Hexane Adsorption Research Articles

Silicon rib waveguide with palladium coated gold nanorods overlayer for hexane and N-methylaniline detection

The adsorption of hexane and N-methylaniline was investigated by on-chip vibrational spectroscopy. The interaction with the Pd surface significantly perturbs the vibrational modes of hexane. Near-infrared absorption spectroscopy on the waveguide detected a redshifted CH stretching vibration. We showed that while rapid evaporation of one component may occur, the modification facilitates the sensing for large molecules and mixtures of substances. Rib waveguides were modified with palladium to exhibit an enhanced electromagnetic field effect due to the electrostatic interaction of Pd and hydrogen, showing the drop in the amine overtone absorption of 7.6 dB and the overtone related to the bond of carbon to hydrogen of 6.8 dB. The absorption of hexane bonds in water is 5.5 dB. The obtained values are 100 times higher than those predicted by the electromagnetic simulator for pure rib waveguides. This may be explained by CH bonds in hexane that can be activated through a hydrogen bond-like interaction with metal substrates. This achievement holds promising potential for advancing hexane and N-Methylailine detection and analysis technologies, with implications for diverse applications in various industries, such as environmental monitoring, industrial processes, and safety measures.

Adaptive Peptide Molecule as the Promising Highly-Efficient Gas-Sensor Material: In Silico Study.

Gas sensors are currently employed in various applications in fields such as medicine, ecology, and food processing, and serve as monitoring tools for the protection of human health, safety, and quality of life. Herein, we discuss a promising direction in the research and development of gas sensors based on peptides-biomolecules with high selectivity and sensitivity to various gases. Thanks to the technique developed in this work, which uses a framework based on the density-functional tight-binding theory (DFTB), the most probable adsorption centers were identified and used to describe the interaction of some analyte molecules with peptides. The DFTB method revealed that the physical adsorption of acetone, ammonium, benzene, ethanol, hexane, methanol, toluene, and trinitrotoluene had a binding energy in the range from -0.28 eV to -1.46 eV. It was found that peptides may adapt to the approaching analyte by changing their volume up to a maximum value of approx. 13%, in order to confine electron clouds around the adsorbed molecule. Based on the results obtained, the prospects for using the proposed peptide configurations in gas sensor devices are good.

Direct Resolution of the Interactions of a Hydrocarbon Gas with Adsorbed Surfactant Monolayers at the Water/Air Interface Using Neutron Reflectometry

We have directly resolved in the present work the interfacial composition during and after the interactions of a saturated atmosphere of oil vapor with soluble surfactant solutions at a planar water/air interface for the first time. Experiments were conducted on interactions of hexane vapor with solutions of alkyltrimethylammonium bromides and sodium dodecyl sulfate to observe the balance between cooperativity and competition of the components at the interface. In all cases, hexane adsorption was strongly enhanced by the presence of the surfactant, even at bulk surfactant concentrations four orders of magnitude below the critical micelle concentration. Cooperativity of the surfactant adsorption was observed only for sodium dodecyl sulfate at intermediate bulk concentrations, yet for all four systems, competition set in at higher concentrations, as hexane adsorption reduced the surfactant surface excess. The data fully supported the complete removal of hexane from the interface following venting of the system to remove the saturated atmosphere of oil vapor. These results help to identify future experiments that would elaborate and could explain the cooperativity of surfactant adsorption, such as on cationic surfactants with short alkyl chains and a broader series of anionic surfactants. This work holds relevance for oil recovery applications with foam, where there is a gas phase saturated with oil vapor.

Cotton fabrics modified with tannic acid/long-chain alkylamine grafting for oil/water separation

BackgroundsCotton fabrics were modified on surface wettability for efficient oil/water separation. The modification adopted in previous literature are commonly complicated in steps, expensive in chemicals applied, and not environmentally begien in solvents used. ExperimentsThis article applied a novel one-step modification protocol to modified cotton fabrics using tannic acid (TA) grafted via Michael addition/Schiff base reactions with long-chain alkylamines, including 1-tetradecylamine (TDA), 1-hexadecylamine (HDA), and 1-octadecylamine (ODA) with 14, 16 and 18 methyl groups, respectively, were applied in this study for cotton fabrics modification. The TA, an inexpensive natural polyphenol, was adopted for providing excess catechol groups for linking the cotton surface and the alkylamines. The grafting reactions via Michael addition/Schiff base reaction were performed at room temperature and pH 8.5 with catalysts CuSO4/H2O2 for significantly reducing the reaction time needed. ResultsThe chemical analysis confirmed the modification of the cotton fabrics to possess hydrophobic surface, with contact angles for water droplets on the modified surface as 133.3o, 136.0o and 142.9° for TA-TDA, TA-HDA, and TA-ODA cotton fabrics, respectively; and diiodinemethane droplets on the modified surface being 56.0o, 58.8o and 59.3o, respectively. The modified cotton surface has intermediate dispersive component of surface energy (29.0–31.2 mJ/m2) and low polar component (4.2–6.2 mJ/m2), yielding high affinity to oil but low affinity to water. Parametric study revealed that the pH value and reaction time are the most important parameters for the alkylamine grafting reactions, while the reduction of catalyst amount used but still with sufficient modification on cotton fabrics can be achieved. The oil absorption tests with cotton fabrics contacting hexane (top)-water (bottom) layers revealed high hexane adsorption capacity: 0.96, 1.22, 1.25 g hexane/g cotton for TA-TDA, TA-HAD and TA-ODA cotton fabrics, respectively. The absorption tests with cotton fabrics contacting water first for 30 s then hexane for another 30 s had much lower absorption capability of hexane: 0.52, 0.85, 0.87 g hexane/g cotton for TA-TDA, TA-HAD and TA-ODA cotton fabrics, respectively, since water would penetrate the major pores for inhibiting further oil absorption.

First-principles studies on sensing properties of delta arsenene nanoribbons towards hexane and heptane molecules

The adsorption of hexane and heptane on delta arsenene nanoribbon (delta-AsNR) are studied with regard to the density functional theory method. Firstly, the structural stability of delta-AsNR is ascertained with formation energy. The band structure of delta-AsNR shows semiconductor behaviour. The delta-AsNR is used as a sensing substrate for hexane and heptane molecules. Based on the energy of assimilation, average band gap alteration, and Bader charge transference, the surface assimilation of hexane and heptane molecules on delta-AsNR are explored. The density of states variation of delta-AsNR upon hexane and heptane adsorption also shows the variation in electronic properties of delta-AsNR. Thus, based on the results it is evident that delta-AsNR can be deployed as a novel chemosensor for hexane and heptane molecules evolved from the sewage.

Comparative Study of Toluene and Hexane Adsorption on Activated Carbons From Gas and Liquid Phase. Enthalpy and Isotherms

Activated carbons with different chemical and textural properties were used to carry out the adsorption of toluene and hexane from gas phase and from liquid phase for toluene-hexane solutions where toluene was used as a solute and hexane as the solvent, complementing the process with the evaluation of the immersion enthalpy for the pure components and toluene-hexane mixtures at different molar fractions. The adsorption capacities for the gas phase were between 3.40 mmol g-1 and 0.05 mmol g-1, being higher for toluene because of the π-π interaction with the solid; when evaluating the liquid phase, the adsorption capacities were 0.24 and 0.74 mmol g-1, where the adsorption of toluene decreased compared to the gas phase because of the solute-solute, solvent-solvent, solute-solvent interaction. The immersion enthalpies for the pure solvents were between -40.87 J g-1 and -126.10 J g-1 being higher also for toluene confirming a greater interaction compared to hexane; for the mixtures, immersion enthalpy was higher than hexane enthalpies, but lower than toluene enthalpies with values between -59.79 J g-1 and -107.95 J g-1. It was found that there was a greater interaction between the sample with a lower content of acid groups and a greater surface area with toluene due to the high electron density of carbon and London-type as π- π interactions with the aromatic compound. For mixtures, hexane decreased the adsorption capacity and interaction with respect to toluene because there was competition for adsorption sites and subsequent displacement of hexane molecules when the amount of toluene on the surface increased.

Fabrication of diverse carbon forms and their reversed applications in hexane/water separation.

Melamine foam is an important material in production and life. A series of porous carbon foams were obtained through a simple carbonization process of melamine foam at different temperatures. The carbon foams obtained at the carbonization temperature of 400 and 600 °C reveal a hydrophobic and even super-hydrophobic property (water contact angle larger than 150°) with a hexane adsorption much larger than that of melamine foam. However, the carbon foam obtained at the carbonization temperature of 800 °C reveals a super-hydrophilic property (water contact angle smaller than 5°) due to its severest shrinkage during the carbonization process. Interestingly, this series of carbon foams have an excellent performance in oil adsorption. However, the carbon membranes derived from the 800 °C carbon foam reveals oleophobicity under water (the adsorbed water at the surface was extremely important), which allows the penetration of water and blocks the infiltration of hexane at the same time. These different carbon forms have reversed applications in hexane/water separation.

Green hybrid zeolite coatings for on-orbit molecular decontamination

FAU-type and MFI-type green hybrid zeolite coatings were developed for on-orbit molecular decontamination application by using a mixture of an organic binder (silicone resin) and an inorganic binder (suspension of colloidal silica nanoparticles). The zeolite content in the final dry coatings varies from 80 to 85 wt % whereas the total amount of binders varies from 15 to 20 wt %. This amount of binder was sufficient to give the zeolite coating interesting adhesion and cohesion properties. In fact, by using an equal amount of each binder, homogeneous films without significant cracks were obtained on an aluminum alloy substrate which is the main constituent of satellites. Nitrogen adsorption-desorption measurements revealed almost no loss of micropore volume of zeolite coatings. Adsorption experiments of an organic pollutant were carried out using n -hexane as probe molecule. The n -hexane adsorption capacities of FAU-type hybrid zeolite coatings (136–143 mg/g anhydrous zeolite ) are lower than that of pure FAU-type zeolite (180 mg/g anhydrous zeolite ) due to water co-adsorption. The n -hexane adsorption capacities of MFI-type zeolite coatings (103–106 mg/g anhydrous zeolite ) are similar to that of pure MFI-type zeolite (110 mg/g anhydrous zeolite ). • Hybrid zeolite coatings were developed with high zeolite contents (80 and 85 wt %). • A combination between an organic binder an inorganic binder was studied. • Good adhesion properties of zeolite coatings on an aluminum alloy substrate. • Interesting adsorption capacities of n -hexane by zeolite coatings. • Potential applications for VOCs adsorption.

Drop Size Dependence of the Apparent Surface Tension of Aqueous Solutions in Hexane Vapor as Studied by Drop Profile Analysis Tensiometry

Surface tension experiments were performed using the drop profile analysis tensiometry method. The hexane was injected into the measuring cell at certain times before the formation of the solution drop. The influence of the capillary diameter and solution drop size on the measured apparent dynamic surface tension was studied. The amount of hexane transferred from the vapor phase to the drop was estimated. For large pure water drops, it was shown that the ageing of the drop in the hexane vapor during a long time resulted in the formation of a liquid hexane phase covering the drop, but the volume of this phase did not exceed 0.5 mm3. On the contrary, for surfactant solution drops the volume of the hexane phase covering the drop was essentially larger. Experiments with solution drops were performed to measure the surface tension within a wide range of surfactant concentration. It was found that the dependencies of dynamic surface tension on the C13DMPO and C14EO8 solutions concentration exhibit maxima at concentrations of about 1–2 μmol/L for C14EO8 and 2–5 μmol/L for C13DMPO at ageing times of 100 to 1000 s; these maxima were shown to exist also at equilibrium. This phenomenon is presumably ascribed to the competitive character of simultaneous adsorption of hexane and surfactant.

High n-Hexane Adsorption Capacity of Composite Adsorbents Based on MOFs and Graphene with Various Morphologies

Adsorption is an important technique for the separation and purification of various gases. In this study, two types of graphene materials with various morphologies are employed to modify metal–orga...

Interfacial Properties of Tridecyl Dimethyl Phosphine Oxide Adsorbed at the Surface of a Solution Drop in Hexane Saturated Air

The surface tension of C13DMPO aqueous solution drops in hexane vapor is studied using the drop profile method. The hexane was injected into the measuring cell at three different conditions: before the formation of the solution drop, at a certain moment during the adsorption process, and after reaching the equilibrium of surfactant adsorption. The surface tension values for all experiments at the same concentration and different injection situations ultimately coincide with each other after attaining the final equilibration stage. The equilibrium surface tension isotherms of C13DMPO solutions, and the adsorption of both components—surfactant and hexane—were calculated. It was shown that the presence of surfactant leads to an increased hexane adsorption.

Random surface statistical associating fluid theory: Adsorption of n-alkanes on rough surface.

Adsorption properties of chain fluids are of interest from both fundamental and industrial points of view. Density Functional Theory (DFT) based models are among the most appropriate techniques allowing to describe surface phenomena. At the same time, Statistical Associating Fluid Theory (SAFT) successfully describes bulk pressure-volume-temperature properties of chain-fluids. In this study, we have developed a novel version of the SAFT-DFT approach entitled Random Surface (RS)-SAFT which is capable of describing adsorption of short hydrocarbons on geometrically rough surfaces. A major advantage of our theory is the application to adsorption on natural rough surfaces with normal and lateral heterogeneity. For this reason, we have proposed a workflow where the surface of a real solid sample is analyzed using a theoretical approach developed in our previous work [T. Aslyamov and A. Khlyupin, J. Chem. Phys. 147, 154703 (2017)] and experimentally by means of low temperature adsorption isotherm measurements for simple fluids. As a result, RS-SAFT can predict adsorption properties of chain fluids taking into account the geometry of the surface sample under consideration. In order to test our workflow, we have investigated hexane adsorption on carbon black with the initially unknown geometry. Theoretical predictions for hexane adsorption at 303 K and 293 K fit corresponding experimental data well.

Adsorption model development for mass transport characteristics of MFEP structure by physisorption method

A novel heterogeneous contacting structure, microfibrous entrapped particles (MFEP) structure, was developed to intensify chemical processes including heterogeneous catalytic reactions and the gas–solid adsorption process. MFEP is characterized by its extremely high heat and mass transfer efficiency, which is critical for thermal and/or mass transfer limited reactions. To investigate the mass transport characteristics of MFEP, a physisorption (hexane adsorption onto activated carbon) was used as a probe process. A theoretical adsorption model was developed based on the linear driving force approximation and constant pattern behavior. Mass transfer mechanisms including external diffusion, intraparticle molecular diffusion, Knudsen diffusion, and surface diffusion, were considered in the model. This model was then used to analyze the experimental breakthrough data and calculate the mass transfer coefficient. The experimental results showed that for MFEP with a particle diameter of approximately 200 µm, the volumetric mass transfer coefficient is more than 10 times higher than that of a packed bed. Combining the experimental results and theoretical analysis, it was also found that in the particle diameter range of 2000 to 100 µm, the system’s mass transfer resistance is primarily the result of both the external and internal mass transfer resistances. This leads to the conclusion that decreasing the particles size can effectively increase the mass transfer rate. However, when the particle size is less than 100 µm, axial dispersion becomes the rate-limiting resistance, potentially reducing the residence time of the adsorbate in the adsorbent bed. The current study was aimed at understanding the mass transfer behavior in the MFEP structure, and optimizing of MFEP for specific heterogeneous contacting applications.

Microporous frameworks with conjugated π-electron skeletons for enhanced gas and organic vapor capture

Novel conjugated microporous frameworks based on adamantane (CMF-Ads) have been successfully synthesized under mild conditions. Eight-arm tetraphenyl “knots” and a conjugated π-electron skeleton endowed the target CMF-Ads with ultra-high thermal stability (up to 500 °C), high surface area (up to 907 m2 g−1), excellent CO2 uptake capacity of 15.13 wt % at 273 K and 1 bar, as well as superior organic vapor (benzene, hexane) adsorption. The ultra-high gas uptake capacity and selectivity of these CMF-Ads herein exceeds most conjugated microporous frameworks reported to date, highlighting their potential as materials for clean energy application.

Impact of styrenic polymer one-step hyper-cross-linking on volatile organic compound adsorption and desorption performance

A novel one-step hyper-cross-linking method, using 1,2-dichloroethane (DCE) and 1,6-dichlorohexane (DCH) cross-linkers, expands the micropore volume of commercial styrenic polymers. Performance of virgin and modified polymers was evaluated by measuring hexane, toluene, and methyl-ethyl-ketone (MEK) adsorption capacity, adsorption/desorption kinetics, and desorption efficiency. Hyper-cross-linked polymers have up to 128% higher adsorption capacity than virgin polymers at P/P0 = 0.05 due to micropore volume increases up to 330%. Improvements are most pronounced with the DCE cross-linker. Hyper-cross-linking has minimal impact on hexane adsorption kinetics, but adsorption rates for toluene and MEK decrease by 6–41%. Desorption rates decreased (3–36%) for all materials after hyper-cross-linking, with larger decreases for DCE hyper-cross-linked polymers due to smaller average pore widths. For room temperature desorption, 20–220% more adsorbate remains in hyper-cross-linked polymers after regeneration compared to virgin materials. DCE hyper-cross-linked polymers have 13–92% more residual adsorbate than DCH counterparts. Higher temperatures were required for DCE hyper-cross-linked polymers to completely desorb VOCs compared to the DCH hyper-cross-linked and virgin counterparts. Results show that the one-step hyper-cross-linking method for modifying styrenic polymers improves adsorption capacity because of added micropores, but decreases adsorption/desorption kinetics and desorption efficiency for large VOCs due to a decrease in average pore width.

Study of Hexane Adsorption on Activated Carbons with Differences in Their Surface Chemistry.

The study of aliphatic compounds adsorption on activated carbon can be carried out from the energetic change involved in the interaction; the energy values can be determined from isotherms or by the immersion enthalpy. Vapor phase adsorption isotherms of hexane at 263 K on five activated carbons with different content of oxygenated groups and the immersion enthalpy of the activated carbons in hexane and water were determined in order to characterize the interactions in the solid–liquid system, and for calculating the hydrophobic factor of the activated carbons. The micropore volume and characteristic energy from adsorption isotherms of hexane, the BET (Brunauer–Emmett–Teller) surface area from the adsorption isotherms of N2, and the area accessible to the hexane from the immersion enthalpy were calculated. The activated carbon with the lowest content of oxygenated groups (0.30 µmolg−1) and the highest surface area (996 m2g−1) had the highest hexane adsorption value: 0.27 mmol g−1; the values for Eo were between 5650 and 6920 Jmol−1 and for ΔHim were between −66.1 and −16.4 Jg−1. These determinations allow us to correlate energetic parameters with the surface area and the chemical modifications that were made to the solids, where the surface hydrophobic character of the activated carbon favors the interaction.

Selection of solvent for the mechanical activation process: A molecular dynamics simulation and experiment study

Herein, molecular dynamics simulations and experiments were carried to select solvent for the mechanical activation process. The interaction between solvent and each component of the Al‐PTFE mechanical activated energy composites has been studied by means of molecular dynamics. Then, the status of Al and PTFE in solvent was analyzed, and the microstructure of the composite was also studied combined with experiment. At last, the mechanical activated energy composites were prepared with n‐hexane as the solvent. The results show that the adsorption of PTFE, toluene, and hexane on the (0 0 1), (0 1 0), and (100) surface of Al2O3 is stable. Al2O3 (0 0 1) surface and Al2O3 (0 1 0) surface interact with 3 substances mainly via the electrostatic force. Al2O3 (1 0 0) surface interacts with 3 substances mainly via the van der Waals force. The binding energies of toluene‐Al2O3 and hexane‐Al2O3 are larger than PTFE‐Al2O3. PTFE cannot adsorb on the surface of aluminum in the existence of n‐hexane and toluene. n‐Hexane can make PTFE disperse uniformly, and a considerable part of these PTFE will be coated on the surface of Al after n‐hexane is removed. The uniformity of Al/PTFE mechanical activated energetic composites prepared in n‐hexane is good, and it increases with the milling time.

Adsorption of hexane and cyclohexane vapours at the water drop surface

Adsorption of hexane and cyclohexane vapours at the water drop surface

SORBOSTRICTION OF MICROPOROUS CARBON ADSORBENT FAS-3 AT ADSORPTION OF ORGANIC SUBSTANCES VAPORS FROM NITROGEN FLOW

For the first time, complex studies were carried out on adsorption deformation – sorbostriction of microporous carbon adsorbent FAS-3 at adsorption of hexane, benzene and carbon tetrachloride from the flow of carrier gas – nitrogen in non-equilibrium conditions. The results of this phenomenon were analyzed. In work a microporous carbon adsorbent FAS-3, obtained on the basis of furfural was used. Active coals on the basis of thermosetting plastics grades of FAS are significantly better than commercially-produced carbon adsorbents based on coal and peat on their mechanical properties and low ash content at a much greater development of the volume of the adsorbent micropores. We used the facility for studies of adsorption deformation of a solid adsorbent, manufactured in the Institute of Physical Chemistry and Electrochemistry of RAS. For the measurements we used a flow dilatometer, allowing measuring the adsorption deformation of the adsorbent while passing through it portions of the test substance or mixture in the carrier gas flow. It is shown that values of the maxima on the curves of deformation increase with increasing the concentrations of the components of the mixture. The area under the curve of barbastelle depends on the amount of injected material in a flow of carrier gas. Exit time curves of barbastelle to the maximum is individually for each of the studied substances, which enables you to use the effect of barbastelle to detect the presence of certain substances in the mixture. The results of the wave sorbostriction of microporous carbon adsorbent FAS-3 at adsorption of benzene, hexane, carbon tetrachloride from the flow of carrier gas - nitrogen allow to conclude on the high selectivity of adsorption and the possibility of using the adsorbent as a sensor to control the content of these substances in a flow of nitrogen.For citation:Zaytsev D.S., Tvardovskiy A.V., Shkolin A.V., Fomkin A.A. Sorbostriction of microporous carbon adsorbent FAS-3 at adsorption of organic substances vapors from nitrogen flow. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 4. P. 54-59.

Hydrocarbon Trapping over Ag-Beta Zeolite for Cold-Start Emission Control

Toluene, hexane, ethane, ethylene and CO adsorption and desorption on/from model Ag-exchanged beta zeolites were evaluated. The presence of water significantly inhibited adsorption of ethylene below 100 °C, whereas hexane and toluene adsorption were not affected. The addition of Ag increased adsorption capacities and desorption temperatures for both ethylene and toluene, while no difference was observed for hexane. Under conditions containing all hydrocarbons, ethylene adsorption was absent, and the toluene adsorption rate decreased. Results with binary mixtures demonstrate the inhibition of ethylene adsorption is due to toluene and the slower rate of toluene adsorption is caused by hexane.