Gaseous Benzene Research Articles

Photocatalytic Degradation of Gaseous Benzene Using Cu/Fe-Doped TiO2 Nanocatalysts under Visible Light.

Visible-light-enhanced TiO2 nanocatalysts doped with Cu and Fe were synthesized using the sol-gel method to investigate their performance in degrading gaseous benzene. The structure and morphology of mono- and co-doped TiO2 (i.e., Cu/Fe-TiO2, Cu-Fe-TiO2) were characterized using SEM, EDS, XRD, BET, Raman, UV-vis-DRS, and XPS techniques. The results indicated that the presence of Cu/Fe mono- and co-doped TiO2 leads to the formation of an anatase phase similar to pure TiO2. Furthermore, the introduction of Cu/Fe enhanced the presence of lattice defects and increased the specific surface area of TiO2. This enhancement can be attributed to the increase in oxygen vacancies, especially in the case of Cu-Fe-TiO2. Additionally, Cu-Fe-TiO2 showed a higher concentration of surface-bound hydroxyl groups/chemically adsorbed oxygen and a narrower bandgap than pure TiO2. Consequently, Cu-Fe-TiO2 exhibited the highest photocatalytic performance of 658.33 μgC6H6/(g·h), achieving a benzene degradation rate of 88.87%, surpassing that of pure TiO2 (5.09%), Cu-TiO2 (66.92%), and Fe-TiO2 (59.99%). Reusability tests demonstrated that Cu-Fe-TiO2 maintained a high benzene degradation efficiency of 71.4%, even after five experimental cycles, highlighting its exceptional stability and reusability. In summary, the addition of Cu/Fe to TiO2 enhances its ability to degrade gaseous benzene by prolonging the catalyst's lifespan and expanding its photoresponse range to include visible light.

Bioaerosols released from multistage biofilter for gaseous benzene removal: Escape behavior and pathogenicity

Biological deodorization systems are widely used to control odors and volatile organic compounds. However, the secondary contamination of bioaerosol emissions is a noteworthy issue in the operation of biofilters for off-gas purification. In this study, a multistage biofilter for benzene treatment was utilized to investigate the bioaerosol emissions under different flow rates and spray intervals. At the outlet of the biofilter, 99–7173 CFU/m3 of bioaerosols were detected, among which pathogens accounted for 8.93–98.73 %. Proteobacteria and Firmicutes dominated bioaerosols at the phylum level. The Mantel test based on the Bray-Curtis distance revealed strong influences of flow rate introduced to the biofilter and biomass colonized on the packing materials (PMs) on bioaerosol emissions. The non-metric multidimensional scaling results suggested a correlation between the bioaerosol community and bacteria on the PMs. Bacillus and Stenotrophomonas were the two main genera stripped from the biofilm on PMs to form the bioaerosols. SourceTracker analysis confirmed that microorganisms from the PMs near outlet contributed an average of 22.3 % to bioaerosols. Pathogenic bacteria carried by bioaerosols included Bacillus, Serratia, Stenotrophomonas, Achromobacter, Enterococcus, and Pseudomonas. Bioaerosols were predicted to cause human diseases, with antimicrobial drug resistance and bacterial infectious disease being the two main pathogenic pathways. Stenotrophomonas sp. LMG 19833, Pseudomonas sp., and Stenotrophomonas sp. were the keystone species in the bioaerosol co-occurrence network. Overall, results of present study promote the insight of bioaerosols, particularly pathogen emissions, and provide a basis for controlling bioaerosol contamination from biofilters.

S-scheme SnO/TiO2 heterojunction with high hole mobility for boosting photocatalytic degradation of gaseous benzene

Enhancing the efficiency of carrier migration and separation plays a pivotal role in promoting photocatalytic performance. Constructing S-scheme heterojunction is a promising strategy to achieve this desired objective. Here, we rationally designed and preciously synthesized SnO{001}/TiO2{001} S-scheme heterojunction with exceptionally high hole mobility (1122 cm2/(V·s)), which ranks among the best of reported works. SnO{001}/TiO2{001} heterojunctions exhibited outstanding performance of gaseous benzene degrading. The degradation rate constant of SnO/TiO2 heterojunction is 2.4675 h−1, and is boosted by 5.3 times compared with TiO2 (0.4595 h−1). Through the combination of theoretical calculation and experiment, S-scheme mode of carrier transferring was verified. The promoted hole mobility in SnO/TiO2 heterojunction enhances the production of ·OH, further boosting photocatalytic performance. By analyzing the detected intermediates, we proposed degradation pathways for benzene, which provide a profound and elucidating view of complex processes in benzene photocatalytic degradation.

The discharge characteristics and benzene degradation performance of a three-electrode DBD reactor powered by dual AC power generators

A three-electrode hybrid volume/surface dielectric barrier discharge (V-SDBD) configuration with two plane electrodes and six grounded strips electrode was designed for enhancing the generation of discharge plasma to degrade gaseous benzene. Two plane electrodes were separately powered by a 5 kHz AC generator and a 50 Hz AC generator, respectively. Compared with the typical two-electrode volume DBD (VDBD) reactor excited by 50 Hz AC generator, the hybrid V-SDBD reactor has lower onset discharge voltage and better discharge homogeneity, and the benzene degradation efficiency of V-SDBD was 1.12 times higher than that of VDBD at a similar energy efficiency. Moreover, an increase in the voltage on HVE-II promoted benzene degradation, but decreased the energy efficiency of benzene degradation.

Development of benzene, toluene, ethyl benzene, m-xylene, p-xylene and o-xylene (BTEX) gas reference standards for air pollution monitoring in South Africa

Direct monitoring of volatile organic compounds emitted from industrial sources as well as the monitoring of ambient levels thereof in the atmosphere play an important role in providing data for various legislative requirements. There are many volatile organic compounds emitted to the atmosphere, from biomass burning, power stations, and many other sources. Primary reference gas mixtures of volatile organic compounds containing six components, namely benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (BTEX) were prepared by gravimetric methods at nominal amount of substance fractions of 10 µmol/mol. The preparation was performed using the stainless steel (loop) method and direct liquid injection method using gas tight syringe connected to a dedicated syringe heater for comparison purposes. The results of the gravimetric values for both methods were within 1 % of the nominal amount of substance fraction. After the preparation, comparison was achieved by analysis of the BTEX gas mixtures using gas chromatography with flame ionisation detection (GC-FID) and showed comparability to within 2 % of the gravimetric values. The contributions to the uncertainty of measurement were from weighing stainless steel tubes, syringes, and gas cylinders, as well as purity data. The contribution to the uncertainty of measurement from the analysis by GC-FID were repeatability and reproducibility. The combined expanded uncertainty of measurement was between 1.09 % and 3.51 %. The larger deviation from the gravimetric values and associated uncertainty was observed for benzene due to its higher volatility compared to the other components. The BTEX reference gas mixtures prepared in this study are currently being used as a source of traceability in South Africa for air pollution monitoring purposes.

Investigating the mechanism behind the synergistic ultraviolet photooxidation degradation of gaseous benzene through modified ACF

The effects of relative humidity were studied on the direct conversion efficiency, mineralization rate and components of waste gas from benzene photooxidation degradation. The adsorption energies, adsorption types, and molecular interaction forces of activated carbon fiber (ACF) modified with nitrogen and oxygen-containing functional groups were calculated using quantum chemical density functional theory (DFT) calculations and wave function analysis. Five polar intermediate products including acetone, acetol, hexanal, benzaldehyde, and acetophenone generated from benzene photooxidation degradation were selected as the computational object. The independent gradient model method based on Hirshfeld partition was used to study the weak interactions among the five equilibrium molecular adsorption configurations. The results demonstrated that the direct conversion efficiency of benzene increased first and then decreased with increasing relative humidity. The maximum direct conversion efficiency was 82% observed at a relative humidity of 50%. The mineralization rate decreased significantly at higher relative humidity, and the lowest value was 2%. The overall adsorption effect of nitrogen-containing functional groups on the modified ACF surface is higher than that of oxygen-containing functional groups. The functional groups with the best adsorption effect are ACF modified by pyridone, amino and carboxyl groups. Combined with electron localization function (ELF) analysis and Mayer bond-level calculation, it was found that all the modified ACF surfaces do not form chemical bonds for the equilibrium molecular adsorption configurations of the five organic compounds, which belong to physical adsorption. The adsorption of five intermediate products by modified ACF mainly depended on hydrogen bonds or van der Waals forces. The existence of hydrogen bonds greatly improved the adsorption capacity of modified ACF to organic molecules.

Enhancing water resistance of α-MnO2 catalyst for efficient airborne benzene oxidation at mild temperatures via facile Ag incorporation

Facile structural modification of α-MnO2via single incorporation of Ag element was applied to achieve high-efficiency oxidation removal of benzene, particularly under wet gas. Ag+ ions could enter the MnO2 structure by partially replacing the tunnel K+ ions, leading to lower crystallinity, smaller crystallite and distorted lattice arrangement. Due to electron transfer from Ag+ to lattice oxygen, Ag decoration weakened Mn-O bonds and the bulk lattice oxygen became more mobile to migrate towards the Ag-MnO2 surface, resulting in the larger number of surface lattice oxygen. Along with the abundance of oxygen species, the reactivity of surface adsorbed oxygen and lattice oxygen was significantly improved as well by Ag modification. All these factors were favorable to the complete C6H6-to-CO2 conversion. Gaseous benzene could be directly oxidized by oxygen species over the pristine MnO2 catalyst, while the adsorptive activation of gaseous benzene was required for the Ag-MnO2 before further oxidation. As to the Ag-MnO2’s endurability of moisture-aroused inactivation, Ag species oppressed water adsorption in the form of strong adsorbate, thus preventing structural damage of the catalyst during humid benzene oxidation. Moreover, water molecules could enhance the “Ag-MnO2vs. adsorbed benzene” interaction, which increased the oxidation efficiency of adsorbed benzene. However, the strong binding of water vapor with the MnO2 surface would cause strong restriction of gaseous benzene from approaching the surface oxygen species, resulting in much less benzene being oxidized under wet gas.

Quantification of natural gas and other hydrocarbons from production sites in northern West Virginia using tracer flux ratio methodology.

Tracer flux ratio (TFR) methodology performed downwind of 15 active oil and natural gas production sites in Ohio County, West Virginia sought to quantify air pollutant emissions over two weeks in April 2018. In coordination with a production company, sites were randomly selected depending on wind forecasts and nearby road access. Methane (CH4), ethane (C2H6), and tracer gas compounds (acetylene and nitrous oxide) were measured via tunable infrared direct absorption spectroscopy. Ion signals attributed to benzene (C6H6) and other volatile gases (e.g., C7 - C9 aromatics) were measured via proton-transfer reaction time-of-flight mass spectrometry. Short-term whole facility emission rates for 12 sites are reported. Results from TFR were systematically higher than the sum of concurrent on-site full flow sampler measurements, though not all sources were assessed on-site in most cases. In downwind plumes, the mode of the C2H6:CH4 molar ratio distribution for all sites was 0.2, which agreed with spot sample analysis from the site operator. Distribution of C6H6:CH4 ratios was skew but values between 1 and 5 pptv ppbv-1 were common. Additionally, the aromatic profile has been attributed to condensate storage tank emissions. Average ratios of C7 - C9 to C6H6 were similar to other literature values reported for natural gas wells.

Highly sensitive and selective detection of benzene, toluene, xylene, and formaldehyde using Au-coated SnO2 nanorod arrays for indoor air quality monitoring

We report the high performance of Au-coated SnO2 nanorod gas sensors for the detection of hazardous indoor volatile organic compounds (VOCs), such as benzene, toluene, xylene, and formaldehyde (BTXF) gases. Densely ordered SnO2 nanorod arrays were prepared via glancing angle deposition with an electron beam evaporator. The Au layer coating was used as a heterogeneous catalyst to promote the oxidation of VOCs, such as hydrocarbons. After optimizing the Au thickness, the sensor exhibited an excellent sensing response and a rapid response time of < 2.5 s for 10 ppm of BTXF gases. The maximum response was ∼662 for formaldehyde at 400 °C, ∼328 for toluene at 450 °C, ∼170 for xylene at 400 °C, and ∼139 for benzene at 500 °C, which are significantly higher than those of previously reported metal-oxide-semiconductor-based sensors. Each gas was selectively detected by integrating the sensor into a miniaturized gas chromatography (GC) system. The sensors detected ppb-level gas concentrations. Significantly, GC analysis revealed that four types of gases could be separately detected in a mixed gas within 5 min. Our study shows that Au-coated SnO2 nanorod gas sensors integrated with GC can be used as a facile indoor pollutant monitoring system.

TiO2/WO3/graphene for photocatalytic H2 generation and benzene removal: Widely employed still an ambiguous system

Clean energy, as well as air and water pollution, have emerged as significant challenges in today's society. Photocatalysis offers a potential solution to address these issues. It is an advanced oxidation process that utilises light to activate a semiconductor. Among photocatalytically active materials, titanium dioxide (TiO2) semiconductors are widely recognised. However, the performance of TiO2 is hindered by its wide band gap (∼3.2 eV) and high recombination rate of photo-generated electron-hole (e−−h+) pairs. To overcome these limitations, TiO2 in heterojunction with tungsten trioxide (WO3) has gained substantial attention for various photocatalytic applications. However, the literature reports contradictory behaviours due to variations in synthesis techniques and photocatalytic applications.In this study, we extensively investigated the photocatalytic properties of the TiO2/WO3 system for the removal of gaseous benzene, and H2 generation. To enhance the transport and lifetime of photo-generated excitons, graphene nanoplatelets were incorporated into the TiO2/WO3 system. We examined several parameters that influenced the photocatalytic activity of the synthesised materials, including the WO3 to TiO2 ratio, the presence of graphene, and the specific photocatalytic application. Interestingly, the position of the conduction bands played a crucial role in hydrogen generation. The TiO2/WO3 system exhibited a type-II heterojunction. While the hybridisation of TiO2 with WO3 was found to be detrimental to light-induced benzene removal and H2 generation, the modification of TiO2/WO3 with graphene nanoplatelets significantly improved the photocatalytic hydrogen generation. Notably, the specimen with 15 mol% WO3 and 1 wt% graphene demonstrated a five-fold increase in yield compared to its counterpart without graphene. These findings provide valuable insights for data-driven catalysis research.

Comparison of the gaseous benzene adsorption capacity by activated carbons from Fraxinus excelsior L. as a lignocellulosic residual

Comparison of the gaseous benzene adsorption capacity by activated carbons from Fraxinus excelsior L. as a lignocellulosic residual

Performance assessment of the MOF adsorbent MIL-101 for removal of gaseous benzene and toluene: kinetic column modeling and simulation studies of fixed-bed adsorption.

The adsorbent MIL-101, a metal-organic framework material, was synthesized, characterized, and tested for removal of relatively low concentrations of benzene and toluene adsorbates (200 ppm) from a gas phase in a continuous flow system. Breakthrough studies were modeled based on Thomas, Yoon-Nelson, Yan, Clark, Bohart-Adams, bed-depth service time, modified dose response, Wolborska, and Gompertz in the continuous fixed-bed operation. Through statistical analysis, it was determined which type of regression is most suitable for the studied models, linear or nonlinear. By comparing the values of error functions, it was possible to infer that the Thomas model is the best match for the experimental breakthrough curves for benzene (with maximum solid-phase concentration qT=126,750 mg/g) and the Gompertz model for toluene (parameter β=0.01 min-1). Overall, when compared to the model parameters of the linear regression, those obtained through nonlinear regression show a stronger correlation with the results found experimentally. Thus, this type of regression is more suitable for the adsorption model analysis. The liquid film and intraparticle diffusion analysis was described, and it was suggested that both types of diffusion contribute to the adsorption mechanism of benzene and toluene on MIL-101. As for the isotherms, the adsorption process was better fitted by the Freundlich isotherm. The reusability of MIL-101 after six cycles was 76.5% for benzene and 62.4% for toluene, indicating that MIL-101 was a better adsorbent for the removal of benzene in comparison with toluene.

Preparation of dual-use GPTES@ZnO photocatalyst from waste warm filter cake and evaluation of its synergic photocatalytic degradation for air-water purification

Organic pollutants are the most critical threats to the health of air and water resources. On this basis, fabricating a photocatalytic acrylic film with dual-use (i.e. removing benzene from air and MB/MO dyes from water) was aimed in this research. For this purpose, waste warm filter cake (WWFC) was used to extract zinc from it. Zinc element was separated from WWFC by a basic leaching method and acidified to prepare zinc oxide nanoparticles. In the following, a simple hydrothermal method was used to increase the surface functionality of the extracted ZnO nanoparticles in order to establish active reaction sites for reaction to silane coupling agent and increase in the holes that were prepared during photo-excitation. Thereafter, the nanoparticles were modified with 3-glycidoxypropyltriethoxysilane (GPTES) at different concentrations. The band gap of the modified nanoparticles decreased from 3.25 to 3.1 eV by surface modification. The photocatalytic performance of ZnO nanoparticles was assessed by degradation of MB and MO aqueous solution (50 ppm) under simulated UV/Visible irradiations. MB and MO were degraded 91 and 60% under UV light and 65 and 50% under visible light after 150 min of irradiation. The photo degradation rate increased after adding carboxy methyl cellulose (CMC) surfactant to methylene blue and adding cocamide-dea (CDE-G) surfactant to methyl orange. The results confirmed that the green surfactants improve the dispersion and surface interaction of the modified nanoparticles in the dyes solution and cause more electron charge transfer which creates effective photocatalytic sites. The prepared nanocomposite films were placed in a photo-reactor to remove gaseous benzene from air under UV/visible irradiation. Gas chromatography (GC) results showed that the modified nanoparticles removed up to 35.25 and 20.34% of benzene from air. Colorimetric analysis (ΔE*) showed that the acrylic film contained modified nanoparticles degraded 91 and 82% of MB, and 85 and 76% of MO under UV/visible lights, respectively. In the end, it can be said that these photocatalytic films are able to remove environmental pollution in air and water.

Performance and Mechanism of Chlorine Dioxide on BTEX Removal in Liquid and Indoor Air.

With the development of the chemical industry, benzene, toluene, ethylbenzene, and xylene (BTEX) have gradually become the major indoor air pollutants. Various gas treatment techniques are widely used to prevent the physical and mental health hazards of BTEX in semi-enclosed spaces. Chlorine dioxide (ClO2) is an alternative to chlorine as a secondary disinfectant with a strong oxidation ability, a wide range of action, and no carcinogenic effects. In addition, ClO2 has a unique permeability which allows it to eliminate volatile contaminants from the source. However, little attention has been paid to the removal of BTEX by ClO2, due to the difficulty of removing BTEX in semi-enclosed areas and the lack of testing methods for the reaction intermediates. Therefore, this study explored the performance of ClO2 advanced oxidation technology on both liquid and gaseous benzene, toluene, o-xylene, and m-xylene. The results showed that ClO2 was efficient in the removal of BTEX. The byproducts were detected by gas chromatography-mass spectrometry (GC-MS) and the reaction mechanism was speculated using the ab initio molecular orbital calculations method. The results demonstrated that ClO2 could remove the BTEX from the water and the air without causing secondary pollution.

25 Strategy for Assessing Exposure of Ship Painters to a Mixture of Organic Solvents

Abstract Background Painters are exposed to different substances, among which volatile organic compounds. Similar Exposure Groups (SEG) should be identified according to the European Standard EN:689/2019 to perform representative measurements of exposure. This approach was applied to 15 ship painters. Methods Two SEGs were identified considering environment and application technique: 6 spray painters (group A) working inside a hangar and 9 roller painters (group B) working on the ship. Gaseous toluene, xylenes, acetone, ethylacetate, n-butyl acetate, ethylbenzene and benzene were collected using Radiello samplers and determined by GC/MS. Results The ratios between each exposure value and the corresponding occupational exposure limit (Italian for toluene, xylenes, acetone, ethylbenzene, and benzene; German for ethylacetate and n-butyl acetate) were below 0.5 for Group A and well below 0.1 for Group B. Considering the common neurotoxic effect, workers’ exposure was also evaluated for the additive contribution of each component to the mixture. The mixture exposure index resulted 1.01 for spray painters and 0.09 for roller painters. Short Discussion/Conclusions Considering single substances, exposure levels were below the limits for both groups; when the mixture exposure is assessed, it reaches the mixture occupational limit for group A (spray) while it remains well below for group B (rollers). Results confirm that environment features and application techniques significantly affect the exposure levels, that are to be monitored on a SEG basis, and that considering the exposure to the mixture is crucial in order to orient the medical surveillance to prevent the neurotoxic effect in spray painters.

Electrochemical removal of gaseous benzene using a flow-through reactor with efficient and ultra-stable titanium suboxide/titanium-foam anode at ambient temperature

Catalytic oxidation technology is currently considered as a feasible approach to degrade and mineralize volatile organic compounds (VOCs). However, it is still challenging to realize efficient removal of VOCs through catalytic oxidation at room temperature. In our study, a novel flow-through electrocatalytic reactor was designed, composed of porous solid-electrolyte, gas-permeable titanium sub-oxides/titanium-foam (TiSO/Ti-foam) as anode and platinum coated titanium foam (Pt/Ti-foam) as cathode. This device could oxidize nearly 100% of benzene (10 ppm) to carbon dioxide at a current density of 1.2 mA/cm2 under room temperature. More importantly, the device maintained excellent stability over 1000 h. Mechanism of benzene mineralization was discussed. Hydroxyl radicals generated on the TiSO/Ti-foam anode played a crucial role in the oxidation of benzene. This study provides a promising prototype of the electrochemical air purifier, and may find its application in domestic and industrial air pollution control.

New insights into the catalytic mechanism of VOCs abatement over Pt/Beta with active sites regulated by zeolite acidity

Zeolite-supported noble metal catalysts have good low-temperature activity and efficacy in eliminating VOCs contaminants. Regulating the nature of active sites is beneficial for improving the catalytic oxidation performance and decreasing coke deposition for further increase in the durability. In this work, Pt/Beta catalysts for toluene oxidation with different valence states, location, and dispersion of Pt were achieved through regulation of active sites using the acidity of zeolites with different Si/Al ratios. It was revealed that Ptδ+ were highly dispersed on the low Si/Al ratio of 6 including isolated Z[Pt2+(OH)]+ originated from Pt2+ ions anchored on ion-exchange sites (strong Brønsted acid sites) of Beta zeolites, while Pt0 nanoparticles were the main active sites of Beta zeolites with the high Si/Al ratio of 260 without H2 post-treatment. The Pt/Beta catalysts with high silica had better catalytic oxidation performance than that with low silica because Pt0 had stronger activation ability towards O2 as well as more facile oxygen replenishment than Ptδ+. It was noted that the key role of OH groups led to the enhanced oxidation of toluene driven by water vapor. Both high-silica and low-silica Pt/Beta catalysts exhibited excellent durability for 60 h of operation with no detectable decrease in catalytic performance and followed similar toluene oxidation pathways, forming intermediates including alkoxides, carboxylates, and anhydrides. The difference was that the quantity of gaseous benzene generated on high-silica Pt/Beta was much lower than that on low-silica Pt/Beta, indicating that Pt0 rather than Ptδ+ was conducive to the benzene ring opening reaction. The strong ability of Pt0 to activate O2 and the reduction of Ptδ+ into Pt0 during the reaction process could be responsible for the excellent durability and similar reaction pathways towards both low-silica and high-silica Pt/Beta. This study provides guidance for the regulation of active sites and design of efficient zeolite-based catalysts for VOCs abatement.

A Study on the Gaseous Benzene Removal Based on Adsorption onto the Cost-Effective and Environmentally Friendly Adsorbent.

Removal of benzene is essential for human and environmental health because it has toxic and hazardous properties at various concentrations. Theseneed to be effectively eliminated with carbon-based adsorbents. PASACs, carbon-based adsorbents obtained from using the needles of Pseudotsuga menziesii, were produced by optimized HCl- and H2SO4-impregnated approaches. Regarding physicochemical structure, the optimized PASAC23 and PASAC35 with surface areas of 657 and 581 m2/g and total pore volumes of 0.36 and 0.32 cm3/g showed ideal temperatures of 800 °C. In order to investigate and compare internal benzene removal efficiency, PASAC23 and PASAC35 were studied separately. Initial concentrations were found to range from 5 to 500 mg/m3, and between 25 and 45 °C. The removal rate of benzene by PASAC23 and PASAC35 was 97 and 94% at low concentrations, respectively. While the highest capture amount for PASAC23 and PASAC35 was found to be at 25 °C with 141 and 116 mg/g, the adsorption capacity decreased to 102 and 90 mg/g at 45 °C. The holding capacity decreased between 22.41 and 27.66% due to increasing temperatures. After five cycles of PASAC23 and PASAC35 regeneration, we found that they could remove 62.37 and 58.46% of benzene, respectively. These results confirmed that PASAC23 is a promising environmentally adsorbent for effectively removing benzene with a competitive yield.

Photo-Activated Direct Catalytic Oxidation of Gaseous Benzene with a Cu-Connected Serial Heterojunction Array of Co3 O4 /Cux O/Foam Cu Assembled via Layer upon Layer Oxidation.

The foam copper (FCu) has been first used as a promising supporting material to prepare a photo-activated catalyst of Co3 O4 /Cux O/FCu, in which the fine Co3 O4 particles are inlayed on the Cux O nanowires to form a Z-type heterojunction array connected by substrate Cu. The prepared samples have been used as a photo-activated catalyst to directly decompose gaseous benzene and the optimized Co3 O4 /Cux O/FCu demonstrates a 99.5% removal efficiency and 100% mineralizing rate within 15min in benzene concentration range from 350 to 4000ppm under simulate solar light irradiation. To track the reactive mechanism, a series of MOx /Cux O/FCu (M = Mn, Fe, Co, Ni, Cu, Zn) is prepared and a novel photo-activated direct catalytic oxidation route is proposed based on the comparative investigation of material properties. Moreover, the approach grew in situ via layer upon layer oxidation on FCu dedicates to the extra lasting reusability and the easy accessibility in the diverse situations. This work provides a novel strategy for the preparation of Cu connected series multidimensional heterojunction array and a promising application for the quick abatement of the high-leveled concentration gaseous benzene and its derivatives from the industrial discharged flow or the accident scene's leakage.

Performance and mechanisms of iron/copper-doped zirconium-based catalyst containing hydroxyl radicals for enhanced removal of gaseous benzene.

In the present study, novel copper-doped zirconium-based MOF (UIO-66) and copper-doped iron-based UIO-66 catalysts were prepared by hydrothermal synthesis method to improve the removal performance of gaseous benzene. The characteristics of the catalysts were analyzed by means of XRD, SEM, XPS, BET, and EPR. The copper loading catalyst had high crystallinity and irregular globular. The three kinds of catalysts with different Cu/Fe ratios had regular cubic shape. Compared with the catalyst supported with single copper, the bimetal Cu/Fe modification had a certain adjustment effect on the morphology, which specifically reflected in the uniform size and shape of catalyst particles with better dispersibility. The factors of different metal loading, dose of H2O2, and reaction temperature on benzene removal have been studied. It has been observed that in heterogeneous advanced oxidation removal of benzene, 3-Cu@UIO-66 and Cu1.5/Fe1.5@UIO-66 achieved the highest benzene removal efficiency of 81.2% and 94.6%, respectively. EPR results showed that the increase of Cu loading and different Cu/Fe ratios promoted the yield of hydroxyl radicals, thus promoted the benzene removal efficiency. The efficiency of heterogeneous oxidation removal of benzene first increased and then decreased with the increase of temperature due to H2O2 instability. DFT calculations exhibited that the Feoct-Cu-O site was a more effective activation site than the single Feoct-O site. Dissociative adsorption occurred with the O-O bond of H2O2 cracked, and the formed hydroxyls parallel adsorbed on the benzene surface. The combination of benzene and hydroxyls was strong chemisorption with the torsion angle of benzene ring obviously turned. The work was of great importance for identifying the roles of the novel catalyst for the removal of benzene pollutant from waste gases.