role of polymer–drug association in supersaturation stabilization. These findings demonstrate that PEDES performance emerges from a hydration-dependent balance between solvent structuring and drug–polymer interactions, highlighting hydration and polymer functionality as key parameters for the rational design of liquid supersaturating systems. Full article

Ammonia is one of the most important and widely produced basic chemicals worldwide. However, this highly toxic gas is also produced in livestock farming and a variety of industrial processes, posing a potential threat to humans, animals and the environment and also significantly contributing to the formation of persistent particulate matter. The aim of this project was to develop a textile-based adsorber material and to demonstrate a suitable test system for purifying ammonia-contaminated air from production-related sources using the example of pig fattening and PCB production. This aim was achieved through the wash-resistant immobilization of polyacrylic acid on a polyester needle felt at laboratory, pilot plant and industrial scales. In addition, various system concepts have been developed in which air or phosphoric acid can flow through the adsorber textile, whereby in the latter case, the phosphoric acid is both actively involved in ammonia adsorption and also serves to elute the bound ammonia, enabling continuous and low-maintenance operation. Concurrently, the high-quality inorganic fertilizer ammonium phosphate is produced. In summary, an efficient alternative to existing solutions for ammonia minimization has been developed, which is fundamentally characterized by its universal applicability in different load scenarios, including small mobile systems in production facilities with local ammonia pollution, in addition to scenarios for large-scale agricultural operations. Full article

Using disposable screen-printed electrodes faces major challenges when attempting to monitor a continuous process, especially in systems where there is pronounced adsorption, fouling, degradation, or in cases of irreversible electrochemical reactions. Methylene Blue (MB) exhibits some therapeutic properties and is commonly used as a redox reporter in DNA sensors, but is also considered a toxic pollutant in aquatic systems. MB demonstrates strong adsorption to carbon materials, which prevents its electroanalytical determination in multiple measurements with a single electrode. Our work details direct electrochemical determination of MB with only the native carbon screen-printed working electrode as sensing material and optimization of the analytical method. In batch mode, we significantly improved sensitivity and interelectrode reproducibility by introducing a prepolarization step, but successive measurements in lower concentrations were not feasible due to strong adsorption. A fully customizable, modular flow cell was 3D printed to allow in operando replacement of the planar screen-printed three-electrode system after measurement during continuous flow. As confirmed by mechanical properties testing, the rigid polyacrylate upper section of the flow cell provides structural stability, combined with a flexible TPU lower section which enables effortless sensor hot swapping and effective sealing during flow. With an optimized hot swapping flow detection method, MB was detected via square wave voltammetry with a sensitivity of 65.59 µA/µM and a calculated LOD of 7.75 nM, which outperforms similar systems from the literature. We envisage this approach can be integrated into low-cost continuous environmental monitoring systems or in-line quality control, especially in flow chemistry synthesis. Full article

This work investigates the reactive crystallization of lithium carbonate (Li₂CO₃) by rapidly mixing concentrated aqueous solutions of LiCl (3.0–4.0 M) and Na₂CO₃ (1.5–2.0 M) at 65 °C, using focused beam reflectance measurement (FBRM) for online, in situ monitoring. The effect of low concentrations of poly(acrylic acid) (PAA), sodium hexametaphosphate (SHMP), and sodium tripolyphosphate (STPP) on nucleation and growth dynamics was systematically analyzed. The results show that the process is dominated by an intense initial supersaturation pulse, which governs early nucleation and subsequent population restructuring through growth and aggregation. Additives significantly modify the nucleation-growth coupling: PAA exhibits concentration- and time-dependent behavior, suppressing the detectable fines population and promoting consolidation into coarse fractions under high supersaturation; SHMP acts as a strong kinetic inhibitor, markedly reducing nucleation and, to a greater extent, growth; while STPP exhibits an intermediate, dose-dependent response, maintaining nucleation but limiting effective growth at high concentrations. Scanning electron microscopy observations confirm the formation of spherulitic Li₂CO₃ aggregates in all cases, with compactness and radial organization dependent on the additive. These results demonstrate that targeted additive selection allows for precise control of population dynamics and solid properties in reactive crystallization systems, within the investigated high-supersaturation concentration window, with useful mechanistic guidance for the design and control of Li₂CO₃ precipitation processes. Full article

The textile industry is seeking alternative coloration methods to comply with the global demands for eco-friendly and non-hazardous dyes, as synthetic colorants are costly and substantially toxic in nature, having deleterious effects on the environment as well as ecosystems. This research aimed to develop a printed functional cotton fabric using a new bio-based pigment from acacia wood waste (Acacia nilotica) charcoal. Acacia charcoal was ground into fine powder and added into pigment paste with polyacrylic binder and screen printed on cotton fabric, followed by drying and curing. The printed fabric was tested for color strength (K/S), colorfastness, flame resistance, contact angle (for checking the hydrophobicity), thermal insulation, and tensile strength following standard testing protocols. Using different charcoal concentrations (in the range of 0.5–5%), the samples presented light to dark gray color and the K/S value gradually increased from 1.85 (0.5%) to 12.31 (5%), demonstrating stronger color depth. The printed fabrics revealed good results in terms of color fastness ratings (washing 3–5, dry rubbing 3–5, wet rubbing 3–5), satisfactory flame resistance, good thermal insulation, and excellent hydrophobicity. The obtained results contribute to sustainable and durable textile development for achieving better performance. Full article

The water absorption of polyvinyl alcohol (PVA) freeze-dried porous polymer is critically influenced by its molecular structure. The hydrolysis degree and molecular weight of PVA were identified as key factors in the design of freeze-dried porous polymers for enhanced structure and stability. The complex interactions between water absorption and structural characteristics in freeze-dried porous polymers were investigated. This was achieved by varying the degree of hydrolysis and molecular weight of the PVA. The results indicate that as the degree of PVA hydrolysis increases, the water absorption and structural stability of the freeze-dried porous polymer are significantly improved. These performance enhancements are attributed to the synergistic effects of hydrogen bonding interactions and molecular chain entanglement between PVA-sodium polyacrylate (PAAS) chains and PVA-PVA chains, collectively forming a denser and more stable three-dimensional network structure. Additionally, the incorporation of high molecular weight PVA significantly reduced the water absorption capacity of the freeze-dried porous polymer. However, freeze-dried porous polymers prepared using low molecular weight polyvinyl alcohol exhibit poor structural stability. Specifically, when the PVA molecular weight is 7200-8100, and the degree of hydrolysis is 99%, the freeze-dried porous polymer exhibits a maximum porosity of 92%, a density of 82 mg/cm³, and a water absorption capacity of 38 g/g. Overall, this work provides the theoretical basis and technical support for its application in absorbent pads. Full article

Microplastic (MP) pollution poses a significant and emerging threat to global marine ecosystems; however, regional data for the Caribbean remain limited. This study presents a spatial and temporal characterization of MPs in surface and mid-waters of the Colombian Caribbean (Atlántico and Magdalena departments), which were analyzed as independent compartments due to methodological differences in sampling strategies. Sixteen sampling stations were established across two anthropogenic influence zones: Zone 1 (nearshore/bather zone) and Zone 2 (offshore). MPs were quantified and characterized according to shape, color, size, and polymer composition using attenuated total reflectance Fourier transform infrared microspectroscopy (µATR-FTIR) and multivariate techniques. MPs were detected in 100% of samples. Surface water MP abundance was higher in Magdalena (4.5 MPs m⁻³) than in Atlántico (1.7 MPs m⁻³). Mid-water MP concentrations reached maximum values during the high rainfall season in Atlántico, reflecting localized hydrological and anthropogenic influences rather than vertical gradients. Higher concentrations were generally observed in the nearshore Zone 1 compared to offshore Zone 2, although these differences were not consistently statistically significant. Fibers and fragments were the predominant shapes, and synthetic–natural polymer blends, polyethylene terephthalate (PET), polypropylene (PP), and polyacrylic acid (PAA) were the most prevalent. Generalized Additive Models (GAM) indicated that strong fluvial inputs and proximity to urban and riverine sources were factors driving MP distribution. Additionally, the detection of polymers reported in the literature as rare and high-risk, such as acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), styrene–ethylene–butylene–styrene (SEBS), and polyvinyl stearate (PVS), highlights the complexity of MP sources in the region. Overall, these results provide the first spatial and temporal characterization of MPs in the surface and mid-water of the Colombian Caribbean and identify critical contamination hotspots that warrant targeted mitigation strategies. Full article

The application of MXene–polymer composites to wearable and implantable medical devices requires the development of hydrophilic and biocompatible MXene–polymer hydrogel composites with high electromechanical response, flexibility, and durability. Here, we formulate low weight percentage MXene–hydrogel copolymer inks enabling the direct light processing (DLP) of Ti₃C₂T_x MXene–polyvinyl alcohol (PVA)–polyacrylic acid (PAA)–hydrogel composites. The low wt% MXene–PVA–PAA composites demonstrate high biocompatibility, mechanical flexibility, high sensitivity and high precision for sensing acute bending angles. The sub-millidegree angle resolution of these electromechanical sensors demonstrates their suitability for applications such as the highly precise tracking of joint movements. In addition, the synthesized MXene membranes show promise for applications in osmotic energy conversion, with a harvested electric power density of 6.79 Wm⁻². Full article

The objective of this in vitro study was to investigate the effects of dentin pretreatment protocols and thermocycling on the shear bond strength (SBS) of a self-adhesive resin cement (Maxcem elite chroma) on dentin. A total of 168 extracted human third molars were randomly divided into four main groups according to dentin pretreatment: no treatment, 10% polyacrylic acid, Optibond universal, and Scotchbond universal plus. Half of these were subjected to thermocycling (5000 cycles; 5–55 °C). Composite resin rods were bonded using the self-adhesive resin cement, and SBS was measured with a universal testing machine. Two-way ANOVA showed that dentin pretreatment and thermocycling significantly affected SBS, with significant interaction between factors (p < 0.001). The highest SBS was observed in the Optibond universal group (18.71 ± 0.43 MPa), while the lowest SBS occurred in the 10% polyacrylic acid-treated group after thermocycling (2.69 ± 0.39 MPa). Thermocycling significantly reduced SBS in all groups. These results indicate that pretreatment with a compatible universal adhesive improves bond durability, whereas 10% polyacrylic acid pretreatment adversely affects bonding performance. Full article

The extreme persistence of per- and polyfluoroalkyl substances (PFAS), exemplified by perfluorooctanoic acid (PFOA), demands remediation technologies that surpass conventional approaches. This study introduces a novel closed-loop adsorption–regeneration–distillation–plasma (ARDP) process designed for high-efficiency PFOA removal with low energy and chemical consumption. Comparative evaluation of anion-exchange resins identified D311 (macroporous methyl polyacrylate) as the optimal adsorbent. In batch experiments with an initial PFOA concentration of 100 mg/L, D311 achieved an adsorption capacity of ~20 mg/g, exhibited rapid kinetics, and achieved high regeneration efficiency (up to 100% under optimized conditions) via a methanol–NaCl solution. Distillation of the spent regenerant recovered approximately 80% of methanol while simultaneously concentrating PFOA for subsequent destruction, accomplished by utilizing waste heat from the plasma system, without the need for additional thermal energy input. Subsequent dielectric barrier discharge (DBD) plasma treatment of the residue achieved 100% PFOA degradation and up to 69% defluorination. The ARDP process proves to be a highly sustainable strategy, characterized by a low specific energy input (4.15 kWh/m³) and minimized secondary waste, making it a promising approach for practical PFAS remediation. Full article

To investigate the improvement effect of sodium polyacrylate on the shear strength of silty clay, this study explores the curing treatment of silty clay using sodium polyacrylate. Liquid-plastic limit tests and triaxial shear tests were conducted to examine the impact of sodium polyacrylate on the liquid-plastic limits and shear strength of silty clay, as well as to determine the optimal dosage. Additionally, low-field nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) tests were performed to further reveal the micro-mechanism of sodium polyacrylate’s action. The results show that as the sodium polyacrylate content increases, the liquid-plastic limits of silty clay increase significantly. Compared to untreated samples, when the sodium polyacrylate content is 7%, the liquid limit and plastic limit increase by 132.7% and 167.3%, respectively. Meanwhile, the cohesion of the modified samples increases with the sodium polyacrylate content, while the internal friction angle first increases and then decreases. When the sodium polyacrylate content rises from 0% to 7%, the cohesion and internal friction angles of the modified samples increase by 522.9% and 70.6%, respectively. Through comprehensive analysis of the experimental results, it was determined that the optimal dosage of sodium polyacrylate is 5%. Microstructural analysis indicates that sodium polyacrylate interacts with soil particles through hydrogen bonding and ion bridging, filling the pores between particles and encapsulating their surfaces. This improves the pore structure of the soil and enhances the bonding strength between particles. This study provides a theoretical basis for the application of sodium polyacrylate in soft soil improvement. Full article

Efficient oil-water separation remains a major challenge in oily wastewater treatment, highlighting the need for advanced materials that combine superwettability, structural durability, and long-term recyclability. Here, we develop a hierarchical ZOMO-PAA@CuC₂O₄ NR@CM membrane via sequential chemical oxidation, oxalic acid etching, and spray-coating of ε-Keggin-type Na-ZnM ZOMO nanoparticles within a polyacrylic acid (PAA) matrix. The resulting architecture couples CuC₂O₄ nanorods with hydrophilic ZOMO-PAA coatings to achieve superhydrophilicity and underwater superoleophobicity. Structural characterization confirmed uniform nanoparticle dispersion, high crystallinity, and robust framework integrity. The membrane exhibits ultrafast water spreading (0°), underwater oil contact angles above 150°, and sliding angles as low as 4°, enabling broad-spectrum oil repellence, antifouling, and self-cleaning. The as-prepared membrane efficiently separates both surfactant-free and surfactant-stabilized emulsions, including aliphatic and aromatic oils stabilized by cationic, anionic, and non-ionic surfactants, with high water fluxes (1695–2675 L·m⁻²·h⁻¹ and ~900 L·m⁻²·h⁻¹, respectively) and separation efficiencies above 99.1%. The membrane further demonstrates chemical stability under acidic, alkaline, and saline conditions, alongside consistent oil–water separation behavior across multiple cycles. These findings establish ZOMO-PAA@CuC₂O₄ NR@CM as a robust and scalable platform for advanced oily wastewater treatment. Full article

This study investigates the utilization of a sodium polyacrylate (SP)/CaCl₂ composite as an adsorbent in a low-grade-heat desalination configuration designed for Saudi Arabian conditions. A dynamic system model was developed and validated for an adsorption desalination (AD) cycle integrated with a dual-ejector and a humidification–dehumidification (HDH) unit. Two operating modes were evaluated, including a production-oriented configuration that applies internal evaporator–condenser heat recovery (HR) when no cooling effect is required. Without HR, the AD–EJ–HDH system achieves 41–56 m³/ton·day SDWP and 2.6–2.9 GOR, with a freshwater cost of 1.8–2.4 $/m³ under solar driving and 0.70–0.90 $/m³ under waste heat. With HR, performance increases to SDWP 95–155 m³/ton·day and GOR 2.9–3.1, while costs decrease to about 1.34 $/m³ (solar) and 0.38 $/m³ (waste heat) in June. The SP/CaCl₂ composite yields about 85% higher freshwater production than silica gel in the same system, highlighting the material’s potential for high-output hybrid adsorption desalination in hot-climate regions. Full article