Formation Of Adsorption Layer Research Articles

Heat transfer performance study of Cu-ethanol/ethylene glycol/propylene glycol-water nanofluids in a wavy-walled tube heat exchanger

With the rapid consumption of nonrenewable energy sources, improving the heat transfer efficiency of conventional fixed tube plate heat exchangers, optimizing their structure, and finding more efficient coolants have become popular topics. In this paper, the cooling effect of ethanol/ethylene glycol/propylene glycol-water solution with a mass fraction of 50 % in a wavy-walled tube heat exchanger was investigated, while Cu nanoparticles with volume fractions of 1.5 % and 3.0 % were added to the cold working mass to form three different nanofluids. The effects of the three nanofluids at different volume fractions on the heat transfer performance of the wavy-walled tube heat exchanger were analyzed with numerical simulations, while the microscopic mechanism of the enhanced thermal conductivity of the nanofluids was investigated using molecular dynamics simulations. The results showed that the thermal conductivity of the nanofluids was greatly enhanced due to the formation of adsorption layers with different properties on the nanoparticle surfaces, and the Cu–ethylene glycol-water nanofluid showed the largest increase in thermal conductivity among the three nanofluids. It was also found that the shell-side pressure drop, convective heat transfer coefficient, and heat exchange quantity of the nanofluid in the wavy-walled tube heat exchanger significantly increased with an increase of volume fraction. The comprehensive heat transfer performance of the three nanofluids was found to be better compared to the base fluid. Cu-ethanol/EG/PG-water nanofluid with a volume fraction of 3.0 % increased the PEC of the heat exchanger by 10.4 %, 19.8 % and 27.6 %, respectively, at a volume flow rate of 1.53 m3/h. Therefore, the Cu-propylene glycol-water nanofluid had the best comprehensive heat transfer performance. Cu-ethanol-water nanofluid volume fraction of 3.0 % reaches a maximum PEC value of about 3.12 at Qv near about 2.0 m3/h, and Cu-EG-water nanofluid volume fraction of 3.0 % has a peak PEC value of about 4.07 at Qv of near about 2.0 m3/h. Therefore, the Cu-ethanol-water and Cu-ethylene glycol-water nanofluids are the optimal solutions for the combined heat transfer performance within the study.

3,4-Dimethoxy phenyl thiosemicarbazone as an effective corrosion inhibitor of copper under acidic solution: comprehensive experimental, characterization and theoretical investigations.

This study investigates the corrosion inhibition potential of 3,4-dimethoxy phenyl thiosemicarbazone (DMPTS) for copper in 1 M hydrochloric acid (HCl) solutions, aiming to disclose the mechanism behind its protective action. Through an integrative methodology encompassing electrochemical analyses-such as weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS)-we quantitatively evaluate the corrosion protection efficacy of DMPTS. It was determined that the optimal concentration of DMPTS markedly boosts the corrosion resistance of copper, achieving an impressive inhibition efficiency of up to 89% at 400 ppm. The formation of a protective layer on the copper surface, a critical aspect of DMPTS's inhibitory action, was characterized using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). These techniques provided empirical evidence of surface morphology modifications and roughness changes, affirming the formation of a protective barrier against corrosion. A significant advancement in our study was the application of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, which identified chemical adsorption as the definitive mechanism of corrosion inhibition by DMPTS. The ATR-FTIR results explicitly demonstrated the specific interactions between DMPTS molecules and the copper surface, indicative of a robust protective adsorbed layer formation. This mechanistic insight, crucial to understanding the inhibitory process, aligns with the protective efficacy observed in electrochemical and surface analyses. Theoretical support, provided by the Quantum Theory of Atoms in Molecules (QTAIM) and quantum chemical computations, further validated the strong molecular interaction between DMPTS and copper, corroborating the experimental findings. Collectively, this research not only confirms the superior corrosion inhibition performance of DMPTS in an acidic setting but also elucidates the chemical adsorption mechanism as the foundation of its action, offering valuable insights for the development of effective corrosion inhibitors in industrial applications.

Mechanism for adjusting the strength of interphase adsorption layers of "Skimmed milk – surfactant substance" in dessert products

Today, the range of dessert products produced by the restaurant industry of Ukraine is wide and diverse and is determined by its nomenclature. Mousse is one of the most common dessert dishes ordered in restaurants of various levels. The traditional technological scheme of mousses production is to some extent labor-intensive, and this makes it difficult to satisfy consumer demand. Therefore, the use of a dry mixture in the recipe composition of mousses is justified. This article is devoted to the investigating the regulatory mechanisms of interphase adsorption layer strength at the interface of the water – oil and water – air phases by introducing surfactants into the dry mixture for the manufacture of dessert products. The choice of surfactants and their concentrations for the formation of interfacial adsorption layers in systems is based on the consideration of surface activity, hydrophilic-lipophilic balance (HLB) and protein concentration, which determines the behavior of the mixture of surfactants in the system. The issue of the influence of surfactants with high and low HLB and their mixtures and the use of a system with three surfactants E472e-E472b-E322, which allow to obtain whipped emulsions from a dry mixture, are considered.

Mechanisms of formation of wear-resistant dissipative structures in non-stationary lubrication conditions

The work aimed to determine the influence of the processes of supramolecular self-organization in the lubricating layer on the patterns of wear of friction pairs. The mechanisms of structural adaptability of tribocoupler elements were analyzed, and the regularities of the manifestation of a large-scale and energy jump, which characterizes the transition of the tribosystem to a metastable state, were determined. An evaluation of the tribotechnical characteristics of commercial transmission oils was carried out on a software-hardware complex that, using a roller analogy, simulates the operation of gears in conditions of rolling with slipping. It was established that the activation of contact surfaces in the mode of frequent starts and stops leads to active interaction of the lubricant's components and the metal's surface layers with the gradual formation of boundary adsorption layers. For transmission oil 'Bora B' T-Shyp, an increase in anti-friction properties has been established due to the effective lubricating ability of the oil when forming the hydro- and non-hydrodynamic components of the lubricating layer thickness. The effect of the chemical activity of the zinc dialkyl dithiophosphate antiwear additive and the hydrocarbon components of the base of transmission oils on the effectiveness of the formation of boundary films is considered. It was determined that the formation of stable boundary films of the lubricant is the leading process in manifesting their damping properties concerning the localization of elastic-plastic deformation along the depth of the metal. When boundary films are formed on 90-95% of the contact area, the change in the microstructure of the near-surface layers is fixed at a depth of up to 20 microns; when boundary films are formed on 20...50% of the surface area, the spread of elastic-plastic deformation reaches a depth of up to 50 microns. The kinetics of the formation of boundary films by the lubricant and the indicators of the specific work of friction in contact are correlated with the intensity of wear of the contact surfaces

MECHANISM FOR ADJUSTING THE STRENGTH OF INTERPHASE ADSORPTION LAYERS OF "SKIMMED MILK – SURFACTANT SUBSTANCE" IN DESSERT PRODUCTS

Today, the range of dessert products produced by the restaurant industry of Ukraine is wide and diverse and is determined by its nomenclature. Mousse is one of the most common dessert dishes ordered in restaurants of various levels. The traditional technological scheme of mousses production is to some extent labor-intensive, and this makes it difficult to satisfy consumer demand. Therefore, the use of a dry mixture in the recipe composition of mousses is justified. This article is devoted to the investigating the regulatory mechanisms of interphase adsorption layer strength at the interface of the water–oil and water–air phases by introducing surfactants into the dry mixture for the manufacture of dessert products. The choice of surfactants and their concentrations for the formation of interfacial adsorption layers in systems is based on the consideration of surface activity, hydrophilic-lipophilic balance (HLB) and protein concentration, which determines the behavior of the mixture of surfactants in the system. The issue of the influence of surfactants with high and low HLB and their mixtures and the use of a system with three surfactants E472e-E472b-E322, which allow to obtain whipped emulsions from a dry mixture, are considered.

Elaboration of thermophysical performance enhancement mechanism of functionalized boron nitride/graphite hybrid nanofluids

This study mainly investigated the physicochemical characteristics of ethylene glycol/ water (EG/W) based hydroxyl-functionalized boron nitride (BN-OH) and graphite (G) hybrid nanofluids. A novel simple and efficient annealing method was proposed to have hexagonal boron nitride (h-BN) nanoparticles functionalized to improve the synergistic role between hybrid G/BN-OH nanoparticles. Meanwhile, the dispersion stability, thermal stability, and rheological behavior of diverse nanofluids (h-BN, BN-OH, G, G/BN and G/BH-OH) were comprehensively evaluated. The results showed that the G/BN-OH hybrid nanofluids demonstrate both better dispersion stability and thermal stability, as well as a lower increase in viscosity. In addition, the thermal conductivity of G/BN-OH hybrid nanofluids was increased by up to 18.05% with a concentration of 0.2 wt% when compared to the base fluid. Ultimately, the complicated theoretical mechanism of thermophysical performance augment for G/BH-OH hybrid nanofluids was reliably presented. The enhanced thermal conductivity of nanofluids may be attributed to the formation of adsorption layers and the synergistic effect of the thermal conductivity network.

Designing Gastric-Stable Adsorption Layers by Whey Protein-Pectin Complexation at the Oil-Water Interface.

This work aims to design gastric-stable emulsions with food-grade biopolymers using a novel multiscale approach. The adsorption layer formation at the oil-water interface was based on opposite charge interactions between whey proteins and pectin (with different esterification levels) at pH 3.0 by a sequential adsorption method. The interfacial assembly and disassembly (interfacial complexation, proteolysis, lipolysis) during in vitro gastric digestion were evaluated using a quartz crystal microbalance with dissipation monitoring, ζ-potential, dynamic interfacial tension, and interfacial dilatational rheology. Besides, the evolution of the particle size and microstructure of bulk emulsions during the digestion was investigated by static light scattering and light microscopy. Compared with whey protein isolate (WPI)-stabilized emulsions, the presence of an additional pectin layer can prevent or at least largely delay gastric destabilization (giving rise to coalescence or/and oiling off). Especially, the esterification degree of the pectin used was found to largely affect the emulsion stability upon gastric digestion.

Biopolymer sodium alginate based titania and magnetite nanocomposites as natural corrosion inhibitors for mild steel in acidic medium

Green biopolymeric materials and its hybrid nanocomposites, i.e. sodium alginate grafted polymethylmethacrylate based titanium dioxide and iron oxide (SA-g-PMMA/TiO2 and SA-g-PMMA/Fe3O4) have been explored for the prevention of mild steel's corrosion in 15% HCl. It is reflected from the electrochemical impedance data that SA-g-PMMA/TiO2 exhibits maximum inhibition efficiency of 97.28% followed by SA-g-PMMA/Fe3O4 that gives 96.82% efficiency while the unmodified sodium alginate possess merely 84.74% efficiency. The declining trend of inhibition efficiency with rising temperature has been explained through gravimetric studies conducted at 303 K- 333 K. The thermodynamic activation and adsorption parameters revealed the mixed mode of adsorption of inhibitors over mild steel surface which follow Langmuir adsorption isotherm. It has been observed from tafel polarization studies that all studied inhibitors are mixed type in nature. The surface morphological inspection of the mild steel samples was done through FE-SEM and AFM, which revealed the formation of better protective adsorption layer over the exposed metallic surface by the nanocomposites in comparison to sodium alginate alone. In addition to this, the elemental composition of adsorbed film on inhibited mild steel specimens was obtained by XPS technique. Quantum parameters obtained through Density Functional Theory (DFT) further corroborate the experimental outcomes.

Расчет эффективности собственно моющего действия детергентов

Detergents actively neutralize acidic foods and prevent the formation of deposits at high temperatures. This is realized by solubilization and through the formation of adsorption layers from micelle detergents. The article discusses aspects of the possible calculation of the detergent effect

Surface wettability effects on evaporating meniscus in nanochannels

Systematic investigations of self-regulation of evaporating menisci in nanochannels are conducted as a function of the surface wettability under various applied heat flux conditions. The simulation system is designed to result in steady-state response so that a stable meniscus region can be produced. Non-equilibrium molecular dynamics simulations are performed for argon fluid in platinum channels. Depending on the surface wettability and the applied heat flux the meniscus can be in the pinned regime or it can recede inside the channel. Adsorbed layer formation becomes evident for the latter case. Higher wettability enables the formation of a thicker adsorbed layer reducing the radius of curvature of the meniscus and the overall evaporation rate in the channel. Adsorbed layer reduces the thermal resistance of the evaporator, providing a higher critical heat flux. While evaporation from the adsorbed layer is negligible for macroscopic systems, it can contribute up to 80% of the total evaporating mass in nanoscale systems. The current work provides insights into the capillary-driven thin-film evaporation in ultra-small channels and the findings are meaningful for next-generation thermal management systems.

Influence of water on the electrochemical characteristics and nanostructure of Bi(hkl)│Ionic liquid interface

In electrochemical applications of ionic liquids (ILs), the presence of residual amounts of water can influence the performance of ILs as electrolytes when developing novel electrochemical devices. In this work, the influence of water additive on the electrical double layer formation and adsorption of ions from 1-ethyl-3-methylimidazolium trifluromethanesulfonate IL at semi-metallic bismuth single crystal electrodes has been studied via cyclic voltammetry, electrochemical impedance spectroscopy, and in situ scanning tunneling microscopy methods. Major differences in water-adsorbed IL mixtures are observed at bismuth single crystal electrodes within a wide potential region: increased current densities and anomalous capacitance maxima, especially at positive polarization conditions. The kinetics of adsorption layer formation significantly are strongly affected by the adsorption processes of both cations and anions under polarization conditions, shown by the characteristic relaxation time constant results. Interfacial distribution of ions and surface nanostructure is visualized at the atomic resolution under in situ scanning tunneling microscopy study. These results provide a detailed understanding of the Bi(hkl) surface structure and the ion adsorption processes dependence on electrode polarization.

Pristine and activated bentonite for toxic metal removal from wastewater

AbstractNatural bentonite clay (NBC) was activated using nitric acid (HNO3). Characterization techniques including FTIR, SEM, XRD and BET were employed to examine the morphology of NBC and ABC (activated bentonite clay) sorbents. Comparative application of ABC and NBC to remove heavy metals (Fe2+, Zn2+, Ni2+) from pharmaceutical effluents was investigated under various experimental conditions. The maximum proportional removal by ABC was 88.90, 81.80 and 75.50% at pH 8, and 63.90, 59.60, 58.70% at pH 10 for NBC, both for Zn2+, Fe2+ and Ni2+ respectively. The Freundlich multilayer adsorption model and pseudo-second-order kinetics best fit the experimental data, suggesting the formation of multiple adsorption layers via strong ionic and electrostatic interactions. Heavy metals adsorption is more favorable with ABC than NBC, due to the availability of more sorption sites and a larger specific surface. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) revealed that the adsorption is endothermic and spontaneous in nature for both ABC and NBC.

Recent Progress in Microfiltration/Ultrafiltration Membranes for Separation of Oil and Water Emulsions.

Oily wastewater has become one of the leading causes of environmental pollution. A massive quantity of oily wastewater is released from industries, oil spills, and routine activities, endangering the ecosystem's sustainability. Due to the enormous negative impact, researchers put strenuous efforts into developing a sustainable solution to treat oily wastewater. Microfiltration/ultrafiltration membranes are considered an efficient solution to treat oily wastewater due to their low cost, small footprint, facile operation, and high separation efficiencies. However, membranes severely fouled during the separation process due to oil's adsorption and cake layer formation, which shortens the membranes' life. This review has critically discussed the microfiltration/ultrafiltration membrane synthesizing methods and their emulsion's separation performance. In the end, key challenges and their possible solutions are highlighted to provide future direction to synthesize next-generation membranes.

Сорбційні властивості природних вуглецевих матеріалів при видаленні пар із водних розчинів

SORPTION PROPERTIES OF NATURAL CARBON MATERIALS IN THE SEPARATION OF SURFACTANTS FROM WATER SOLUTIONS © I.V. Yakupova, I.M. Kosygina, Phd, A.S. Makarov, Doctor Of Technical Sciences, I.M. Kryuchko (INSTITUTE OF COLOID AND WATER CHEMISTRY NAS OF UKRAINE, Akademika Vernadskogo Blvd., 42, Kyiv, 03142, Ukraine) More than 40 % of the world's electricity production comes from thermal power plants. The main (97.5 %) type of fuel for Ukrainian thermal power plants is coal, which is explained by the cheapness and availability of this raw material. Low efficiency and environmental problems in the use of coal determine the relevance of the search for alternative fuels in Ukraine, and one of the main ones is coal-water fuel – a highly concentrated dispersed system in which a dispersed fraction of coal of any calorific value and a liquid phase consisting of water with plasticizer additives are used as a combustible base and stabilizers. To give stability and the necessary fluidity, a small amount of a surfactant plasticizer is introduced into the suspension. The formation of surfactant adsorption layers on the surface of particles of the dispersed phase is a necessary condition for the formation of the structure of suspensions and its stabilization. The amount of surfactant adsorption, in addition to the physicochemical composition of coal, is largely affected by the nature of the surface and the cellular structure of materials. To study the sorption efficiency of carbon materials, rigid surfactants widely used in the construction industry were used: sodium salt of sulfonated naphthalene formaldehyde (NF), dophene (technical NF), sulfomelamin formaldehyde (SMF), sodium lignosulfonate (LSTNa). The processes of surfactant adsorption on coal of Ukraine with different degrees of metamorphism have been studied. Conclusions are drawn that allow a better understanding of the processes of interaction of surfactants with solid particles of sorbents. It has been established that the sorption properties of surfactants with the use of carbon sorbents decrease in the series LST → dophene → NF → SMF, which is explained by the structure of surfactants. Comparative characterization of the data obtained also allows us to state that the sorption properties with respect to surfactant compounds increase in a number of studied carbon sorbents: lean coal (P) → long-flame gas coal (DG) → anthracite. The similarity of adsorption processes on the surface of coal grade DG and anthracite gives grounds for the assumption that the mechanisms of stabilization of water-coal suspensions by surfactant compounds during the creation of water-coal fuel are similar. Keywords: natural coal, surfactant, adsorption, outer layer, micelles, aggregation. Corresponding author I.M. Kosygina, e-mail: kosygina@ukr.net

The structure, formation, and effect of plasma protein layer on the blood contact materials: A review

Understanding material-protein interactions is the basis for regulating material-blood interactions, which is a common topic of interest for medical material developers. In recent years, researchers have conducted extensive studies on (1) the structural characteristics of the plasma protein adsorption layer on the material surface, including the evolution of the protein adsorption layer and its typical binary structure. (2) Influence factors of the protein adsorption layer formation include protein factors (e.g., isoelectric point, structural stability), material factors (e.g., wettability, surface charge, morphology, size), and environmental factors. (3) Effects of some common plasma proteins in the protein adsorption layer on material-blood interactions. Here, we review the important research results in this field, hoping to provide a reference for future development of advanced blood contact materials.

Corrosion behavior of the reinforcement in chloride-contaminated alkali-activated fly ash pore solution

Corrosion performance of the reinforcement was dramatically affected by chemical compositions of pore solution in alkali-activated fly ash. In this study, the electrochemical behavior and surface properties of reinforcement were characterized in chloride-contaminated simulated alkali-activated fly ash pore (SAFP) solution. The results indicated that due to the high alkalinity and formation of zeolite-like adsorption layer (about 20 nm), the reinforcement was still in passive state and exhibited high corrosion resistance in chloride-contaminated SAFP solution. However, the protective effect of passivation film (consisted of mainly FeOOH outer film and FeO inner film) and corrosion resistance of the reinforcement were reduced by chlorides. Further, the chloride threshold in SAFP solution was 10 times larger than simulated cement pore solution, due to the competitive adsorption between OH−/silicates and chlorides.

Direct Visualization and Characterization of Interfacially Adsorbed Polymer atop Nanoparticles and within Nanocomposites

Irreversible adsorption at polymer/substrate interfaces has been reported to influence glassy properties in thin films. However, consideration has yet to be extended to the nanocomposite geometry, wherein a large interfacial area and high processing temperatures afford especially favorable conditions for irreversible adsorption at the polymer/nanoparticle interface. Here, we present an approach for directly measuring the site-specific glassy properties at the polystyrene (PS)-adsorbed layer interface in PS–silica nanocomposites. We achieved this using a stepwise assembly approach to localize fluorescent dyes within the nanocomposite adsorbed layer, subsequently measuring the glass transition temperature (Tg) via fluorescence. We found that PS adsorption within nanocomposites strongly influenced the local Tg. By measuring the thickness of the PS-adsorbed layers atop nanoparticles via transmission electron microscopy, we found a correlation between adsorbed layer Tg and thickness. Our results provide compelling evidence that adsorbed layer formation within polymer nanocomposites can have a profound impact on local interfacial properties.

Influence of Temperature on Rising Bubble Dynamics in Water and n-pentanol Solutions

Data in the literature on the influence of water temperature on the terminal velocity of a single rising bubble are highly contradictory. Different variations in bubble velocity with temperature are reported even for potentially pure systems. This paper presents a systematic study on the influence of temperature between 5 °C and 45 °C on the motion of a single bubble of practically constant size (equivalent radius 0.74 ± 0.01 mm) rising in a clean water and n-pentanol solution of different concentrations. The bubble velocity was measured by a camera, an ultrasonic sensor reproduced in numerical simulations. Results obtained by image analysis (camera) were compared to the data measured by an ultrasonic sensor to reveal the similar scientific potential of the latter. It is shown that temperature has a significant effect on the velocity of the rising bubble. In pure liquid, this effect is caused only by modifying the physicochemical properties of the water phase, not by changing the hydrodynamic boundary conditions at the bubble surface. In the case of the solutions with surface-active substances, the temperature-change kinetics of the dynamic adsorption layer formation facilitate the immobilization of the liquid/gas interface.

DNA Interaction with a Polyelectrolyte Monolayer at Solution-Air Interface.

The formation of ordered 2D nanostructures of double stranded DNA molecules at various interfaces attracts more and more focus in medical and engineering research, but the underlying intermolecular interactions still require elucidation. Recently, it has been revealed that mixtures of DNA with a series of hydrophobic cationic polyelectrolytes including poly(N,N-diallyl-N-hexyl-N-methylammonium) chloride (PDAHMAC) form a network of ribbonlike or threadlike aggregates at the solution—air interface. In the present work, we adopt a novel approach to confine the same polyelectrolyte at the solution—air interface by spreading it on a subphase with elevated ionic strength. A suite of techniques–rheology, microscopy, ellipsometry, and spectroscopy–are applied to gain insight into main steps of the adsorption layer formation, which results in non-monotonic kinetic dependencies of various surface properties. A long induction period of the kinetic dependencies after DNA is exposed to the surface film results only if the initial surface pressure corresponds to a quasiplateau region of the compression isotherm of a PDAHMAC monolayer. Despite the different aggregation mechanisms, the micromorphology of the mixed PDAHMAC/DNA does not depend noticeably on the initial surface pressure. The results provide new perspective on nanostructure formation involving nucleic acids building blocks.

Surface and Antibacterial Properties of Titanium Dioxide Nanoparticles Synthesized in Plasma Discharge under Ultrasonic Cavitation

In this work, it is shown that intensive treatment of dispersed systems with ultrasound is an effective method for enhancing the interaction of particles and polymer with the subsequent formation of adsorption layers of high thickness and strength. This makes possible to obtain highly stable dispersed systems with a modified surface of the solid phase. The studies proved the important role of intensive ultrasonic action for controlling the properties of the nanoparticles surface in heterophase systems. It is shown that an increase in the activity of the surface of nanoparticles as a result of ultrasonic treatment is of great importance for the study of their antibacterial activity: after ultrasonic activation, nanoparticles are more active in interaction with cell membranes.