Benzene Homologues Research Articles

Ultramicroporous metal-organic frameworks for capillary gas chromatographic separation

Fine-tuning of the SiF62--containing metal-organic frameworks (SIFSIX) through the substitution of metal centers and ligands changed the apertures from 8.3 Å to 3.8 Å, resulting in ultramicropores and notably improving the separation performance of alkane isomers. Herein, we reported SIFSIX-1-Zn, SIFSIX-1-Cu and SIFSIX-3-Zn as representative stationary phases for capillary gas chromatography (GC). The capillary column coated with ultramicroporous SIFSIX-3-Zn efficiently separated the alkane isomers and benzene homologues, which outperformed SIFSIX-1-Zn and SIFSIX-1-Cu. This resulted from size matching between the window of the ultramicroporous SIFSIX-3-Zn and the analytes, which was also supported by McReynolds constants, column efficiency and peak tailing effect. It opened up a new avenue for ultramicroporous materials in the chromatography separation of isomers.

Flue gas composition of waste rubber modified asphalt (WRMA) and effect of deodorants on hazardous constituents and WRMA

Waste rubber modified asphalt (WRMA) produces hazardous flue gas during preparation, which severely pollutes the environment and endangers the health of construction personnel. This paper designed an asphalt flue gas generation with a collection device and proposed the extraction methods of solid, liquid, and gas components separately. Deodorant was incorporated into WRMA to alleviate the negativity of detrimental pollutant emissions. Then, gas chromatography-mass spectrometry, electrochemical sensing technology, Fourier transform infrared spectroscopy, fluorescence microscopy, and waste rubber extraction test were combined to explore the main compositions of asphalt flue gas and illustrate the effect of deodorants on hazardous flue gas and WRMA. Results reveal that the main hazardous constituents are sulfur-containing organics, benzene homologs, and H2S in the WRMA flue gas. Deodorants can improve the stability of waste rubber in WRMA, inhibit the degradation of waste rubber, reduce the release concentration of H2S, enhance the oxidation resistance of sulfur-containing groups, and further promote the aging resistance of WRMA to realize deodorization and environmental protection. Therefore, the addition of deodorants can alleviate the release of hazardous flue gas from WRMA, which is conducive to the popularization and application of WRMA in pavement engineering.

In situ growth of COF-rLZU1 on the surface of silica sphere as stationary phase for high performance liquid chromatography

The composite materials consist of Covalent Organic Frameworks (COFs) and silica have been regarded as a kind of promising stationary phases due to combination of the large specific surface area and good mechanical strength of porous silica microspheres and the porous structure and the excellent stability of COFs. Herein, a novel COFs-silica composite (SiO2@rLZU1, reduced Lan Zhou University-1) was prepared via an in-situ growth strategy with a 32 nm-thick COFs layer on the surface of silica and a 2.2 nm-thick COFs layer on the inner surface of the mesopores of spherical silica (5 μm, 120 Å). With secondary amine and phenyl groups, the novel stationary phase provided hydrophilic, hydrophobic and π-π interactions when used in HPLC, showing different selectivity from typical reversed-phase stationary phases. Probe molecules with aromatic moieties varying in polarity, including acidic (phenol, pyrocatechol, and pyrogallol), basic (aniline, 4-chloroaniline, and 4-nitroaniline) and neutral (benzene homologues) compounds, were all baseline separated on the SiO2@rLZU1 column, indicating its excellent separation performance. Besides, the SiO2@rLZU1 column also exhibited great repeatability with intraday RSDs of the retention time of three anilines less than 0.31% (n = 6) and peak area less than 1.63% (n = 6). On the SiO2@rLZU1 column, satisfied results were achieved in the separation of real samples such as fullerenes and coking wastewater, suggesting the great potential of the as-synthesized stationary phase in HPLC applications.

Preparation of poly (KH570-co-DVB) microspheres and application in HPLC for separation of benzene and benzene homologs

High-performance liquid chromatography (HPLC) is one of the most widely used separations and analysis methods, which has become an indispensable part of the separation and detection of mixtures, qualitative and quantitative analysis and other scientific research and social production fields. Because of the decisive effect of the chromatographic column on analysis and separation, it has become the core of research in the chromatographic system. In the past decades, the research and development of new chromatographic column stationary phase have been highly concerned. Monodisperse polymer microsphere, because of its special large pore structure, has good permeability and high specific surface area, which can be used as special materials in various fields, such as adsorption materials in the separation process, HPLC column packing, catalyst carrier, preparation template of nanomaterials and nuclear fusion targeting materials. When it is used in HPLC, because of the good permeability of microspheres, it can effectively improve the separation efficiency and performance. In this article, based on the previous work, a number of new polymer microspheres were prepared, and the prepared microspheres were used for the separation and detection of HPLC, and their physical and chemical properties were studied.

Roles of metal, ligand and post synthetic modification on metal organic frameworks to extend their hydrophobicity and applicability toward ultra–trace determination of priority organic pollutants

Implementation of metal organic frameworks (MOFs) in the separation science has attracted many researchers attention. In this study, the role of metal, ligand, the reaction condition and modification on the extraction efficiency of some MOFs was investigated. Among the prevalent reported MOFs, some members of the MIL and MOF–5 families were chosen, and eleven MOF–based sorbents were prepared by changing the metal and ligand type, reaction condition, and/or functionality through post synthetic modification (PSM). MIL–101 and MIL–101–NH2 based structures were initially synthesized based on the chromium and iron salts. Also, three zinc–based structures including MOF–5, [NH2(CH3)2]2 [Zn3(C6H4(CO2)2)4].DMF.H2O and [NH2(CH3)2]2 [Zn3((C6H4)2(CO2)2)4].5DMF were synthesized. The PSM hydrophobic–oriented products of MILs were obtained by their reactions with benzyl alcohol. The resulted MOFs were characterized by FT–IR, PXRD, SEM, BET, BJH, water contact angle and TG analyses. The extraction trends of these nanostructures were studied toward some priority environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs), chlorobenzenes (CBs), and benzene homologs. The extraction procedures were performed via adapting a home–made headspace needle trap extraction (HS–NTE) setup, and determinations were followed by gas chromatography-mass spectrometry (GC–MS). Among all the synthesized nanostructures, the chromium–based PSM product of MIL–101–NH–CH2C6H5 proves its improved extraction capability for most of the model compounds. Eventually, the superior MOF was applied as the extractive phase in a HS–NTE–GC–MS method for isolation and trace determination of PAHs, in tea, coffee, and some other environmental water samples. Under the optimized conditions, the linear dynamic range (LDR) was in the range of 1–1000 ng L−1 (R2 > 0.992) while the limits of detection (LOD) and limits of quantification (LOQ) values were 0.1–0.2 and 0.3–0.7 ng L−1, respectively. Also, the extraction capability of the Cr–based MIL–101–NH–CH2C6H5 was compared with commercial polydimethyl siloxane–divinyl benzene (PDMS–DVB) fiber coating. The intra–and inter–day relative standard deviations for three replicates at the concentration levels of 20 and 500 ng L−1 were in the range of 4–7% and 5–10%, respectively. The needle–to–needle reproducibility was also found to be in the range of 6–10%. Acceptable relative recovery values at the concentration levels of 20 and 500 ng L−1 ranged from 89 to 98%, showing no significant matrix effect.

Perylene Diimide-Based Fluorescent and Colorimetric Sensors for Environmental Detection.

Perylene tetracarboxylic diimide (PDI) and its derivatives exhibit excellent thermal, chemical and optical stability, strong electron affinity, strong visible-light absorption and unique fluorescence on/off features. The combination of these features makes PDIs ideal molecular frameworks for development in a broad range of sensors for detecting environmental pollutants such as heavy metal ions (e.g., Cu2+, Cd2+, Hg2+, Pd2+, etc.), inorganic anions (e.g., F−, ClO4−, PO4−, etc.), as well as poisonous organic compounds such as nitriles, amines, nitroaromatics, benzene homologues, etc. In this review, we provide a comprehensive overview of the recent advance in research and development of PDI-based fluorescent sensors, as well as related colorimetric and multi-mode sensor systems, for environmental detection in aqueous, organic or mixed solutions. The molecular design of PDIs and structural optimization of the sensor system (regarding both sensitivity and selectivity) in response to varying analytes are discussed in detail. At the end, a perspective summary is provided covering both the key challenges and potential solutions for the future development of PDI-based optical sensors.

Facile construction of superhydrophobic hybrids of metal-organic framework grown on nanosheet for high-performance extraction of benzene homologues

Encapsulating functional nanomaterials within the bulk of metal-organic frameworks (MOFs) offers the opportunity to construct high-performance hybrid coating materials for solid phase microextraction (SPME). In this work, we proposed the facile synthesis of a superhydrophobic MOF composite material (NSZIF-8Si) by growing ZIF-8 on MnxOy nanosheet (NS) and subsequently depositing short-chain polysiloxane on the surface of the composite. A novel SPME fiber was successfully prepared based on the NSZIF-8Si composite. The NSZIF-8Si fiber possessed outstanding thermal stability (up to 450 °C). In headspace SPME of BTEX, the home-made fiber exhibited extraction efficiencies much higher than the commercially available PDMS fiber. This phenomenon was due to the synergetic cooperation of the π-π stacking and the hydrophobic interactions between the NSZIF-8Si coating and the analyte molecules, as well as the increased aspect ratio of the MOF grown on the nanosheet. The established method achieved wide linearity (5–2000 ng L−1) and low LODs (0.02 ng L−1 to 0.21 ng L−1). Satisfactory recoveries were obtained in the analysis of real water samples collected from the Pearl River, indicative of the good reliability of the established method for real-scenario applications. This work might provide critical insights in constructing novel NS/MOF composite materials for the development of high-performance SPME fiber coatings.

Preparation and Evaluation of a Cholesterol Derivatized β-Cyclodextrin-bonded Phase for Achiral and Chiral HPLC.

A cholesterol mono-derivatized β-cyclodextrin was synthesized and bonded onto silica gel (SBA-15) to obtain a cholesterol mono-derivatized β-cyclodextrin-bonded stationary phase (CHCDP). The chemical structures of mono-derivatized β-cyclodextrin and CHCDP were characterized by infrared spectroscopy, mass spectrometry, elemental analysis and thermogravimetric analysis, correspondingly. Furthermore, the separation ability of CHCDP in terms of achiral compounds was systematically evaluated by separating benzene homologs, polycyclic aromatic hydrocarbons (PAHs) and some positional isomers. As a result, CHCDP completely separated five benzene homologs and nine PAHs within 30 min under the reversed-phase. In addition, the chiral chromatographic property of CHCDP was also evaluated by separating some racemic compounds including flavanones, triazoles, β-blockers, etc. The results showed that the CHCDP exhibited high enantioselectivities towards most of selected analytes. The enantioresolutions were in the range from 1.43 to 2.51 on CHCDP. Especially the resolutions of 2'-hydroxyflavanone, hexaconazole, Dns-serine and atenolol were as high as 1.94, 1.91, 2.15 and 1.57, respectively. Obviously, the CHCDP was a versatile stationary phase with chiral and achiral separation capabilities in multi-mode chromatography, which was related to the introduction of cholesterol to the port of cyclodextrin, enhancing the hydrophobic interaction of cyclodextrin with achiral compounds, while maintaining the inclusion complexation of it with chiral compounds as well.

Concentration Levels and Impact Factors of Benzene Series in Chinese Residential Building

From December 2016 to December 2017, the concentrations of the benzene series (benzene, toluene, xylene, and ethyl-benzene) in air were analyzed in 223 residential buildings in five climatic regions of China during different seasons. The arithmetic average concentrations of benzene, toluene, xylene, and ethyl-benzene were 6.78, 17.4, 17.68, and 9.87 μg·m-3, respectively. Indoor benzene series concentrations in China were slightly higher than that in other countries; the standard limits for indoor benzene series concentrations in China are much higher than those of other countries and organizations. Among the many factors affecting the concentration of the benzene series in the rooms, the relationship between the completion time of decoration, smoking, and cooking frequency and the concentration of benzene homologues was studied. The results showed that the concentration of toluene decreased with the prolongation of decoration time, the concentration of benzene in smoking households was higher than that in non-smoking families, and there was no direct correlation between cooking frequency and indoor concentration of the benzene series. The study provides statistical data on exposure to the benzene series in decorated homes and a discussion of setting values of relevant standards.

Effective extrapolation models for ecotoxicity of benzene, toluene, ethylbenzene, and xylene (BTEX)

Benzene homologues have significant toxic effects to aquatic organisms. In this study, the acute toxicity data of benzene, toluene, ethylbenzene and xylene (BTEX) were collected and screened, and the toxicity extrapolation model of paired BTEX was established. The results showed that except the correlation between benzene and xylene was not strong due to insufficient data, the linear correlation of the other five paired BTEX was good (p < 0.01), and R2 fitted by the four out of five paired BTEX was greater than 0.85. The cross validation showed that ethylbenzene-xylene model was optimal, and for most species (81.8%), the established five BTEX models had a prediction error of less than 10%. Also, these extrapolation models were validated by experimental results of Pseudorasbora parva. The difference between the predicted and measured values of the acute toxicity of BTEX was less than 1 fold, which indicated that the extrapolation model had high accuracy.

Benzene homologues contaminants in a former herbicide factory site: distribution, attenuation, risk, and remediation implication.

Benzene homologues often used as organic raw materials or as detergents in chemical industry are prone to accidental release into the environment which can cause serious long-term soil pollutions. In a large former herbicide factory site, we investigated 43 locations for benzene homologues contaminations in soil, soil gas, and groundwater and studied the hydrogeological conditions. An inverse distance weighted interpolation method was employed to determine the pollutants three-dimensional spatial distribution in the soils. Results showed that benzene homologues residues were mainly originated from the herbicide production workshop and that the pollution had horizontally expanded at the deeper soil layer. Contaminants had already migrated 15m downward from ground surface. Contaminant phase distribution study showed that NAPL was the primary phase (> 99%) for the pollutants accumulated in the unsaturated zone, while it had not migrated to groundwater. The primary mechanism for contaminant transport and attenuation included dissolution of "occluded" NAPL into pore water and pollutant volatilization into soil pore space. Risk assessment revealed that the pollutants brought unacceptable high carcinogenic and non-carcinogenic risks to public health. In order to convert this former chemical processing factory site into a residential area, a remediation to the polluted production workshop sites is urgently required.

A Thioether-Embedded Mixed-Mode Cyano-Bonded Chromatographic Stationary Phase: Preparation, Characterization and Retention Mechanism

In this paper, a thioether-embedded mixed-mode cyano-bonded chromatographic packing has been prepared by using gas silylation method and thiol-ene click chemistry. The solid-state 13C CP/MAS NMR and elemental analysis have been used to characterize the synthesized materials. Detailed chromatographic characterization of the new phase was performed by alkyl benzene homologues in reversed-phase liquid chromatography (RPLC) and was characterized by nucleic acid bases and nucleosides in hydrophilic interaction liquid chromatography (HILIC). The hydrothermal stability has been studied by n-butylbenzene, and results show that the novel cyano-phase had higher stability. In addition, linear solvation energy relationships (LSERs) have been used to investigate the effect of stationary phase property on the retention factor of seven aromatic solutes. The results have shown that the Sil–S–CN phase has a pronounced strong polarity and dipole interactions between stationary phases and analytes.

Recent advances in metal-organic frameworks for adsorption of common aromatic pollutants.

This review (with 85 refs.) summarizes the recent literature on the adsorption of common aromatic pollutants by using modified metal-organic frameworks (MOFs). Four kinds of aromatic pollutants are discussed, namely benzene homologues, polycyclic aromatic hydrocarbons (PAHs), organic dyes and their intermediates, and pharmaceuticals and personal care products (PPCPs). MOFs are shown to be excellent adsorbents that can be employed to both the elimination of pollutants and to their extraction and quantitation. Adsorption mechanisms and interactions between aromatic pollutants and MOFs are discussed. Finally, the actual challenges of existence and the perspective routes towards future improvements in the field are addressed. Graphical abstract Recent advance on adsorption of common aromatic pollutants including benzene series, polycyclic aromatic hydrocarbons, organic dyes and their intermediates, pharmaceuticals and personal care products by metal-organic frameworks.

Performance of an innovative VUV-PCO purifier with nanoporous TiO2 film for simultaneous elimination of VOCs and by-product ozone in indoor air

An innovative vacuum ultraviolet photocatalytic oxidation (VUV-PCO) air purifier, consisting of a photocatalytic unit bearing nanoporous TiO2 film, an ozone removal unit bearing Mn-Fe catalyst and a radial fan, was designed and constructed. The performance of the VUV-PCO air purifier in simultaneous elimination of VOCs and O3 by-product was, for the first time, evaluated in a sealed actual room. The evaluation was conducted in both intermittent on/off and continuous operations. The results illustrated that the air purifier had high efficiency in removing formaldehyde and moderate efficiency in removing benzene, toluene, ofm-xylene, ortho-xylene, pentanal, octanal and nonanal, which were released from particleboard into the sealed room. During the removal of formaldehyde decomposition and TVOC in intermittent three-time on/off operation, the air purifier exhibited good stability. During the operation without heating, the air purifier had high formaldehyde and TVOC removal efficiencies, reaching values of about 48.00% and 78.71%, respectively after 90 min. During the continuous operation, the air purifier was able to continuously and effectively remove formaldehyde, benzene homologues, aldehyde and ketone compounds, while the ozone removal unit was able to effectively eliminate ozone generated during VUV photocatalysis. The removal of TVOC by 38.25% was reached after 240 min. In addition, heating the ozone removal unit was found to not only accelerate the release of VOCs from particleboard, but also promote the decomposition of ozone. The ozone removal unit operated with heating was able to reduce ozone content from 250 to 75 ppb.

Thiol-ene click derived structurally well-defined per(3,5-dimethyl)phenylcarbamoylated cationic cyclodextrin separation material for achiral and chiral chromatography.

In this work, a novel single sulfoether-bridged cationic per(3,5-dimethyl)phenylcarbamoylated-β-cyclodextrin separation material was prepared by thiol-ene click chemistry and characterized by using FTIR spectroscopy, solid-state 13 C NMR spectroscopy and elemental analysis, which confirmed the correct structure. The separation material exhibited a good achiral separation performance for benzene homologues and phenylamine analogs, especially o-xylene and m-xylene, and m-phenylenediamine and o-phenylenediamine can be discriminated by the (3,5-dimethyl)phenylcarbamoyl cyclodextrins. The chiral resolving ability of the separation material was evaluated by discriminating various isoxazolines, flavonoids, and β-blockers in reversed-phase high-performance liquid chromatography. For isoxazolines, the material showed the best chiral discrimination toward 3-aryl-5-(2-oxopyrrolidin-1-yl)-isoxazolines, where the resolution for 3ClPh-OPrreached 6.03. For flavonoids, it exhibited more efficient separation to the ones with more hydrophobic substituents, with a resolution of 5.93 for 6-hydroxyflavanone. β-Blockers were also enantioseparated satisfactorily on the material. The as-prepared separation material is a good member of the thiol-ene click derived cyclodextrin stationary phase family.

Graphene-doped electrochemical copolymer coating of 2,2-bithiophene and 3-methylthiophene for the highly effective solid-phase microextraction of volatile benzene homologues.

We report the electrochemical fabrication of a poly(2,2-bithiophene-co-3-methylthiophene)-graphene composite coating and its application in the headspace solid-phase microextraction and gas chromatography determination of benzenes (i.e., bromobenzene, 4-bromotoluene, 2-nitrotoluene, 3-nitrotoluene and 1,2,4-trichlorobenzene). The coating was uniform and showed cauliflower-like microstructure. It had high thermal stability (up to 375°C) and could be used for at least 180 times of solid-phase microextraction without a decrease in extraction performance. Furthermore, it presented high extraction capacity for the benzenes due to the hydrophobic effect and π-π interaction between the analytes and the coating. Under optimized extraction conditions, good linearity (correlation coefficients higher than 0.9946), wide linear range (0.01-50 μg/L), and low limits of detection (5.25-12.5ng/L) were achieved for these analytes. The relative standard deviation was lower than 5.7% for five successive measurements with one fiber, and the relative standard deviation for fiber-to-fiber was 4.9-6.8% (n=5). The solid-phase microextraction and gas chromatography method was successfully applied for the determination of three real samples, and the recoveries for standards added were 89.6-106% for nail polish, 85.8-110% for hair dye, and 90-106.2% for correction fluid, respectively.

Incorporation of carbon nanotubes into graphene for highly efficient solid-phase microextraction of benzene homologues

3D graphene-carbon nanotubes (G-CNTs) composite with unique morphology and structure was prepared by one-step insertion of CNTs into graphene. Subsequently, the G-CNTs composite as a fiber coating material for solid-phase microextraction (SPME) was fabricated on the surface of a stainless steel wire by direct coating method. The prepared coating was tested by the extraction of benzene homologues (BTEX, benzene, toluene, ethylbenzene and m-xylene). Compared with a commercial polydimethylsiloxane (PDMS) fiber, the home-made coating exhibited higher extraction performance for BTEX, and the reasons were discussed systematically. Under the optimized conditions, the prepared coating coupled with chromatography-mass spectrometry (GC–MS) for the analysis of BTEX exhibited wide linear ranges, low limits of detection (3S/N) (LODs, 0.59–2.68ngL−1), low limits of quantification (10S/N) (LOQs, 1.96–8.92ngL−1), good repeatability (3.2–5.5%, n=6) and reproducibility (3.7–9.1%, n=3). Finally, the developed method was successfully applied to the analysis of BTEX in environmental water samples with satisfactory recoveries (84.7–108.1%). This study is expected to further the exploration of high-performance SPME coating materials, and broaden the applications of graphene-based materials.

Supramolecular recognition of benzene homologues in a 2D coordination polymer through variable inter-layer π–π interaction

A 2D network 1 was synthesized. After immersing 1 in benzene homologues, the crystal structures of 2 and 3 were gotten, demonstrating that the introduction of benzene homologues has transformed the π–π packing mode, further altering the host framework and fluorescence performance.

Emission Characteristics of VOCs from On-Road Vehicles in an Urban Tunnel in Eastern China and Predictions for 2017–2026

Automobile exhaust emissions represent the main source of atmospheric volatile organic compound (VOC) pollution in urban areas of China. To accurately determine recent emission characteristics of vehicles during urban road conditions, an optimized tunnel experiment was conducted in Longchuan Tunnel, Hefei, in eastern China. Based on preliminary experiments examining the spatial and temporal characteristics of VOCs within the tunnel, a sampling scheme was designed to quantitatively analyze 51 VOCs. Among the 36 detected VOCs, about 52% were alkanes (mainly branched alkanes), with a total average emission factor of 41.39 ± 12.81 mg km–1 veh–1. Benzene homologues contributed the second largest proportion, and alkenes accounted for the smallest fraction. Dimethylbutane exhibited the highest average emission factor (13.3 ± 3.19 mg km–1 veh–1), followed by toluene (7.06 ± 3.14 mg km–1 veh–1) and then 2-methylpentane (6.44 ± 2.10 mg km–1 veh–1). The emission factors of the VOCs in Longchuan Tunnel were consistent with those from other studies in recent years but were considerably lower than those measured in tunnels in 2004. Based on the average emission factors of VOCs for light-duty and heavy-duty vehicles (81 ± 27 and 99 ± 42 mg km–1 veh–1, respectively), the predicted vehicle population, and vehicle-kilometers-traveled data, the emissions of VOCs were predicted for 2017–2026. The results show that if no control measures are taken, the total VOC emission volume and emission intensity will increase from 2510 ± 850 tons yr–1 to 3270 ± 1120 tons yr–1 and from 1859 ± 630 kg km–2 to 2422 ± 830 kg km–2, respectively, between 2017 and 2026.

Adsorption of Benzene Homologs Materials from Organic Wastewater onto Modified Bentonite

Bentonite has been purified by suspension method and sodiumed with sodium carbonate, and then modified with polyaniline. Finally, characterized by the polarizing microscope, the X-ray diffractometer(XRD) and Fourier infrared spectrometer (FT-IR), in order to determine the optimal preparation technology of polyaniline/bentonite. And the optimal preparation of PAn/MMT is used to research the adsorption dynamics analysis on phenol. The result shows that the sodium ion enters into the bentonite interlayer through ion exchange; When the dosage of bentonite is 5 g, the dosage of FeCl3·6H2O is 2.7 g, the dosage of aniline is 46.5 g, and the dosage of DBSA is 3.26 g, its layer spacing of modified bentonite is 2.823nm, increaseing 1.600nm than the first, so the hydrophobicity and separation effects of the modified bentonite get greatly improvement. And the dosage of PAn/MMT is 0.1 g and the initial concentration of phenol、P-nitrophenol、o-cresol is 10 mg/L, their adsorption rates reach to 51.50%, 80.56%, 62.93%, more high than the sodium bentonite under the same conditinns. It indicates that the modified bentonite is more suitable for the adsorption of benzene homologs.