Benzene Vapor Research Articles

Plasmachemical synthesis of coatings using a vacuum arc discharge

Summary In this paper we discuss the issues of applying protective coatings on the copper anodes of powerful generator tubes. As a synthesized material due to its high operational properties was chosen titanium carbide obtained by sputtering a titanium cathode in benzene vapors. Scheme of a vacuum arc device used in this work and also the technological processes for the plasmachemical synthesis of coatings on complex shape anodes are described. For a correct choice of the technological parameters it was considered a model of penetration of the plasma flux into the hollow copper anode that was verified by experiments using a setup with a variable cavity diameter. On the emission spectrum of the discharge in the process of coating deposition shown in this work were recorded spectral lines corresponding to the atoms and ions of titanium and carbon ions. We investigated the distribution of elements across the thickness of the formed coating immediately after deposition and after annealing in vacuum, also the X-ray diffraction pattern and a microsection for the obtained titanium carbide coating are presented. As a result of the work it can be noted that the described sequence of technological processes, subject to the control of plasma flux parameters, allows obtaining a high quality protective coating on parts of complex shape.

Field-electron emission microscopy of carbon-saturated rhenium

The growth of carbon structures on the surface of a rhenium point field emitter has been studied by field electron microscopy (FEM). It is established that graphene formation takes place on close-packed crystal faces of rhenium and leads to decrease in their work function. For rhenium exposed in benzene vapors, the formation of graphene islands requires a much longer time than that for iridium. Heating of carbon-saturated rhenium point field emitter up to temperatures close to its melting point with subsequent cooling does not lead to changes in the work function and FEM image of the emitter surface. The observed phenomena are explained by high solubility of carbon in rhenium.

Gas-sensitive properties of thin nickel oxide films

The results of a study of the gas-sensitive properties of nickel oxide layers with respect to n-hexane, acetone, ethanol, benzene, o-xylene, toluene and ammonia are presented. NiO layers 100 ± 5 nm thick were obtained by chemical vapor deposition in the systems (EtCp)2Ni–О2–Ar and (EtCp)2Ni–О3–О2–Ar. The electrical resistance of the layers changes in the presence of hexane, ethanol, benzene, and ammonia vapors. The electrical resistance of the obtained layers changed in the presence of vapors of hexane, ethanol, benzene and ammonia. Response and recovery time of the sensing element of the gas sensors did not exceed 6 s in the temperature range 500–600 K.

Portable High Surface Area TiO2 Nanotube Array Sensor for the Detection of Benzene at Room Temperature

Benzene is one of the few known human carcinogens as identified by the International Agency for Research on Cancer. It is a common indoor and outdoor pollutant, with sources ranging from cigarette smoke to traffic. Hence, there is an increasing need to detect low concentrations of benzene. Metal-oxide based nano-sensors, with their simple sensing mechanisms make for a good choice. Thin films based on titanium dioxide (TiO2) have previously been shown to respond to benzene (1), however these sensors are run at high temperatures (160-200°C), require a complex setup for operation, and have low surface area for sensing. This paper presents the development of TiO2 nanotube based sensor array (Figure 1) that has high surface area, is highly sensitive, and operates at room temperature using portable and simple instrumentation. TiO2 nanotubes were synthesized through anodization in electrolytic solution of ammonium fluoride (NH4F)-ethylene glycol (EG) and oxygen annealed for up to 500°C. The response of the synthesized hollow nanotubes was studied at room temperature for different concentrations of benzene vapor (100-500ppm). The response of the sensor coupons to benzene vapor was measured using an amperometric technique. The results showed an increase in current that was directly proportional to the concentration of benzene in the sample which indicates a quantitative nature of the sensor (Figure 2). The sensor was placed in a portable system which can be deployed to potential contamination sites for real-time monitoring applications. Results on sensing mechanism, stability of the sensor over time, sensor reusability, and detection limit will be presented. (1) Mabrook M., Hawkins P. (2001) Sensors and Actuators, B: Chemical 75, 197-202. Figure 1

Evaluating the impact of ambient benzene vapor concentrations on product water from Condensation Water From Air technology

Globally, drinking water resources are diminishing in both quantity and quality. This situation has renewed interest in Condensation Water From Air (CWFA) technology, which utilizes water vapor in the air to produce water for both potable and non-potable purposes. However, there are currently insufficient data available to determine the relationship between air contaminants and the rate at which they are transferred from the air into CWFA untreated product water. This study implemented a novel experimental method utilizing an environmental test chamber to evaluate how air quality and temperature affects CWFA untreated product water quality in order to collect data that will inform the type of water treatment required to protect human health. This study found that temperature and benzene air concentration affected the untreated product water from a CWFA system. Benzene vapor concentrations representing a polluted outdoor environment resulted in benzene product water concentrations between 15% and 23% of the USEPA drinking water limit of 5μg/l. In contrast, product water benzene concentrations representing an indoor industrial environment were between 1.4 and 2.4 times higher than the drinking water limit. Lower condenser coil temperatures were correlated with an increased concentration of benzene in the product water. Environmental health professionals and engineers can integrate the results of this assessment to predict benzene concentrations in the product water and take appropriate health protective measures.

Optical Properties and Swelling Behavior of Fe3O4Functionalized Graphene Oxide Composite Thin Film

The optical characterization and gas sensing properties of Fe3O4 functionalized graphene oxide (GO) composite [Fe3O4-(3-aminopropyl)triethoxysilane GO (APTES-GO)] thin film are discussed in this paper by using spin coating, UV-visible spectroscopy, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction measurements, Surface Plasmon Resonance, and quartz crystal microbalance (QCM) techniques. The Fe3O4-APTES-GO thin films with thickness in the range between 14 and 31 nm have been successfully prepared, when films were spun at speeds between 1000 and 4000 rpm with a refractive index values of between 1.32 and 1.37. In this paper, the swelling behaviors of the Fe3O4-APTES-GO thin films were investigated with respect to volatile organic compounds (VOCs) at room temperature by using the QCM method. The swelling processes could be investigated using the early-time Fick’s law of diffusion. Diffusion coefficients were found to be $24.17\times 10^{\mathrm {\mathbf {-16}}}$ , $13.99\times 10^{\mathrm {\mathbf {-16}}}$ , $3.97\times 10^{\mathrm {\mathbf {-16}}}$ , and $1.73\times 10^{\mathrm {\mathbf {-16}}}$ cm2 $\text{s}^{\mathrm {\mathbf {-1}}}$ for dichloromethane, chloroform, benzene, and toluene vapors, respectively. The response of the Fe3O4-APTES-GO films to the these VOCs has been investigated in the conditions of physical properties of the solvents, and the films were obtained to be largely sensitive to dichloromethane and chloroform vapors compared with other studied vapors.

On the possibility of controlling the hydrophilic/hydrophobic characteristics of toroid Mo138 nanocluster polyoxometalates

The possibility of changing the hydrophilic (polar) surfaces of toroid nanocluster polyoxomolibdates to hydrophobic (nonpolar) surfaces via the modification of Mo138 nanoclusters by surfactant molecules (dodecylpyridinium chloride) as a result of the interaction between these compounds in solutions is demonstrated. Benzene and methanol are used as molecular probes (indicators of the condition of nanocluster surfaces). Comparative characteristics of the equilibrium sorption of benzene and methanol vapors on the initial and modified surfaces of the solid polyoxometalate, and data on the sorption of organic molecules on the surfaces of Rhodamine B-modified nanoclusters of the toroid (Mo138) and keplerate (Mo132) types are obtained.

The Relationship Between Benzene Vapor's Exposure and Immunoglobulin among Shoes Worker in the Village of Tambak OSO Wilangun Surabaya

Glue is one of the most important ingredient in the making of shoes, that it contains an organic solvent which is benzene. Benzene solvent in glues known by 1-2. Benzene is known as a carcinogen category A1,confirmed human carcinogen, meaning that benzene has been ascertained and proven carcinogen in humans. Chronic exposure to benzene affects on cellular and humoral immunity. Benzene evaporates into the air very quickly allowing to be inhaled by workers. The purpose of this study are(1) to measure the levels of benzene vapor in the work environment, (2) to determine the concentration of A Immunoglobulin among workers and (3) to determine the relationship between benzene vapor exposure and workers� IgA concentration. The method used to measure the levels of benzene vapor in the workplace was gas chromatography method using GC / FID (Flame Ionization Detector) and to determine the concentration of A Immunoglobulin, venous blood sampling was done and then analyzed by Immunoturbidimetric Assay. Benzene vapor�s levels of shoes workers in workplacewas varied, from 0.0129 ppm to 2.3330 ppm which was 0.5116 ppm in average and IgA concentration experienced a value of 0.86 mg/ml to 3.80 mg/ml. Pearson product moment test was conducted on worker characteristics (age, year of service), Spearman�s rank test on nutritional status and contingency coefficient C test for gender and smoking habits with IgA concentration of workers obtained all the variables had a value of p> 0.05. The result showed that the IgA concentrations among workers which were 8 workers noted as under normal ( 3 mg/ml) with ppm benzene levels 0.0129- 2.3330 ppm and average levels of benzene in the air amounted to 0.5116 ppm>TVL (0.5 ppm). In conclusion, twelve workers witnessed an abnormal IgA concentration (decrease / increase of the normal value). © 2017, Indian Journal of Public Health Research and Development. All rights reserved.

A quartz crystal microbalance study of the adsorption of benzene and acetone vapors onto coumarin-substituted manganese phthalocyanine film

A novel coumarin-substituted manganese phthalocyanine (5) was successfully synthesized and used as sensing element for benzene and acetone vapor detection. The effects of water vapor on the benzene and acetone vapor-sensing properties and adsorption isotherms on thin film of 5 were also studied. Our preliminary results indicated that the presence of humidity modifies the baseline frequency but not the sensitivity of the sensor toward benzene and acetone vapors. Two isotherm models, Langmuir and Jovanovic isotherms, were selected to describe the adsorption process. Linear regression analysis, which is the most basic and commonly used predictive analysis method, was used to estimate the suitability of the selected isotherm models. The Jovanovic model was found to be adequate for describing benzene and acetone adsorption onto compound 5.

Use of cement-fly ash-based stabilization techniques for the treatment of waste containing aromatic contaminants

Research on evaluation of evaporation rate of volatile organic compounds from soil beds during processing is presented. For the experiment, soil samples were prepared with the same amounts of benzene and stabilized using a mixture of CEMI 42.5R cement and fly ash from pit-coal combustion. Solidification of soils contaminated with BTEX hydrocarbons using hydraulic binders involves a risk of releasing vapours of these compounds during homogenization of waste with stabilizing mixture introduced and its dilution with water. The primary purposes of the research were: analysis of benzene volume emitted from soil during stabilization/solidification process and characterization of factors that may negatively affect the quality of measurements/the course of stabilization process. Analysis of benzene emission intensity during the process was based on concentration (C 6 H 6 ) values, recorded with flame-ionization detector above the surface of reacting mixture. At the same time, gaseous contaminants emitted during waste stabilization were passed through pipes filled with activated carbon (SCK, Anasorb CSC). Benzene vapours adsorbed on activated carbon were subjected to analysis using gas chromatograph Varian 450-GC. Evaporation characteristics of benzene during processing contaminated soils revealed the stages creating the highest danger to workers’ health, as well as a need for actions connected with modification of technological line.

Dubinin isotherms versus the Brouers–Sotolongo family isotherms: A case study

We show how the Dubinin isotherm and its extensions can be related to the isotherms derived from the general Brouers–Sotolongo isotherm. We compare them using benzene vapor adsorbed on activated carbon data from one of the original Dubinin’s paper. We use the same procedure to analyze data from the thesis of Francois Marquez-Montesino on the adsorption on activated carbons prepared from Pinus caribaea saw dust. We conclude by proposing a simple methodology to determine the macroscopic information given by genuine statistical isotherms.

Synthesis of porous carbon beads with controllable pore structure for volatile organic compounds removal

Spherical porous carbon materials (SPCMs) have attracted considerable interest due to the excellent mechanical performance and abundant pore structure. In this work, porous carbon beads (PCBs) of around 1.5mm were synthesized via phase inversion route followed by carbonization. Specially, porous polymeric beads (PPBs) were obtained by injecting of polyvinylidene fluoride (PVDF) polymer solution containing phenolic resins into coagulation bath. The porous structure of PPBs can be adjusted by simply altering the composition of coagulation bath, which further determined the final microstructure of PCBs. Mercury porosimeter, SEM and N2 adsorption-desorption isotherms characterization revealed that the resultant PCBs possess uniform spherical shape, abundant macrospore and high mesoporosity. The sample obtained under the moderate phase inversion condition, i.e. PCBs-2, possesses highest BET surface area (1166m2/g), mesoporous pore volume (0.249cm3/g) and pore size (2.87nm). To present the removal performance of PCBs for volatile organic compounds (VOCs), the adsorption behaviors under static and dynamic conditions were investigated. The static adsorption result indicated that PCBs-2 exhibits the largest adsorption capacities for benzene (1.467g/g), toluene (1.229g/g), n-hexane (0.600g/g) and acetone (0.770g/g). Dynamic adsorption on thermogravimetric analyzer reveled that PCBs-2 presents higher adsorption capacity and faster adsorption kinetics for benzene vapor. Breakthrough curves obtained from fixed bed on PCBs-2 and commercialized granular activated carbon further confirms the enhanced adsorption capacity was achieved on PCBs-2. After 6 adsorption-desorption cycles, the steady dynamic adsorption capacity can be reserved with negligible change. These results imply that PCBs-2 has great potential as a promising candidate for the abatement of VOCs.

ELECTROCATALYSTS BASED ON Ni-, Co-SPINELS

The synthesis of Ni-, Co-spinels was performed using coprecipitation method with precursors Ni and Co nitrates under different conditions: using precipitators NaOH and NH4OH, at different pH values and different aging durations.Structural, adsorption and catalytic properties by of Ni-, Co-spinels were determined by X-ray diffraction, desiccator method of adsorption of benzene vapor and in redox reactionof hydrogen peroxide decomposition. The size of the crystallites of obtained spinels was calculated from X-ray diffraction patterns and all of the samples were nano-dispersed with developed surface area from 92 to 320 m2/g. Electrocatalytic investigations have shown thatthe most active spinels were obtained by precipitation with NH4OH at pH 9,0. The highest catalytic activity from all of the twelve spinels samples in hydrogen peroxide decomposition reaction had Ni-, Co-spinel, precipitated by NH4OH at pH 9,0 and aged for 3 days whichshown 100% decomposition degree of H2O2 after 45 seconds of contact.According to the results, the conditions of synthesis of Ni-, Co-spinels highly effect on their catalytic activity. Significantly lower catalytic activity of samples precipitated by NaOH, in our opinion, explained by the inhibitory effect of sodium, which is formed by the heat treatment of samples containing NaOH in trace amounts. Established that with decreasing pH values to neutral the activity of Ni-, Co-spinels increases and with increasing durationof aging of samples their catalytic activity is reduced due to the recrystallization process sediment, resulting in the number of active sites on the surface of Ni-, Co-spinels decreases.

Enhanced adsorption of benzene vapor on granular activated carbon under humid conditions due to shifts in hydrophobicity and total micropore volume

A series of hydrophobic-modified (polydimethylsiloxane (PDMS) coating) activated carbons (ACs) were developed to answer a fundamental question: what are the determinants that dominate the adsorption on ACs under humid conditions? Using column experiments, an inter-comparison among bare-AC and PDMS-coated ACs was conducted regarding the association of surface characteristics and adsorption capacity. Primary outcomes occurred in two dominating markers, hydrophobicity and total micropore volume, which played a key role in water adsorption on ACs. However, their contributions to water adsorption on ACs substantially differed under different Pwater/Pair conditions. Hydrophobicity was the only contributor in Pwater/Pair=0.1–0.6, while the two markers contributed equally in Pwater/Pair=0.7–1.0. Furthermore, PDMS-coated AC had a significant increase in benzene adsorption capacities compared to bare-AC at 0–90% relative humidity, while these differences were not significant among PDMS-coated ACs. It is thus presumed that the balance between the two markers can be shifted to favor almost unchanged benzene adsorption capacities among PDMS-coated ACs over a large range of relative humidity. These findings suggest potential benefits of PDMS coating onto ACs in enhancing selective adsorption of hydrophobic volatile organic compounds under high humid conditions. To develop new porous materials with both high total micropore volume and hydrophobicity should thus be considered.

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.

SAW mono sensor for identification of harmful vapors using PCA and ANN

A functionalized polymer (SXFA: fluoroalcoholpolysiloxane) coated single surface acoustic wave (SAW) sensor E-Nose is proposed for the detection of harmful vapors by operating at different temperature. The polymer coated SAW sensor is used along with a reference SAW device in dual Colpitt's oscillator configuration. The sensor is tested with four different classes of vapors at different concentrations in an environmental chamber whose temperature can be varied in the range −20 to +70°C. The sensor showed variation in response with exposure to benzene, methanol, diesel and DMMP vapors at different temperatures. The polymer coated SAW sensor was giving frequency shifts of 0.21–1.12kHz for methanol (1000–4000ppm), 0.3–2.69kHz for benzene (400–1600ppm), 0.81–7.39kHz for diesel (12–48ppm) and 4.27–8.07kHz for DMMP (1–10ppm) vapors at 30°C operating temperature. Principal component analysis and artificial neural network algorithms are successfully implemented to classify and detect the target vapors.

Histone Deacetylase Inhibitors Trichostatin A and MCP30 Relieve Benzene-Induced Hematotoxicity via Restoring Topoisomerase IIα.

Dysfunction of histone acetylation inhibits topoisomerase IIα (Topo IIα), which is implicated in benzene-induced hematotoxicity in patients with chronic benzene exposure. Whether histone deacetylase (HDAC) inhibitors can relieve benzene-induced hematotoxicity remains unclear. Here we showed that hydroquinone, a main metabolite of benzene, increased the HDAC activity, decreased the Topo IIα expression and induced apoptosis in human bone marrow mononuclear cells in vitro, and treatment with two HDAC inhibitors, namely trichostatin A (TSA) or a mixture of ribosome-inactivating proteins MCP30, almost completely reversed these effects. We further established a benzene poisoning murine model by inhaling benzene vapor in a container and found that benzene poisoning decreased the expression and activity of Topo IIα, and impaired acetylation of histone H4 and H3. The analysis of regulatory factors of Topo IIα promoter found that benzene poisoning decreased the mRNA levels of SP1 and C-MYB, and increased the mRNA level of SP3. Both TSA and MCP30 significantly enhanced the acetylation of histone H3 and H4 in Topo IIα promoter and increased the expression and activity of Topo IIα in benzene poisoning mice, which contributed to relieve the symptoms of hematotoxicity. Thus, treatment with HDAC inhibitors represents an attractive approach to reduce benzene-induced hematotoxicity.

Synthesis and characterization of mesoporous graphite carbon, and adsorption performance for benzene

In this paper, graphite carbon with a mesoporous structure was synthesized using the template–catalysis procedure with hydrated metal oxide nanoparticle as template and catalyst, phenol and formaldehyde as carbon source. XRD, Raman, BET and TEM analyses were performed to study the effluence of synthetic conditions on the structure of samples. The adsorption performances for benzene vapor were evaluated. The results show that CCo and CFe samples have mesoporous graphitized carbon structures. The molar amount of template to carbon source significantly affects the specific surface area, pore structure and adsorption–desorption performance. The specific surface area of CCo-1, with the best graphite structure, was 287.638 m2/g, the pore size was 19.075 nm, and the adsorption capacity for benzene vapor was 19.615 mmol/g. The synergistic effect between the cobalt element and graphite carbons affects the adsorption capacity of CCo-3, which was 34.643 mmol/g. However, the desorption efficiency was only 89 %, and the adsorption performance of CCo-3 material was degraded greatly after three times run.

A Dendrimer‐Based Electropolymerized Microporous Film: Multifunctional, Reversible, and Highly Sensitive Fluorescent Probe

A dendrimer PYTPAG2 composed of a central pyrene “core” and four exterior “arms” capped with electroactive triphenylamine is developed as an electroactive precursor to prepare fluorescent films through electropolymerization (EP). The fluorescence emission comes from the central pyrene “core” and the steric hindrance of the exterior “arms” is beneficial for the formation of microporous morphology. The stable and highly cross‐linked fluorescent EP films can be obtained even as free‐standing films. Further, these dendrimer EP films are first studied as the multifunctional fluorescent probe: the emission of EP films exposed to trinitrotoluene vapor is quenched by 82% in 120 s; while the fluorescence is increased to nearly 400% in 120 s upon exposure to benzene vapor, EP films also act as the fluorescent sensor to Fe3+ in solution and the limit of detection is obtained to be 8.5 × 10−8 m. All the above detection processes exhibit remarkable reversibility. These excellent performances are attributed to both the specific molecular features of PYTPAG2 and the intrinsic properties of EP films.

Integrated Gas Sensing System of SWCNT and Cellulose Polymer Concentrator for Benzene, Toluene, and Xylenes.

An integrated cellulose polymer concentrator/single-walled carbon nanotube (SWCNT) sensing system is demonstrated to detect benzene, toluene, and xylenes (BTX) vapors. The sensing system consists of functionalized cellulose as a selective concentrator disposed directly on top of a conductive SWCNT sensing layer. Functionalized cellulose concentrator (top layer) selectively adsorbs the target analyte and delivers the concentrated analyte as near as possible to the SWCNT sensing layer (bottom layer), which enables the simultaneous concentrating and sensing within a few seconds. The selectivity can be achieved by functionalizing cellulose acetate with a pentafluorophenylacetyl selector that interacts strongly with the target BTX analytes. A new design of the integrated cellulose concentrator/SWCNT sensing system allows high sensitivity with limits of detection for benzene, toluene, and m-xylene vapors of 55 ppm, 19 ppm, and 14 ppm, respectively, selectivity, and fast responses (<10 s to reach equilibrium), exhibiting the potential ability for on-site, real-time sensing applications. The sensing mechanism involves the selective adsorption of analytes in the concentrator film, which in turn mediates changes in the electronic potentials at the polymer-SWCNT interface and potentially changes in the tunneling barriers between nanotubes.