Benzene Vapor Research Articles

Chemical composition and sorption properties of lignocellulosic complexes of fruit seed shells and walnut shells

We investigated chemical composition and sorption properties of lignocellulosic complexes of wastes of agroindustrial complex, namely crushed shells of apricot, cherry and peach seeds, and walnut shells. Chemical analysis revealed that walnut shells show the highest content of polysaccharide components. Cherry and peach seed shells are characterized by a higher content of aromatic components (lignin). Based on the results of sorption of benzene vapor, the following sequence of the volumes of adsorption pores was found: walnut shells (0.03 cm3 g–1)=apricot seed shells (0.03 cm3 g–1)>peach seed shells (0.02 cm3 g–1)>cherry seed shells (0.01 cm3 g–1). The sorption capacity of biosorbents towards methylene blue was investigated as a function of pH of an aqueous solution, process duration, and initial dye concentration. It was established that the maximum efficiency of sorption is achieved at pH 6, while the minimum value corresponds to low pH values. Probably, an increase in pH value leads to deprotonation of carboxyl groups of biosorbents followed by changes in their surface charge into negative. This causes a decrease in electrostatic repulsion forces between the positively charged dye cation and the surface of the biosorbents. Therefore, the sorption centers are formed. The data on kinetics of sorption showed that during the first 30 min of contact the absorption of 55–60% of the dye cations occurs on the biosorbents, whereas complete sorption equilibrium is achieved within 120–180 min. The following sequence of the sorption capacity of lignocellulosic materials towards methylene blue was established: apricot seed shells (43.9 mg g–1)>walnut shells (37.8 mg g–1)>peach seed shells (30.1 mg g–1)>cherry seed shells (26.5 mg g–1). The Freundlich isotherm is the most suitable for describing the cationic dye absorption by biosorbents, and the calculated values are in good agreement with the experimental data.

Adsorption properties of benzene vapors on activated carbon from coke and asphalt

The industry produces a variety of wastes in production processes. This has a negative impact on the state of ecological balance. Today, in the oil industry, many different types of oil waste are accumulated as reserves. Focusing them on targeted production is one of the most pressing issues today. The use of a high-vacuum adsorption device is important in producing adsorbents from coke and asphalt from residual oil products and in the complete determination of the sorption properties of the obtained adsorbents. Benzene and toluene adsorption isotherms, the sorption volume, and properties of the new adsorbent can be described in detail by studying the adsorption heat.

Surface modification of TiO2 with Pd nanoparticles for enhanced photocatalytic oxidation of benzene micropollutants

This paper describes a simple method for the modification of TiO2 surface with palladium to prepare a highly active photocatalyst for oxidation of benzene micropollutants in air. The method consists of the impregnation of anatase TiO2 with a solution of palladium (II) acetate (Pd(OAc)2) in acetone followed by photodecomposition of Pd(OAc)2 under UV irradiation. No additional electron donor is required for Pd photodeposition because acetate ligands play this role. Photodecomposition of Pd(OAc)2 can be efficiently performed either before the target photocatalytic reaction or in situ during the reaction. Pd-loaded photocatalysts were characterized using UV–vis DRS, XPS, TEM, EDX, and CO chemisorption techniques. The formation of metallic (Pd0) and oxidized (PdOx) palladium on the TiO2 surface was shown. An increased amount of metallic Pd was observed during photodecomposition of Pd(OAc)2 compared to its thermal decomposition at low temperature. The modification of TiO2 with Pd nanoparticles substantially increased its photocatalytic activity in the oxidation of benzene vapor under UV light. A Pd content of 1 wt.% was found to be optimum, which provided a three-fold increase in activity compared to pristine TiO2. In addition to increasing the oxidation rate, Pd nanoparticles suppressed the formation of CO as a byproduct during the process that increased the efficiency of air purification by the photocatalytic oxidation method. The proposed preparation techniques can be employed for easy modification of powdered photocatalysts or fabric filters used in photocatalytic air purifiers.

The dynamic competition in adsorption between gaseous benzene and moisture on metal-organic frameworks across their varying concentration levels

Metal-organic frameworks (MOFs) have opened a new path for the construction of air/gas purification systems through a number of technological routes (e.g., adsorption and/or catalysis). To develop MOFs with upgraded adsorption performance, the breakthrough (BT) behavior of two MOF sorbents (e.g., MOF-199 and UiO-66-NH 2 ) was investigated using gaseous benzene under the interactive conditions between the two key variables: (i) the inlet benzene vapor concentration (10 to 200 ppm) and (ii) relative humidity (RH = 0 to 100%). According to the comparison of adsorption performance derived using gaseous benzene, MOF-199 outperformed UiO-66-NH 2 by 2 to 16-fold when assessed at 10% BT and zero RH. This observation thus reflects the high reactivity of Cu-metal sites for interaction with benzene ring compared with Zr sites. The dynamic adsorption data for the two MOFs at various RH conditions also indicated the competitive inhibition effect of water vapor on benzene adsorption mechanism, especially at low benzene concentrations (< 100 ppm) and high RH level of > 50%. Adsorption kinetics of benzene onto the two MOFs showed good fitting with both pseudo-first and -second-order kinetics at low RH (0–20%) conditions, whereas the results at high RH (> 50%) failed to fit with both kinetics (e.g., R 2 ≤ 0.87) because of the high roll-up effect. The water vapor acted as a competitive component, reducing the performance of the MOF adsorbents in purifying humidified gaseous streams. That effect became more prominent as the benzene concentration decreased (≤ 50 ppm), reflecting the dynamic interaction between multiple adsorbates (water and benzene) and the adsorbent. In addition, the exothermic adsorption property was evident for both MOFs under the dry conditions, while the patterns were reversed under humid conditions (e.g., 100% RH). Overall, the adsorption properties of VOCs onto MOFs and their uptake mechanisms are affected sensitively by an interplay between the key variables (e.g., concentration levels of competing adsorbates) along with the structural stabilities of sorbents against water vapor. • The adsorption of VOCs is compared at varying RH levels for MOF-199 and UiO-66-NH 2. • The performance of MOFs is assessed w.r.t. competition between benzene and water vapor. • Their performance was evaluated using key metrics like breakthrough volumes. • MOF-199 displayed the better performance at all benzene concentration levels under dry condition. • Moisture had negative effects on benzene adsorption, especially MOF-199 at low benzene levels.

Excellent adsorptive performance of novel magnetic nano-adsorbent functionalized with 8-hydroxyquinoline-5-sulfonic acid for the removal of volatile organic compounds (BTX) vapors

In this study, magnetic Fe3O4/AC@SiO2 nanoparticles functionalized with 8-hydroxyquinoline-5-sulfonic acid (Fe3O4/AC@SiO2@8HQ5SA) were innovatively prepared, characterized, and applied as a novel nano-adsorbent to efficiently remove volatile organic compounds, namely benzene, toluene, and xylene (BTX) vapors. Fe3O4/AC@SiO2@8HQ5SA was synthesized via the co-precipitation and sol–gel methods. The characterization of Fe3O4/AC@SiO2@8HQ5SA as a proposed nano-adsorbent was performed by various spectroscopic methods including FTIR, SEM, TGA/DTA, BET, VSM, XPS, and EDS. The operating factors namely retention time, inlet BTX concentration and temperature were substantially analyzed and optimized to achieve the maximum adsorption capacity of Fe3O4/AC@SiO2@8HQ5SA towards the uptake of the BTX vapors. The adsorption phenomena of Fe3O4/AC@SiO2@8HQ5SA towards the BTX vapors were clarified by the investigation of the kinetic and isotherm criteria. According to the results of the adsorption experiments Fe3O4/AC@SiO2@8HQ5SA demonstrated an admirable performance for the removal of the BTX vapors. The maximum adsorption capacities of the BTX vapors by Fe3O4/AC@SiO2@8HQ5SA were determined as 555.85, 620.80 and 745.54 mg/g, respectively. In addition to the distinctive adsorptive behavior in removing the BTX vapors, the reusability experiments with five adsorption–desorption cycles indicated that Fe3O4/AC@SiO2@8HQ5SA showed excellent reusability. After five consecutive adsorption–desorption cycle tests, Fe3O4/AC@SiO2@8HQ5SA maintained the reuse efficiencies of 91.92%, 91.17% and 90.65% for the BTX vapors, respectively. The findings of this study suggested that the functionalization of the Fe3O4/AC@SiO2 nanoparticles with 8HQ5SA was an effective strategy to greatly increase the removal capacity of BTX vapors, and that the magnetic Fe3O4/AC@SiO2@8HQ5SA was a promising and regenerable nano-adsorbent for the efficient treatment of volatile organic compound pollutants.

Dynamic and static removal of benzene from air based on task-specific ionic liquid coated on MWCNTs by sorbent tube-headspace solid-phase extraction procedure

Human exposure to high levels of benzene in the air leads to toxic effects in human body and so, it is necessary to determine by high sensitivity and precision methodology. A simple and efficient method based on the triphenyl(3-sulfopropyl)phosphonium p-toluenesulfonate as TSIL was coated on multi-walled carbon nanotubes ([TPhPP][SUTO]–MWCNTs) and used for benzene vapor removal from air. By procedure, the tube and headspace sorbent based on solid-phase extraction coupled to gas chromatography-flame ionization detector (ST/HS-SPE-GC-FID) was used in dynamic and static systems, respectively. All effected factors including the flow rate, the mass sorbent, benzene concentration, the contact time and the temperature were optimized in dynamic and static systems. Chamber was designed for benzene generation in pure air, and then, mixture of gas moved to passive thermal desorption tubes (ST) or head space (HS) in the glass chromatography vials as dynamic and static methods, respectively. The benzene was eliminated from air with 10 mg of ([TPhPP][SUTO]–MWCNTs); C28H29O6PS2–MWCNTs, 1:1] at 25 °C, desorbed from the sorbent at 95 °C and measured by GC-FID. The removal efficiency and the absorption capacity of [TPhPP][SUTO]–MWCNTs for benzene were obtained to be 98.8% and 169.6 mg g−1 at flow rate of 300 ml min−1. The chemical adsorption of benzene from air was related to π–π, electrostatic, hydrophobic interactions between aromatic chains of TSILs with the benzene molecules, and it caused the increase the removal efficiently of benzene vapor from air more than 95%. The results were validated by GC–MS and spiking of real samples which was determined by GC-FID.

Fast benzene vapor capture by natural macroporous carbonized fibers improved with carbon nanostructures

We investigated the adsorption of benzene, as a model volatile organic compound from gasoline, in a novel macroporous carbon material, with the intention of improving the kinetics performance of porous materials in automotive canisters. In this research, we proposed agave bagasse fibers, that when pyrolyzed develop wide pores all along the fiber, that are helpful in vapor diffusion. To enhance the surface area of the carbonized fibers, we grew diverse carbon nanostructures onto fibers surface by chemical vapor deposition. The as-produced materials were characterized by N2 physisorption, FTIR, SEM, TEM, XRD and Raman spectroscopy. The carbon nanostructures formed, such as bamboo-like carbon nanotubes, onion-like carbon and carbon black, increased the surface area of carbonized fibers from 120 to 185 m2 g−1, while their thermal post-treatment at 800 °C doubled the surface area, up to 243 m2 g−1, of the pristine carbonized fibers. The adsorption of benzene vapor showed that carbonized fibers containing carbon nanostructures have 1.8 faster adsorption kinetics (0.0064 mmol min−1) and 1.5 higher adsorption capacity (55.53 mg g−1) after 26 h of static adsorption than a commercial granular activated carbon, which is used nowadays in automotive canisters. The pseudo-second order model provided the best fit to the kinetic rates.

Mathematical modeling and experimental study of VOC adsorption by Pistachio shell-based activated carbon.

The adsorption of benzene vapor, as a volatile organic component, from inert gas (N2) by activated carbon was studied experimentally in the isothermal fixed bed reactor at various operating conditions. The activated carbon used in this study had pistachio shell base with high surface area. To improve the adsorption capacity of VOC vapor, the activated carbon was chemically treated with H2SO4, HNO3, NaOH, and NH3 solutions. The saturated adsorption capacities of benzene on initial activated carbon and treated samples were measured and compared. The results showed that the activated carbon treated with nitric acid had higher adsorption capacity than others samples, 640 mg/g. In addition, a mathematical model for adsorption in a fixed bed reactor was proposed in this study. The model results had good agreement with experimental data. In order to demonstrate the effects of operating conditions on adsorption and breakthrough curve, the experimental tests and simulation runs were carried out at various gas flow rate, temperature, and benzene concentration. The results showed that with increase VOC concentration from 700 to 1000 ppm, the total time of adsorption was decreased from 25 to 21 h and breakthrough point appeared earlier.

DEPOSITION OF HARD SILICON CARBONITRIDE COATINGS FROM HEXAMETHYLDISILAZANE (HMDS) AND HMDS+BENZENE VAPORS IN LASER PLASMA

Hard silicon carbonitride coatings are prepared using Ar and Ar (10 vol.% He) laser plasma from hexamethyldisilazane (HMDS) [(CH3)3Si]2NH and HMDS+benzene vapors. The coatings are characterized by infrared (IR), Raman, and X-ray photoelectron spectroscopies, transmission electron microscopy, and atomic force microscopy. The obtained coatings are amorphous and uniform in composition and over the film thickness. The microhardness of coatings synthesized on steel from a HMDS+ benzene mixture increases from 12 GPa to 18 GPa provided that other parameters remain constant.

Atomic Layer Deposited Ni/ZrO2-SiO2 for Combined Capture and Oxidation of VOCs.

This work reports on the development of novel Ni nanoparticle-deposited mixed-metal oxides ZrO2-SiO2 through atomic layer deposition (ALD) method and their application in combined capture and oxidation of benzene, as a model compound of aromatic VOCs. Concentrating ppm-level VOCs in situ, before their oxidation, offers a practical approach to reduce the catalyst inventory and capital cost associated with VOC emissions abatement. The benzene vapor adsorption isotherms were measured at 25 °C and in the pressure range of 0 to benzene saturation vapor pressure thereof (0.13 bar). In the combined capture-reaction tests, the materials were first exposed to ca. 86 100 ppmv benzene vapor at 25 °C, followed by desorption and catalytic oxidation while raising the bed temperature to 250 °C. The textural properties revealed that ALD of Ni or ZrO2 on SiO2 decreased surface area and pore volume, while sequential doping with ZrO2 and then Ni caused the otherwise. The benzene vapor adsorption isotherms followed the type-IV isotherm classification, revealing a combination of monolayer-multilayer and capillary condensation adsorption mechanisms in sequence. At saturation vapor pressure, an average equilibrium adsorption capacity of 15 mmol/g was obtained across the materials. However, the dynamic adsorption capacities were up to 50% less than the corresponding equilibrium uptake for the materials. Benzene desorption temperature was observed around 90 °C, and conversion of 85-95% and TOF of 1.28-16.42 mmolC6H6/molNi/s were obtained over the materials, with 3Ni/ZrO2-SiO2, prepared with 3 ALD cycles, exhibiting the maximum conversion and TOF indicating synergistic effects of Ni nanoparticles and ZrO2 support based on the number of ALD cycles. However, the yields of CO2 and H2O were about 5% and 40%, respectively. The small value of the CO2 yield was hypothesized to be due to simultaneous high-temperature adsorption of CO2 as the catalytic reaction progressed. The high adsorption affinity, low desorption temperature, and high catalytic activity of the materials investigated in this study made these materials as promising candidates for the abatement of BTX.

On-Chip Template-Directed Conversion of Metal Hydroxides to Metal-Organic Framework Films with Enhanced Adhesion.

Interfacial compatibility between metal-organic framework (MOF) films and the underlying substrates determines the integrity of MOF films and their associated functions, and thus it has been gaining growing attention. Herein, we present a comparison of adhesion properties at the chip level of two disparate nickel (Ni)-MOF films, respectively, obtained by direct hydro/solvothermal growth and template-directed conversion approaches. We demonstrate that the on-chip delamination/corrugation of the films obtained by the direct growth approach can be circumvented by adopting the template-directed approach, which enables delicate dissolution of primarily grown nanoflaked nickel hydroxide (Ni(OH)2) films and thus triggers the controllable formation of Ni-MOF films. Successful on-chip conversions of Ni(OH)2 layers to different Ni-MOF thin films with good homogeneity, compactness, and appreciable affinity to the substrates are verified by multiple microscopic and spectroscopic techniques. Notably, the resultant Ni-MOF films do not show delamination even after activation with additional treatments, such as solvent soaking, nitrogen (N2) blowing for 1 h, and scotch-tape tests. As a demonstration of the application of MOF films, a Ni-NDC (NDC stands for 2,6-naphthalenedicarboxylate) MOF-coated sensor exhibits selective detection toward benzene vapor. This study highlights the importance of interfaces between MOF films and substrates and provides new perspectives for integrating MOF films onto microelectronic devices with robust adhesion for practical applications.

The potential utility of HKUST-1 for adsorptive removal of benzene vapor from gaseous streams using a denuder versus a packed-bed adsorption system

The feasibility of various sorption methods has been explored to remove volatile organic compounds from indoor air (e.g., a packed bed-based air filtration system). However, the large space velocity/pressure drop is a common operational challenge associated with the use of a packed-bed adsorber, especially when using fine powdery adsorbent. Accordingly, this research was carried out to evaluate the effectiveness of two contrasting adsorptive removal systems (i.e., denuder vs. packed-bed) using a metal-organic framework (MOF: Hong Kong University of Science and Technology (HKUST-1) as a model adsorbent) as the test media. In the denuder design, HKUST-1 was coated as a thin layer (thickness 90 μm) on the inner wall of a 90 mm length quartz tube (internal diameter ≈ 4 mm) with the help of a polyvinyl alcohol binder. Additionally, an identical quartz tube was prepared with a HKUST-1 packed bed. The potential applicability of the denuder versus packed-bed was evaluated using gaseous benzene (0.1–10 partial pressure) in a N2 inlet stream at near-ambient conditions (298 K and 1 atm). A comparison of the breakthrough volume and adsorption performance data (capacity and partition coefficient) revealed that the packed bed outperformed the denuder design by four to five-fold at all inlet benzene partial pressures (0.1–10 Pa). Better performance was seen in the denuder system when benzene uptake was conducted at high benzene partial pressures (5–10 Pa) rather than at low partial pressure (<5 Pa) in the inlet stream. The evaluation of pressure drop data indicated the efficacy of the denuder over a packed bed in terms of pressure/space velocity drop, especially at a high flow rate (e.g., 330 mL min-1). However, in terms of uptake rate and space time yield, the denuder was 25 times less efficient than the packed bed.

Thermodynamics of Adsorbed Methane Storage Systems Based on Peat-Derived Activated Carbons.

Two activated carbons (ACs) were prepared from peat using thermochemical K2SO4 activation at 1053–1133 K for 1 h, and steam activation at 1173 K for 30 (AC-4) and 45 (AC-6) min. The steam activation duration affected the microporous structure and chemical composition of ACs, which are crucial for their adsorption performance in the methane storage technique. AC-6 displays a higher micropore volume (0.60 cm3/g), specific BET surface (1334 m2/g), and a lower fraction of mesopores calculated from the benzene vapor adsorption/desorption isotherms at 293 K. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and small-angle X-ray scattering (SAXS) investigations of ACs revealed their heterogeneous morphology and chemical composition determined by the precursor and activation conditions. A thermodynamic analysis of methane adsorption at pressures up to 25 MPa and temperatures from 178 to 360 K extended to impacts of the nonideality of a gaseous phase and non-inertness of an adsorbent made it possible to evaluate the heat effects and thermodynamic state functions in the methane-AC adsorption systems. At 270 K and methane adsorption value of ~8 mmol/g, the isosteric heat capacity of the methane-AC-4 system exceeded by ~45% that evaluated for the methane-AC-6 system. The higher micropore volume and structural heterogeneity of the more activated AC-6 compared to AC-4 determine its superior methane adsorption performance.

Calix[4]arene-triazine conjugate intermediate: optical properties and gas sensing responses against aromatic hydrocarbons in Langmuir–Blodgett films

The detection of organic vapors by chemically based sensors was achieved with macromolecules having convenient molecular cavities. Addressed herein, a calix[4]arene derivative 25,27-(4-chloro-2-phenylamino-1,3,5-triazine)-26,28-dihydroxycalix[4]arene (C4AsTr) was synthesized and Langmuir–Blodgett (LB) thin films of this compound modified with heterocyclic units were examined for its optical properties and gas sensing capabilities against trace vapor of aromatic BTX hydrocarbons (benzene, toluene, xylene) through surface plasmon resonance technique. In line with this purpose, the experimental SPR data were fitted using the Winspall software to evaluate optical properties of the C4AsTr film. Such thickness and refractive index values of C4AsTr LB films were determined as 1.19 ± 0.02 nm for the thickness per monolayer, and 1.60 ± 0.04 for the refractive index. Exposed to above-mentioned organic vapors were measured with SPR technique, and the photodetector responses of these optical sensors, ΔI, were recorded as a function of time during kinetic process. In order to quantify real-time SPR data, early time Fick’s diffusion law was handled to extract the diffusion coefficients. There were two different regions observed with two slopes indicating that one belongs to fast surface diffusion and second one slow for bulk diffusion into C4AsTr LB film. All SPR results both theoretical and experimental indicated that C4AsTr optical LB thin-film sensors exhibit high response, a good sensitivity and selectivity for saturated benzene vapor than others. These optical thin-film sensors with aniline substituted triazine heterocycle have been potential candidates for organic vapor sensing applications with simple and low-cost preparation at room temperature.

Features of Field Desorption of Sodium and Cesium from the Surface of a Carbonized Rhenium Field Emitter

We used field emission microscopy to study the field desorption of sodium and cesium atoms from a rhenium field emitter precarbonized in benzene vapor. The dependences of the ion currents of sodium and cesium on the voltage applied to the field emitter differ. The difference in the ion current dependences is explained by the formation of multilayer graphene on the crystalline surface of a rhenium field emitter in the regions of low-index faces and its intercalation by alkali metal atoms with different ionization potentials and different atomic and ionic radii.

Metal Oxide Nanoparticle-Decorated Few Layer Graphene Nanoflake Chemoresistors for the Detection of Aromatic Volatile Organic Compounds.

Benzene, toluene, and xylene, commonly known as BTX, are hazardous aromatic organic vapors with high toxicity towards living organisms. Many techniques are being developed to provide the community with portable, cost effective, and high performance BTX sensing devices in order to effectively monitor the quality of air. In this paper, we study the effect of decorating graphene with tin oxide (SnO2) or tungsten oxide (WO3) nanoparticles on its performance as a chemoresistive material for detecting BTX vapors. Transmission electron microscopy and environmental scanning electron microscopy are used as morphological characterization techniques. SnO2-decorated graphene displayed high sensitivity towards benzene, toluene, and xylene with the lowest tested concentrations of 2 ppm, 1.5 ppm, and 0.2 ppm, respectively. In addition, we found that, by employing these nanomaterials, the observed response could provide a unique double signal confirmation to identify the presence of benzene vapors for monitoring occupational exposure in the textiles, painting, and adhesives industries or in fuel stations.

Pentiptycene Polymer/Single-Walled Carbon Nanotube Complexes: Applications in Benzene, Toluene, and o-Xylene Detection.

We report the dispersion of single-walled carbon nanotubes (SWCNTs) using pentiptycene polymers and their use in chemiresistance-based and QCM-D sensors. Poly(p-phenylene ethynylene)s (PPEs) incorporating pentiptycene moieties present a concave surface that promotes π-π interactions and van der Waals interactions with SWCNTs. In contrast to more common polymer-dispersing mechanisms that involve the wrapping of polymers around the SWCNTs, we conclude that the H-shape of pentiptycene groups and the linear rigid-rod structure creates a slot for nanotube binding. UV-vis-NIR, Raman, and fluorescence spectra and TEM images of polymer/SWCNTs support this dispersion model, which shows size selectivity to SWCNTs with diameters of 0.8-0.9 nm. Steric bulk on the channels is problematic, and tert-butylated pentiptycenes do not form stable dispersions with SWCNTs. This result, along with the diameter preference, supports the model in which the SWCNTs are bound to the concave clefts of the pentiptycenes. The binding model suggests that the polymer/SWCNTs complex creates galleries, and we have demonstrated the binding of benzene, toluene, and o-xylene (BTX) vapors as the basis for a robust, sensitive, and selective sensing platform for BTX detection. The utility of our sensors is demonstrated by the detection of benzene at the OSHA short-term exposure limit of 5 ppm in air.

Acarbose protects from central and peripheral metabolic imbalance induced by benzene exposure

Benzene is a well-known human carcinogen that is one of the major components of air pollution. Sources of benzene in ambient air include cigarette smoke, e-cigarettes vaping, and evaporation of benzene containing petrol processes. While the carcinogenic effects of benzene exposure have been well studied, less is known about the metabolic effects of benzene exposure. We show that chronic exposure to benzene at low levels induces a severe metabolic imbalance in a sex-specific manner, and is associated with hypothalamic inflammation and endoplasmic reticulum (ER) stress. Benzene exposure rapidly activates hypothalamic ER stress and neuroinflammatory responses in male mice, while pharmacological inhibition of ER stress response by inhibiting IRE1α-XBP1 pathway significantly alleviates benzene-induced glial inflammatory responses. Additionally, feeding mice with Acarbose, a clinically available anti-diabetes drug, protected against benzene induced central and peripheral metabolic imbalance. Acarbose imitates the slowing of dietary carbohydrate digestion, suggesting that choosing a diet with a low glycemic index might be a potential strategy for reducing the negative metabolic effect of chronic exposure to benzene for smokers or people living/working in urban environments with high concentrations of exposure to automobile exhausts.

Carbon molecular sieve production from defatted spent coffee ground using ZnCl2 and benzene for gas purification

The aim of the current study is to manufacture molecular sieve from the defatted spent coffee ground. The defatted spent coffee ground for the specified particle size (100 μm) was chemically activated with different agents (ZnCl2, H3PO4, KOH) and then carbonized at different temperatures (400–900 °C). A thorough characterization of the produced activated carbon was performed and activated carbons with the highest BET surface area were subsequently used to produce carbon molecular sieve. The surface modification was performed with benzene vapor at different temperatures (600–900 °C) and different combustion times (30–90 min.). In addition to the BET analysis, SEM, TGA and FT-IR analysis were also undertaken. The results obtained through characterizations showed that the pore diameters of carbon molecular sieve produced from defatted spent coffee ground varied from 2 to 4 Å. To conclude, the results suggest that the fabricated carbon molecular sieve can be used for the removal of impurities such as CH4, CO2, NOx and other impurities in natural and biogas considering the porosity of the sieves.

Gas-sensing properties of poly(p-xylylene) - titanium thin film nanocomposite, prepared by vapor deposition polymerization

Poly(p-xylylene) – titanium thin film nanocomposites were synthesized by vacuum deposition polymerization and proposed to serve as a gas sensor. They can reversibly and selectively detect several parts per thousand water, ethanol and even n-propyl benzene vapors with short response time. The presence of polar molecules affects conductance and capacitance, while nonpolar vapors such as benzene and toluene have no effect on electrical properties. Polarization and depolarization currents were recorded and it was found that composition of gaseous medium affected the parameters of dielectric response function. The frequency dependences of complex capacitance were fit by the Debye equations; correlations of the fit parameters and titanium concentration, as well as dipole moment of analyte molecules in atmosphere were found. The model was proposed, that explains dielectric behavior of nanocomposites and assumes the existence of several dielectric relaxation processes with different characteristic times: orientation of physically adsorbed polar molecules, charge exchange of surface states, generated by chemisorbed molecules at the interface nanoparticle/polymer matrix and Maxwell-Wagner interfacial polarization phenomena.