Adsorption Behavior Of Benzene Research Articles

Anti-competitive adsorption of gaseous benzene on hydrophilic microporous carbon in humid conditions

The adsorption capture of ambient volatile organic compounds (VOCs) is of practical importance for air quality management. Herein, unique anti-competitive adsorption behavior of benzene on a hydrophilic activated carbon (Procarb-900 (P900)) is evidenced in the presence of competing components (e.g., formaldehyde (FA) and/or moisture). Contrary to general expectations, the adsorption capacity of 10 Pa benzene (QB) onto P900 (30 mg) at the 99 % breakthrough level improves from 144.8 to 187 mg g−1 as the relative humidity (RH) increases from 0 to 25 %. Such pattern is maintained at 183.9 mg g−1 even at the relatively high RH of 50 %. Furthermore, QB exhibits a remarkable increase of 56.1 % (to 226.0 mg g−1) in the binary phase (100 ppm benzene plus 50 ppm FA) relative to its single phase (144.8 mg g−1). The kinetic studies confirm the occurrence of anti-competitive adsorption of benzene under humid conditions with the unusual decrease in rate constants at the elevated RHs (i.e., 25 and 50 %). The thermodynamic studies suggest the exothermic nature of benzene adsorption onto P900. The hydrophilicity of P900's outer surface promotes the preferential adsorption of polar FA and water vapor over non-polar benzene, which deforms the activated carbon texture and lowers the pore size distribution (PSD). The narrow PSD enhances benzene uptake in the complex systems due to the confinement effect. Overall, this study offers insights into the unique anti-competitive adsorption of non-polar VOCs (e.g., benzene) on hydrophilic microporous adsorbents in the presence of potential interferences such as polar water vapor and FA. These findings offer a guideline for the practical implementation of adsorption techniques for gaseous VOCs in humid conditions.

Adsorption behavior of benzene on clay mineral surfaces at different temperatures and air humidity based on molecular simulation

Benzene poses a severe threat to human health due to its prevalence and carcinogenicity. The adsorption behavior of benzene on clay mineral surfaces is significant to its migration and retention in soils. Therefore, it is crucial to understand the mechanism of benzene adsorption behavior under different environmental conditions. In this study, a series of Grand Monte Carlo (GCMC) simulations were performed to obtain benzene isotherms on clay under various temperatures and air humidity. The adsorption mechanisms were investigated via analysis of the distribution of interaction energy, density, and orientation of adsorbed benzene and water. Results show that benzene form multiple layers on mineral surfaces, and surfaces have a great impact on the first layer of adsorbed benzene. The impedance effect of temperature on benzene adsorption is attributed to the temperature-dependent chemical potential of benzene, but not the interaction between benzene and surfaces, which is slightly temperature-reliant. Humidity shows different inhibition effects on benzene adsorption due to different surface hydration behavior and competitive adsorption between water and benzene. Benzene tends to be adsorbed on hollow sites on kaolinite surfaces, which is the same as water. The surface cations on montmorillonite and mica are significant to benzene and water adsorption, and their density distribution causes different competitive adsorption behavior.

Mechanistic effects of graphitization degrees and surface oxygen heteroatoms on VOCs adsorptive separation: Experimental and theoretical perspective

The porous carbon is considered to be one of the most suitable materials for volatile organic compounds (VOCs) adsorption and separation. Revealing the adsorption behavior and molecular interaction mechanism is of great significance for the preparation and synthesis of porous carbon adsorbents. Herein, we investigated detailed mechanistic effects of graphitization degrees and surface oxygen heteroatoms of porous carbon on their benzene and ethanol adsorptive separation performance by combining experiments and theoretical calculations. The results show that graphitized carbon surface has a stronger van der Waals interaction with benzene molecules compared to the disordered carbon surface, and thus exhibit a higher benzene adsorption performance and benzene/ethanol selectivity. While the introduction of oxygen functional groups enhances electrostatic affinity of porous carbon surface, resulting in higher ethanol adsorption capacity and ethanol/benzene selectivity under the entire pressure range. Subsequent theoretical calculations studied the adsorption behaviors of benzene and ethanol molecules in porous carbon models (with different graphitization degrees and oxygen contents) from the perspective of the weak interactions, and found the different molecular configurations of benzene and ethanol is the main leading cause of their different adsorption preferences. This study provided mechanistic insights on how the graphitization degrees and oxygen heteroatoms affected the capture and separation properties of porous carbon, which would further provide a rational alternative strategy in the preparation and synthesis of porous carbons for the effective gas mixture capture and separation.

Dynamic adsorption behavior of benzene, toluene, and xylene VOCs in single- and multi-component systems by activated carbon derived from defatted black cumin (Nigella sativa L.) biowaste

In the current study, activated carbon (AC) was produced from defatted black cumin (Nigella sativa L.) biowaste (DBCB) with ZnCl2 activation by means of the response surface methodology. The optimum process conditions for the production of DBCB-AC with a high iodine number of 1055.02 mg/g were predicted as an activation time of 57 min, activation temperature of 550 °C, and impregnation ratio of 105%. The surface and textural properties of the optimal DBCB-AC were characterized by SEM, FTIR, and BET analysis techniques. The DBCB-AC exhibited a highly porous structure with a specific surface area of 1213.32 m2/g, total pore volume of 0.89 cm3/g, and micropore surface area of 787.65 m2/g. Exploring the comparative and competitive adsorption behavior of volatile organic compounds (VOCs) is of both practical and scientific interest. Therefore, the competitive adsorption of multi-component benzene, toluene, and xylene (BTX) vapors by the DBCB-AC was elucidated. In the single-component system, the adsorption capacities of the BTX vapors at inlet concentrations of 20 mg/L were determined as 495, 580, and 674 mg/g, respectively. In contrast, in the binary-component system, the adsorption capacity of the B-vapor at 20 mg/L B + 10 mg/L T and 20 mg/L B + 10 mg/L X decreased by approximately 42% and 56%, respectively. Similarly, the adsorption capacity of the T-vapor at 20 mg/L T + 10 mg/L X decreased by approximately 47%. In the ternary-component system, the adsorption capacity of the X-vapor remained consistent. The adsorption mechanism of the BTX was explained by adsorption kinetic and isotherm models. The reuse efficiency of the DBCB-AC for the BTX was assessed through five cycles of adsorption-desorption tests and was found to be 89.45%, 88.02%, and 87.25%, respectively. The DBCB-AC, which had high-performance in terms of both reuse efficiency and adsorption capacity, can be recommended as a promising adsorbent for removal of VOC pollutants.

Polyvinyl alcohol-polyvinylpyrrolidone-hydroxy apatite (PVA-PVP-Hap) membrane for effective removal of benzene from aqueous solutions:-Kinetic, isotherm, and thermodynamic studies

Benzene is a widely used organic compound that is hazardous to human health and the environment. Exposure to benzene leads to cancer and is also harmful to reproductive organs. Our study deals with the adsorptive removal of benzene from aqueous solutions using Polyvinyl alcohol-Polyvinylpyrrolidone-Hydroxyapatite (PVA-PVP-Hap) membrane. The removal efficiency of the PVA-PVP-Hap membrane was found to be 94.79% with 10 ppm benzene solution at room temperature. The adsorption behavior of benzene on the previously synthesized membrane was analyzed by UV–Visible spectrophotometer at a wavelength of 252 nm. The adsorption mechanism of the composite membrane was analyzed by batch adsorption experiments. The result shows that the adsorption of benzene onto the membrane is best computed by the Freundlich isotherm model and pseudo-second-order kinetic model. The adsorption isotherm study reveals that the adsorption of benzene onto the membrane follows physisorption. Benzene adsorbed PVA-PVP-Hap membrane was successfully regenerated by 2-propanol and 80% removal of benzene was shown by the membrane even after the 6th cycle of regeneration.

On the capture of ultralow-level benzene in indoor environments: Experiments, modeling and molecular simulation

Benzene is one of the major indoor air pollutants, according to the World Health Organization (WHO), and understanding its adsorption and the difference between the adsorption behavior of benzene and water are essential in developing high-performance, water-resistant adsorbents. This paper presents a comprehensive study of benzene adsorption in carbon nano-porous materials by combining high-resolution measurement, modeling and molecular simulation. High-resolution isotherms and isosteric heats of benzene adsorption in two materials, microporous activated carbon fiber (ACF) and micro-mesoporous CMK-3 were provided. It is found that CMK-3 has higher specific adsorption capacity than ACF at very low pressures (<10−3 P/P0), making it a promising adsorbent for benzene capture in indoor environments. The Dubinin – Radushkevich model were used to fit the isotherms over the low-pressure regions. Furthermore, the experimental isotherm and the isosteric heat were analyzed with molecular simulation results, and the emphasis is placed on the behavior at ultralow pressures of benzene, typically found in indoor environments. Suggestion on the evaluation and management of adsorbents in terms of minimizing the impacts of ambient moisture were provided.

High-performance gas-phase adsorption of benzene and toluene on activated carbon: response surface optimization, reusability, equilibrium, kinetic, and competitive adsorption studies.

In recent years, volatile organic compounds (VOCs) have become a group of major pollutants that endanger human health and the ecological environment. The main purpose of this study was to investigate the gas-phase adsorption processes of benzene and toluene, which are important VOCs, on the activated carbon (AC) produced from Elaeagnus angustifolia seeds by physical activation method. In this context, the central composite design (CCD) approach-based response surface methodology (RSM) was applied to examine and optimize the effects of process parameters on the adsorption of benzene and toluene by AC adsorbent. The characterization of the produced AC was performed by the Brunauer-Emmett-Teller surface area, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The optimum process parameters were achieved (adsorption time of 74.98min, initial benzene concentration of 16.68ppm, and temperature of 26.97°C, and adsorption time of 73.26min, initial toluene concentration of 18.46ppm and temperature of 29.80°C) for benzene and toluene, respectively. The maximum adsorption capacities of benzene and toluene on AC were determined to be 437.36 and 512.03mg/g, respectively, under optimum parameters. The adsorption process kinetics and equilibrium isotherms were also evaluated. Besides, AC reusability studies were performed five times for the gas-phase adsorption and desorption of benzene and toluene. After five cycles, it was observed that the benzene and toluene adsorption capacity of the AC decreased slightly by 8.10% and 7.42%, respectively. The results revealed that the produced AC could be utilized successfully for the removal of benzene and toluene in the gas-phase adsorption systems because of its high surface area, high adsorption capacity, and high reusability performance. Furthermore, the adsorption processes of benzene and toluene were investigated, both sole components and in a binary mixture. It was concluded that the adsorption behaviors of benzene and toluene against AC were quite different when they were in the competition (in a binary mixture) and without competition (sole components). Graphical abstract.

Using Aliphatic Alcohols to Tune Benzene Adsorption in MAF‐6

AbstractThis simulation study deals with benzene adsorption in the metal azolate framework, MAF‐6, and on the inversion of the adsorption behavior in presence of aliphatic alcohols with varying chain length. To this aim, a new set of Lennard‐Jones interacting parameters for the MAF structure with benzene, methanol, ethanol, and 1‐propanol is developed in order to reproduce experimental adsorption. Pure component and binary benzene/alcohol mixtures are analyzed using Monte Carlo simulations. The distribution of the molecules inside the structure is studied in terms of radial distribution functions, calculated to understand the adsorption mechanisms. Adsorption selectivity provides a better understanding of the effect exerted by the adsorption of alcohols. It is found that the adsorption of benzene from benzene/methanol mixtures is similar to its pure component isotherm. However, for increasing length of the aliphatic chain of the alcohols the adsorption behavior is reversed preventing benzene to be adsorbed. The effect of open metal sites is discarded as main responsible for the preferential adsorption of alcohols, while the entropy and the molecular packing of alcohols are revealed as the reason for the different adsorption behavior of benzene.

Computer simulations of the structure and properties of organic pillared MFI zeolite catalyst

Multifunctional porous hybrid materials have recently received a lot of attentions because they combine the advantages of incorporating both inorganic oxides and organic species into the structure to solve the limitation of sole component material. This paper reports a type of model of organic pillared MFI zeolite catalyst, in which the full-atom mimetic model is constructed by using molecular modeling technique. Dreiding force field is used to calculate the interactions between sorbate–sorbate and sorbate–sorbent in the organic pillared MFI zeolite. The optimized model is characterized by calculating low-angle and high-angle X-ray diffraction patterns. Besides, the adsorption behavior of benzene and toluene is also investigated through the mimetic model. Simulated adsorption isotherms of benzene and toluene are agreement with the experimental data at low pressure. Density distributions of benzene and toluene show that toluene adsorbs preferentially in the region of interlayer space of lamellar MFI zeolite while benzene tends to adsorb in the area of micropores at low pressure. With increasing pressure, the guest molecules gradually fill in the area of micropores and mesopores of the organic pillared MFI zeolite. Moreover, the developed strategy in the present work can be applied to build other model for organic pillared zeolite catalyst by arranging different zeolite frameworks or organic species.

ADSORPTION OF BENZENE AND PYRIDINE VAPORS BY VARIOUS CARBON ADSORBENTS

For the first time with the help of express-method we compare adsorption of benzene and pyridine vapors by carbon adsorbents (CA) that differ in raw materials, methods of production and textural characteristics. With the BET and Aranovich (AR) equations we define the interval of relative pressure, in which the adsorption of studied components is described by suggested models of polymolecular adsorption, and calculated general characteristics of adsorption. A comparative analysis of these equations shows that adsorption isotherms of benzene vapors should be described with the Aranocich model and pyridine vapors with the BET model. It is stated that the adsorption of both benzene and pyridine is characterized by the low energy constant C that means weak adsorption localization on a carbon surface and difficulty with exact determination of monolayer capacity. We stated that with benzene adsorption by CA and pyridine adsorption by lignite sorbent the area taken by adsorbate molecule exceeds molecule’s own size. Such action is typical for realized specific sorbent-sorbate interaction which is expected by molecular structure of adsorbates and surface state of adsorbents and is proved by the amount of calculated adsorption heat. It is stated that pyridine molecules when adsorbed are oriented in parallel to the adsorbent surface and for benzene molecules such reaction exists only for granular carbon adsorbents. Random orientation of benzene molecules when adsorbed by granular CA can be connected with overall attraction-repulsion effect of π-electron system of benzene and polar groups on the adsorbent surface. We define the exponent of the Dubinin-Astakhov equation using the theory of volume filling of micropores (TVFM), calculate the limiting adsorption volume and size of pores occupied by components. We state that both benzene and pyridine adsorption proceeds similarly in available at size micro- and mesopores of adsorbents. Differences in adsorption behavior of benzene and pyridine with a filled monolayer are probably connected with peculiarities of molecule structure of pyridine which has an additional potential center of adsorption that is an unshared electron pair of nitrogen.

An efficient approach to explore the adsorption of benzene and phenol on nanostructured catalysts: a DFT analysis

The adsorption behavior of benzene and phenol on the zeolite is attributed to the differences in the strength of their interactions.

Effect of the Intrinsic Properties of Metals on the Adsorption Behavior of MoleculesCompetitive and Cooperative Adsorption of Benzene and Other Species on Pt and Rh Surfaces

Our previous study of benzene adsorption on Pt groups reveals the marked effect of the intrinsic properties of the metals. In the present paper, we further investigated the competitive and cooperative adsorption effects of halogen ions, SCN-, and pyridine on benzene adsorption on Pt and Rh surfaces using in situ electrochemical surface-enhanced Raman spectroscopy (SERS). The effect of the adsorption strength and the concentration of these species, the electrode potential, and the surface morphology on the adsorption behavior of benzene were systematically studied. Very different effects have been found on Pt and Rh surfaces. On Pt surfaces, Br- and I- competed with the chemisorbed benzene; meanwhile, the chemisorbed ions induced the physisorption of benzene. However, on Rh surfaces, a much weaker coadsorption was observed for I- and benzene. With the addition of a 1/100 amount of pyridine, the chemisorbed benzene was totally removed from the Pt surface. However, on the Rh surface, signals from both benzen...

Effect of Intrinsic Properties of Metals on the Adsorption Behavior of Molecules: Benzene Adsorption on Pt Group Metals

Investigation of benzene adsorption on different metal surfaces closer to a practical system appears to be a very important intermediate stage to utilize the conclusion obtained on single-crystal surfaces. In this paper, we studied the electrochemical adsorption behaviors of benzene on roughened Pt group electrodes using surface enhanced Raman spectroscopy (SERS). The effects of potential, surface roughness, and benzene concentration were investigated. Significant difference in surface Raman spectra of benzene on Ru, Rh, Pd, and Pt surfaces were found. On Pt surfaces, the parallel-chemisorbed benzene, the vertical dissociated chemisorbed benzene, and the physisorbed benzene were observed, evidenced by the ring vibration mode appearing at 872, 1012, and 991 cm(-1), respectively. On Pd, only parallel-chemisorbed benzene and physisorbed benzene were found. On Rh and Ru, the SERS signals were mainly from the parallel-chemisorbed benzene, with an extremely weak signal from the physisorbed benzene. The potential dependent study reveals that the parallel-chemisorbed species interacts strongest with the substrate, while the physisorbed species can be easily removed at positive potentials. The models for the adsorbed benzene were given to account for the different types of benzene on these Pt group metals. The difference in the atomization heat of the four metals was used to interpret the different interaction strength of benzene with Pt group metals.

Adsorption of benzene on the five-fold surface of the i-Al70Pd21Mn9 quasicrystal

The adsorption behaviour of benzene (C6H6) on the five-fold surface of the icosahedral Al70Pd21Mn9 quasicrystal has been investigated. Reflection absorption infrared spectroscopy (RAIRS) data taken at a temperature of 92 K indicate molecular adsorption. The adsorption geometry of the molecules is found to change from parallel to the surface to oblique geometries as the dose is increased from monolayer to multilayer coverages. Scanning tunnelling microscopy (STM) images show that the molecules adsorb in a disordered fashion. The adsorbate layer is found to completely desorb at 153 K leaving the substrate unchanged.

Benzene Adsorption in Microporous Materials

The adsorption behaviour of benzene in silicalite-1, AlPO4-5 and EU-1 has been investigated using gravimetric techniques and molecular simulation methods. For the one-dimensional, 12-membered ring (MR) channels of AlPO4-5 and the unidirectional, 10-MR channels with 12-MR side pockets of EU-1, the isotherms of benzene show simple type I behaviour. For the three dimensional 10-MR channels of silicalite-1, an anomalous behaviour of the benzene molecules sorbed has been observed. Two steps at loadings of ca. 4 and 6 molecules per unit cell [m.(u.c.)−1], respectively, and an hysteresis loop between loadings from 6 to 8 m.(u.c.)−1 can be found in the isotherms of this system. These stepped isotherms can be classified as showing type VI isotherm behaviour but in this system the reasons behind the steps are of a new and novel nature. These abnormal adsorption properties have been ascribed to the subtle interplay of increased sorbate-sorbate interactions and decreases in the entropy of sorption due to the energetically heterogeneous surfaces which are present in silicalite-1. The composition and structure of the silicalite-1 samples also play an important role on the adsorption properties of this system.

Coverage-dependent adsorption behavior of benzene on Si(100): A high-resolution photoemission study

The adsorption of benzene molecules on Si(100) is investigated by high-resolution core-level photoelectron spectroscopy using synchrotron radiation as well as ultraviolet photoelectron spectroscopy (UPS) for valence bands. The C $1s$ photoelectron spectra of benzene adsorbates are found to consist of two different components, which represent carbon atoms with or without a direct $\mathrm{Si}\ensuremath{-}\mathrm{C}$ bond. The population ratio of these two components exhibits a drastic change upon increasing the molecular coverage. This is explained by the coverage-dependent change of the adsorbate structure, which is corroborated by the noticeable variation of the molecular orbitals in the valence bands as observed by UPS. From these results, it is deduced that the population of the di-$\ensuremath{\sigma}$ structure increases significantly at a high coverage over the tetra-$\ensuremath{\sigma}$ structure which is energetically favored at a low coverage. This indicates the importance of the interaction between the adsorbate molecules at a high coverage.

Adsorption of Benzene on a Mo(112)−c(2 × 2)-[SiO4] Surface

The orientation and growth of benzene and pyridine on a well-ordered Mo(112)−c(2 × 2)-[SiO4] have been investigated with high-resolution electron energy loss spectroscopy (HREELS), Auger spectroscopy (AES) and low-energy electron diffraction (LEED). Benzene on the c(2 × 2)-[SiO4] surface is bound with its molecular plane parallel to the surface plane at submonolayer coverages. At intermediate coverages (1−3 ML), in contrast to benzene adsorption on metal surfaces, a layer-by-layer growth mode is observed with the benzene molecules bonded parallel to the surface. Pyridine on the c(2 × 2)−[SiO4] surface, on the other hand, undergoes a phase transition from a parallel to a tilted configuration. This is the first reported observation of benzene multilayer growth in which the benzene molecules bond exclusively parallel to the surface plane. The origin for this unusual adsorption behavior of benzene is discussed.

Study on adsorption kinetic of aromatic hydrocarbons onto activated carbon in gaseous flow method

The adsorption behavior of benzene, toluene, o -xylene, m -xylene, and p -xylene onto activated carbon was investigated using the flow method. The removal efficiency of aromatic hydrocarbons in the gaseous phase was estimated based on the adsorption kinetic constants and the saturated amount of aromatic hydrocarbons adsorbed on the activated carbon. The saturated amount of benzene and toluene adsorbed was greater than that of xylene adsorbed because the molecular sizes of benzene and toluene are smaller than that of xylene. The adsorption kinetic constant increased in the order of xylene, toluene, and benzene. Those of the three xylene isomers were similar. These results indicated that the adsorption rate of benzene by the activated carbon was the fastest and the kinetic constant depended upon the different between the boiling point and the melting point and the molecular size of the aromatic hydrocarbons.

Study on adsorption kinetic of aromatic hydrocarbons onto activated carbon in gaseous flow method

The adsorption behavior of benzene, toluene, o-xylene, m-xylene, and p-xylene onto activated carbon was investigated using the flow method. The removal efficiency of aromatic hydrocarbons in the gaseous phase was estimated based on the adsorption kinetic constants and the saturated amount of aromatic hydrocarbons adsorbed on the activated carbon. The saturated amount of benzene and toluene adsorbed was greater than that of xylene adsorbed because the molecular sizes of benzene and toluene are smaller than that of xylene. The adsorption kinetic constant increased in the order of xylene, toluene, and benzene. Those of the three xylene isomers were similar. These results indicated that the adsorption rate of benzene by the activated carbon was the fastest and the kinetic constant depended upon the different between the boiling point and the melting point and the molecular size of the aromatic hydrocarbons.

Location of benzene and cations in Si-rich NaY zeolites: a comparative and quantitative infrared spectroscopic study

The location of benzene molecules and Na + ions in two Si-rich NaY (NaY s and NaY d) zeolites (Si/Al≈3.5), prepared by different methods, has been investigated using FTIR spectroscopy and compared with that in NaY (Si/Al=2.3), and NaEMT (Si/Al=3.6) zeolites. Two adsorption sites for benzene, Na + ions and 12R windows, have been evidenced in two Si-rich NaY and in NaY zeolite instead of one, i.e. Na + ions, in NaEMT. The desorption experiments have revealed that the interaction of benzene with Na + ions is stronger than that with 12R windows and there are various strengths of interaction of benzene with Na + ions in NaEMT. The total benzene adsorption capacity and the selectivity of benzene adsorbed have been quantitatively analyzed. The adsorption behavior of benzene has been correlated with the Al distribution, the location of Na + ions, the average negative charge of oxygen atoms, the zeolite structure and the interaction strength of benzene with one site or another.