Search Results (28)

Traditional cement-based foamed lightweight soils suffer from high construction costs, poor durability, and low solid waste utilization efficiency, which severely restrict their engineering application. A novel polyvinyl alcohol (PVA)-reinforced solid waste-based foamed lightweight soil is fabricated using Bayer red mud, mineral powder, and fly ash. To clarify the durability evolution mechanisms, systematic freeze–thaw cycling, long-term water immersion, and sodium sulfate erosion tests were conducted on PVA-reinforced solid waste-based, unreinforced solid waste-based, and pure cement-based specimens. The results demonstrate that the PVA-reinforced specimen achieves optimal freeze–thaw resistance with only 17.10% strength loss after 50 cycles, owing to the internal three-dimensional fiber network that restrains crack propagation and enhances matrix toughness. It also exhibits excellent long-term water immersion stability, with a mild strength increment of 4.04–10.33% after 120 days. In contrast, the CN exhibited a strength increase of 43.62%, attributed to its lower initial strength caused by incomplete hydration; however, its final strength remained between those of the other two groups. In sulfate environments, unreinforced solid waste-based specimens present superior corrosion resistance, while PVA fiber-induced interconnected pores slightly weaken sulfate erosion resistance. Microscopic analysis confirms that the generation of alunite and gypsum hydration products fundamentally causes performance discrepancies among different specimens. Different from previous studies focusing on single fiber modification or single solid waste partial replacement of cement, this study innovatively adopts a composite modification strategy of “multi-solid waste alkali-activated matrix + PVA fiber toughening”, and systematically reveals the durability evolution mechanism under multiple harsh environments. Full article

The utilization of saline–alkali lands and the competition between medicinal plants and grain crops are urgent issues. This study aimed to evaluate the effects of combined biochar and phosphogypsum application on soil physicochemical properties, microbial communities, and safflower growth, yield, and bioactive component accumulation in moderately saline–alkali soil of western Jilin, and to identify key soil factors driving these responses. To achieve this, outdoor pot experiments were conducted using safflower (Carthamus tinctorius L.), with the application of 1% biochar + 1% phosphogypsum to moderately saline–alkali soil. The results showed that the amendment significantly reduced bulk density (BD), pH, sodium adsorption ratio (SAR), total alkalinity (TA), and exchangeable sodium percentage (ESP), while increasing soil water content (SWC), soil organic matter (SOM), nitrogen, phosphorus, potassium, and beneficial ions. Soil sucrase, urease, alkaline phosphatase, and catalase activities were enhanced. Copiotrophic taxa (Pseudomonadota, Sphingomonas, Vicinamibacter) increased, whereas oligotrophic taxa (Gemmatimonadetes, Longimicrobium, Luteitalea) decreased, with stronger effects on bacteria than fungi. Safflower growth indices improved; leaf Na⁺/K⁺ ratio, superoxide radicals, and malondialdehyde decreased; and soluble protein, proline, and antioxidant enzyme activities increased. Bioactive components (hydroxysafflor yellow A, kaempferol) and yield reached 1.41%, 0.056%, and 343.23 mg/plant, representing 1.74–27.68-fold increases over moderate and mild saline–alkali soils. Correlation analysis identified SOM, total nitrogen (TN), available phosphorus (AP), BD, SWC, pH, SAR, TA, and ESP as key factors. In conclusion, co-application of 1% biochar and 1% phosphogypsum improves soil physicochemical and microbial properties, alleviates saline–alkali stress, and enhances safflower quality and yield. Full article

Opal glass, known for its mechanical strength, hygiene, and aesthetic appeal, contains fluorides that hinder recycling and often lead to landfilling. This study investigates the use of discarded opal glass for the production of sustainable alkali-activated materials (AAMs), contributing to waste valorization and reduced raw material consumption. By optimizing the activation process, dense products with high compressive strength, comparable to conventional concretes, were obtained using low-molarity alkaline solutions and low-temperature curing (60 °C). In addition, lightweight porous structures with porosity exceeding 80% were successfully produced through direct foaming and salt templating. The developed materials exhibited good chemical stability under aggressive conditions. Preliminary biological tests indicated antimicrobial activity and low toxicity, supporting their potential use in applications where hygiene and durability are important. The results highlight the versatility of mild alkali activation for transforming waste opal glass into dense and porous materials with tunable properties. Full article

Soil alkalinization constitutes a significant abiotic stress factor that severely constrains global agricultural productivity. The application of alkali-tolerant endophytes represents a promising strategy for enhancing crop resilience. This study focused on the isolation and characterization of alkali-resistant endophytic fungi derived from wild soybean (Glycine soja), aiming to elucidate their potential in promoting host plant growth and to investigate their molecular responses to alkali stress. From an initial collection of 39 wild soybean endophytic fungal isolates, 12 strains demonstrated significant alkali tolerance, as evidenced by increased mycelial dry weight under both mild and intense alkali stress. Among these, two strains, designated WDR2 and WDR5, demonstrated particularly pronounced biomass enhancement and were taxonomically identified as Fusarium verticillioides through comprehensive morphological and molecular analyses. Subsequent inoculation assays conducted on maize (Zea mays) revealed that both fungal strains significantly alleviated the inhibitory effects of alkali stress on root system architecture. Comparative evaluations in soybean indicated that the growth-promoting effects of these endophytes were host-specific and varied according to fungal strain, stress intensity, and inoculation timing. Transcriptomic profiling via RNA-Seq under mild alkali stress identified 589 and 182 differentially expressed genes (DEGs) in WDR2 and WDR5, respectively, with only 43 DEGs shared between the two strains, indicating largely strain-specific transcriptional adaptations. Functional enrichment analysis revealed several shared mechanisms underlying alkaline adaptation in both fungi species, including the maintenance of ion homeostasis, remodeling of the cell wall, and regulation of protein complex assembly and oxidative stress responses. Moreover, distinct metabolic adaptations were identified: WDR2 exhibited significant enrichment in cellular integrity and modulation of membrane-related processes, as well as amino sugar and nucleotide sugar metabolism pathways. In contrast, WDR5 was enriched in phosphate ion transport and related transporter functions, glycerol kinase activity, and glycerolipid and glutathione metabolism. In summary, this study successfully identified two novel alkali-tolerant wild soybean endophytic fungi, WDR2 and WDR5. The results provide valuable insights into their divergent molecular adaptation strategies and highlight their potential application as bio-inoculants to enhance crop productivity in alkaline soils. Full article

Solid base catalysts hold significant promise for replacing traditional homogeneous bases with green chemical processes. However, the construction of their strong basic sites typically relies on high-temperature calcination, which often leads to the collapse of the carrier structure and high energy consumption. This study proposes a novel “carrier reducibility tuning” strategy, which involves endowing the carrier with intrinsic reducibility to induce the low-temperature decomposition of alkali precursors via a redox pathway, thereby enabling the mild construction of strong basic sites. Low-valence Cr³⁺ was doped into a mesoporous zirconia framework, successfully fabricating an MCZ carrier with a mesostructure and reducible characteristics. Characterization results indicate that a significant redox interaction between the Cr³⁺ in the carrier and the supported KNO₃ occurs at 500 °C. This interaction facilitates the complete conversion of KNO₃ into highly dispersed, strongly basic K₂O species, while Cr³⁺ is predominantly oxidized to Cr⁶⁺. This activation temperature is approximately 300 °C lower than that required for the conventional thermal decomposition pathway and effectively preserves the structural integrity of the material. In the transesterification reaction for synthesizing dimethyl carbonate, the prepared catalyst exhibits superior catalytic activity, significantly outperforming classic solid bases like MgO and other reference catalysts. Full article

A novel and facile route for intercalating alkali-metal ions and ammonium ions into the layered mixed-ion compound tungsten oxychloride (WO₂Cl₂) has been developed using the iodide–triiodide redox couple as a mild redox-active reagent. Unlike traditional intercalation techniques employing highly reducing and air-sensitive reagents such as n-butyllithium, alkali triethylborohydride, and naphthalenide, the I⁻/I₃⁻ redox system operates at a moderate potential (0.536 V vs. SHE), enabling safer handling under ambient conditions without stringent inert-atmosphere requirements. This redox pair promotes the reduction of W⁶⁺ to W⁵⁺, thereby facilitating cation insertion into the van der Waal (vdW) gaps of WO₂Cl₂. This method uniquely enables ammonium ion intercalation into WO₂Cl₂, a first for this system. Intercalation was confirmed by X-ray diffraction, scanning electron microscopy (SEM/EDS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), with measured lattice expansion correlating well with Shannon ionic radii and coordinating environments. Electrical transport measurements reveal a transition from insulating WO₂Cl₂ to a semiconducting phase for K_0.5WO₂Cl₂, exhibiting a resistance drop of over four orders of magnitude. This work demonstrates the I⁻/I₃⁻ couple as a general, safe, and versatile method for layered mixed-anion materials, broadening the chemical toolkit for low-temperature, solution-based tuning of structures and properties. Full article

This research constitutes a novel experimental approach to valorizing an industrial by-product: the ‘brick’. Studies put emphasis on the importance of detailed structural characterization of brickminerals and their chemical evolution upon heating, contributing rationally to the design and development of new glass–ceramic forms that would be suitable for efficiently encapsulating radio-nuclides. The brick used is a complex material composed of metakaolinite, illite, sand and impurities such as rutile and iron oxides/hydroxides. Raw brick was first activated with a range of sodium hydroxide concentrations, and, second, cured at different temperatures from 90 °C to 1200 °C. Alkali-brick frameworks gradually decomposed during the firing, and turned into crystalline ceramic phases (analcime and leucite) embedded inside an amorphous silica-rich phase. After each heating stage, the cured-brick sample was exhaustively characterized by using a variety of advanced analytical techniques, including powder X-ray diffraction, ESEM/EDS microscopy and ²⁹Si-²⁷Al-MAS-NMR spectroscopy. Ultra-high magnetic field NMR (28.2 T) was used to distinguish and quantify Al(IV), Al(V) and Al(VI) configurations, and to better follow distinctive changes in ²⁷Al environments of brickminerals under thermal effects. Glass-ceramized brick exhibited high specific density (~2.6 g·cm⁻³), high compactness and good corrosion resistance under static, mild and aggressive conditions, attesting to its high solidification and chemical durability. Full article

Soil salinization restricts the sustainable development of global agriculture, expanding at an annual rate of approximately 1 million hectares. In China, the total area of saline–alkali land reaches 170 million hectares, of which the arable land area exceeds 50 million hectares. The arid northwest region witnesses worsening soil salinization due to arid climate and improper irrigation practices, which seriously affects the yield of crops such as spinach (Spinacia oleracea L.). As a leafy vegetable with high nutritional value and economic significance, spinach exhibits growth inhibition, leaf yellowing, and disrupted physiological metabolism under saline–alkali stress. Therefore, this study investigates the alleviating effects and mechanisms of Attapulgite Clay-g-(AA-co-AAm) Hydrogel (ACH) on spinach under salt stress (NaCl) and alkaline stress (NaHCO₃). The results show that ACH has a loose, porous structure. As the addition of Attapulgite Clay increases, the surface roughness and porosity improve while retaining organic functional groups (amide groups, carboxyl groups) and inorganic Si-O bonds, providing a structural foundation for stress mitigation. In terms of yield enhancement, ACH effectively alleviates salt–alkali stress: under severe salt stress (SS2), 0.2% ACH increased leaf area by 91% and leaf weight by 95.69%; under mild alkaline stress (AS1), 0.2% ACH increased leaf area by 46.3% and leaf weight by 46.21%; and under severe mixed salt–alkali stress (MS2), 0.4% ACH increased root weight by 49.83%. Physiologically, ACH reduced proline content (51.25% reduction under severe mixed stress) and malondialdehyde (MDA) content (68.98% reduction under severe alkaline stress) while increasing soluble sugar content (63.54% increase under mixed stress) and antioxidant enzyme activity (SOD, POD, CAT). In terms of ion regulation, ACH reduced Na⁺ accumulation in roots and leaves (61.12% reduction in roots and 36.4% reduction in leaves under severe salt stress) and maintained potassium–sodium balance. To conclude, ACH mitigates the adverse effects of salt–alkali stress by coordinately modulating spinach’s growth, physiological metabolic processes, and ion balance. This synergistic regulatory effect ultimately contributes to sustaining high yields of spinach. Full article

The recycling of glass presently poses several challenges, predominantly to the heterogeneous chemical compositions of various glass types, along with the waste glass particle size distribution, both of which critically influence the efficiency and feasibility of recycling operations. Numerous studies have elucidated the potential of converting non-recyclable glass waste into valuable materials thanks to the up-cycling strategies, including stoneware, glass wool fibres, glass foams, glass-ceramics, and geopolymers. Among the promising alternatives for improving waste valorisation of glass, alkali-activated materials (AAMs) emerge as a solution. Waste glasses can be employed both as aggregates and as precursors, with a focus on its application as the sole raw material for synthesis. This overview systematically explores the optimisation of precursor selection from a sustainability standpoint, specifically addressing the mild alkali activation process (<3 mol/L) of waste glasses. The molecular mechanisms governing the hardening process associated with this emerging class of materials are elucidated. Formulating sustainable approaches for the valorisation of glass waste is becoming increasingly critical in response to the rising quantities of non-recyclable glass and growing priority on circular economy principles. In addition, the paper highlights the innovative prospects of alkali-activated materials derived from waste glass, emphasising their emerging roles beyond conventional structural applications. Environmentally relevant applications for alkali-activated materials are reported, including the adsorption of dyes and heavy metals, immobilisation of nuclear waste, and an innovative technique for hardening as microwave-assisted processing. Full article

Water and salt stress significantly impact the accumulation of crop biomass (TB); however, the relative contributions of photosynthetic, physiological, and morphological factors remain poorly understood. This study aims to comprehensively investigate the effects of water and salt stress on crop growth physiology and identify the primary factors influencing biomass accumulation. We examined four quinoa varieties (Qingli No.1, Qingli No.8, Gongza No.4, and Black quinoa) under four salinity levels (s0: 0 mmol/L, s1: 100 mmol/L, s2: 200 mmol/L, and s3: 300 mmol/L) and two moisture levels (w1: 30% field capacity (FC), w2: 80% FC). Using principal component analysis (PCA) and correlation analysis, we constructed a random forest model (RF) and a partial least-squares path modeling (PLS-PM) framework to elucidate the effects of water and salt stress on quinoa growth physiology and clarify the adaptive mechanisms of quinoa under varying salinity conditions. The results indicate that (1) salinity has a more substantial regulatory effect on the accumulation of proline (Pro) and sodium ions (Na⁺) than water availability. Under conditions of adequate moisture (w2), the activity of antioxidant enzymes increased in response to mild salinity stress (s1). However, with escalating salinity levels, a significant decrease in enzyme activity was observed (p < 0.05). (2) PCA identified salinity as a key factor significantly influencing physiological changes in quinoa growth. The RF model indicated that, under severe salinity conditions (s3), intrinsic water-use efficiency (iWUE) emerged as a critical driver affecting biomass (TB) accumulation. (3) The PLS-PM model quantified the relative contribution rates of various factors to total biomass (TB). It revealed that, as salinity increased, the path coefficients of photosynthetic factors also rose, but their relative contribution diminished due to a corresponding reduction in the contribution of morphological factors. These findings offer a theoretical foundation and decision-making support for the integrated management of water–salt conditions in saline–alkali agricultural fields, as well as for the cultivation of salt-tolerant crops. Full article

Epichloë endophytic fungi are important microbial resources in agriculture and animal husbandry. Because of their stable symbiosis, species transmission, and positive effects on host plants, the use of endophytic fungi in grass breeding is of great significance. In this study, six inoculation methods were used, including the sterile seedling slit inoculation method, sterile seedling cut inoculation method, sterile seedling injection inoculation method, seed soaking inoculation method, seed piercing and then soaking inoculation method, and seed slit inoculation method. Spectrometry was used to construct new symbionts, and Liquid Chromatography–mass spectrometry was used to analyze the effects of endophytic fungi on the metabolism of new hosts. The physiological response of the new symbionts to salt and alkali stress was studied using a pot experiment. The results were as follows: In this study, Epichloë bromicola was successfully inoculated into Bromus inermis via the sterile seedling slit inoculation method, and new symbionts (EI) were obtained; the vaccination rate was 2.1%. Metabolites up-regulated by EI are significantly enriched in citrate cycle and ascorbate and aldarate metabolism, suggesting that the symbiosis of endophytic fungi indirectly triggers the production of reactive oxygen species (ROS) through multiple metabolic pathways. The saline–alkali stress test showed that the host antioxidant system was active after inoculation, and the total antioxidant capacity was significantly increased compared with non-symbionts (EF) under mild stress (p < 0.05), which provided important clues to reveal the complex mechanism of plant–fungus symbiosis. This study provides practical guidance and a theoretical basis for plant adaptation under climate change, health management of grass seeds, and soil improvement through endophytic fungi. Full article

The utilization of silicomanganese slag (SiMnS) as a precursor for alkali-activated materials (AAMs) is considered as an efficient approach for sustainable and eco-friendly large-scale resource utilization. However, sodium silicate solutions account for more than 50% of the production costs and carbon emissions of AAMs. In this study, AAM activators were prepared by silica-containing waste (acid leaching residue of boron mud, BM-AR) and NaOH as raw materials, and were successfully substituted for commercial sodium silicate-NaOH activators. Results indicated that the NaOH dosage had a great effect on the concentration and modulus of the activator. With the appropriate dosage of NaOH (NaOH: BM-AR = 0.4–0.7), suitable moduli of AAM activators can be produced at a wide range of solid/liquid ratios (L/S = 3–4.5) under mild conditions (80–100 °C). The compressive strength of the SiMnS AAM specimens prepared by this activator can reach 68.58 MPa, and its hydration products were mainly hydrated calcium silicate and amorphous silica–alumina gel, indicating the successful preparation of AAM. Calculation showed that the carbon emission of the AAMs prepared in this study was 12.4% and 37.6% of that of OPC and commercial water glass/NaOH-activated AAMs, and the cost was only 67.14% and 60.78% of them. The process achieves the use of waste materials to replace commercial activators, and is expected to be extended to a variety of AAMs raw materials and silica-containing waste. This makes it a highly promising alternative method for the production of AAMs, particularly the ‘just add water’ AAMs. Full article

Rice husk ash (RHA), an agricultural waste byproduct, has already been tested as a component in geopolymeric binders, typically as part of the precursor solid mix, alongside materials like fly ash (FA), slag, and cement. This study presents a novel approach where RHA is employed to create a solid activator, aimed at entirely replacing commercial sodium silicates. The synthesis process involves mixing RHA, NaOH (NH), and water by applying a SiO₂/Na₂O molar ratio equal to 1, followed by mild thermal treatment at 150 °C for 1 h, resulting in the production of a solid powder characterized by high Na₂SiO₃ content (60–76%). Additionally, microwave treatment (SiO₂/Na₂O = 1, 460 W for 5 min) increases the environmental and economical sustainability of alkali silicates production from RHA since this processing is 12 times faster than conventional thermal treatment reducing at the same time the final product’s embodied energy. The efficacy of this new material as a sole solid activator for the geopolymerization of Greek FA is investigated through various techniques (XRD, FTIR, SEM). One-part geopolymers prepared with RHA-based solid activators demonstrated mechanical performance comparable to those prepared with commercial products (~62 MPa at 7 days). This research contributes to the advancement of sustainable construction practices emphasizing the importance of local materials and reduced environmental impact in achieving long-term sustainability goals. Full article

Cotton stalks are residual biomass resulting from cotton bud harvesting, and they are composed primarily of lignocellulosic material. This material could be a source of functional polyphenols. To investigate this prospect, this study was undertaken with the view to examining whether an ethanol-based organosolv treatment could be suitable for producing extracts enriched in polyphenolic compounds. To this end, alkali catalysis was employed, and two catalysts, sodium hydroxide and sodium carbonate, were tested. The initial approach based on treatment severity showed that both catalysts may be equally effective in the recovery of polyphenols, yet in most cases studied, no clear trend between treatment severity and total polyphenol yield was recorded. The following study, based on response surface methodology, provided optimized conditions for both treatments, sodium hydroxide and sodium carbonate, where the recommended catalyst concentrations were 0.67 and 4%, respectively. Under a constant temperature of 90 °C and residence time of 300 min, the treatments with sodium hydroxide and sodium carbonate afforded total polyphenol yields of 18.4 ± 1 and 15.6 ± 1.9 mg CAE g⁻¹ DM, respectively, which showed no significant statistical difference (p > 0.05). However, high-performance liquid chromatography analyses revealed that the sodium carbonate-catalyzed treatment produced extract particularly enriched in two hydroxycinnamate derivatives, ferulic and p-coumaric acid. This extract also exhibited increased antioxidant activity. The outcome of this study strongly suggests cotton stalks as a bioresource of functional substances, while mild alkali-catalyzed ethanol organosolv treatment appears to be a very promising technique for effectively delivering hydroxycinnamate-enriched extracts. Full article

Lewis acid zeolites play an important role in industrially important green reactions closely related to fine chemical and biomass conversion. Titanium-doped TS-1 zeolite is a milestone Lewis acid zeolite widely used in industrially significant green oxidation processes with hydrogen peroxide as an oxidant under mild conditions. TS-1 zeolites are normally synthesized in basic conditions under hydrothermal treatment. Up to now, there has still been no success in synthesizing active TS-1 Lewis acid zeolites by using inorganic alkali, e.g., NaOH or KOH as base, which is cheaper and more stable compared to the quaternary ammonium hydroxide or organic amines used in traditional synthesis. Here, an inorganic base of NaOH was employed in synthesizing active TS-1 zeolites for the first time. The crucial factor was the control of adverse effects of sodium cations on the incorporation of active titanium cations. Higher catalytic activity was achieved by further reducing the size of the TS-1 crystal by using the seed-added strategy, which uses the catalytic activity of a commercial catalyst, the production cost being much lower than commercial TS-1 catalysts, indicating great commercial potential and the possibility of preparing other cheap Lewis acid catalysts by using inorganic alkali. Full article