Search Results (68)

To address freshwater scarcity in agriculture, the use of brackish and reclaimed water for alternate irrigation has emerged as a viable alternative. This study evaluated four biochars (rice husk, peanut shell, rice straw, and wheat straw, applied at 2%) and three silicon fertilizers (Lang-Si (S1), Nayou-Si (S2), and sodium metasilicate pentahydrate (S3)) as amendments for sandy loam soil (Lang-Si, Nayou-Si, foliar spray at 1000× dilution; sodium metasilicate pentahydrate, foliar spray at 150 mg∙L⁻¹). Their effects on soil salinity, physicochemical properties, and microbial community structure were assessed under alternate irrigation with brackish and reclaimed water. Alternate irrigation reduced soil electrical conductivity and increased total phosphorus (TP) content compared to single-source irrigation. The effects of amendments varied by type. Biochars improved soil fertility and reduced salinity: peanut shell biochar decreased EC by 15.5%; rice husk biochar increased total nitrogen (TN), TP, and organic matter (OM) by 11.8%, 8.2%, and 10.1%, respectively; and wheat straw biochar elevated subsurface soil TN and OM by 14.1% and 40.0%. Straw-derived biochars and sodium metasilicate pentahydrate maintained higher bacterial α-diversity (Shannon index ≥ 6.67). These effects corresponded with the nutrient adsorption capacity of biochars and the ionic stress alleviation by soluble silicon. The correlation analysis identified OM, TN, TP, and EC as the key drivers shifting the microbial community. Straw-derived biochars and sodium metasilicate pentahydrate are suitable amendments for alternate irrigation systems. These materials balance salinity control, fertility improvement, and microbial conservation, offering practical options for sustainable use of brackish and reclaimed water in agriculture. Full article

A microwave–hydrothermal (M-H) method was developed for synthesizing barium silicate from solutions of barium salts and sodium silicate. Advanced techniques (DTA, XRD, IR spectroscopy, SEM and TEM) were used to study the optical, granulometric, electrical and other functional characteristics of barium silicate. BaSiO₃ synthesized at 100 °C is an amorphous nano-sized powder (10–20 nm); however, the product synthesized at 240 °C has a crystalline structure (20–27 nm), whereas the crystalline phase of BaSiO₃ is typically obtained using known methods at temperatures above 400 °C (12–40 nm). During M-H synthesis, it was found that the structure formation mechanism and particle size of BaSiO₃ changed due to the peculiar features of microwave heating. The synthesized barium metasilicate exhibits a high diffuse reflectance coefficient of 92%. It is a wide-band-gap semiconductor with a band gap width of Eg = 4.1 eV. Both amorphous and crystalline phases of BaSiO₃ exhibit high photocatalytic activity in the UV range. This study shows that the developed M-H method enables the production of nano-sized powder and enhances the functional properties of barium silicate. Compared with conventional methods, the M-H method is more efficient due to reduced synthesis time and lower energy costs. Full article

Silicon (Si) application is recognized for its beneficial roles in crop growth. This study examines the effects of two forms: zeolite and sodium metasilicate (SMS), on rice under hydroponic (EP I) and soil (EP II) conditions. Four treatments were used at the early stage of rice: 4 ppm and 2 ppm of Si from zeolite, 4 ppm of Si from SMS, and a control. In EP I, only 4 ppm of SMS significantly improved root traits: total root length (36%), surface area (34%), root volume (23%), tips (46%), and forks (34%) by day seven compared to the control. Zeolite-based Si had minimal effects, except on the average diameter. However, in EP II, all Si forms enhanced root traits: total root length (50–73%), surface area (51–58%), average diameter (32–50%), root volume (54–72%), tips (29–68%) and increased shoot and root dry weights by 19–24% and 79–106%, respectively, compared to the control. In EP II, starting from the first and fifth day of treatment, the Si applied groups showed a significant increase in photosynthetic traits and vegetative indices, respectively. On the last day of treatment, particularly for 2 ppm of Si zeolite, the electron transport rate increased by 5 times, the apparent transpiration by 3 times, total conductance and stomatal conductance by around 50%, normalized difference vegetative index by 6–8%, and photochemical reflectance index by 14–33%. These results suggest that the effectiveness of Si is highly dependent on the growth medium and the type of Si, with soil enabling better Si availability, uptake, and physiological response compared to hydroponics. The superior performance of zeolite in EP II indicates its potential as a slow-release Si source that enhances root development and photosynthetic efficiency over time. Thus, it is concluded that zeolite has more potential in soil, and soluble silicon sources should be selected in hydroponics. Full article

In this study, the aim was to improve the mechanical and durability properties of kaolin clay (KC)-based soil by stabilizing it with geopolymer and natural fiber. In the production of the geopolymer, rice husk ash (RHA) was used as a binder, sodium metasilicate (SMS) as an activator, and another hemp fiber (HF)was used for soil stabilization. Within the scope of the presented study, RHA and SMS were used at three different rates (5%, 7.5%, and 10%), while HF was used in six different volumes (0.5%, 1%, 1.5%, 2%, 2.5%, and 3%) and two different lengths (6 and 12 mm). The study also examined how much water was in the combinations, which was measured at the optimum level and at −5, +5, and +10 compared to the optimum level. The unconfined compressive strength (UCS) was used to check the mechanical qualities of the test specimens and 5- and 10-cycle freeze–thaw (F-T) tests to check the durability properties. The test results indicated that the mixed formulation with 5% RHA, 10% SMS, 2.5% HF, and the optimum water content resulted in the best results for both the UCS and F-T tests. The SEM investigation for this mix found that the microstructural properties for the specimen were directly related to the dense gel phases and the strong fiber–matrix bonding. According to the carbon emissions (CO₂-e) and carbon index (CI) analysis from the mix component analyses, it was found that the HF-strengthened geopolymer is a sustainable solution for soil stabilization. The optimum mixture achieved a UCS of 1202 kPa (4.5 times higher than untreated soil), while the strength losses after 10 freeze–thaw cycles were reduced to below 10% in optimized compositions. The carbon index (CI) decreased by up to 65%, demonstrating the strong sustainability benefits of the proposed system. The novelty of this study lies in the combined use of hemp fiber (HF) and rice husk ash (RHA)–sodium metasilicate (SMS)-based geopolymer for kaolin clay stabilization, which has not been comprehensively investigated in previous research. Unlike traditional studies focusing on either geopolymer or natural fiber reinforcement alone, this work simultaneously evaluates the mechanical performance, freeze–thaw durability, microstructural evolution, and carbon footprint to develop a fully sustainable soil improvement framework. Full article

Cabbage is an important vegetable crop worldwide. In Taiwan, during cabbage production, bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum often leads to significant yield losses. Aligning with the Sustainable Development Goals, there is a high demand for sustainable disease control strategies. Silicates are considered to be effective elicitors in activating plant defense responses and are reported to improve resistance to certain plant diseases. Bacillus amyloliquefaciens PMB05 fermentation liquid has been shown to enhance plant immunity and control many bacterial diseases. The supplementation of silicates to the PMB05 fermentation liquid may further improve its efficacy to control bacterial soft rot in cabbage. This study evaluated the effects of sodium metasilicate and potassium silicate on PMB05-mediated plant immune responses and disease control. Initial assays confirmed that treatment with B. amyloliquefaciens PMB05 suspension significantly increased HrpN-triggered reactive oxygen species (ROS) generation and callose deposition; moreover, PMB05 treatment alone reduced bacterial soft rot severity by 39.7%. When combined with B. amyloliquefaceins PMB05 fermentation liquid, sodium metasilicate at 2000 μM further enhanced ROS generation and callose deposition by 100% and 133%, respectively, compared to the treatment of PMB05 alone (p < 0.05). In contrast, potassium silicate exhibited inconsistent effects on ROS production, with both 500 and 1000 µM concentrations significantly reducing ROS generation by 26% and 38%, respectively, while none of the tested concentrations affected callose deposition (p < 0.05). Lastly, disease severity assessments in cabbage inoculated with P. carotovorum subsp. carotovorum PCCSB1 revealed that B. amyloliquefaciens PMB05 fermentation liquid was able to reduce bacterial soft rot symptoms by 60.3%. Supplementation with 1500 and 2000 µM sodium metasilicate further decreased disease severity by 77.9% and 76.4%, respectively (p < 0.05). Although the supplementation of potassium silicate also significantly reduced disease severity compared to P. carotovorum subsp. carotovorum PCCSB1 alone, it was less effective than PMB05 fermentation alone. Overall, these results demonstrate that sodium metasilicate enhances the biocontrol activity of B. amyloliquefaciens PMB05 by further intensifying plant immune responses. This approach may broaden the large-scale use of B. amyloliquefaciens PMB05 fermentation liquid for sustainable soft rot management in cabbage, although the stability and cost-effectiveness of sodium metasilicate under field conditions still require validation. Full article

The UPV technique has been widely employed to predict the hardened properties of Portland cement mixtures. This article assesses the hardened properties of alkali-activated blast furnace slag mortars by comparing UPV measurements with compressive strength and dry density and calculating the dynamic modulus of elasticity from UPV results. The mixtures were prepared varying the type of activator (sodium metasilicate and sodium silicate), the content of Na₂O in the activators (3.0, 4.5, 6.0, and 7.5%), and the water/binder ratio. The results showed that exponential models showed medium and high determination coefficients (R²), which explained the correlation between UPV and hardened properties. It was observed a limitation on the measurements of UPV, which did not surpass 4.4 km/s, which made it difficult to predict compressive strength value above 50 MPa. The dynamic modulus of elasticity calculated from UPV showed reliable results, even varying the Poisson’s coefficient between 0.15 and 0.25. Lastly, it was also observed that a correlation between the content of C-S-H and UPV suggested that this technique can also be used to predict the evolution of the hydration products in alkali-activated slag mixtures. Full article

The availability of key precursors of alkali-activated binder (AAB) systems is declining, requiring sources. Calcined clays (CCs) stand out as a promising alternative due to their widespread accessibility. Although the properties of CC and blast furnace slag (BFS)-based two-part AABs have been well reported in the literature, the effect of minor additives on the properties of a one-part AAB system composed of CC and BFS remains unexplored. In this research, calcined magnesia (CM), aerial lime (AL), hydraulic lime (NHL), quicklime (QL), borax (BR), and zeolite (ZP) have been used as minor additives and incorporated into the AAB system at between 2% and 15%. The specimens were activated with sodium–metasilicate, and the fresh, physical, mechanical, durability and microstructural properties of mortars have been investigated. Key findings indicate that all minor additives, except for BR, enhanced the early- and later-age mechanical properties. Notably, 10% QL addition significantly increased compressive strength by up to 55% at 28 days (50.9 MPa), compared to the reference. BR and ZP usage eliminated the efflorescence formation without compromising other properties. Furthermore, incorporating QL, AL, CM, and BR markedly reduced the chloride permeability of the mortars and decreased D_nssm value by as much as 81%, compared to the reference. Full article

In this study, gangue-based solid waste was utilized as the primary raw material to prepare filling materials using a composite alkali activator comprising calcium oxide (CaO) and sodium metasilicate (Na₂SiO₃). By varying the proportions and total content of the alkali activators, with the total content fixed at 12 wt% of coal gangue, the resulting filling materials were systematically investigated. The mineralogical composition, morphology, and hydration degree of the materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). In addition, the compressive strength of the materials was measured. The results demonstrated that both the type and dosage of alkali activators significantly influenced the mineral phases and surface morphology of the filling materials. CaO and Na₂SiO₃ exhibited distinct effects on the degree of hydration, and the curing age was also found to be a critical influencing factor. For single-component activators, the compressive strength of the filling materials initially increased and then decreased with increasing activator content, with optimal values observed at CaO contents between 6% and 9% and Na₂SiO₃ content around 2%. In the case of the composite CaO–Na₂SiO₃ system, the uniaxial compressive strength exhibited a similar trend, increasing first and then decreasing with the CaO-to-Na₂SiO₃ ratio, with the optimal ratio determined to be 3:1. Furthermore, a positive correlation between curing age and compressive strength was observed. This study elucidates the synergistic mechanism of CaO and Na₂SiO₃, identifies optimal mix proportions, and quantifies empirical relationships between raw material properties, reaction conditions (activator ratio/content, curing age), and compressive strength. These relationships serve as core data for subsequent construction of a “raw material–reaction condition–strength” correlation model, providing support for formulation optimization of gangue-based filling materials. Full article

Geopolymers have attracted wide attention as effective soil stabilisers, presenting significant potential for several geotechnical engineering applications. These binders offer environmental benefits by utilising abandoned aluminosilicate industrial by-products, such as fly ash and slag, through mixing with an alkaline solution. In addition, they also decrease dependency on conventional Ordinary Portland Cement (OPC), which is identified with substantial artificial greenhouse gas emissions and high energy consumption during manufacture. However, the practical utilisation of geopolymers for the stabilisation of road materials is hindered by the intricate preparation process, which necessitates precise control over the proportions of the ingredients to achieve the required mechanical properties. This complexity becomes more pronounced when compared to the relatively simple method of using conventional cement, which requires fewer safety precautions while mixing with soil. This study investigates the development of a One-Part Geopolymer (OPG) powder, specifically formulated for the stabilisation of a Crushed Rock Base (CRB) material used for road construction. The optimal blend of OPG powder, comprising fly ash, slag and sodium metasilicate, is identified by assessing the monotonic and dynamic mechanical performances of the treated CRB compacted at the optimum moisture content using Unconfined Compressive Strength (UCS) and Repeated Load Triaxial (RLT) tests. The results of the study indicate that enhancing the strength performance of the OPG-treated CRB requires the calibration of the sodium oxide (Na₂O) content in the alkaline activator with the total binder. It was also found that increasing the OPG content from 1% to 3% significantly enhances both the uniaxial strength and resilient modulus of the treated CRB, while simultaneously reducing the permanent deformation. Notably, the CRB specimens stabilised with 2% OPG exhibit mechanical properties comparable to those of bound Portland cemented materials. Full article

Climate change is leading to a decline in global potato production. To ensure food security, it is essential to adapt cultivation practices to the changing climate. The effects of foliar-applied silicon on potato growth and productivity under various hydrothermal conditions were investigated. Potato plants were treated with three Si-based biostimulants: Actisil (6 g of Si and 20 g of Ca per liter; choline-stabilized orthosilicic acid; Chol-sSa + Ca); Krzemix (6 g of Si per liter; choline-stabilized ammonium metasilicate; Chol-sNH₄-Sil); and Optysil (93 g of Si and 24 g of Fe per liter; sodium metasilicate and iron chelate Fe-EDTA; Na-Sil + Fe-EDTA). Biostimulants were foliar-applied twice, at the leaf development stage (BBCH 13–15) and two weeks after the first treatment, at 0.5 L/ha in each treatment. The plants treated with biostimulants were taller and produced greater above-ground biomass and a higher tuber weight than the control plants (without a biostimulant). As a result, the total tuber yield was higher, on average, by 10% to 13% and the marketable tuber yield by 11% to 15%. The plant-growth-promoting and yield-increasing effects of the Si-based biostimulants depended on the hydrothermal conditions during potato growth. Chol-sSA + Ca (Actisil) applications were the most effective. Na-Sil + Fe-EDTA (Optysil) produced better results during a warm and very dry year, while Chol-sNH₄-Sil (Krzemix) was effective during colder years with a periodic water deficit. Silicon foliar application can be a new method for increasing early crop potato yields under water shortage conditions. Full article

This study explores the feasibility of preparing a one-part alkali-activated binder produced from tungsten-molybdenum (W-Mo) tailings with sodium metasilicate (SM). A series of alkali-activated mortar samples were prepared, and the effects of the water/binder (W/B) ratio and mixture proportion on mechanical properties were investigated. Additionally, the microstructure and composition of the alkali-activated W-Mo tailings were characterized by using a combination of scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy techniques. Optimal results were achieved with a W/B ratio of 0.35 and a formulation containing 20% by weight of SM. Under these conditions, the cured samples exhibited an unconfined compressive strength of 11.2 MPa and a bulk density of 1726 kg/m³ after 28 days. The findings show the potential to advance tungsten-molybdenum mine waste upcycling and contribute to the production of environmentally sustainable building materials. Full article

Nitrogen fixation in legume nodules is crucial for plant growth and development. Therefore, this study aims to investigate the effects of nitric oxide [S-nitrosoglutathione (GSNO)] and silicon [sodium metasilicate (Si)], both individually and in combination, on soybean growth, nodule formation, leghaemoglobin (Lb) synthesis, and potential post-translational modifications. At the V1 stage, soybean plants were treated for 2 weeks with 150 µM GSNO, and Si at concentrations of 1 mM, 2 mM, and 4 mM. The results showed that NO and Si enhance the nodulation process by increasing phenylalanine ammonia-lyase activity and Nod factors (NIP2-1), attracting rhizobia and accelerating nodule formation. This leads to a greater number and larger diameter of nodules. Individually, NO and Si support the synthesis of Lb and leghaemoglobin protein (Lba) expression, ferric leghaemoglobin reductases (FLbRs), and S-nitrosoglutathione reductase (GSNOR). However, when used in combination, NO and Si inhibit these processes, leading to elevated levels of S-nitrosothiols in the roots and nodules. This combined inhibition may potentially induce post-translational modifications in FLbRs, pivotal for the reduction of Lb³⁺ to Lb²⁺. These findings underscore the critical role of NO and Si in the nodulation process and provide insight into their combined effects on this essential plant function. Full article

The growing demand for sustainable building materials has boosted research on plant-based composite materials, including hemp shives bound with biodegradable binders. This study investigates the enhancement of potato-starch-based binders with sodium metasilicate and glycerol to produce eco-friendly bio-composites incorporating hemp shives. Potato starch, while renewable, often results in suboptimal mechanical properties and durability in its unmodified form. The addition of sodium metasilicate is known to improve the mechanical strength and thermal stability of starch-based materials, while glycerol acts as a plasticizer, potentially enhancing flexibility and workability. Bio-composites were produced with varying concentrations of sodium metasilicate (0–107% by mass of starch) and glycerol (0–133% by mass of starch), and their properties were evaluated through thermal analysis, density measurements, water absorption tests, compressive strength assessments, and thermal conductivity evaluations. The results demonstrate that sodium metasilicate significantly increases the bulk density, water resistance, and compressive strength of the bio-composites, with enhancements up to 19.3% in density and up to 2.3 times in compressive strength. Glycerol further improves flexibility and workability, though excessive amounts can reduce compressive strength. The combination of sodium metasilicate and glycerol provides optimal performance, achieving the best results with an 80% sodium metasilicate and 33% glycerol mixture by weight of starch. These modified bio-composites offer promising alternatives t2 o conventional building materials with improved mechanical properties and environmental benefits, making them suitable for sustainable construction applications. Full article

Geopolymer concrete, a cement-free concrete with recycled concrete aggregate (RCA), offers an eco-friendly solution for reducing carbon emissions from cement production and reusing a significant amount of old concrete from construction and demolition waste. This research on self-compacted, ambient-cured, and low-carbon concrete demonstrates the superior performance of one-part geopolymer concrete made from recycled materials. It is achieved by optimally replacing treated RCA with a unique method that involves coating the recycled aggregates with a one-part geopolymer slurry composed of fly ash, micro fly ash, slag, and anhydrous sodium metasilicate. The research presented in this paper introduces predictive models to assist researchers in optimising concrete mix designs based on RCA rates and treatment methods, including the incorporation of coated recycled concrete aggregates and basalt fibres. This study addresses the knowledge gap regarding geopolymer concrete based on recycled aggregate, various RCA rates, and novel RCA treatments. The novelty of the paper also lies in presenting the effectiveness of Artificial Neural Network (ANN) models in accurately predicting the compressive strength, splitting tensile strength, and modulus of elasticity for self-compacting geopolymer concrete with various rates of RCA replacement. This addresses a knowledge gap in existing research on ANN models for the prediction of geopolymer concrete properties based on RCA rate and treatment. The ANN models developed in this research predict results that are more comparable to experimental outcomes, showcasing superior accuracy compared to linear regression models. Full article

This study presents the durability, strength and microstructure of non-heat-cured geopolymer mortars (GMs) containing metakaolin (MK), ground granulated blast furnace slag (GGBFS), potassium hydroxide (KOH), sodium metasilicate (Na₂SiO₃), CEN sand and network water. Optimum MK, GGBFS and activator solution ratios were investigated, and the compressive strength of non-heat-cured 28-day GMs reached 55 MPa. Analysis of GMs using scanning electron microscopy (SEM), energy-dispersive X-ray spectrophotometry (EDX) and X-ray powder diffraction (XRD) revealed alumino-silicate formation, potassium from KOH solution and calcium from GGBFS. It showed that the grains containing high silica in the form of quartz crystals were found in the gel formation. The strength and durability of MK- and GGBFS-based GMs exposed to freeze–thawing, a high temperature, wear loss, magnesium sulfate (MgSO₄), sodium sulfate (Na₂SO₄) and HCl solutions were found to be sufficient. Full article