Search Results (258)

Biosurfactant-producing microorganisms play an important ecological role in soils impacted by hydrophobic contaminants by enhancing substrate bioavailability and influencing microbial interactions. In this study, we critically evaluated the reliability of commonly used screening methods for biosurfactant detection. A total of 71 microbial isolates (16 bacteria and 55 fungi) were obtained from vegetable oil-contaminated soil and screened using a multi-step approach combining enzymatic assays (lipolytic and hemolytic activity) and physicochemical methods, including drop-collapse, oil spreading, emulsification index (E₂₄), and surface tension reduction. Although 21 isolates exhibited lipolytic activity and 9 showed hemolysis, inconsistent responses among assays revealed significant limitations of individual screening methods. Only two bacterial isolates consistently tested positive across all criteria. When cultivated in mineral salt medium supplemented with hydrophobic substrates, both isolates produced stable emulsions and significantly reduced surface tension (from 54.26 mN/m to 31.46 mN/m). Substrate-dependent variation was observed for isolate C3, which showed reduced surface tension (39.63 mN/m) when grown with biodiesel. These findings highlight the risk of relying on single assays and emphasize the need for integrated screening strategies to ensure reliable detection of biosurfactant-producing microorganisms. Full article

High-viscosity reservoirs are widely distributed across various countries with abundant reserves. However, their high resin and asphaltene content leads to elevated oil viscosity and low recovery rates. Conventional chemical flooding techniques are unsuitable for the development of such high-viscosity oilfields. Chemical viscosity reduction technologies face challenges such as low viscosity reduction efficiency, poor economic feasibility, and unclear mechanisms. Microbial-assisted chemical viscosity reduction represents a relatively novel approach. This study systematically investigated the enhanced oil recovery performance of a microbial-assisted chemical viscosity reducer. The results demonstrated that this microbial-assisted chemical viscosity reducer achieved a viscosity reduction rate exceeding 85% for five different crude oil samples. It effectively altered the wettability of oil-wet surfaces, improved the oil film stripping rate by 50–65% compared to pure chemical flooding agents, and achieved ultra-low oil–water interfacial tension on the order of 10⁻³ mN/m with crude oil, leading to an enhanced oil recovery (EOR) enhancement of 22–26%. The underlying mechanism is that viscosity-reducing bacteria degrade asphaltene in heavy oil, thereby weakening intermolecular forces. Their metabolites enhance the emulsion stability of the chemical viscosity reduction process. Chemical viscosity reducers enhance the physiological cycle and metabolic activity of microorganisms while also emulsifying and dispersing heavy oil and improving emulsion stability. Therefore, this novel microbial-assisted chemical viscosity reduction technology offers a new and effective EOR method for high-viscosity reservoirs. Full article

Low-salinity water flooding (LSWF) has been widely investigated as an enhanced oil recovery (EOR) method for carbonate reservoirs; however, the relative contributions of wettability alteration and oil–brine interfacial tension (IFT) reduction remain poorly understood, particularly under strongly oil-wet conditions. This study systematically investigates the physicochemical mechanisms governing oil recovery during hybrid LSWF–surfactant flooding in oil-wet carbonate systems. Oil-wet Indiana limestone cores were used as representative carbonate reservoir rocks. Seawater and its diluted analogs were employed as base brines and combined with anionic and cationic surfactants at varying concentrations. Zeta potential and pH measurements were conducted to characterize electrostatic interactions at the rock–brine and oil–brine interfaces, while dynamic contact angle and pendant-drop IFT measurements were used to quantify wettability evolution and fluid–fluid interactions. Core flooding experiments were subsequently performed to link interfacial phenomena to macroscopic oil recovery behavior. The results demonstrate that brine dilution induces more negative surface charges at both interfaces, promoting double-layer expansion and electrostatic repulsion, which stabilizes the aqueous film and drives wettability alteration toward a water-wet state. The addition of anionic surfactants further amplifies this effect by increasing surface charge negativity, whereas cationic surfactants preferentially adsorb onto the negatively charged rock surface, limiting wettability alteration despite producing greater IFT reduction. Sulfate ions enhance wettability alteration by facilitating divalent cation interactions with adsorbed oil components; however, excessive sulfate concentrations lead to precipitation-induced flow impairment. Core flooding results reveal that diluted seawater combined with an anionic surfactant yields the highest incremental oil recovery. Our findings conclusively demonstrate that wettability alteration—rather than IFT reduction—is the more dominant recovery mechanism in oil-wet carbonate reservoirs under the investigated conditions. These results provide mechanistic guidance for optimized brine and surfactant design in hybrid LSWF–chemical EOR applications. Full article

Droplet size is a key factor in minimizing spray drift. Different types of adjuvants and sprayer operating pressures can affect the droplet size distribution in various ways. This study aimed to evaluate the effects of commercial adjuvants, namely, acids and surfactant (AS), silicone surfactant (SS), organosilicone surfactant (OS), mineral oil (MO and MO₂), and copolymer (CP) adjuvants, on the droplet spectra and physicochemical properties of aqueous solutions. Hydrogen potential (pH), volumetric mass ($VM$), electrical conductivity (EC), surface tension (ST), contact angle (CA), and droplet spectra were measured. The droplet spectrum variables, including volumetric diameters ($D_{v0.1}$, $D_{v0.5}$, and $D_{v0.9}$), the Relative Span Factor ($RSF$), and percentages of the total volume of droplets with a diameter smaller than 100 µm (V100) and larger than 500 µm (V500), were determined using a laser diffraction particle analyzer (Malvern Spraytec). Spraying tests were carried out using the AXI 11003 flat fan nozzle at pressures of (0.1, 0.2, 0.3, 0.4, and 0.5) MPa. The increase in pressure increased the V100 and the $RSF$, with greater sensitivity observed for SS. Adjuvants such as AS, MO₂ and OS showed a more balanced trend, with a smaller increase in fine droplets and a greater reduction in coarse droplets. The principal component analysis (PCA) revealed that the droplet spectrum variables were the ones that best explained the variation among the solutions. A negative correlation was identified between EC and other physicochemical properties, such as pH, ST, and CA. Therefore, these properties alone did not determine the atomization pattern. The study demonstrates that optimizing spray quality and minimizing drift require a combined consideration of adjuvant physicochemical properties and their interaction with operational pressure. Full article

This study addresses the challenges posed by weakly cemented strata in mine tunnels, where surrounding rock softens and deforms upon water exposure, which promotes the development of seepage pathways, and exhibits insufficient stability in bolt (cable) support systems. This study conducts laboratory grouting tests using silica sol on typical weakly cemented sandstone from Xinjiang mining areas. The mineral composition and pore structure were characterized using XRD, SEM, and mercury porosimetry. The injectable mixing ratio parameters for silica sol and the catalyst were determined through viscosity-time evolution tests. Grouting was performed using a custom-built constant-pressure grouting apparatus. After curing, unconfined compressive strength (UCS) and porosity-permeability tests were conducted to evaluate the micro-mechanism of grouting effects on the mechanical and permeability properties of weakly cemented sandstone. The results indicate: (1) The sandstone exhibits a high clay mineral content of 39.8%, dominated by illite. Its pores are primarily small-scale (10–100 nm), accounting for 79.31% of the total pore volume. This scale matches that of silica sol nanoparticles (approximately 9–20 nm), facilitating slurry penetration into micro-pores; (2) microscopic analyses reveal that silica sol effectively reconstructs pore structures through permeation filling and surface coating. Compared to KCl-induced gelation (with approximately 8% gel coverage), NaCl-induced gelation forms a more continuous gel film with more complete pore filling, achieving coverage of around 22%. Furthermore, the larger surface area of the gel aggregates indicates a more thorough filling of micro- and nano-pores, effectively enhancing rock mass compactness. (3) Permeability decreased from 6.91 mD to 3.55 mD, a reduction of 48.6%, while porosity decreased from 16.94% to 13.55%, showing a phased reduction during the grouting process; (4) following pressure grouting stabilization, the uniaxial compressive strength of sandstone increased appropriately by approximately 7–14%, while the elastic modulus rose by about 18–28%. The failure mechanism shifted from shear brittleness to a shear-tension composite state, with enhanced post-peak bearing capacity. These findings provide support for optimizing silica sol grouting parameters in weakly cemented strata tunnels and for the synergistic reinforcement of rock mass permeability and strength. Full article

Tunnel roof is subjected to a complex tension-shear stress state after excavation. A tensile cut-off strength criterion is introduced in this study and combined with the upper bound limit analysis method to investigate the stability of a rectangular tunnel roof. First, the expression for the internal energy dissipation rate is derived for the circular cut-off segment of the failure criterion. Power functionals Φ are established for both two-dimensional and three-dimensional rotational collapse mechanisms. The analytical equations for the failure surface are obtained using the variational method. The strength reduction method that incorporates the cut-off criterion is proposed to quantify roof stability. The investigation into the morphology of the collapsing block indicates that the supporting pressure and the reduction coefficient ξ have a significant influence on the collapse shape of the tunnel, suggesting that attention should be paid to the suspension effect of the tunnel roof on stability. The range of the collapsing block under three-dimensional conditions is found to be larger than that under two-dimensional conditions. Parametric influences on the safety factor are examined. Finally, dimensionless design charts for the critical reinforcement pressure are provided for practical tunnel support design. Full article

Environmental pollution caused by persistent chemical compounds, particularly heavy metals, poses a significant global challenge. Current strategies focus on eco-friendly and sustainable approaches, such as the application of microorganisms, to mitigate this issue. In this study, four strains of Bacillus and Pseudomonas were phylogenetically identified and assessed for their resistance to three heavy metals: copper (Cu), chromium (Cr), and cadmium (Cd) up to 500 µg/mL. Various tolerance mechanisms related to heavy metal resistance were elucidated, including salinity tolerance, antibiotic resistance, production of exopolysaccharides (EPS), and biosurfactant synthesis. The antifungal activities of these strains were evaluated against the fungal isolates Fusarium oxysporum fs. phaseoli (Fop) and Stemphylium botryosum (St-bt) using dual culture assays. Phylogenetic analysis revealed that three strains belong to the genus Bacillus, while one strain is classified under Pseudomonas. Additionally, these strains exhibited diverse mechanisms for heavy metal tolerance, including salinity tolerance (up to 600 mM), multi-antibiotic resistance (to imipenem, ampicillin, and sodium fusidate), and the production of viscous, slimy colonies indicative of EPS synthesis. Biosurfactant production led to a significant reduction in surface tension, ranging from 10.51 ± 3.87% to 82.89 ± 5.01%. The antifungal assays demonstrated that the strains effectively inhibited the mycelial growth of the fungal isolates, with inhibition percentages varying from 0% to 83.34 ± 2.22%. The strains characterized in this study exhibit considerable potential for application in the bioremediation of metal-contaminated soils and as biocontrol agents. Full article

The evaporation of a thin liquid film representative of power-law rheology flowing along an inclined channel wall under the combined influence of gravity and surface tension is investigated using a semi-analytical modelling framework. The evolution of film thickness, heat transfer characteristics, and dry-out behaviour are examined as functions of the power-law exponent, Weber number, and inlet film thickness. The results show that a decrease in the power-law exponent leads to a slower reduction in film thickness, resulting in a significant increase in the dry-out length for a fixed value of consistency. This behaviour is attributed to the large effective viscosity developing near the free surface for shear-thinning fluids, in contrast to the negligible surface viscosity observed for shear-thickening fluids. The local Nusselt number increases gradually along the flow direction, followed by a sharp terminal rise marking the onset of dry-out. The mean Nusselt number decreases with increasing power-law exponent, which is consistent with the dry-out length variation with the power-law exponent. The dry-out length is found to be largely insensitive to surface tension for a fixed normalised inlet film thickness, while exhibiting an approximately linear dependence on the inlet film thickness that is nearly independent of the power-law index. Overall, the study establishes a hierarchy of controlling parameters for evaporating power-law films in inclined micro-channels, demonstrating that inlet film thickness primarily governs the dry-out location, while rheology and surface tension exert secondary influences within the parameter ranges considered. Full article

Microbial biosurfactants have emerged as natural and sustainable alternatives to synthetic surfactants used in the food industry, due to the growing demand for biodegradable and safe ingredients. Produced by bacteria, fungi, and yeasts, these compounds exhibit important physicochemical properties, such as emulsifying capacity, surface tension reduction, foam stabilization, and favorable interaction with different food matrices. In addition to their technological function, they exhibit relevant biological activities, including antioxidant and antimicrobial action, which contribute to the control of lipid oxidation and microbiological deterioration. These characteristics make biosurfactants attractive for applications in emulsions, fermented beverages, aerated products, probiotic systems, and bioactive packaging. The objective of this work is to provide a narrative literature review that integrates recent advances in the production, functionality, safety, sustainability, and application perspectives of biosurfactants in the food sector. In the field of production, biotechnological advances have made it possible to overcome historical limitations such as high cost and low yield. Strategies such as the use of agro-industrial waste, metabolic engineering, microbial co-cultures, continuous fermentations, and in situ removal techniques have increased efficiency and reduced environmental impacts. Despite the advances, significant challenges remain. Future prospects and advances tend to facilitate industrial adoption and consolidate biosurfactants as strategic ingredients for the development of more sustainable, functional, and technologically advanced foods. Full article

The steel industry contributes to approximately 7%–9% of global anthropogenic CO_2(g) emissions, with traditional blast furnace–basic oxygen furnace (BF–BOF) routes emitting up to 1.8 t_CO2 per ton of steel. In contrast, Electric Arc Furnace (EAF) steelmaking, especially when integrated with hydrogen direct-reduced iron (DRI), can reduce emissions by over 40%, positioning EAFs as a key enabler of low-carbon metallurgy. However, despite its lower direct emissions, the EAF process still depends on fossil carbon sources for slag foaming and FeO reduction, which are essential for arc stability and energy efficiency. Slag foaming plays a critical role in controlling the thermal efficiency of the EAF by shielding the electric arc, reducing radiative heat losses, and stabilizing the arc’s behavior. This review examines the mechanisms of slag foaming, discussed through empirical models that consider the foaming index (Σ) and slag foaming rate as critical parameters, and highlights the influence of physical properties such as slag viscosity, surface tension, and density on gas bubble retention. Also, the work embraces the potential use of alternative carbon sources including biochar, biomass, and waste-derived materials such as plastics and rubber to replace fossil-based reductants and foaming agents in EAF operations. Finally, it discusses the use of new materials with a biological base, such as nanocellulose, to serve as reactive templates for producing nanohybrid materials, containing both oxides, which can contribute to slag basicity (MgO and/or CaO, for example), together with a reactive carbonaceous phase, derived from the organic fiber’s thermal degradation, which could contribute to slag foaming, and could replace part of the fossil fuel charge to be employed in the EAF process. In this context, the development and characterization of renewable carbonaceous materials capable of simultaneously reducing FeO and promoting slag foaming are essential to achieving net-zero steel production and enhancing the sustainability of EAF-based steelmaking. Full article

Illite, a clay mineral, is used in diverse fields such as agriculture, cosmetics, and the food-related industry due to its many advantages, including biocompatibility, UV protection, antibacterial activity, high adsorption capacity for hazardous substances, and cost-effectiveness. However, its relatively large size, broad size distribution, and irregular morphology limit its broader applications. This study investigated the control of particle size and distribution during wet ball milling (WBM) using five media—acetone, ethanol, water, aqueous NaCl solution, and aqueous phosphoric acid solution—over milling times of 2–10 h. Prolonged milling progressively reduced particle size and narrowed the size distribution. Acetone and ethanol exhibited notably superior size-reduction performance compared with the aqueous systems, among which phosphoric acid solution showed the least effectiveness, likely attributed to variations in their physicochemical properties, including viscosity (η) and surface tension (σ), and in their interfacial interactions with illite. Optimal milling in acetone for 10 h resulted in the smallest particles (~700 nm), the narrowest distribution, the largest specific surface area, and the highest moisture retention. Overall, these findings demonstrate that the physicochemical properties of the milling medium, which govern WBM efficiency through fluid dynamics and particle–medium interactions, thereby determine the size and distribution of milled particles. Full article

Due to the heightened flood risk resulting from climate change, innovative and advanced green building materials are required to enhance the durability and biological resistance of concrete structures exposed to persistent moisture. This study investigates the use of nanosilver-enriched plasticizers as a novel modification of concrete for applications in flood-prone environments. The findings demonstrate that the incorporation of nanosilver enhances the mechanical strength of concrete by reducing surface tension and porosity, thereby enhancing durability and extending service life. Moreover, nanosilver-modified concrete exhibits significant antimicrobial activity, effectively limiting microbial-induced corrosion. Preliminary microbiological analyses showed a reduction of sulfur-oxidizing bacteria (SOB) and sulfate-reducing bacteria (SRB) by 85–92%, as well as a decrease of over 80% in potentially pathogenic microbial genera. This study also highlights the importance of skilled labor and adequate training to ensure the responsible implementation of nanosilver-based technologies in sustainable construction. Overall, nanosilver-enriched plasticizers represent an innovative green building material that supports flood-resilient, durable, and sustainable concrete construction. Full article

In this study, cationic surfactant cetyltrimethylammonium bromide (CTAB) and anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) are employed to systematically investigate surface and wetting properties on hydrophobic surfaces, specifically in mixed solvents composed of ethylene glycol (EG) and water at 298.15 K. By varying the concentration of each surfactant within the EG–water mixture, both surface tension and contact angle measurements are performed to elucidate how surfactant type and solvent composition influence interfacial behavior and wettability. PTFE and wax surfaces were chosen as model hydrophobic surfaces. Surface tension measurements obtained in pure water and in water–EG mixtures containing 5, 10, and 20 volume percentage EG reveal a consistent decrease in the premicellar slope (${\displaystyle \frac{d\gamma }{d\mathit{log}C}}$) with increasing EG content. This reduction reflects weakened hydrophobic interactions and less effective surfactant adsorption at the air–solution interface. The corresponding decline in maximum surface excess (${\Gamma }_{max}$) and increase in minimum area per molecule ($A_{min}$) confirm looser interfacial packing due to EG participation in the solvation layer. Plots of adhesion tension (A_T) versus surface tension (γ) exhibit negative slopes, consistent with reduced solid–liquid interfacial tension (${\Gamma }_{LG}$) and greater redistribution of surfactant molecules toward the solid–liquid interface. AOT shows stronger sensitivity to EG compared to CTAB, reflecting structural headgroup-specific adsorption behavior. Work of adhesion (W_A) measurements demonstrate enhanced wettability at higher EG concentrations, highlighting the cooperative impact of co-solvent environment and surfactant type on wetting phenomena. Full article

Back pain in horses is a frequent musculoskeletal issue that affects performance and welfare. Magnetotherapy has been proposed as a complementary, non-invasive treatment to reduce pain and support soft tissue recovery, but studies in horses remain limited. This pilot study aimed to evaluate the effects of low-frequency pulsed magnetic field therapy on horses with hypersensitivity to palpation along the longissimus dorsi muscle. Four recreational horses participated in a 10-session magnetotherapy program, with changes assessed using palpation, neck flexibility tests, heart rate measurements and thermal imaging. Results showed a reduction in pain sensitivity and muscle tension, particularly in the withers, thoracic, lumbar and sacral regions. Heart rate decreased after treatment, which may indicate a relaxing effect. Thermal imaging confirmed that magnetotherapy did not increase surface temperature, confirming its non-thermal nature. No adverse effects or swelling were observed in any of the horses. These findings provide preliminary data from this pilot study, suggesting that magnetotherapy may be a beneficial adjunct in the treatment of back pain in horses, promoting relaxation and pain relief without inducing tissue heating. Further research on larger populations with a negative control group is needed to validate these findings and support broader clinical application. Full article

Surfactants are essential in cosmetic and food formulations but are still dominated by petrochemical-derived anionic systems associated with irritation, aquatic toxicity and sustainability concerns. Plant-derived saponins offer renewable, biodegradable alternatives, yet only a small subset of saponin-producing species has been developed into commercial ingredients. The genus Albizia is chemically diverse and widely used in traditional medicine, with several species empirically employed as cleansers. This review examines Albizia amara and related Albizia species as prospective sources of plant-derived surfactants for cosmetic and food applications. We summarise ethnobotanical and phytochemical data with emphasis on saponins, flavonoids and macrocyclic alkaloids, and collate the limited quantitative evidence for surface activity, focusing on foaming behaviour, surface tension reduction and shampoo-type formulations, where A. procera provides the main interfacial benchmark within the genus. Potential roles of A. amara-derived fractions in hair-care products and prospective food systems are discussed alongside current knowledge on toxicity, safety and regulatory constraints. Overall, A. amara emerges as a promising but under-characterised saponin source. Priority areas for future work include robust tensiometric characterisation, surfactant-focused extraction and fractionation, systematic formulation studies, and dedicated safety and sustainability assessments to enable evidence-based evaluation against established plant and synthetic surfactants. Full article