Search Results (2,070)

Afforestation is critical for enhancing soil quality and optimizing land use in coastal saline–alkali regions. However, the dynamics of soil quality and ecosystem multifunctionality (EMF) during afforestation, as well as their coupling relationships, remain poorly understood. In this study, the effects of four stand ages (6, 12, 22, and 36 years) of a leguminous tree species (Robinia pseudoacacia) on the soil quality index (SQI), enzymatic stoichiometry, and soil ecosystem multifunctionality (EMF) were investigated in coastal saline–alkaline lands of the Yellow River Delta, China. Results showed that compared to non-afforestation, afforestation increased the SQI by 81%, 74%, 146%, and 184% in the 6-, 12-, 22-, and 36-year-old stands, respectively. Concurrently, afforestation increased the activities of the carbon acquisition (C_acq), nitrogen acquisition (N_acq), and phosphorus acquisition (P_acq) enzymes and alleviated microbial N limitation. Afforestation increased the soil EMF by 182%, 243%, 263%, and 295% in the 6-, 12-, 22-, and 36-year-old stands, respectively. The SQI was significantly positively correlated with soil EMF, regardless of afforestation age. Soil salinity, SOC, TN, and TP were the best predictors of soil EMF. The afforestation of Robinia pseudoacacia improved the soil quality and stimulated enzyme activity, thereby increasing the soil EMF. Our findings provide a theoretical foundation for the sustainable management of stands in coastal saline–alkali lands. Full article

Drought and salt stresses are critical environmental constraints affecting plant growth and development, and microorganisms can enhance plant tolerance to these abiotic stresses through complex mechanisms. This review systematically synthesizes the core mechanisms by which microorganisms regulate plant physiological and biochemical processes under such stresses, specifically including the following: (1) regulating the perception and transduction of abiotic stress signals to enhance plant adaptive responses; (2) boosting gene expression and protein synthesis for overall plant metabolic regulation; (3) activating the antioxidant system to strengthen plant tolerance; (4) modulating plant hormone levels to stimulate growth in response to adversity; (5) enhancing plant nutrition and absorption to improve resilience; (6) optimizing the photosynthesis system to promote the synthesis of essential substances, safeguarding plant growth and development amidst adversity. Finally, the application of microbial inoculants in saline–alkali soil improvement and crop cultivation in arid areas and prospective research directions are discussed. Full article

This study systematically investigates the influence of CaO reactivity on the fresh-state rheological behavior and long-term mechanical performance of GGBFS binders. Four types of industrial quicklime, characterized by distinct slaking kinetics (t_max ranging from 9 to 36 min), were used as primary activators, with dosages of 5%, 9%, and 13% by binder mass. The results reveal that CaO reactivity significantly affects water demand, yield stress, and setting times, with extremely reactive quicklime inducing the greatest increases in water demand and plastic viscosity. Setting behavior was strongly dependent on both activator content and curing environment, with less reactive limes failing to induce setting under water immersion. Compressive strength development was largely unaffected by CaO reactivity up to 120 days, but at 720 days, higher CaO contents (≥9%) contributed to significant strength gains, likely due to carbonation-induced matrix densification. These findings demonstrate that controlling CaO reactivity and dosage is essential for optimizing the workability and durability of CaO-activated slag binders. Full article

Soil alkalinity severely restricts the cultivation of Lupinus angustifolius, a valuable legume. Wild soybean (Glycine soja) is a leguminous plant with extremely strong alkaline resistance (pH 8.5). Transferring the alkali-tolerant genes from wild soybeans into lupinus can effectively enhance the alkali tolerance. In this study, we combined transcriptome profiling and genetic transformation to elucidate the molecular basis of alkaline stress response in lupinus. RNA-seq analysis of root tips under acid (HCl, pH 4.0) and alkali (NaHCO₃, pH 8.5) stress revealed 104,353 annotated unigenes, with differential expression patterns highlighting enrichment in cellular component, binding, and catalytic activity categories. KEGG pathway analysis indicated that early responses involved ribosome-related pathways, while later stages activated plant hormone signaling and MAPK pathways. Notably, no homeodomain-leucine zipper (HD-Zip) family genes were identified in the lupinus genome. Therefore, we transferred GsHZ4, an alkali-resistant HD-Zip transcription factor from wild soybean into lupinus hairy roots via Agrobacterium rhizogenes-mediated transformation. Overexpression of GsHZ4 significantly enhanced antioxidant enzyme activities (CAT, POD, and SOD) and reduced malondialdehyde content under NaHCO₃ stress. Furthermore, the promoter of GsHZ4 expression was strongly induced by indole-3-acetic acid (IAA). Key alkali-responsive genes (LaKIN, LaMYB34, LaDnaJ1, LaDnaJ20, LaNAC22, and LaNAC35) were upregulated in transgenic lines, suggesting that GsHZ4 integrates into the endogenous stress-regulation network. Our findings demonstrate that heterologous expression of GsHZ4 can enhance alkaline tolerance of lupinus, providing a novel strategy for breeding stress-resistant varieties and expanding lupinus cultivation in saline–alkali soils. Full article

In recent years, research in the field of the sustainable production of refractory ceramics has become topical. Significant attention has been paid to the use of secondary raw materials for obtaining high-quality materials. The purpose of the current study was to develop new high-temperature porous materials based on the magnesium sulfate-refractory clay–chamotte–aluminum system using environmentally friendly raw components. To synthesize porous refractories, rice husk and the by-products of its thermal processing were used as substitutes for ingredients usually introduced into the composition of high-temperature materials. Ground rice husk was used as both a burnout additive and a silica source. It was added to the mixture instead of chamotte. An organic condensate from rice husk pyrolysis was used as a binder. A sodium silicate solution, after activating pyrolyzed rice husk with alkali, was also tested as a binder. These liquid ingredients served as replacements for lignosulfonate and liquid glass. The new raw material components and the porous refractories obtained with their use were studied using methods of chemical analysis, XRD, GC-MS, TA, SEM, and EDS. Standard methods for studying the properties of refractories were used to evaluate the physicomechanical and thermal characteristics of the experimental materials. The sample with the maximum content of rice husk (14.4 wt.%) and organic condensate from its pyrolysis (10.5 wt.%) demonstrated promising properties as a light porous refractory: an apparent porosity of 44%, a volumetric weight of 1.1 g·cm⁻³, compressive strength of 2.1 MPa, tensile strength in bending of 4.5 MPa, bond strength of 0.01 MPa, thermal shock resistance of 155 thermal cycles, and thermal conductivity of 0.05 W (m·K)⁻¹. It can be used as a prospective thermal insulating material. Full article

This study investigates the valorization of municipal solid waste incineration (MSWI) residues—specifically bottom ash with slag (BA + S) and fly ash (FA)—through alkaline activation in geopolymer and cementitious systems. The research demonstrates that alkali activation significantly improves mechanical properties, with compressive strengths up to 45.9 MPa for cement mortars and 33.2 MPa for geopolymers. A key innovation includes the quantification of hydrogen gas release during activation, with up to 72.5 dm³/kg H₂ from BA + S, offering insights into binder design and potential green hydrogen recovery. Environmental leachability assessments confirmed that activated BA + S immobilizes heavy metals effectively, although FA showed higher barium and lead leaching. Morphological analysis (SEM, granulometry) revealed microstructural changes enhancing reactivity. Additionally, a practical swelling test is proposed for early detection of expansion risk. The findings contribute to the development of sustainable, high-performance binders from waste, with implications for circular economy and energy valorization strategies. Full article

To address the challenges associated with Ordinary Portland Cement (OPC) in mine backfilling, including high costs, the large carbon footprint, and performance limitations, a novel cementitious powder (CP) based on alkali-activated slag is developed in this work. The mechanical performance and microstructural strengthening mechanism of this CP as a substitute for OPC in cemented copper tailing backfill (CTB) were systematically evaluated. The effects of key parameters, including the solid content (SC), tailing-to-cement ratio (TCR), and curing age (CA), were investigated using uniaxial compressive strength (UCS) tests and scanning electron microscopy (SEM) analysis. The results demonstrate that the novel binder exhibits superior performance. At a solid content of 73%, the CTB prepared with CP at a TCR of 10 or 12 achieved a compressive strength comparable to or exceeding that of the OPC-based counterpart with a TCR of 8. This represents a 33% reduction in binder dosage without sacrificing performance. The UCS of the CTB increased significantly with a decreasing TCR and an increasing CA, with the most rapid strength development observed during the early curing stages (≤7 days). The stress–strain behavior transitioned from plastic yielding to strain-softening with prolonged curing, and the macroscopic failure was predominantly governed by tensile cracking. Microstructural analysis revealed that the strength development of the CTB originates from the continuous formation of hydration products, such as calcium-silicate-hydrate (C-S-H) gel and ettringite. These products progressively fill pores and encapsulate tailing particles, creating a dense and interlocking skeletal structure. A lower TCR and a longer CA promote the formation of a more integrated and compact micro-network, thereby enhancing the macroscopic mechanical strength. This study confirms the viability of the slag-based binder as a sustainable alternative to OPC in mining backfill applications, providing a critical theoretical basis and technical support for the low-cost, eco-friendly utilization of mining solid waste. Full article

The risk of explosive spalling in high-strength cement-based materials during fire exposure poses a significant threat to structural integrity. To help mitigate this issue, this study explores the use of expanded polystyrene (EPS) beads as both a lightweight filler and a potential spalling-reduction agent in lightweight geopolymer and conventional cementitious mortars. Two EPS-containing mortars were developed: a lightweight alkali-activated slag (LWAS) mortar and a conventional lightweight Portland cement (LWPC) mortar, both incorporating EPS beads as a 50% volumetric replacement for sand. Specimens from both mortars were subjected to elevated temperatures of 200 °C, 400 °C, and 600 °C at a heating rate of 10 °C/min to simulate a rapid-fire scenario. Following thermal exposure, two cooling regimes were employed: gradual cooling within the furnace and rapid cooling by water immersion. Mechanical performance was evaluated through compressive, splitting tensile, and impact tests at room and elevated temperatures. Microstructural analysis was also conducted to examine internal changes and heat-induced damage. The results indicated that LWAS showed remarkable resistance to spalling, remaining intact up to 600 °C due to its nanoporous geopolymer structure, which allowed controlled steam release, while LWPC failed explosively at 550 °C despite EPS pores. At 400 °C, EPS beads enhanced thermal insulation in LWAS, lowering internal temperature by over 100 °C, but increased porosity led to faster strength loss. Both mortars gained strength at 200 °C from continued curing, yet LWAS retained strength better at high temperatures than LWPC. Microscopy revealed that EPS created beneficial fine cracks in the slag matrix but harmful voids in cement. Overall, LWAS composites offer excellent spalling resistance for fire-prone environments, though reinforcement is recommended to mitigate strength loss. Full article

Corn stover (CS) is an abundant biomaterial, which is regularly rejected during corn harvesting. This biowaste is a typical lignocellulosic source rich in hydroxycinnamates, which are mainly represented by p-coumaric acid and ferulic acid. These polyphenols are largely bound onto the lignocellulosic complex and can be effectively liberated using alkaline catalysis. On this basis, the work described herein targeted at developing a high-performance process for producing hydroxycinnamate-enriched extracts, by deploying alkali-catalyzed hydrothermal and organosolv treatments. For this purpose, sodium carbonate was tested as a benign, natural alkali catalyst, along with the well-studied sodium hydroxide. The kinetic study demonstrated that both the alkali catalyst and the organic solvent (ethanol) may significantly affect polyphenol recovery, a fact further investigated by carrying out response surface optimization. The hydrothermal treatment was shown to be more efficacious than the organosolv one, with regard to total polyphenol recovery, while the sodium carbonate catalysis was less efficient compared to the sodium hydroxide one. Under optimized conditions, the hydrothermal treatment afforded 74.4 ± 3.6 mg gallic acid equivalents per g of dry CS mass. On the other hand, a more thorough investigation of the polyphenolic profile of the extracts obtained clearly demonstrated that the sodium hydroxide-catalyzed organosolv treatment provided almost 76 and 98% higher yields for p-coumaric and ferulic acid, respectively, compared to the hydrothermal treatment. Extract composition impacted the antioxidant activity, and it was revealed that the higher the p-coumaric acid/ferulic acid ratio, the stronger the antioxidant effect. It is proposed that the sodium hydroxide-catalyzed ethanol organosolv treatment of CS may be a particularly promising technique in a lignocellulose biorefinery frame, although improvements might be necessary to further increase treatment performance. Such a process might contribute to fully valorizing agricultural biowastes for the production of high value-added chemicals, in line with the “lignin first’ philosophy. Full article

Selective oxidation of benzyl alcohol to benzaldehyde is crucial for sustainable chemical synthesis, which provides the atom-economical and environmentally benign pathways. In this work, we used the in situ reduction immobilization to synthesize a series of Au nanoparticles supported by CoAlO_x support with spinel structure for alkali-free oxidation of benzyl alcohol. The synthesis methodology was preliminarily optimized and the influence of Co/Al molar ratio in Au/CoAlO_x on the catalytic performances was subsequently revealed based on characterizations. Results suggested that the electronic interaction between Au and CoAlO_x can be regulated and maximized under the Co/Al ratio of 3. It became a main factor to modulate the dispersion of Au nanoparticles, surface chemical composition, as well as the oxygen adsorption/activation ability. Benefiting from such synergistic interaction, the optimized Au/Co₃AlO_x catalyst achieved 86.1% BnOH conversion under 99.9% benzaldehyde selectivity with well-maintained structural stability under recycle tests. This work provides a rational design strategy for developing highly efficient gold catalysts with well-constructed Au-support interfaces for the alkali-free oxidation of alcohol. Full article

The growing concern with carbon dioxide emissions from the cement industry has driven the search for alternative binders with lower environmental impact. Among these, alkali-activated cements (AACs) stand out due to their ability to produce cementitious matrices from aluminosilicate precursors and alkaline activators. However, comparisons between One-Part and Two-Part systems remain limited. This study evaluated the technical feasibility of producing AAC using sugarcane bagasse ash (SCBA) as precursor, carbide lime (CL) as calcium source, and sodium hydroxide (NaOH) as activator. Different parameters were tested, including NaOH molarities (1.0–2.5 M), SCBA/CL ratios (9.00–1.50), curing times (3, 7, and 28 days), and preparation methods. Mortars were produced at constant water/solid ratio of 1.40 and cured at room temperature (23 °C). Unconfined compressive strength (UCS) and leaching tests were performed, along with statistical analysis and Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) analyses. ACC synthesized by the Two-Part method (2.0 M NaOH, SCBA:CL 70:30) reached an UCS of 1.60 MPa at 28 days, compared to 1.39 MPa for the One-Part method. Curing time was identified as the most significant factor, followed by SCBA/CL ratio and activator molarity, while preparation method had minimal effect. The material developed alkali-activated gels, and leaching tests indicated no toxicity, although Ba concentrations exceeded regulatory limits for water quality. Potential applications include mine tailings stabilization, soil improvement, shallow foundations, and urban furniture production. Full article

To enhance the efficient utilization of industrial solid waste and support the low-carbon transition of cementitious materials, this study used steel slag, coal-fired slag, and desulfurization gypsum as the primary raw materials. A high-performance composite cementitious material system was developed based on the synergistic effects of physical activation (mechanical grinding) and chemical activation (alkali stimulation). This study systematically investigates the raw material characteristics, mix proportion optimization, mechanical behavior, and durability of composite cementitious materials through the integration of response surface optimization design and multi-scale analysis methods. The results indicate that the optimal mix proportions of the composite cementitious material are: 37.2% steel slag, 33.2% coal-fired slag, 9.6% desulfurized gypsum, 20% cement, 4% sodium silicate, and 0.1% superplasticizer. At this mix proportion, the measured 28-day average compressive strength of the composite cementitious material was 40.8 MPa, which closely matched the predicted value of 41.2 MPa from the response surface regression model, thereby confirming the model’s accuracy and applicability. The composite cementitious material demonstrated superior volume stability compared to ordinary cement under both water-curing and drying conditions. However, its freeze–thaw resistance and carbonation resistance were lower than those of cement. Therefore, considering these factors comprehensively, the composite cementitious material is recommended for application in road base and subbase layers. 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

Geopolymer materials possess several outstanding advantages, including the wide availability of raw materials, an energy-saving and environmentally friendly production process, and excellent engineering technical performance. They are regarded as a new type of green building material that can achieve high-value-added resource utilization of industrial solid waste. They are one of the current research hotspots in the field of materials. Fly ash and slag, the most common industrial wastes in China, have been discharged in large quantities, significantly impacting the country’s ecological environment. Based on this, this paper primarily investigates the mechanical properties and strength formation mechanism of geopolymer paste to develop geopolymer materials with enhanced mechanical properties. This research uses metakaolin as the silicate raw material and uses sodium silicate mixed with NaOH as the alkali activator to prepare geopolymer paste. By adding fly ash and slag, the mechanical properties of the geopolymer paste are improved. The effects of the alkali activator modulus, Na₂O equivalent, and content of fly ash and slag on the setting time and strength of geopolymer paste are studied. XRD, FTIR, and SEM are employed to characterize the phase, molecular structure, and microscopic morphology of geopolymer paste, as well as to analyze the microstructure and reaction mechanism of these materials. The results show that the setting time of the geopolymer increases with the increase in modulus and shortens with the increase in Na₂O equivalent. Fly ash and slag, respectively, act as retarders and early strength promoters. The ratio of n(SiO₂)/n(A1₂O₃) (that is, the modulus of the alkali activator) of the geopolymer is an important factor affecting its strength. The metakaolin and fly ash–slag–metakaolin exhibit the best mechanical properties when their molar ratios are 2.97 and 3.26, respectively. Through microscopic characterization using XRD, FTIR, and SEM, it is observed that fly ash–slag–metakaolin exhibits the most complete polymerization reaction, generates the most amorphous silicate aluminosilicate gel, and displays the best inter-gel bonding effect, resulting in the best mechanical properties. Full article

Xylooligosaccharides (XOS) are functional oligosaccharides with recognized prebiotic properties and growing industrial relevance, typically obtained through enzymatic depolymerization of xylan-rich lignocellulosic substrates. In this study, a recombinant endo-β-1,4-xylanase (XynA) from Clostridium acetobutylicum was employed for XOS production. The xynA gene was cloned into the expression vector pET-21a(+) and heterologously expressed in Escherichia coli BL21(DE3) under induction with isopropyl β-D-1-thiogalactopyranoside (IPTG). The recombinant protein, with an estimated molecular mass of 37.5 kDa, was verified by SDS-PAGE and Western blot analysis. Functional characterization via thin-layer chromatography revealed that XynA efficiently hydrolyzed beechwood xylan and rye arabinoxylan, predominantly yielding xylobiose. Additionally, the enzyme catalyzed the conversion of xylotriose into xylobiose and trace amounts of xylose. Notably, XynA demonstrated hydrolytic activity against autohydrolysed and alkali-pretreated coconut husk biomass, facilitating the release of XOS. These results underscore the potential of C. acetobutylicum XynA as a biocatalyst for the valorization of lignocellulosic residues into high-value oligosaccharides. Full article