Search Results (312)

Phosphoric acid-doped polybenzimidazole membranes are a leading fluorine-free electrolyte platform for high-temperature proton exchange membrane fuel cells, enabling proton transport under anhydrous conditions. However, recent evidence shows that conductivity, mechanical stability, and acid retention are intrinsically coupled, preventing independent optimization of these properties. This review establishes a unified framework in which membrane performance is governed by a multidimensional design space defined by acid doping level, activation energy (E_a), hydrogen-bond network topology, and mechanical confinement. Conductivity is shown to scale with both carrier density and hopping energetics, while mechanical stability decays with increasing ADL due to acid-induced plasticization, described through a semi-empirical relationship. Analysis across molecular architectures, including molecular weight control, crosslinking, backbone modification, topological design, and free-volume engineering, demonstrates that performance emerges from a balance between transport efficiency and structural stability. Device-level benchmarking further reveals that similar conductivity values can correspond to orders-of-magnitude differences in voltage decay rate, confirming that durability is governed primarily by mechanical confinement and acid mobility rather than σ alone. A multivariate stability corridor is identified, within which phosphoric acid-doped polybenzimidazole membranes achieve σ ≈ 0.14–0.20 S·cm⁻¹ while maintaining low degradation rates under realistic high temperature proton exchange membrane conditions. Based on this framework, quantitative design rules are derived linking acid doping level, activation, topology, and mechanical properties. This work shifts membrane design from conductivity-driven optimization toward predictive structure–property–durability engineering, providing a basis for the development of next-generation HT-PEM fuel cells with sustained long-term performance. Full article

Aquaculture wastewater containing tetracycline hydrochloride (TCH) poses significant environmental problems and health risks. We investigated the adsorption of TCH onto phosphoric acid-activated corncob biochar (PCC) as a sustainable and efficient removal strategy. PCC was synthesized from cob feedstock activated by phosphoric acid under a pyrolysis temperature of 300 °C in a limited-air atmosphere. It was characterized extensively, revealing a high specific surface area (1071.75 m²/g), high porosity with total pore volume of 0.912 cm³/g, and abundant surface functional groups including phosphate, carboxylic, and amine groups. Batch adsorption experiments demonstrated an ultrahigh adsorption capacity for TCH, with a maximum theoretical capacity (Langmuir model) of 953.62 mg/g at 313 K. Its adsorption isotherms transfer from Langmuir type to Freundlich type as temperature rises, indicating a transition from monolayer to multilayer adsorption. The adsorption kinetics were governed by a synergistic mechanism involving surface adsorption and a pore-filling effect (intra-particle diffusion). Critically, the adsorption dynamics exhibit an intra-particle diffusion-controlled process at a low pH (3.0) during the final stage of adsorption. Strong hydrogen bonding led to high initial adsorption rates, and the adsorption converted to diffusion-controlled mode eventually. In contrast, at higher pH (≥7.0), electrostatic repulsion between PCC adsorbents and TCH molecules hindered intra-particle diffusion, causing the final adsorption stage to deviate from diffusion control. This work provides comprehensive insights into the pH-dependent interfacial interactions and kinetics governing TCH removal by corncob-derived, phosphoric acid-activated biochar. Full article

Background/Objectives: We evaluated whether resin infiltration treatment of demineralized enamel improves shear bond strength (SBS). Methods: Thirty permanent bovine incisor teeth were assigned randomly into three groups (n = 10 per group): control group, demineralized enamel pretreated with ICON^® resin infiltrant (Exp1 group), and demineralized enamel without pretreatment (Exp2). Demineralization was induced using a pH 4.5 solution for 21 days and was monitored using swept-source optical coherence tomography on days 0, 7, 14, and 21. The lesion depth (LD) was quantified and evaluated using ImageJ software. In the Exp1 group, ICON^® was applied prior to bracket bonding; no pretreatment was applied in the Exp2 group. In all groups, brackets were bonded using Super-Bond/Clear fluoride-free self-cure adhesive resin (4-META/MMA-TBB, Sun Medical) following Phosphoric acid (65%; Red Activator, Sun Medical). After debonding, enamel surfaces were evaluated to determine the adhesive remnant index (ARI). Results: No significant difference (p = 0.631) was noted in LD between Exp1 and Exp2 groups. The SBS values significantly differed (p < 0.05) between the control (4.1 ± 1.0 MPa) and Exp1 (5.5 ± 1.4 MPa) groups and between the Exp1 and Exp2 (3.8 ± 1.3 MPa) groups. However, SBS did not differ significantly between the control and Exp2 groups. Furthermore, ARI scores showed no significant difference between the control and Exp1 groups, whereas the Exp2 group recorded significantly elevated ARI scores relative to the control group (p = 0.0127). Conclusions: These findings suggest that resin infiltration with ICON^® may improve bracket adhesion on demineralized enamel. Full article

The combination of photochemistry with stereoselective catalysis has emerged as an effective strategy to achieve stereocontrol in light-driven transformations. Chiral phosphoric acids (CPAs) have recently attracted attention in this context due to their ability to activate substrates while providing a defined chiral environment. This minireview highlights recent developments in CPA-enabled asymmetric photochemical transformations, focusing on systems in which CPAs incorporate a chromophore on the chiral backbone or form light-absorbing CPA-substrate complexes that enable photoactivation without the presence of an external photocatalyst. The main catalytic strategies, mechanistic features, and current limitations are discussed. Full article

This work establishes a map between deposition, structure, and properties that enables the design of Ni-P coatings for advanced surface engineering applications. The coatings were electrodeposited on 316L stainless steel substrates using electrolytes of different phosphorus contents, achieved by systematically varying the phosphorous acid (H₃PO₃) concentrations. The influence of phosphorus content and intrinsic pH on elemental composition, cathodic current efficiency (CCE), thickness, microstructure, surface topography, crystalline structure, optical properties, and tribological behavior was investigated. The incorporation of phosphorus follows the H₃PO₃ concentration increase in a non-linear trend, achieving a maximum value of 22.17 at.% P at the highest bath concentration. The CCE presented an opposite trend, decreasing from approximately 96% to 40%, due to intense activity of hydrogen evolution reactions, and evidencing indirect phosphorus incorporation mechanisms. A transition from crystalline to amorphous structures was observed as the phosphorus content increased, being accompanied by grain refinement and significant roughness reduction to a minimum Sa = 8 ± 1 nm at ~15 at.% P. The optical properties, such as diffuse reflectivity and CIE Lab* color coordinates, were strongly correlated to surface roughness and microstructural evolution, demonstrating the influence of phosphorus through structural changes. Tribological behavior of the coatings revealed a complex interplay between composition, roughness, and wear mechanisms. The lower and more stable coefficients of friction were observed for high phosphorus coatings, although their durability depended on the balance between brittleness and grain refinement. The results demonstrate the combined role of phosphorus concentration and intrinsic pH changes as an effective tool for tailoring the structural, optical, and tribological properties of electrodeposited Ni-P coatings. Full article

Population growth and rapid urbanization have significantly increased construction activities and the demand for building materials. It is estimated that approximately 39% of global CO₂ emissions are associated with the construction sector, with nearly 8% directly attributed to Portland cement production. In addition to greenhouse gas emissions, the cement industry is responsible for substantial environmental impacts, including natural resource depletion, soil degradation, and air and water pollution. In this context, the development of alternative and more sustainable binder systems has become a global research priority. Geopolymers have emerged as promising materials produced through either alkaline or acid activation routes, offering advantages such as a reduced carbon footprint, high durability, and rapid strength development. Among these systems, acid-activated materials, particularly phosphate-based geopolymers, differ fundamentally from conventional alkali-activated binders in terms of reaction chemistry and binding phases. The formation of aluminum phosphate (AlPO₄) networks plays a key role in governing the mechanical performance and microstructural stability of these materials. This mini-review provides a critical overview of the fundamental principles of acid activation applied to alternative cementitious materials, with emphasis on dissolution mechanisms, polycondensation reactions, and the nature of binding phases in phosphate-based systems. Unlike previous reviews, this study integrates recent findings on reaction mechanisms with a comparative analysis between acid and alkaline activation routes, highlighting underexplored aspects of precursor reactivity and binder formation. The main types of acids used as activators, the influence of precursor chemical composition, and the conceptual differences between acid and alkaline activation are discussed. In addition, recent advances, current challenges, and future perspectives of acid activation are addressed, highlighting its potential as a viable low-carbon binder route for sustainable construction materials, with strong prospects for partially replacing Portland cement, particularly in high-performance applications requiring enhanced chemical resistance and thermal stability. Full article

Activated carbons are usually prepared from natural precursors (e.g., fruit stones or nutshells) by carbonization and activation processes carried out at 400–1000 °C. They exhibit well-developed porosity, and chemical activation introduces hydrophilic functional groups on their surface, providing excellent sorption properties. However, the high temperatures required during thermal treatment increase production costs. In this work, cost-reducing methods for preparing carbon sorbents are proposed. Carbonization of H₃PO₄ activated waste pistachio nutshells was performed using classical pyrolysis (500 or 550 °C, 30 min, N₂ atmosphere) and microwave treatment (power 1000 W, 20 min). The properties of the synthesized carbons were characterized using thermogravimetry and spectroscopic techniques including infrared (ATR), Raman, photoelectron (XPS) spectroscopies, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Porous structure parameters were determined using nitrogen adsorption experiments. The efficiency of Pb²⁺ removal from spiked ultrapure, tap and river water was evaluated by batch sorption experiments and inductively coupled plasma–mass spectrometry. The most porous carbons were those prepared at 500 and 550 °C, with specific surface areas of 910 and 256 m²/g, respectively. Surface phosphates increased the Pb²⁺ sorption efficiency to 99% from ultrapure water, at an initial concentration of 300 µg Pb²⁺/L. The material obtained with the microwave method was not fully carbonized and remained nonporous, but it also exhibited 99% Pb²⁺ uptake from ultrapure water due to the presence of oxygen-containing surface groups. The Pb²⁺ removal from spiked tap and river water reached up to 84% and 94%, respectively, at the spiking level of 300 µg Pb²⁺/L. Full article

Triazine herbicides are widely used for weed control in agricultural systems, and their occurrence in water bodies has been frequently reported worldwide. This study assessed the efficiency of a hydrochar derived from the epicarp and mesocarp of passion fruit residues for the removal of three triazine herbicides (atrazine, ametryn, and metribuzin), with the aim of developing a material suitable for application in water remediation programs. The adsorption capacity of biomass and hydrochar derived from passion fruit residues was evaluated with and without activation using 0.5 mol L⁻¹ phosphoric acid. The adsorption of herbicides was not significantly affected by pH within the range of 4 to 8. The acid hydrochar, which exhibited the highest removal capacity among the evaluated adsorbents, presented adsorption capacities of 18.05, 10.83, and 5.05 µg g⁻¹ for atrazine, ametryn, and metribuzin, respectively. These values correspond to removal efficiencies of approximately 62%, 72%, and 52% at initial concentrations of 0.33, 0.25, and 0.15 mg L⁻¹. The adsorption equilibrium time varied among the herbicides, reaching 4 h for atrazine and ametryn and 5 h for metribuzin. The adsorption dynamics between the adsorbents and adsorbates were best described by the pseudo-second-order kinetic model for ametryn and metribuzin, while atrazine had a higher correlation with the Elovich equation. The Weber–Morris model did not adequately describe the adsorption process. Among the isotherms tested, the Freundlich model provided the best fit for all three herbicides. The desorption rates of the acid hydrochar were 51%, 13%, and 83% for atrazine, ametryn, and metribuzin, respectively. Therefore, hydrochar derived from passion fruit residues represents a promising alternative for the remediation of triazine herbicides. Full article

In the present study, we evaluate the CO₂ uptake capacities of four activated carbons (ACs) obtained from olive stones. Two of the samples were generated using a chemical process utilizing phosphoric acid, thereafter undergoing carbonization in a nitrogen steam, yielding both granular and pellet forms, designated CH-ACG-410 and CH-ACP-410, respectively. The third sample, labeled CO-ACG-390, was produced by carbonization under a steam-nitrogen flow, while the fourth sample, designated PH-ACG-850, was prepared by a physical process involving water vapor at 850 °C. The carbon materials obtained in granular and pellet form were subjected to textural characterization using N₂ and CO₂ adsorption isotherms at 77 K and 273 K, respectively. Additionally, surface chemistry was analyzed using FTIR, Boehm titration, and TPD-MS. The materials were also assessed for CO₂ adsorption in a binary mixture consisting of 10% CO₂ and 90% N₂ at two temperatures, 25 and 50 °C. The results demonstrated that all prepared adsorbents exhibited competitive CO₂ capture performance, with the CH-ACP-410 sample (pellet form), showing the highest adsorption capacities, achieving approximately 4.6 wt. % at 25 °C and 2.2 wt. % at 50 °C. This superior behavior can be attributed to the conditioning methods applied to this material, which significantly influenced its textural properties and, consequently, its CO₂ adsorption capability. 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

The influence of phosphoric acid (H₃PO₄) and sodium hydroxide (NaOH) impregnation on the pyrolysis and CO₂ gasification behavior of dairy manure was evaluated using thermogravimetric analysis (TGA), with kinetic parameters assessed through iso-conversional kinetic analysis (Frieman method). H₃PO₄ pretreatment altered early decomposition by partially removing hemicellulose and promoting the formation of thermally stable, condensed char structures. The resulting chars exhibited reduced CO₂ reactivity, as evidenced by higher gasification temperatures, lower syngas yields, and elevated activation energies, indicating hindered CO₂ diffusion and slower Boudouard reaction kinetics. In contrast, NaOH pretreatment caused only minor changes in both pyrolysis and gasification behavior. A slight reduction in pyrolysis activation energy suggested Na⁺ catalyzed bond-cleavage reactions; however, this effect did not enhance CO₂ gasification reactivity. Chars produced from NaOH-treated manure exhibited slightly higher activation energies during CO₂ gasification and syngas yields, which remained close to or slightly above those of raw manure, attributed to complex mineral interactions that diminish the catalytic influence of sodium. Overall, these findings clarify how acid and base chemical pretreatments govern char evolution and carbon-CO₂ reactivity, providing a foundation for optimizing pretreatment strategies and reactor conditions for manure conversion in CO₂-based pyrolysis and gasification systems. Full article

There is an urgent demand for sustainable agricultural practices that minimize environmental impacts and reduce the reliance on synthetic pesticides and fertilizers. Endophytes represent a largely untapped resource of beneficial microorganisms with multiple potential applications as natural biocontrol agents and promoters of plant growth and development. This paper aimed at identifying new fungal strains and performing a series of preliminary in vitro screenings to evaluate their potential use for plant-growth promotion and antifungal activity. A total of 102 fungal endophytes were isolated from different plant tissues of seven wild relatives of barley (Brachypodium sylvaticum, Bromus hordeaceus, Bromus sterilis, Elymus farctus, Elymus repens, Leymus arenarius and Lolium perenne) that were sourced from 22 contrasting wild habitats. Fungal endophytes were isolated using standard culture-based methods and identified via DNA barcoding of the nrITS marker. Based on a literature search, a sub-group of endophytes were selected and evaluated for indole-3-acetic acid (IAA) synthesis, ammonia production and phosphorous (P) solubilization. From these, 15 endophytes were also tested for antifungal activity against Ramularia collo-cygni, Pyrenophora teres, and Gaeumannomyces tritici. All the endophytes were positive for ammonia production at variable rates, but no P solubilization nor IAA synthesis without L-tryptophan were observed. On the contrary, five promising isolates (2 Daldinia concentrica, Metapochonia suchlasporia, Chaetomium sp., and Ophiocordyceps sinensis) had mean pathogen growth inhibition rates above 80%, compared to the untreated negative controls. To the best of our knowledge, this study is the first published report that investigates natural antagonism against Ramularia collo-cygni and expands the list of endophytic strains with natural antagonism on the tested cereal pathogens. Results are discussed in the context of endophytes application to barley cultivation within the European regulatory framework. Full article

Phosphogypsum, the primary solid waste from the wet-process phosphoric acid industry, poses significant environmental and health risks due to large-scale stockpiling. To promote its resource utilisation, this study systematically evaluated the solidification and stabilisation performance of phosphogypsum–coal fly ash cementitious material (PAC) for Cr(VI)-contaminated soil under high-chloride conditions. Phosphogypsum reactivity was enhanced via mechanical activation and high-temperature calcination. An orthogonal experimental design was employed to analyse the effects of multiple factors—including calcination temperature and duration—on compressive strength and heavy metal leaching behaviour. Results show that PAC prepared from coal ash calcined at 600 °C for 3 h exhibits excellent mechanical properties and Cr(VI) stabilisation efficacy under high-chloride conditions, achieving a maximum compressive strength of 28.75 MPa and a Cr(VI) leaching concentration as low as 15.69 μg/L. Microstructural characterisation revealed the synergistic formation of a dense framework between C–S–H gel and calcium aluminate, conferring superior mechanical strength. Substitution and chelation mechanisms of Cl⁻ ions played a key role in enhancing corrosion resistance. This study provides theoretical support and technical guidance for the high-value utilisation of phosphogypsum-based materials in remediating saline–alkali-contaminated soils. Full article

Phosphogypsum (PG) is a byproduct of wet-process phosphoric acid production and contains soluble phosphorus (P), fluorine (F), and other harmful impurities in addition to calcium sulfate. Its acidic leachate enriched with P and F poses long-term risks to soil and surrounding water bodies. Owing to the incorporation of soluble P and F within calcium sulfate crystal interlayers, these contaminants are gradually released during storage, making it difficult to achieve an economically efficient and environmentally benign treatment of PG at an industrial scale. In this study, a low-cost and sustainable process for the effective and long-term immobilization of soluble P and F in PG was developed using sulfuric acid-activated red mud (RM), an industrial waste rich in Fe and Al. After pulping PG with water, activated RM was added, followed by pH adjustment with Ca(OH)₂, leading to the in situ formation of amorphous calcium aluminate and calcium ferrite polymers with strong adsorption affinity toward soluble P and F. The immobilization mechanism and phase evolution were systematically investigated using inductively coupled plasma optical emission spectroscopy (ICP-OES, PS-6PLASMA SPECTROVAC, BAIRD, USA), on a Rigaku Miniflex diffractometer (Rigaku Corporation, Tokyo, Japan), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), and zeta potential analysis. The leachate of PG treated with activated RM and Ca(OH)₂ contained P < 0.5 mg/L and F < 10 mg/L at pH 8.5–9.0, meeting environmental requirements (pH = 6–9, P ≤ 0.5 mg/L, F ≤ 10 mg/L). Moreover, the immobilized P and F exhibited enhanced stability during long-term stacking, indicating the formation of durable immobilization products. This study demonstrates an effective “treating waste with waste” strategy for the large-scale, environmentally safe utilization of phosphogypsum. Full article

Tetracycline is a low-cost broad-spectrum antibiotic and widely used in medicine and aquaculture. Its residues are usually released into the environment through wastewater, which may lead to the spread of antibiotic resistance genes and pose ecological risks. To address this environmental issue, a hierarchical lignin-derived porous carbon (LPHC) was synthesized using renewable biomass lignin as the precursor through a combined phosphoric acid-activated hydrothermal pretreatment. The resulting LPHC was used to effectively remove tetracycline from aqueous solutions. Characterization results indicated that LPHC had a high specific surface area (1157.25 m²·g⁻¹), a well-developed micro-mesoporous structure, and abundant surface oxygen-containing functional groups, which enhanced its interaction with target pollutants. Adsorption experiments showed that LPHC exhibited excellent adsorption performance for tetracycline, with a maximum adsorption capacity of 219.81 mg·g⁻¹. The adsorption process conformed to the Langmuir isotherm model, indicating that monolayer chemical adsorption was dominant. Mechanism analysis further confirmed that the adsorption process was controlled by multiple synergistic interactions, including pore filling, π-π electron donor–acceptor interactions, hydrogen bonding, and electrostatic attraction. This work proposes a feasible strategy to convert waste biomass into high-performance and environmentally friendly adsorbents, which provides technical feasibility for sustainable water purification technologies. Full article