Degradation Of Benzene Research Articles

Description of Defluviimonas salinarum sp. nov. with the potential of benzene-degradation isolated from saltern in the Yellow Seacoast.

Strain CAU 1641T was isolated from saltern collected in Ganghwa Island, Republic of Korea. The bacterium was an aerobic, Gram-negative, catalase-positive, oxidase-positive, motile, and rod-shaped bacterium. Cell of strain CAU 1641T could grow at 20-40°C and pH 6.0-9.0 with 1.0-3.0% (w/v) NaCl. Stain CAU 1641T shared high 16S rRNA gene sequence similarities with Defluviimonas aquaemixtae KCTC 42108T (98.0%), Defluviimonas denitrificans DSM 18921T (97.6%), and Defluviimonas aestuarii KACC 16442T (97.5%). Phylogenetic trees based on the 16S rRNA gene and the core-genome sequences indicated that strain CAU 1641T belonged to genus Defluviimonas. Strain CAU 1641T contained ubiquinone-10 (Q-10) as the sole respiratory quinone and and summed feature 8 (C18:1ω6c and/or C18:1ω7c) as the predominant fatty acid (86.1%). The pan-genome analysis indicated that the genomes of the strain CAU 1641T and 15 reference strains contain a small core genome. The Average Nucleotide Identity and digital DNA-DNA hybridization values among strain CAU 1641T and reference strains of the genus Defluviimonas were in the range of 77.6%-78.8% and 21.1-22.1%, respectively. The genome of strain CAU 1641T has several genes of benzene degradation. The genomic G+C content was 66.6%. Based on polyphasic and genomic analyses, strain CAU 1641T represents a novel species of the genus Defluviimonas, for which the name Defluviimonas salinarum sp. nov., is proposed. The type strain is CAU 1641T ( = KCTC 92081T=MCCC 1K07180T).

Hydrocarbon degradation strategy and pyoverdine production using the salt tolerant Antarctic bacterium Marinomonas sp. ef1.

One of the most concerning environmental problems is represented by petroleum and its derivatives causing contamination of aquatic and underground environments. In this work, the degradation treatment of diesel using Antarctic bacteria is proposed. Marinomonas sp. ef1 is a bacterial strain isolated from a consortium associated with the Antarctic marine ciliate Euplotes focardii. Its potential in the degradation of hydrocarbons commonly present in diesel oil were studied. The bacterial growth was evaluated in culturing conditions that resembled the marine environment with 1% (v/v) of either diesel or biodiesel added; in both cases, Marinomonas sp. ef1 was able to grow. The chemical oxygen demand measured after the incubation of bacteria with diesel decreased, demonstrating the ability of bacteria to use diesel hydrocarbons as a carbon source and degrade them. The metabolic potential of Marinomonas to degrade aromatic compounds was supported by the identification in the genome of sequences encoding various enzymes involved in benzene and naphthalene degradation. Moreover, in the presence of biodiesel, a fluorescent yellow pigment was produced; this was isolated, purified and characterized by UV-vis and fluorescence spectroscopy, leading to its identification as a pyoverdine. These results suggest that Marinomonas sp. ef1 can be used in hydrocarbon bioremediation and in the transformation of these pollutants in molecules of interest.

Degradation of Benzene by a Falling Film Gas–Liquid Phase DBD Plasma with Persulfate

Degradation of Benzene by a Falling Film Gas–Liquid Phase DBD Plasma with Persulfate

Comparative taxonomic and functional microbiome profiling of anthrospheric river tributary for xenobiotics degradation study

A metagenomic approach was used to initiate a comparative taxonomical and functional microbial profiling of a polluted site Amlakhadi. After sequencing on Oxford's Nanopore platform, a total of 7864 reads with an average read length of 2800bp, and a mean G + C% of 50 ± 7 were observed. STAMP, METAGENassist, MG RAST, PAST, MEGAN, and Community analyzer were used for the taxonomic and functional screening. The dominant phyla Proteobacteria, Bacteroidetes, Firmicutes, Chlorobi, Actinobacteria and dominant species Sulfuricurvum kujiense, Chlorobaculum tepidum, Allochromaticum vinosum, Desulfomicrobium baculatum, Thiobacillus denitrificans were observed. The metagenomic data was then compared to four metagenomes from the same site which are publicly available on EBI Metagenomics with run accession numbers ERR947518, ERR947519, ERR947520, and ERR947521. At the phyla level, all five metagenomes consist of Proteobacteria, Acidobacteria, Thermotogae, Planctomycetes, Bacteroidetes, Actinobacteria, and at the species level Serratia proteamaculans, T. denitrificans, Serratia odorifera, Strenotrophomonas maltophilia as the core microbes. The functional analysis shows that all metagenomes contain pathways for the degradation of benzene, nitrotoluene, and DDT with the detection of other xenobiotic remediation pathways through MG RAST. While degradation pathways of dehalogenation, atrazine, and aromatic hydrocarbon were commonly found in all five metagenomes through METAGENassist. Enzymes mapped on xenobiotic degradation pathways commonly belong to the class oxidoreductase, lyase, and transferase. Along with basic cell metabolism, genes involved in xenobiotics degradation were also annotated prevalently. This omics-based comparative metagenomic characterization drains out information about pollutants removing novel microbes and will also help in the development of a clean-up scheme for xenobiotics contaminated environments.

Colloidal Cu-doped TiO2 nanocrystals containing oxygen vacancies for highly-efficient photocatalytic degradation of benzene and antibacterial

Development of suitable colloidal photocatalysts with excellent photocatalytic performance under visible light is essential for indoor environmental remediation. In this study, colloidal Cu-doped TiO2 (Cu-TiO2) nanocrystals containing oxygen vacancies (OVs) were synthesized by a facile sol-hydrothermal method and their photocatalytic performances for benzene degradation and antibacterial were investigated. Characterization results revealed that the doping of Cu induced grain size reduction and bandgap narrowing of TiO2 nanocrystals, as well as the formation of abundant OVs in the TiO2 crystal structure, resulting in enhanced light absorption capacity and charge carrier separation efficiency. The optimized colloidal Cu-TiO2 nanocrystals could achieve a maximum degradation rate constant of 0.364 h−1 for the photocatalytic degradation of benzene and a high antibacterial rate of more than 99.99% against both Escherichia coli and Staphylococcus aureus, which were far superior to those of the pristine TiO2. The effects of Cu dopants and OVs on the band structure of TiO2 were revealed by density functional theory (DFT) calculations combined with experimental characterizations, and a possible mechanism for the enhancement of Cu-TiO2 photocatalytic performance was proposed. This work offers a promising method for the synthesis of colloidal TiO2-based nanocrystals with excellent photocatalytic performances for the practical application in indoor environmental remediation.

Low-Temperature Catalytic Ozonation of Multitype VOCs over Zeolite-Supported Catalysts.

Volatile organic compounds (VOCs) are an important source of air pollution, harmful to human health and the environment, and important precursors of secondary organic aerosols, O3 and photochemical smog. This study focused on the low-temperature catalytic oxidation and degradation of benzene, dichloroethane, methanethiol, methanol and methylamine by ozone. Benzene was used as a model compound, and a molecular sieve was selected as a catalyst carrier to prepare a series of supported active metal catalysts by impregnation. The effects of ozone on the catalytic oxidation of VOCs and catalysts' activity were studied. Taking benzene as a model compound, low-temperature ozone catalytic oxidation was conducted to explore the influence of the catalyst carrier, the active metal and the precious metal Pt on the catalytic degradation of benzene. The optimal catalyst appeared to be 0.75%Pt-10%Fe/HZSM(200). The catalytic activity and formation of the by-products methylamine, methanethiol, methanol, dichloroethane and benzene over 0.75%Pt-10%Fe/HZSM(200) were investigated. The structure, oxygen vacancy, surface properties and surface acidity of the catalysts were investigated. XRD, TEM, XPS, H2-TPR, EPR, CO2-TPD, BET, C6H6-TPD and Py-IR were combined to establish the correlation between the surface properties of the catalysts and the degradation activity.

Synthesis of BiOI@NH2-MIL125(Ti)/Zeolite as a novel MOF and advanced hybrid oxidation process application in benzene removal from polluted air stream.

One of the popular process in volatile organic compounds removal in gas phase is advanced oxidation process. We in this research, synthesized BiOI@NH2-MIL125(Ti)/Zeolite nanocomposite as a novel nanocomposite to degradation of benzene in hybrid advanced oxidation process. The nanocomposite synthesized via solvothermal method. The effect of airflow, ozone gas concentration, hydrogen peroxide concentration, relative humidity and initial benzene concentration are the main parameters in the UV/O3/H2O2/ nanocomposite hybrid process that were studied. The characterization by XRD, FT-IR, FESEM, EDS element mapping, TEM, BET, and UV-vis spectra indicated that nanocomposite were well synthesized. Optimal operating conditions of the process were determined at air flow of 0.1l/min, ozone concentration of 0.3mg/min, hydrogen peroxide concentration of 150ppm, relative humidity of 45 ± 3% and benzene concentration of 50 ppmv. Under these conditions, more than 99% of benzene was degraded. The synergistic effect coefficient of the mechanisms is 1.53. The nanocomposite had good stability in the hybrid process and remained above 99% efficiency up to 5 times. The ozone concentration residual the system was reported to be negligible (0.013mg/min). The CO and CO2 emissions in the hybrid process was higher than other processes, which indicates better mineralization in the hybrid process. Formaldehyde, octane, noonan, phenol, decanoic acid were reported as the main by-products. The results indicated that UV/O3/H2O2/ nanocomposite hybrid process has fantastic efficiency in the degradation of benzene as one of the indicators of VOCs.

Surface Acidification of BiOI/TiO2 Composite Enhanced Efficient Photocatalytic Degradation of Benzene

A novel BiOI/TiO2 nano-heterojunction was prepared using hydrothermal and sol-gel methods. The composite material was characterized by X-ray diffraction, ultraviolet-visible diffuse reflection spectroscopy, scanning electron microscopy, and transmission electron microscopy. The crystallinity and response to light of BiOI/TiO2 were controlled by preparation conditions such as the optimal solvent condition and heat treatment temperature. The photocatalytic activity of the BiOI/TiO2 catalyst was examined using benzene as a test molecule. The benzene degradation rate of the composite catalyst under visible light was enhanced compared to pure TiO2, thus reaching 40% of the original benzene concentration, which increased further to >60% after surface acidification. The fluorescence spectra, light current, and electron paramagnetic resonance confirmed that the enhanced activity was attributed to carrier separation by the heterojunction. The acid sites and active chlorine of hydrochloric acidification offer a novel mechanism for photocatalytic reactions.

Catalytic degradation of benzene over non-thermal plasma coupled Co-Ni binary metal oxide nanosheet catalysts

Non-thermal plasma (NTP) has been demonstrated as one of the promising technologies that can degrade volatile organic compounds (VOCs) under ambient condition. However, one of the key challenges of VOCs degradation in NTP is its relatively low mineralization rate, which needs to be addressed by introducing catalysts. Therefore, the design and optimization of catalysts have become the focus of NTP coupling catalysis research. In this work, a series of two-dimensional nanosheet Co-Ni metal oxides were synthesized by microwave method and investigated for the catalytic oxidation of benzene in an NTP-catalysis coupling system. Among them, Co2Ni1Ox achieves 60% carbon dioxide (CO2) selectivity (SCO2) when the benzene removal efficiency (REbenzene) reaches more than 99%, which is a significant enhancement compared with the CO2 selectivity obtained without any catalysts (38%) under the same input power. More intriguingly, this SCO2 is also significantly higher than that of single metal oxides, NiO or Co3O4, which is only around 40%. Such improved performance of this binary metal oxide catalyst is uniquely attributed to the synergistic effects of Co and Ni in Co2Ni1Ox catalyst. The introduction of Co2Ni1Ox was found to promote the generation of acrolein significantly, one of the key intermediates found in NTP alone system reported previously, suggest the benzene ring open reaction is promoted. Compared with monometallic oxides NiO and Co3O4, Co2Ni1Ox also shows higher active oxygen proportion, better oxygen mobility, and stronger low-temperature redox capability. The above factors result in the improved catalytic performance of Co2Ni1Ox in the NTP coupling removal of benzene.

Electron acceptors determine the BTEX degradation capacity of anaerobic microbiota via regulating the microbial community

Anaerobic degradation is the major pathway for microbial degradation of benzene, toluene, ethylbenzene, and xylenes (BTEX) under electron acceptor lacking conditions. However, how exogenous electron acceptors modulate BTEX degradation through shaping the microbial community structure remains poorly understood. Here, we investigated the effect of various exogenous electron acceptors on BTEX degradation as well as methane production in anaerobic microbiota, which were enriched from the same contaminated soil. It was found that the BTEX degradation capacities of the anaerobic microbiota gradually increased along with the increasing redox potentials of the exogenous electron acceptors supplemented (WE: Without exogenous electron acceptors < SS: Sulfate supplement < FS: Ferric iron supplement < NS: Nitrate supplement), while the complexity of the co-occurring networks (e.g., avgK and links) of the microbiota gradually decreased, showing that microbiota supplemented with higher redox potential electron acceptors were less dependent on the formation of complex microbial interactions to perform BTEX degradation. Microbiota NS showed the highest degrading capacity and the broadest substrate-spectrum for BTEX, and it could metabolize BTEX through multiple modules which not only contained fewer species but also different key microbial taxa (eg. Petrimonas, Achromobacter and Comamonas). Microbiota WE and FS, with the highest methanogenic capacities, shared common core species such as Sedimentibacter, Acetobacterium, Methanobacterium and Smithella/Syntrophus, which cooperated with Geobacter (microbiota WE) or Desulfoprunum (microbiota FS) to perform BTEX degradation and methane production. This study demonstrates that electron acceptors may alter microbial function by reshaping microbial community structure and regulating microbial interactions and provides guidelines for electron acceptor selection for bioremediation of aromatic pollutant-contaminated anaerobic sites.

Transient Oxygen Exposure Causes Profound and Lasting Changes to a Benzene-Degrading Methanogenic Community.

We investigated the impact of oxygen on a strictly anaerobic, methanogenic benzene-degrading enrichment culture derived decades ago from oil-contaminated sediment. The culture includes a benzene fermenter from Deltaproteobacteria candidate clade Sva0485 (referred to as ORM2) and methanogenic archaea. A one-time injection of 0.1 mL air , simulating a small leak into 30 mL batch culture bottle, had no measurable impact on benzene degradation rates, although retrospectively, a tiny enrichment of aerobic taxa was detected. A subsequent 100 times larger injection of air stalled methanogenesis and caused drastic perturbation of the microbial community. A benzene-degrading Pseudomonas became highly enriched and consumed all available oxygen. Anaerobic benzene-degrading ORM2 cell numbers plummeted during this time; re-growth and associated recovery of methanogenic benzene degradation took almost 1 year. These results highlight the oxygen sensitivity of this methanogenic culture and confirm that the mechanism for anaerobic biotransformation of benzene is independent of oxygen, fundamentally different from established aerobic pathways, and is carried out by distinct microbial communities. The study also highlights the importance of including microbial decay in characterizing and modeling mixed microbial communities.

Construction of CuBi2O4/BiOBr/Biochar Z-Scheme Heterojunction for Degradation of Gaseous Benzene Under Visible Light

Construction of CuBi2O4/BiOBr/Biochar Z-Scheme Heterojunction for Degradation of Gaseous Benzene Under Visible Light

Intimately coupled photocatalysis and functional bacterial system enhance degradation of 1,2,3- and 1,3,5-trichlorobenzene.

Intimate coupling of photocatalysis and biodegradation (ICPB) is considered a promising approach for the degradation of recalcitrant organic compounds. In this work, using Trichoderma with benzene degradation ability coupled with activated sludge as a biological source and sugarcane bagasse cellulose composite as a carrier, the ICPB system showed excellent degradation and mineralization of trichlorobenzene under visible light induction. The biofilm inside the ICPB carrier can degrade and mineralize the photocatalytic products. ICPB increased the degradation efficiency of 1,2,3-TCB and 1,3,5-TCB by 12.43% and 4.67%, respectively, compared to photocatalysis alone. The biofilms inside the ICPB carriers can mineralize photocatalytic products, which increases the mineralization efficiency by 18.74%. According to the analysis of intermediates, the degradation of 1,2,3-TCB in this coupled system involved stepwise dechlorination and ring opening. The biofilm in ICPB carrier evolved to be enriched in Cutaneotrichosporon, Trichoderma, Apiotrichum, Zoogloea, Dechloromonas, Flavihumibacter and Cupriavidus, which are known for biodegradable aromatic hydrocarbon and halogenate. Novel microbial seeds supplemented with Trichoderma-based ICPB seem to provide a new potential strategy for effective degradation and mineralization of TCB.

Confined cobalt oxide embedded into hierarchical bismuth tungstate in S-scheme micro-heterojunction for enhanced air purification

In this work, a confined cobalt oxide nanocrystals/bismuth tungstate S-scheme micro-heterojunction is successfully synthesized for enhanced air purification. The Co3O4 NCs (5 nm) are highly dispersed onto the surface of hierarchical Bi2WO6 to form the S-scheme heterojunction in a limited area due to the nanoconfined effect and upward valence band (VB) of Co3O4 NCs. The introduced Co3O4 NCs enhance solar harvesting efficiency and reduce transportation barrier of the charge carriers through staggered band offsets, thereby accelerating the photoinduced charge movement. Consequently, the S-scheme micro-heterojunction exhibits increased photocatalytic activities in gaseous benzene degradation under visible light irradiation, which are 2.7 times higher than that of pure Bi2WO6. On the surface of Co3O4 NCs/Bi2WO6 S-scheme micro-heterojunction, the hydroxyl and superoxide radicals are demonstrated to produce efficiently. Furthermore, in-situ FTIR reveals the possible reaction pathways of the photooxidation process of gaseous benzene on the surface of micro-heterojunction.

Compound-specific isotope analysis (CSIA) evaluation of degradation of chlorinated benzenes (CBs) and benzene in a contaminated aquifer

Compound-specific isotope analysis (CSIA) has become a valuable tool in understanding the fate of organic contaminants at field sites. However, its application to chlorinated benzenes (CBs), a group of toxic and persistent groundwater contaminants, has received less attention. This study employed CSIA to investigate the occurrence of natural degradation of various CBs and benzene in a contaminated aquifer. Despite the complexity of the study area (e.g., installation of a sheet pile barrier and the presence of a complex set of contaminants), the substantial enrichments in δ13C values (i.e., >2‰) for all CBs and benzene across the sampling wells indicate in situ degradation of these compounds. In particular, the 13C enrichments for 1,2,4-trichlorobenzene (1,2,4-TCB) and 1,2-dichlorobenzene (1,2-DCB) display good correlations with decreasing groundwater concentrations, consistent with the effects of in situ biodegradation. Using the Rayleigh model, the extent of degradation (EoD) is estimated to be 47-99% for 1,2-DCB, and 21-73% for 1,2,4-TCB. The enrichments observed for the other CBs (1,4-DCB and chlorobenzene (MCB)) and benzene at the site are also suggestive of in situ biodegradation. Due to simultaneous degradation and production of 1,4-DCB (a major 1,2,4-TCB degradation product), MCB (from DCB degradation), and benzene (from MCB degradation), the estimation of EoD for these intermediate compounds is more complex but a modelling simulation supports in situ biodegradation of these daughter products. In particular, the fact that the δ13C values of MCB and benzene (i.e., daughter products of 1,2,4-TCB) are more enriched than the original δ13C value of their parent 1,2,4-TCB provides definitive evidence for the occurrence of in situ biodegradation of the MCB and benzene.

Scaling up anodic TiO2 nanotube layers – Influence of the nanotube layer thickness on the photocatalytic degradation of hexane and benzene

In this work, the preparation of homogenous TiO2 nanotube (TNT) layers with different thicknesses via anodization on Ti substrates with a large geometrical area of two times 5 cm x 10 cm (i.e. both sides of the Ti substrate) is shown for the first time. TNT layers with four different thicknesses of ∼0.65 µm, ∼1 µm, ∼7 µm, and ∼14 µm were prepared with excellent conformality and homogeneity over the anodized area. These TNT layers were successfully employed as photocatalysts for the degradation of hexane and benzene as model compounds in the gas phase under ISO standards, showing an increase of the conversion for both model compounds with the TNT layer thickness. While a stable hexane conversion was observed for all TNT layers during the measuring time of three hours, in case of benzene degradation an initial conversion decrease was monitored before the conversion stabilized. Despite this trend, SEM and XPS analyses did not reveal any significant amount of reaction products on the TNT layer surface.

Influence of current density and inlet gas flow in the treatment of gaseous streams polluted with benzene by electro-absorption

This paper is focused on the evaluation of the electrochemically assisted absorption process (electro-absorption) as a treatment for volatile organic compounds contained in polluted air flows. Benzene degradation was used to test the technology, using a system consisting of a packed absorption column and a single compartment electrochemical cell equipped with boron-doped diamond (BDD) as anode and steel-steal as cathode. The influence of inlet gas flow rate and operation current intensity was evaluated by monitoring the concentration of benzene and intermediates both, in the liquid absorbent / electrolyte and in the outlet gaseous stream. Results show that steady-state values reached, during benzene absorption and electro-absorption, increase when the inlet gas flow rises from 1.5 to 6.0 L h−1 and that the bare absorption process retains benzene only up to this steady-state value of the liquid and then, it has no effect on the removal of benzene. Concentrations of benzene in the absorbent/electrolyte decreases with the increase in the current density during electrochemically assisted processes. As well, mineralization was found to be very important, as expected because of the very low concentrations of benzene into the liquid and the very high efficiencies of the electrolytic degradation with BDD electrodes, and benzoquinone and carboxylic acids were identified as the primary intermediates. These species were not detected in the outlet gas flow. The decrease in the concentration and mass flow of benzene in the outlet streams confirms that electro-absorption is a functional electrochemical application to remove benzene from gaseous streams. When current density rises (10, 50 and 100 mA cm−2), the degradation percentage increases. The values obtained were 43, 61 and 75% with 1,5 L h−1 of inlet gas flow and 10, 25 and 37 % with 6 L h−1. However, the degradation percentage relative to the energy consumption decreases when the current density rises. Results were, correspondingly, 24.7, 4.2 and 2.2 % kWh−1 with 1,5 L h−1 of inlet gas flow and 7.1, 2.1 and 1.4 % with 6 L h−1. This energy efficiency trend was explained because mass transport becomes the bottleneck in the oxidation of diluted organic solutions. These results contribute to expand the understanding of the mechanisms involved in the electro-absorption of benzene and recommend for further research in the topic, due to the relevance of the treatment results.

Intensitive UV–Vis-IR driven catalytic activity of Pt supported on hierarchical ZnO porous nanosheets for benzene degradation via novel photothermocatalytic synergetic effect

Pt supported on hierarchical ZnO porous nanosheets is prepared by the as-prepared hierarchical ZnO porous nanosheets dispersed in Pt(NO3)2 solution and then reduced by NaBH4 solution. The crystal structure, morphology, Pt distribution, surface area, the valence state of elements, the light absorption of Pt/ZnO were characterized by XRD, TEM, SEM, EDX, BET, XPS, PL, and diffusive reflectance UV–Vis-IR absorption. The prepared Pt/ZnO exhibits UV-Vis-IR driven catalytic property even under the irradiation wavelength above 690 nm. The CO2 production rate of Pt/ZnO for the initial 10 min is 49.69 times higher than that of ZnO for the benzene degradation under full solar light irradiation. Pt/ZnO also exhibits considerable thermocatalytic property with T50 of 168 °C and T90 of 197 °C. Impressively, the reaction temperature with full solar light irradiation could reduce 10 °C than that in dark with the same CO2 production rate. The photothermocatalytic synergetic effect on Pt/ZnO originates from accelerated thermocatalysis via the active species generated from photocatalysis. That novel effect can significantly enhance the activity of benzene degradation.

Investigation of microwave enhanced catalytic degradation of VOCs with a novel double ridge field compressed cavity

Volatile organic compounds (VOCs) are common organic pollutants that are harmful to human and the environment. Degradation of VOCs has aroused widespread concern. Catalytic oxidation is considered as an effective method to degrade VOCs. Microwave heating is a promising technology for heterogeneous catalytic gas–solid reactions, which is considered as an alternative to conventional conductive heating. Here, microwave enhanced catalytic degradation of VOCs were carried out in a novel double ridge field compressed cavity, in which Cu-Mn/AC catalyst was applied. The relative permittivity of Cu-Mn/AC at different temperatures were obtained by neural network. Further, based on the relative permittivity obtained, numerical simulations for the double ridge field compressed cavity were conducted at 2.45 GHz by a coupled three-dimensional electromagnetic-thermal model using COMSOL Multiphysics software. The simulation results of electric field distribution and temperature distribution in cavity present similar trend to the experimental results. Experimentally, the degradation of ethanol, benzene and acetone were carried out in this reactor for 50 W and 70 W at 2.45 GHz with the concentration and gas flow rate of 1000 ppm and 18 L/min. At 70 W and 2.45 GHz, the degradation efficiency of ethanol, benzene and acetone reached 99%, 70% and 99%, leading higher energy efficiency than other VOCs degradation methods.

Anaerobic degradation of benzene and other aromatic hydrocarbons in a tar-derived plume: Nitrate versus iron reducing conditions

The anaerobic degradation of aromatic hydrocarbons in a plume originating from a Pintsch gas tar-DNAPL zone was investigated using molecular, isotopic- and microbial analyses. Benzene concentrations diminished at the relatively small meter scale dimensions of the nitrate reducing plume fringe. The ratio of benzene to toluene, ethylbenzene, xylenes and naphthalene (BTEXN) in the fringe zone compared to the plume zone, indicated relatively more loss of benzene in the fringe zone than TEXN. This was substantiated by changes in relative concentrations of BTEXN, and multi-element compound specific isotope analysis for δ2H and δ13C. This was supported by the presence of (abcA) genes, indicating the presumed benzene carboxylase enzyme in the nitrate-reducing plume fringe. Biodegradation of most hydrocarbon contaminants at iron reducing conditions in the plume core, appears to be quantitatively of greater significance due to the large volume of the plume core, rather than relatively faster biodegradation under nitrate reducing conditions at the smaller volume of the plume fringe. Contaminant concentration reductions by biodegradation processes were shown to vary distinctively between the source, plume (both iron-reducing) and fringe (nitrate-reducing) zones of the plume. High anaerobic microbial activity was detected in the plume zone as well as in the dense non aqueous phase liquid (DNAPL) containing source zone. Biodegradation of most, if not all, other water-soluble Pintsch gas tar aromatic hydrocarbon contaminants occur at the relatively large dimensions of the anoxic plume core. The highest diversity and concentrations of metabolites were detected in the iron-reducing plume core, where the sum of parent compounds of aromatic hydrocarbons was greater than 10 mg/L. The relatively high concentrations of metabolites suggest a hot spot for anaerobic degradation in the core of the plume downgradient but relatively close to the DNAPL containing source zone.