Search Results (561)

In this study, by varying the concentrations of the precursors used, copper sulfide films were deposited on FTO glass using the sequential ionic layer adsorption and reaction (SILAR) method and the following copper sulfide phases were detected: anilite, djurleite, chalcocite, and yarrowite. It was found that the films of copper sulfides are unevenly distributed, that the crystallinity of the films increases with increasing annealing temperature from 100 to 400 °C, and that the particles aggregate into agglomerates. The films formed were found to be dominated by copper sulfides, and the calculated molar ratio of copper to sulfur varied with the concentrations of the precursors used, ranging from 1.4 to 2.2. The values of the band gap energy were not significantly affected by the change in the concentrations of the precursors and the annealing temperature, varying between 1.0 and 1.5 and 1.95–2.15 eV. Full article

The deposition of asphaltenes poses a critical challenge to the petroleum industry, reducing the efficiency of oil wells and, in severe cases, clogging pipelines. Dispersants are widely used to enhance asphaltene stability, but asphaltenes are complex, solubility-defined compounds with variable properties, leading to uncertainties in dispersant microscopic mechanisms, macroscopic effects, and their relationships—requiring further study. This work investigated two anionic dispersants (sodium dodecyl benzene sulfonate (SDBS) and dodecyl benzene sulfonic acid (DBSA)) for dispersing GT asphaltene (GT-ASP, isolated from offshore heavy oil), aiming to improve offshore heavy oil stability. Using an asphaltene–toluene system, it analyzed dispersant effects on GT-ASP stability, particle size, and adsorption and underlying mechanisms. DBSA showed superior performance: at 1000 ppm (w/v), it reduced GT-ASP average particle size from ~160 nm to ~29 nm and increased the onset of the flocculation point (OFP) from 33.5 vol% to 63.0 vol%, driven by chemical adsorption, hydrogen bonding, and π–π conjugation. In contrast, SDBS promoted aggregation: particle size reached 257 nm (1000 ppm (w/v)) and 1271 nm (5000 ppm (w/v)), with OFP at 54.6 vol%, likely due to Na⁺-induced charge neutralization, insufficient steric hindrance, and “micellar bridges” via SDBS self-aggregation. Finally, this study makes a valuable contribution to both the theoretical guidance and the practical application of asphaltene dispersants. Full article

The surface tensions (σ) of binary solutions of diiodomethane (DIM, 1)–furfural (FA, 2), DIM (1)–N,N-dimethylformamide (DMF, 2), and FA (1)–DMF (2) were determined at 25 °C over the entire bulk composition range, and the surface adsorption behavior was analyzed using the surface aggregation adsorption (SAA) model proposed recently. In particular, by combining the SAA model with the Gibbs adsorption equation, the changes in the Gibbs surface excess (Γ₂) and the adsorption layer thickness (τ) with the bulk composition (x_2,b) were investigated. The SAA model combined with the modified Eberhart model can well describe the σ-isotherms of the three binary solutions. The surface adsorption trends of component 2 in DIM–FA, DIM–DMF, and FA–DMF decrease in turn. The change trends of Γ₂ and τ with x_2,b are dependent on the SAA model parameters, namely, the adsorption equilibrium constant (K_x) and the average aggregation number (n). With an increase in x_2,b, Γ₂ continuously increases when K_x < 2v₁/[n(2n − 1)v₂] (where v₁ and v₂ are the partial molar volumes of components 1 and 2, respectively); otherwise (i.e., K_x ≥ 2v₁/[n(2n − 1)v₂]), Γ₂ initially increases and then decreases, showing a maximum on the Γ₂-isotherm. When n ≥ 1, τ gradually decreases with an increase in x_2,b; otherwise (i.e., n < 1), τ initially increases and then decreases, showing a maximum on the τ-isotherm. An increase in the adsorption trend leads to a decrease in both Γ₂ and τ. This work provides a better understanding of the surface adsorption behavior of liquid mixtures. Full article

The widespread detection of antibiotics in aquatic environments has raised significant concerns due to their potential risks to human health. Photocatalytic technology has emerged as an effective approach for antibiotic degradation, with cadmium sulfide (CdS) being a promising semiconductor photocatalyst. However, the practical application of CdS is limited by its tendency to aggregate, which reduces the number of accessible active sites and consequently lowers its photocatalytic degradation efficiency. In this study, a series of GO/CdS composites were synthesized via a two-step hydrothermal method for the efficient degradation of tetracycline (TC) antibiotics in aquatic solutions. Results showed that GO/CdS can effectively remove TC via photocatalytic degradation rather than adsorption. The optimized photocatalytic composite achieved a 95% degradation of TC (20 mg L⁻¹) under 60 min of illumination. The corresponding rate constant (k) was 2.87 times higher than that of pristine CdS. After three cycles, the degradation rate still achieved 93%. Moreover, the composite exhibited a wide pH tolerance range from pH 2 to 10, with a removal rate of over 89%. Superoxide radicals (·O₂⁻) were identified as the primary reactive species responsible for TC degradation, and three possible TC degradation pathways were proposed. This work extends the application of GO and offers a novel strategy for constructing GO-based composite materials, providing valuable insights into the mechanisms and pathways of antibiotic degradation. Full article

Nano-silica is widely used to enhance gel properties, but its size, concentrations, and aggregation behaviors all matter. The influencing rules of these factors remain unclear especially in harsh reservoir conditions. This study presented a comprehensive investigation into the gelation, rheological, and plugging properties of phenolic polymer gels reinforced by modified nano-silica (GSNP) of different sizes and concentrations in harsh reservoir conditions. Specifically, the nano-silica was modified with a highly soluble silane, and gel properties were evaluated through rheological, differential scanning calorimetry (DSC), and sandpack flooding tests. The results showed that the incorporation of GSNP prolonged the gelation time, enhanced gel strength, and improved stability, allowing the gelation solution to enter deeper into the formation while maintaining long-time effectiveness. The optimal gel system was obtained with 0.4 wt.% GSNP-30, under which condition the storage modulus increased by approximately 14 times, and the content of non-freezable bound water more than doubled. This system exhibited plugging efficiency exceeding 80% in formations with permeabilities ranging from 1000 to 6000 millidarcy and enhanced the oil recovery factor by over 25%. The reinforcement mechanisms were attributed to the adsorption of GSNP onto polymer chains and its role in filling the gel matrix, which enhanced polymer hydrophilicity, suppressed polymer aggregation/curling, prevented ion penetration, and promoted the formation of a more uniform gel network. Careful optimization of nanoparticle size and concentration was essential to avoid the detrimental effects due to nanoparticle overfilling and aggregation. The novelty of this study lies in the practicable formulation of thermal and salt-tolerant gel systems with facile modified nano-silica of varying sizes and the systematic study of size and concentration effects. These findings offer practical guidance for tailoring nanoparticle parameters to cater for high-temperature and high-salinity reservoir conditions. Full article

Magnetic nanoparticles (MNPs) of iron oxide are becoming increasingly popular due to their excellent physicochemical properties as well as very good adsorption and catalytic properties towards heavy metal ions (HMIs). They are used in many industries and are becoming a desirable electrode material in voltammetry. Unfortunately, they tend to aggregate and easily oxidize. To mitigate these issues, they are often coated with organic or inorganic materials, which reduce oxidation and aggregation, and introduce an additional number of active sites capable of interacting with the analyte. Another approach involves the use of carbon material as a base for nanoparticles, which also improves the parameters of nanoparticles. This review reveals a condensed concept presenting functionalized Fe₃O₄ magnetic nanoparticles from the methods of their synthesis and modification to their application in the voltammetric trace analysis of HMIs. This paper describes the effect of electrode surface modification strategies on the stability of MNPs and the homogeneity of their distribution on the carbonaceous carrier surface. The authors focused on the voltammetric procedures for the single and simultaneous determination of HMIs using different electrode materials modified with Fe₃O₄ magnetic nanoparticles. Full article

Using molecular dynamics (MDs) simulations with Materials Studio 8.0 software, we systematically investigated the adsorption and aggregation behaviors of silicon, tin, and copper atoms on the surface of (7,7) single-walled carbon nanotubes (SWCNTs). Silicon, tin, and copper were selected due to their distinct bonding characteristics—covalent (Si), semi-metallic (Sn), and metallic (Cu)—and their relevance in potential composite interface applications such as energy storage, thermal management, and electronics. The results indicate that silicon atoms form multi-layered concentric shells; however, the rigidity of their covalent bonds makes the resulting structures susceptible to disruption by local density fluctuations. Tin atoms form a limited number of stable concentric shells benefiting from the flexibility of their semi-metallic bonds. In contrast, copper atoms rapidly aggregate into disordered clusters due to their high diffusivity and metallic bonding. Within the confined geometry of the carbon nanotubes, all three types of atoms exhibit a tendency toward spiral growth, but their regularity depends on the properties of their chemical bonds, leading to distinct spiral features. These findings are further supported by linear density and radial distribution function (RDF) analyses. Full article

The kinetic dependencies of the surface pressure, the dilational dynamic surface elasticity and ellipsometric angles of cupin-1.2 and vicilin solutions in 8M urea were measured at different concentrations. The analysis of these kinetics dependencies and the obtained master curves allowed us to determine a few adsorption steps in the investigated systems and showed that the master curves are individual characteristics of the protein for a given solvent. At the same time, the shape of these curves can be different for adsorbed and spread layers of plant proteins indicating different structures of these layers. The dependencies of the dynamic surface elasticity on surface pressure are non-monotonic, unlike the corresponding results for most of the solutions of the investigated plant proteins. The extremums of these dependencies can be connected to the formation of the distal region of the surface layer in agreement with the theory for the surface viscoelasticity of polymer solutions. Full article

Polymer-modified bitumen is difficult to produce and often separates during storage and transport. In contrast, granular bitumen modifiers offer wide applicability, construction flexibility, and ease of transport and storage. This study involved preparing a multipolymer granulated bitumen modifier with a styrene–butadiene–styrene block copolymer, polyethylene, and aromatic oil. To elucidate the modification mechanism of a multipolymer granulated bitumen modifier on bitumen, the elemental composition of bitumen A and B, the micro-morphology of the modifiers, the changes in functional groups, and the distribution state of the polymers in the bitumen were investigated using an elemental analyzer, a scanning electron microscope, Fourier-transform infrared spectroscopy, and fluorescence microscopy. The effects of the multipolymer granulated bitumen modifier on the physical, rheological, and viscoelastic properties of two types of base bituminous binders were investigated at various dosages. The test results show that the Z_H/C ratio of base bitumen A is smaller than that of base bitumen B and that the cross-linking effect with the polymer is optimal. Therefore, the direct-feed modified asphalt of A performs better than the direct-feed modified asphalt of B under the same multipolymer granulated bitumen modifier content. The loose, porous surface structure of styrene–butadiene–styrene block copolymer promotes the adsorption of light components in bitumen, and the microstructure of the multipolymer granulated bitumen modifier is highly coherent. When the multipolymer granulated bitumen modifier content is 20%, the physical, rheological, and viscoelastic properties of the direct-feed modified asphalt of A/direct-feed modified asphalt of B and the commodity styrene–butadiene–styrene block copolymer are essentially identical. While the multipolymer granulated bitumen modifier did not significantly improve the performance of bitumen A/B at contents greater than 20%, the mass loss rate of the direct-feed modified asphalt of A to aggregate stabilized, and the adhesion effect reached stability. Image processing determined the optimum mixing temperature and time for multipolymer granulated bitumen modifier and aggregate to be 185–195 °C and 80–100 s, respectively, at which point the dispersion homogeneity of the multipolymer granulated bitumen modifier in the mixture was at its best. The dynamic stability, fracture energy, freeze–thaw splitting strength ratio, and immersion residual stability of bitumen mixtures were similar to those of commodity styrene–butadiene–styrene block copolymers with a 20% multipolymer granulated bitumen modifier mixing amount, which was equivalent to the wet method. The styrene–butadiene–styrene block copolymer bitumen mixture reached the same technical level. Full article

In this study the influence of the geological formation environment on the physicochemical properties of two natural sepiolites, as collected, was investigated. The samples analyzed were a lacustrine-derived sample from Tolsa, Spain (ST), and a hydrothermal-derived sample from La Adela, Argentine (SA). Comprehensive characterization was carried out using chemical analysis (XRF), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and evaluations of hydrophobicity/hydrophilicity behavior. The results indicate that the ST sample exhibits a higher SiO₂/MgO ratio and contains amorphous silica impurities, while the SA sample shows a composition more closely aligned with the theoretical stoichiometry of sepiolite. Furthermore, the SA sample demonstrates greater crystallinity compared to the ST sample. Morphological analysis revealed that ST consists of compact, aggregated fibrous structures, while SA is composed of disaggregated, needle-like fibers with high aspect ratios and nanometric diameters. Both samples display predominantly hydrophilic behavior; however, only the SA sample exhibits suspended particles at the interface, suggesting a slightly higher hydrophobic character than ST sample. These findings highlight the significant impact of the geological formation environment on the structural and surface characteristics of sepiolite, which, in turn, influence its performance in applications involving dispersion, adsorption, and interfacial interactions. Full article

Water-reducing admixtures are of enormous importance to adjust the workability of alkali-activated materials. Especially in geopolymers activated by highly concentrated alkaline solutions, the polycarboxylate ether (PCE) superplasticizers are less effective than in conventional cementitious systems. The aim of this study was to clarify the reasons for the lower dispersing performance of PCE and the synthesis of alternative dispersing agents based on the biopolymer starch to improve the workability of highly alkaline geopolymers. Furthermore, the focus of investigations was on the role of activator type and concentration as key parameters for geopolymer reaction and interaction of water-reducing agents. Therefore, in this study the conformation of three different types of PCE (MPEG: methacrylate ester, IPEG: isoprenol ether, and HPEG: methallyl ether) and synthesized starch admixtures in sodium and potassium hydroxide solutions (1 mol/L up to 8 mol/L) were studied. Furthermore, the dispersing performance, adsorption behavior, and influence on reaction kinetics in metakaolin-based geopolymer pastes were investigated in dependence on activator type and concentration. While the PCE superplasticizers show coiling and formation of insoluble aggregates at activator concentrations of 3 mol/L and 4 mol/L, the synthesized starch admixtures show no significant change in conformation. The cationic starch admixtures showed a higher dispersing performance in geopolymer pastes at all activator concentrations and types. The obtained adsorption isotherms depend strongly on the activator type and the charge density of the starch admixtures. The reaction kinetics of geopolymer pastes were not significantly influenced using the synthesized starch admixtures. Especially the cationic starch admixtures allow the reduction of liquid/solid ratios, which leads to higher flexural and compressive strengths. Full article

Polypeptides exhibit significant health-promoting effects through diverse biological activities, including antihypertensive, antidiabetic, anti-cancer, antimicrobial, and antioxidant properties. Membrane technology offers an efficient separation approach for polypeptides due to its high efficiency, low energy consumption, operational simplicity, and environmental sustainability. This review briefly described the advancements in membrane separation of polypeptides and highlighted the major implementation challenges, such as membrane fouling, peptide adsorption losses, and compromised separation efficiency caused by peptide aggregation. Contributing factors for each issue based on the progress and reports of relevant research were analyzed. And solutions and strategies were also summarized as feed pretreatment, operational parameter optimization, aggregate elimination, and membrane surface modification. These approaches could reduce product loss and enhance peptide yield during purification. This review can provide reference for the research on efficient membrane separation of polypeptide products. Full article

Although various special materials have been studied for their potential for phosphorus removal in constructed wetlands, varying methodologies make direct comparisons of adsorption capacities observed in laboratory experiments difficult. This paper aims to establish a methodology for determining the optimal ratio of phosphate to material mass for different materials and for achieving the necessary contact time for adsorption isotherms. To minimise the number of experiments required, pretests over 24 h should be repeated to determine the phosphate-specific ratios until they show around 60% of the initial concentration. The tested materials included lava sand and expanded sand (ExS), which showed saturating kinetics curves after 24 to 48 h. However, aggregates containing calcium silicate hydrate (CSH) phases (autoclaved aerated concrete AAC, sand–lime brick SLB, and hydrothermal granules HTG) did not show saturating curves, complicating contact time determination. Consequently, adsorption velocity is proposed to identify the phase with the lowest adsorption rate, which is then used as the contact time in adsorption isotherm experiments. Using this method, adsorption times of 48 h were observed for HTG and SLB, while that for AAC was 24 h. This methodology is intended as an initial approach to establish a common basis for researchers investigating novel materials and make the results comparable. Full article

Zeolites are promising materials for volatile organic compound (VOC) adsorption and catalytic oxidation, where tuning their structure via defect engineering can enhance adsorption capacity and active metal dispersion. In this study, a concentration-sensitive chelation strategy using diethylenetriaminepentaacetic acid (DTPA) was developed to achieve moderate dealumination for Beta and Y zeolites. For Y zeolite, 0.1 M DTPA treatment increased the toluene adsorption capacity from 59 to 110 mg/g. After platinum (Pt) loading, both DTPA-modified Beta- and Y-based catalysts showed improved toluene oxidation efficiency compared to their unmodified counterparts. Remarkably, the Y-DTPA-0.01-Pt catalyst achieved 90% toluene conversion at 150 °C with CO₂ selectivity above 90%. DRIFTS and H₂-TPR results confirmed that moderate dealumination by DTPA generated silanol defects in zeolite Y that strongly anchored Pt²⁺ in a highly dispersed form and suppressed PtO formation. Severe dealumination using 0.1 M DTPA created larger defects that favored the aggregation of Pt⁰ clusters whilst causing significant loss in the micropores, thus reducing the Pt loading content and catalytic activity. This work demonstrates a simple and effective approach to optimize zeolite-based catalysts by controlling defect formation through controllable chelation, offering new insights into VOC abatement via tailored support design. Full article

Extensive studies have established that ultrasonic micro-jets and acoustic cavitation selectively intensify interfacial interactions at multiphase boundaries, thereby enhancing the flotation of soluble salt minerals and oxide ores. Although a growing body of evidence shows that pulp-borne nanoparticles (i.e., nanosolids, colloids, and nanoscale gas nuclei) mediate these effects, their role in the flotation of ultrafine smithsonite after collector addition has not yet been systematically examined. To fill this gap, we compared the flotation response of ultrafine smithsonite under conventional stirring (SC) and ultrasonic conditioning (UC), using sodium oleate (NaOL) as the collector, and dissected the governing mechanisms across three pillars, mineral–NaOL interaction, particle aggregation, and frothability, with particular attention paid to how nanoparticles modulate each dimension. The flotation results show that flotation performance under UC is dictated by NaOL concentration. At low NaOL levels (i.e., below 4 × 10⁻⁴ M), UC depresses both recovery and kinetics relative to SC, while at high NaOL levels, the trend reverses and UC outperforms SC. Mechanistic analysis reveals that sonication erodes mineral surfaces and generates cavitation, flooding the pulp with various nanoparticles. When NaOL is scarce, zinc-containing components and zinc-rich nanosolids sequester the collector through non-selective adsorption and precipitation, leaving smithsonite poorly hydrophobized. Consequently, particle aggregation and pulp frothability are markedly inferior to those in the SC system, so the flotation recovery and kinetics remain lower. As the NaOL concentration rises, smithsonite becomes adequately hydrophobized, and the pulp fills with hydrophobic zinc-rich nanosolids, along with cavitation-induced gas nuclei or tiny bubbles. These nanoparticles now act as bridges, accelerating the aggregation of ultrafine smithsonite once sonication stops and agitation begins, while simultaneously improving frothability. Although the strong dispersive action of ultrasound still suppresses initial flotation kinetics, cumulative recovery ultimately surpasses that of SC. The findings delineate a nanoparticle-regulated flotation paradigm and establish a critical NaOL concentration window for effective UC in ultrafine smithsonite flotation. This framework is readily transferable to the beneficiation of other ultrafine, soluble oxidized minerals (rhodochrosite, dolomite, etc.). Full article