Search Results (509)

Environmental pollution by polycyclic aromatic hydrocarbons (PAHs) is a serious environmental problem. One of the effective methods of cleaning the environment from these toxicants is the use of sorbents based on clay minerals. Special organo-mineral, bio-mineral and bio-organo-mineral complexes were obtained. Organo-mineral complexes (organoclays) were synthesized on the basis of Na-bentonite and anionic, amphoteric and nonionic surfactants. Bio-mineral and bio-organo-mineral complexes were produced by inoculating bentonite and organoclays with a consortium of bacteria. The adsorption characteristics of the complexes to benzopyrene and naphthalene were studied. Modification of bentonite with various types of surfactants leads to a significant increase in the percentage adsorption of both benzopyrene and naphthalene, with benzopyrene being more so. All bio-organo-mineral complexes adsorb more benzopyrene than pure bentonite and the bentonite + bacteria complex. In most cases, this pattern is also characteristic of naphthalene adsorption. Organoclay complexes with bacteria adsorb PAHs in greater quantities than organoclays, typically at the average concentrations of benzopyrene and naphthalene used (30–60 μg mL⁻¹) and when modified with individual surfactants. Based on the determination coefficients, the adsorption of benzopyrene and naphthalene by all studied sorbents is best described by the Langmuir equation. The maximum (limiting) adsorption of benzopyrene by all organo-mineral complexes (organoclays) exceeds the maximum adsorption of benzopyrene by bentonite. Modification of bentonite with surfactants may not change, decrease, or increase the maximum adsorption of naphthalene compared to the original bentonite, depending on the surfactant used. Colonization of the organoclay surface by bacteria, with rare exceptions, results in a decrease in the maximum adsorption values of benzopyrene and naphthalene compared to organoclay, or has no effect at all. Full article

Valorization of agro-industrial waste into functional materials is fundamental to the circular economy, especially for addressing the persistent contamination by anionic azo dyes in textile wastewater. This study evaluates guava seeds modified with hexadecyltrimethylammonium bromide (GS-M) as low-cost biosorbents for the removal of Direct Blue 71 (DB71), comparing their performance with that of natural seeds (GS-N) in batch systems and fixed-bed columns. Characterization by infrared spectroscopy (FTIR) and electron microscopy (SEM-EDS) confirmed successful surfactant immobilization, thereby creating a cationic surface with strong electrostatic affinity for anionic dye molecules. Batch experiments showed that GS-M achieved 98% DB71 removal within 120 min, whereas GS-N reached only 58% after 300 min. For GS-M, both pseudo-first-order and pseudo-second-order models fit the kinetic data well, consistent with concurrent electrostatic and hydrophobic interactions; GS-N was best described by the Elovich model, indicating rate limitation by electrostatic repulsion. GS-M maintained removal efficiency above 84% across pH 3–9, whereas GS-N was effective under acidic conditions. Langmuir maximum adsorption capacity (Q_o) values for GS-M were 6.02 mg/g at pH 4 and 7.87 mg/g at pH 8, a 1.5- to 2.2-fold increase over GS-N under matched conditions. Three adsorption–desorption cycles retained ~49% of the initial GS-M capacity, supporting a short-cycle reuse profile rather than indefinite multi-cycle operation. Fixed-bed column performance was highly sensitive to the hydraulic loading rate (v_c), with breakthrough times increasing nearly eightfold as v_c decreased. The Bed Depth Service Time (BDST), Thomas, and Yoon–Nelson models described the dynamic data consistently, yielding a maximum dynamic capacity of 165.6 mg/L under optimal conditions and providing a quantitative basis for scale-up. These results establish surfactant-modified guava seeds as a low-cost, pH-resilient biosorbent system aligned with circular-economy principles for the sustainable remediation of textile wastewater. Full article

Reducing herbicide input in paddy fields is essential for sustainable rice production and long-term soil health. Florpyrauxifen-benzyl effectively controls the dominant paddy weed barnyardgrass (Echinochloa crus-galli), yet excessive application poses environmental risks. Here, we investigated whether the compound adjuvant Sijiling, containing nonionic and anionic surfactants, could enable significant dose reduction in florpyrauxifen-benzyl while maintaining weed control efficacy and improving soil–plant system functions. Greenhouse dose–response assays and two-year field trials conducted in 2021 and 2022 demonstrated that the adjuvant permitted a 50% reduction in herbicide application without compromising control of barnyardgrass or other paddy weeds. Mechanistically, Sijiling disrupted the leaf cuticular wax barrier and amplified ethylene and ABA biosynthesis over two-fold. The reduced herbicide rate lowered residues in rice and soil, increased soil organic carbon and available potassium, and enhanced microbial diversity, particularly enriching beneficial Acidobacteria. Grain yield increased significantly under the reduced-input strategy, with Mantel analysis linking yield gains to improved soil available potassium and organic carbon. Our findings demonstrate that adjuvant-enabled herbicide dose reduction is an effective and sustainable weed management strategy for paddy rice, maintaining robust weed suppression while delivering measurable co-benefits for soil health and crop productivity, thereby supporting the sustainable intensification of rice-based cropping systems. Full article

Nanomaterials such as cellulose nanocrystals and fumed silica are emerging as excellent thickeners for liquids in a variety of practical applications. Surfactants are often incorporated into the thickening fluids to provide stabilizing components and to control the surface activity of fluids. To develop new thickening materials with desired surface-active properties, it is important to understand the interactions between surfactants and nanoparticles in suspensions. In this work, the interactions between surfactants and nanocrystals/nanoparticles were investigated. Two surfactants, anionic sodium lauryl sulfate-based surfactant (referred to as Stepanol) and cationic hexadecyltrimethylammonium bromide (referred to as HTAB), were studied. Cellulose nanocrystals (referred to as NCC) and fumed-silica nanoparticles (referred to as N20) were used as nanomaterials. The unique feature of this study is that it simultaneously measures rheology, surface activity, and electrical conductivity to determine the influence of ionic surfactants on the behavior and properties of cellulose nanocrystal and fumed silica nanoparticle suspensions. Furthermore, the interactions are observed in the low surfactant concentration range of 0 to 500 ppm. The NCC concentration of NCC–surfactant mixtures was fixed at 1 wt%. Two concentrations of N20 (2 and 5 wt%) were used for N20–surfactant mixtures. The influence of Stepanol was found to be weak whereas HTAB had a strong influence on the rheology of NCC and N20 suspensions. The NCC suspension and surfactant–NCC suspensions were highly non-Newtonian shear-thinning. The N20 suspensions and N20-Stepanol mixtures were nearly Newtonian. The N20-HTAB mixtures were shear-thinning at high HTAB concentrations. The power law model described the rheological behavior of non-Newtonian systems adequately. The consistency and flow behavior indices varied only marginally with the addition of the anionic surfactant Stepanol to NCC and N20 suspensions. With the addition of cationic surfactant HTAB to NCC and N20 suspensions, however, a large increase (20- to 70-fold) in consistency index was observed at high surfactant concentrations. The critical surfactant concentrations where sharp transitions in the rheological properties took place were identified using break points in surface tension and electrical conductivity plots. This study offers valuable insights into tailoring surfactant–nanoparticle systems for practical applications, where precise control of rheological and interfacial properties may be required. Full article

The use of sewage sludge for the bioremediation of hydrocarbon-contaminated soils remains insufficiently documented, particularly regarding microbial dynamics and material behavior during treatment. Although petroleum-hydrocarbon contamination severely disrupts soil functions, sewage sludge—through its high organic matter content, active bacterial communities, and fine mineral fraction—offers potential for the sustainable remediation of such soils. Three soil–sludge mixtures (P1:N1, P2:N1, P1:N2) were monitored to assess hydrocarbon degradation, bacterial community dynamics, and material behavior. Hydrocarbon-degrading and hydrocarbon-tolerant bacteria remained active, while sludge-derived Enterobacteriaceae declined below detection limits. Enrichment cultures of the sludge yielded three hydrocarbon-degrading strains (Providencia alcalifaciens IBBN1, Klebsiella pneumoniae IBBN2, Acinetobacter tandoii IBBN3), highlighting the metabolic potential of the active microbial communities. A moderate increase in surfactant concentrations reflected both residual anionic surfactants and biosurfactant production by these consortia, facilitating hydrocarbon mobilization. Total petroleum hydrocarbons (TPH) decreased by 45–60% (IR), and GC-FID analysis showed preferential degradation of C10–C40 fractions. Heavy-metal concentrations remained stable, indicating no geochemical changes or inhibitory effects on bacterial activity. Overall, the results confirm the potential of sewage sludge as a sustainable amendment that accelerates hydrocarbon biodegradation and supports integrated soil-restoration strategies. Full article

ASP flooding wastewater contains crude oil, suspended solids, anionic polymers and surfactants, with high viscosity, high zeta potential, difficult demulsification, flocculation and slow separation and sedimentation. In order to solve the problem of wastewater treatment of ASP flooding in oil fields, a magnetic branched core was prepared from ethyl silicate (TEOS), nano Fe₃O₄ and aminopropyl triethoxysilane (APTES), and then reacted with polyamine and methyl acrylate to synthesize the magnetic hyperbranched molecule FSNMN with demulsification ability. Using acrylamide (AM), acryloxyethyl trimethylammonium chloride (DAC) and maleic anhydride (MA) as raw materials, cationic polymer long chain (CAMHA) with flocculating properties was synthesized and grafted with hyperbranched molecules. The demulsification flocculation ability of the product regarding ASP flooding wastewater was evaluated, and the demulsification flocculation mechanism was summarized. The results showed that the average molecular weight of 3-FSNMN₄-C was 4.7 million, the cationic degree was 20.5%, and the saturation magnetization was 20 EMU/g. The removal rate of oil and suspended solids was 93.82% and 91.95% respectively when the simulated sewage was treated by magnetic field for 30 min. Magnetic hyperbranched star chain polymer provides a solution to the serious ecological environment problems caused by ASP flooding. Full article

Graphene oxide (GO) has been widely investigated as a nanoreinforcement for cementitious composites; however, its effectiveness depends on stable dispersion within the highly alkaline, calcium-rich environment of fresh cement paste. This study evaluates the dispersion behaviour of GO in deionised (DI) water and saturated calcium hydroxide (Ca(OH)₂) under controlled conditions and assesses the effectiveness of anionic and cationic surfactants in both environments. GO was synthesised using the modified Hummers method and verified by comprehensive physicochemical characterisation. Dispersion stability was assessed using UV-Vis spectroscopy at GO concentrations of 0.04–0.08 mg/mL in DI water, and the 0.08 mg/mL system was further studied in saturated Ca(OH)₂ with and without sodium dodecylbenzene sulphonate (SDBS) and cetyltrimethylammonium bromide (CTAB) at a 1:1 mass ratio. Zeta potential and dynamic light scattering measurements were performed to understand the relation between the surface charge and agglomeration of GO. In DI water, GO retained close to 70% of its initial absorbance after 60 min, and both surfactants improved retention to above 90%. In saturated Ca(OH)₂, retention fell to approximately 40%, and neither surfactant restored stability despite producing zeta values that would conventionally support stable dispersion. The findings indicate that GO aggregation in calcium ion (Ca²⁺)-rich alkaline environments is not governed by net surface charge alone, consistent with the established mechanism of Ca²⁺ chemical cross-linking with GO carboxyl groups. Full article

Pollution of rivers and large water bodies, including reservoirs, by wastewater from various sources is one of the most critical issues in the Donetsk region, requiring continuous monitoring and assessment of surface water quality. The research aims to assess the state of the Kalmius River under anthropogenic pressure, as well as to find correlations between the species composition, photosynthetic activity of phytoplankton, and the degree of water pollution. This study presents the results of biomonitoring of the Kalmius River and its tributaries within Donetsk City, which are under intense anthropogenic pressure. Pollution of the river channel by phenol, anionic surfactants, Ferrum ions, chlorides, and sulfates was identified. Based on the combinatorial pollution index, the water in the Kalmius River and its tributaries can be classified as polluted. The pigment composition of water samples was analyzed, and the species composition of river phytoplankton was determined. Dominant species include Chlorella vulgaris Beij., Dictyosphaerium pulchellum H.C.Wood, Scenedesmus quadricauda Brébisson, and Oscillatoria agardhii M.A.Gomont. Photosynthetic activity of the river’s algal flora was assessed based on chlorophyll fluorescence induction curves of natural phytoplankton. A correlation was established between surface water pollution levels and changes in the photosynthetic apparatus of microalgae cells. A strong negative correlation was found between the content of nitrate nitrogen in the aquatic environment and the photosynthetic activity, pigment composition, and abundance of the main dominant forms of phytoplankton, particularly the microalgae of the genus Cyclotella. The data obtained shows that the Kalmius River’s pollution has a significant impact on phytoplankton biodiversity, leading to the growth of cyanobacteria species. Full article

Adsorption properties of graphene oxide (GO) and its organo-modified analog (GO-HDTMA), treated with the hexadecyltrimethylammonium (HDTMA) cationic surfactant, were evaluated for the removal of persistent pharmaceutical products (PPs): an anionic diclofenac (DCF) anti-inflammatory, a cationic metoprolol (MTP) beta-blocker, and a nonionic sulfamethoxazole (SMX) antibiotic. Adsorption isotherms, fitted by Langmuir and Freundlich models, together with FTIR data, demonstrate that both GO and GO-HDTMA are effective adsorbents for DCF. The adsorption is primarily governed by both π–π and van der Waals interactions, leading to saturation of the accessible C sp² carbon domains at a maximum uptake of 4.2 mmol g⁻¹. In contrast, due to its cationic nature, MTP is not removed using GO-HDTMA, while it is effectively adsorbed at about 0.5 mmol g⁻¹ for GO via electrostatic attractive forces. SMX is adsorbed by both materials, although its uptake remains limited on GO. The presence of hydrophobic domains in GO-HDTMA enhances SMX adsorption through weak intermolecular interactions. These results highlight the tunability of GO-based hybrid materials and their potential for the selective removal of a large spectrum of emerging pharmaceutical contaminants. Full article

The use of surfactants as drag-reducing agents (DRAs) has received significant attention in oil–gas transportation due to their ability to enhance liquid drainage efficiency and reduce operational costs. This work experimentally examines the performance of an anionic sodium lauryl sulphate (SLS) surfactant as a DRA in horizontal two-phase flow through experimental studies focusing on three key aspects, (1) changes in flow patterns, (2) drag reduction (DR%), and (3) liquid holdup reduction (HLR%), with the aim of identifying optimal SLS concentrations for achieving stable and efficient multiphase pipeline flow. The results illustrate that adding SLS shifts the slug flow toward more stable stratified wavy and plug flow patterns, as well as a newly emerging bubbly flow pattern. This in turn significantly decreases the pressure gradient (PG), achieving a maximum DR% of 71% and 83% at 100 and 200 ppm, respectively. In addition, as the SLS concentration increases, the liquid draining efficiency increases, achieving maximum holdup reductions of 69% and 85% at 100 and 200 ppm, respectively. Full article

Developing an ultrasensitive electrochemiluminescence (ECL) detection platform remains challenging due to the limited enrichment efficiency of ECL emitters and co-reactants at the electrode interface, as well as the insufficient catalytic enhancement of co-reactant conversion. Moreover, simultaneous in situ analyte enrichment and efficient anti-interference capability are often difficult to achieve in a single sensing interface. Herein, a new ECL platform was developed based on nanocatalyst-supported nanochannel-confined surfactant micelle (SM) system, which integrates an enhanced luminol-dissolved oxygen (DO) ECL response for the ultrasensitive detection of antibiotic rifampicin (RIF). A nanocomposite comprising nitrogen-doped graphene quantum dots and a molybdenum disulfide nanosheet (NGQDs@MoS₂) was modified on an indium tin oxide (ITO) electrode. This nanocomposite layer catalyzed the oxygen reduction reaction (ORR), boosting the co-reactant efficiency of DO. Vertically ordered mesoporous silica film filled with surfactant micelles (SM@VMSF) was subsequently grown in situ on the NGQDs@MoS₂ surface. The hydrophobic micelles enable the simultaneous enrichment of luminol, DO, and RIF. Integrating the triple-enrichment effect of surfactant micelles with the high electrocatalytic effect of NGQDs@MoS₂ nanocomposite results in significant ECL enhancement of the luminol–DO. SM@VMSF also provides an excellent molecular sieving effect, endowing the sensor with high anti-interference capability and stability. RIF quenches the ECL signal by consuming superoxide anion radicals, enabling sensitive detection. Detection of RIF was established with a high sensitivity (2927 a.u. per nM) wide linear range (10 pM to 10 μM) and a low limit of detection (LOD, 2.5 pM). The fabricated sensor exhibits good selectivity and high fabrication reproducibility (relative standard deviation, RSD, of 1.9%). Additionally, the determination of RIF in eye drops and seawater samples was realized. This work offers new insights for the design of high-performance ECL sensing interfaces and sensitive detection of RIF. Full article

As oil and gas development increasingly targets low and ultra-low permeability reservoirs, conventional recovery techniques often prove insufficient for mobilizing residual oil. Surfactant flooding, a key chemical enhanced oil recovery (EOR) technology, thus requires careful system optimization and mechanistic investigation. This study focuses on low-permeability reservoirs in the Changqing Oilfield, evaluating three surfactant systems—YHS-Z1 (a 7:3 mass ratio blend of hydroxypropyl sulfobetaine and cocamide), YHS-Z2 (a polyether carboxylate, a nonionic-anionic composite) and a middle-phase microemulsion system (Heavy alkylbenzene sulfonate and hydroxysulfobetaine were combined with a mass ratio of 7:3)—through a series of experiments including interfacial tension measurement, contact angle analysis, static and dynamic oil displacement tests, as well as emulsion transport/retention index assessments, to comprehensively characterize their oil displacement properties. Based on the experimental data, this study constructed four classical regression models: Ridge Regression, Random Forest (RF), Gradient Boosting Regression (GBR), and Support Vector Regression (SVR), and conducted a comparative analysis of their predictive performance. The results demonstrate that the Random Forest (RF) model achieved the optimal prediction performance, with a Mean Absolute Error (MAE) of 1.8245, a Mean Absolute Percentage Error (MAPE) of 4.78%, and a coefficient of determination (R²) of 0.9428 on the training set. Further analysis using the SHapley Additive exPlanations (SHAP) algorithm revealed that the retention index is the primary global factor (accounting for 49.79% of the variance), while significant intergroup differences exist in the primary factors across different surfactant systems. Concurrently, single-factor and multi-factor sensitivity analyses were conducted to elucidate synergistic effects and threshold behaviors among parameters. The optimal parameter combination, identified via a random search method, achieved a predicted recovery factor of 45.61%, representing a 6.57% improvement over the highest experimental value. This study demonstrates that machine learning methods can effectively identify the dominant factors in oil displacement and enable synergistic parameter optimization, thereby providing a theoretical foundation for the efficient development of surfactant flooding in low-permeability reservoirs. Full article

Coal-bed gas well production is too low to realize a highly efficient exploitation of the #8 coal seam in the Shanxi formation in the Nalin region. Based on the reservoir characteristics, the designed poly-aromatic-grafted silicon-quantum-dot-based desorption agent (PQS) has been developed. Then, the adsorption/desorption behavior of CBM on the coal surface under the influence of this active chemical has been studied, and the synergy effect with an anionic–nonionic surfactant to desorption of CBM has also been discussed. The results show that the developed poly-aromatic-grafted silicon quantum dot, with a median size of 4.9 nm and +5.6 mV of zeta potential in neutral condition, has a significant emission peak with 470 nm at the excitation of 380 nm and 150,000 mg/L of salinity resistance, which also generates a strong adsorption capacity on the coal surface. A promoting effect to desorption of CBM for PQS nanofluid is exhibited and the Langmuir pressure is obviously increased. However, when the PQS nanofluid is synergized with an anionic–nonionic surfactant, the desorption of CBM is further improved and the wettability of the coal surface is altered from 78.2° to 84.2°. The desorption rate for this compound system reached 65.3%. It can be found that combining the quantum size, π–π stacking, π–π conjugation, and the synergy effect between PQS nanofluid and surfactant fluid with the traditional intermolecular force has a stronger capacity for promoting desorption of CBM than the conventional desorption agent. This study provides guidance for the molecular design of the desorption agent for deep coal rock and the application of silicon quantum dots. 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

In order to determine the condition of drinking water sources in Donetsk Region and assess potential threats related to water pollution from mining and industrial wastewater, it is extremely important to monitor surface waters, which should include an assessment of the condition of gydrobionts. Additionally, declining surface water quality in the region contributes to pollution in the coastal waters of the Sea of Azov. This study presents the monitoring results for the southern part of the Kalmius River basin. Analysis of water samples revealed contamination by phenol, sulfates, chlorides, anionic surfactants, iron, elevated water hardness, and significant exceedances of suspended solids and total dissolved solids. The iron concentration at the Kalmius River estuary reached 0.81 mg∙L⁻¹, exceeding the permissible limit by 2.5-fold. Sulfate and total dissolved solids concentrations attained 1673 and 160 mg∙L⁻¹, respectively. Changes in the species composition of phytoplankton were observed in response to variations in iron, manganese, and phenol concentrations in the water. Specifically, elevated iron levels led to increased abundance of the metal-sensitive species Cyclotella meneghiniana Kützing. Principal component analysis of the data revealed a relationship between increased phenol concentrations in the aquatic environment and a mean 20% reduction in phytoplankton cell photosynthetic activity, as well as the influence of manganese ions on cell abundance and photopigment content. Thus, phytoplankton cell fluorescence, alongside shifts in species composition and photosynthetic pigment content, can serve as an additional indicator of surface water pollution by iron and phenol. Full article