Degradation Of Ethylbenzene Research Articles

Comparison of the Intestinal Bacterial Communities between Captive and Semi-Free-Range Red-Crowned Cranes (Grus japonensis) before Reintroduction in Zhalong National Nature Reserve, China.

The wild populations of red-crowned cranes (Grus japonensis) in west China are gradually decreasing, necessitating the optimization of reintroduction measures. This study used 16S rRNA high-throughput sequencing technology to compare the gut microbiota communities of cranes living in two modes (captive and semi-free-range) before their reintroduction in Zhalong National Nature Reserve, Heilongjiang Province, China. The results showed that Proteobacteria (74.39%) and Firmicutes (25.29%) were the dominant gut bacterial phyla inhabiting these cranes. Significant differences were found in the gut microbiota community composition between semi-free-range and captive cranes (p < 0.01). Psychrobacter, Sporosarcina, and Lactococcus were significantly enriched in captive cranes (p < 0.05), while Pseudomonadaceae_Pseudomonas, Pantoea, Lysobacter, and Enterobacteriaceae_Pseudomonas were more abundant in semi-free-range cranes (p < 0.05). The functions and community structure of gut microbiota were affected by feeding patterns (p < 0.05). The metabolic pathways of ethylbenzene degradation, PPAR signaling pathway, betalain biosynthesis, systemic lupus erythematosus, and shigellosis were up-regulated in semi-free-range cranes (p < 0.05).

Understanding of the synergy effect of DBD plasma discharge combined to photocatalysis in the case of Ethylbenzene removal: Interaction between plasma reactive species and catalyst

Hybrid non-thermal plasma combined with photocatalysis is an efficient technology for the degradation of volatile organic compounds (VOCs) and leads to a synergetic boosting effect of the degradation process. Herein, the degradation of ethylbenzene (EB) in a hybrid lab-scale reactor was performed. In the combined mode (plasma DBD and photocatalysis [TiO2 + UVA]), the degradation of EB was synergetically boosted, and a higher degradation efficiency was reached. In this study, the behavior of the synergetic effect was investigated whilst varying several operational conditions, including the UV light source (UVA and UVC), the TiO2 weight (7.5–22.51 g·m-²), the addition of metallic dopants to the TiO2 at different weight ratios (x%Cu-TiO2 and x%MnO2-TiO2, where x = 1, 3, 5 and 10 for the weight ratios of Cu:TiO2 and MnO2:TiO2) and the catalyst support (glass fiber tissue [GFT] and nickel foam [NF] with different thicknesses [0.3–3.3 mm]). Moreover, the oxygen content (0–100%) in the reactor atmosphere was examined. The results showed an enhancement of the synergetic effect under UVC (TiO2 + UVC + DBD), which may be a consequence of intensive ozone decomposition under UVC and the generation of reactive atomic oxygen. The improvement of the synergetic effect under 1% Cu-TiO2 and 10% MnO2-TiO2 catalysts is assumed to reflect the role of metallic species in the production of oxygen species on the TiO2 surface via the ozone depletion mechanism. Furthermore, TiO2/NF (3.3 mm) showed the highest synergetic effect, likely due to the conductive character and the 3D porous structure of NF. Finally, the rich oxygen composition had an apparent impact on the synergetic effect.

Process optimization of BTEX degradation from petrochemical effluent using integrated advanced oxidation

In this study, an integral treatment consisted of UV/Fenton/ TiO2 system in the batch systems was developed to perform degradation of synthetic Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX). Initially, the efficiency of photo Fenton catalytic degradation was compared with conventional treatment methods. Later, optimum levels of selected variables such as the initial concentration of BTEX, pH, temperature, reaction time, and initial dosage of TiO2 were analyzed using one factor at a time method. Further, screening of variables and optimization were performed using Planckett-Burman design and central composite design, respectively. Photo Fenton catalytic process showed about 1.15 fold increase in efficiency when compared with photo Fenton process. Among the selected seven variables, four variables namely, initial pH, BTEX concentration, H2O2 dosage and TiO2 dosage were identified as significant factors. Under the optimal conditions, chemical oxygen demand reduction reached about 84.54 ± 2.57% using UV/Fenton/ TiO2 system. Finally, first-order kinetic model resulted in prediction of 19.43 kJ/mol of activation energy. Thus, process optimization and kinetic study using the developed photo Fenton catalytic system could be beneficial for real time waste containing BTEX pollutants.

Investigation of photocatalytic-proxone process performance in the degradation of toluene and ethyl benzene from polluted air

In this study, toluene and ethylbenzene were degraded in the photocatalytic-proxone process using BiOI@NH2-MIL125(Ti)/Zeolite nanocomposite. The simultaneous presence of ozone and hydrogen peroxide is known as the proxone process. Nanocomposite Synthesis was carried out using the solvothermal method. Inlet airflow, ozone concentrations, H2O2 concentrations, relative humidity, and initial pollutants concentrations were studied. The nanocomposite was successfully synthesized based on FT-IR, BET, XRD, FESEM, EDS element mapping, UV–Vis spectra and TEM analysis. A flow rate of 0.1 L min−1, 0.3 mg min−1 of ozone, 150 ppm of hydrogen peroxide, 45% relative humidity, and 50 ppmv of pollutants were found to be optimal operating conditions. Both pollutants were degraded in excess of 95% under these conditions. For toluene and ethylbenzene, the synergistic of mechanisms effect coefficients were 1.56 and 1.76, respectively. It remained above 95% efficiency 7 times in the hybrid process and had good stability. Photocatalytic-proxone processes were evaluated for stability over 180 min. The remaining ozone levels in the process was insignificant (0.01 mg min−1). The CO2 and CO production in the photocatalytic-proxone process were 58.4, 5.7 ppm for toluene and 53.7, and 5.5 ppm for ethylbenzene respectively. Oxygen gas promoted and nitrogen gas had an inhibitory effect on the effective removal of pollutants. During the pollutants oxidation, various organic intermediates were identified.

Gaseous ethylbenzene removal by photocatalytic TiO2 nanoparticles immobilized on glass fiber tissue under real conditions: evaluation of reactive oxygen species contribution to the photocatalytic process.

Photocatalytic oxidation (PCO) using a TiO2 catalyst is an effective technique to remove gaseous volatile organic compounds (VOCs). Herein, a lab-scale continuous reactor is used to investigate the photocatalytic performance toward ethylbenzene (EB) vapor removal over TiO2 nanoparticles immobilized on glass fiber tissue. The role of the reactive species in the removal of EB and the degradation pathway were studied. Firstly, the effect of key operating parameters such as EB concentration (13, 26, 60mg/m3), relative humidity levels (From 5 to 80%), gas carrier composition (dry air + EB, O2 + EB and N2 + EB) and ultraviolet (UV) radiation wavelength (UV-A 365nm, UV-C 254nm) were explored. Then, using superoxide dismutase and tert-butanol as trapping agents, the real contribution of superoxide radical anion (O2.-) and hydroxyl radicals (OH.) to EB removal was quantified. The results show that (i) small water vapor content enhances the EB degradation; (ii) the reaction atmosphere plays an important role in the photocatalytic process; and (iii) oxygen atmosphere/UV-C radiation shows the highest EB degradation percentage. The use of radical scavengers confirms the major contribution of the hydroxyl radical to the photocatalytic mechanism with 75% versus 25% for superoxide radical anion.

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.

Characterisation of the redox centers of ethylbenzene dehydrogenase

Ethylbenzene dehydrogenase (EbDH), the initial enzyme of anaerobic ethylbenzene degradation from the beta-proteobacterium Aromatoleumaromaticum, is a soluble periplasmic molybdenum enzyme consisting of three subunits. It contains a Mo-bis-molybdopterin guanine dinucleotide (Mo-bis-MGD) cofactor and an 4Fe–4S cluster (FS0) in the α-subunit, three 4Fe–4S clusters (FS1 to FS3) and a 3Fe–4S cluster (FS4) in the β-subunit and a heme b cofactor in the γ-subunit. Ethylbenzene is hydroxylated by a water molecule in an oxygen-independent manner at the Mo-bis-MGD cofactor, which is reduced from the MoVI to the MoIV state in two subsequent one-electron steps. The electrons are then transferred via the Fe–S clusters to the heme b cofactor. In this report, we determine the midpoint redox potentials of the Mo-bis-MGD cofactor and FS1–FS4 by EPR spectroscopy, and that of the heme b cofactor by electrochemically induced redox difference spectroscopy. We obtained relatively high values of > 250 mV both for the MoVI–MoV redox couple and the heme b cofactor, whereas FS2 is only reduced at a very low redox potential, causing magnetic coupling with the neighboring FS1 and FS3. We compare the results with the data on related enzymes and interpret their significance for the function of EbDH.Graphical abstract

Photocatalytic Degradation of Ethylbenzene in Aqueous Solutions by ZnFe2O4 Nanoparticles Supported on the Copper Slag: Optimization, Kinetics and Thermodynamics Studies

ZnFe2O4/Copper slag (CS) which is an environmentally friendly and cost-effective catalyst was produced by co-precipitation methods and a thermal process. The synthesized catalyst was characterized by XRD, SEM, EDX and BET surface area analysis. The X-rays diffraction pattern confirmed that the crystal structure of ZnFe2O4 after stabilization on CS zeolite has not changed. The SEM images showed that, despite their varying sizes, the particles all have the same shape. Photocatalytic activity of the catalyst was tested for the degradation of ethylbenzene (EB) in water by UV + H2O2 method in the reverse-flow packed bed photo reactor. The process optimization and modeling were performed using the full factorial method. The initial concentration of EB = 30 ppm, pH = 9 and initial H2O2 concentration = 15 ppm were the best conditions. Under ideal process conditions, the removal efficiency of EB was greater than 99.5%. The validity of the Langmuir-Hinshelwood kinetics model was confirmed using EB photocatalytic degradation experimental results. The values of 〖∆H〗^⫲and 〖∆S〗^⫲ for the photocatalytic degradation of EB by ZnFe2O4/CS catalyst in the UV+H2O2 process were calculated based on the transition state theory and gave 1.67 kJ mol-1 and -263.057 J K-1 mol-1 respectively.

Anthropogenic activities change the relationship between microbial community taxonomic composition and functional attributes.

Functional redundancy is considered common in microbial systems, but recent studies have challenged this idea. The mechanism for this contradictory result is not clear. However, in this study, we hypothesize that strong environmental filtering which links to the anthropogenic activities is able to weaken microbial functional redundancy. We used metagenome and 16S rRNA gene high-throughput sequencing to investigate planktonic microbial communities in a subtropical river. We found that the weak anthropogenic activities might result in a low selection pressure in the river upstream area. Therefore, the microbial community functional attributes were stable although the community composition changed with the water temperature and NO3 -N in upstream area (this indicates functional redundancy). However, the strong anthropogenic activities in river downstream area selected pollutant-degraded functions (e.g. nitrogen metabolism, toluene, xylenes and ethylbenzene degradation) and potentially pollutant-degraded (tolerant) microbes, and therefore caused the microbial community composition synchronously changed with the variation of community functional attributes. Our results reveal that strong environmental filtering which associates with the anthropogenic activities not only has effects on microbial community composition and community functional attributes but also on their relationships. These results provide a new insight to refine the functional redundancy idea.

Insights into the mechanism of hydrogen peroxide activation with biochar produced from anaerobically digested residues at different pyrolysis temperatures for the degradation of BTEXS

The disposal of large amounts of biogas residue from anaerobically digested waste is a burden on environment protection. Porous biochars (BCs) were synthesized from biogas residue at three pyrolysis temperatures (300 °C, 550 °C, and 800 °C) and used to catalyze H2O2 for the degradation of benzene, toluene, ethylbenzene, xylene isomers (ortho, para, and meta), and styrene (BTEXS) to develop a new use for biogas residues. The prepared BCs were characterized through scanning electron microscopy, Brunauer–Emmett–Teller method, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy. Results showed that BC800/H2O2 had the highest BTEXS degradation performance over 6 h. The degradation kinetic data were most consistent with the pseudo-second-order model. The different catalytic effect of the three BCs pyrolyzed at different temperatures were attributed to the dominant active sites (C–O/C–OH/C=C/C=O groups, pyridinic N, and graphitic N) that induced the production of reactive oxygen species (ROS). ROS-quenching experiments indicated that the degradation of BTEXS by BC300/H2O2, BC550/H2O2, and BC800/H2O2 involved ∙OH, ∙O2−, and 1O2. ∙OH was the dominant ROS in BC300/H2O2 and BC550/H2O2, and 1O2 was the dominant ROS in BC800/H2O2. Our findings provided new insight into the different catalytic mechanisms for BC production at different pyrolysis temperatures and demonstrated that a porous BC catalyst with high utilization value could be prepared from biogas residue and could hold considerable potential for application in BTEXS treatment in the future.

Photocatalytic Degradation of Ethylbenzene by Nano Photocatalyst in Aerogel form Based on Titania

In this study, a composite of Cu, N co-doped TiO2@SiO2 aerogel as a photocatalyst with enhanced optical absorption in the visible region as well as high specific surface area was synthesized by the sol-gel method and ambient pressure drying process for degradation of Ethylbenzene. The physicochemical properties of the photocatalyst were examined by X-Ray Powder Diffraction, Scanning Electron Microscope, Photoluminescence, Fourier Transform Infrared Spectroscopy, Diffuse Reflectance Spectroscopy, Brouner Emmet Teller Isotherm/Barrett Joyner Halenda analysis. The structure of samples consisted of titanium dioxide crystalline phases in the dominant phase of the rutile and the amorphous structure of silica. The appearance of the Ti-O-Si peak confirmed the formation of TiO2@SiO2 composite. Based on the results of the characterization analysis, the type and concentration of dopants can be effective on the crystalline structure, bandgap energy, particle size, specific surface area, and the recombination of charge carriers. The sample contains 3 at. % of copper and nitrogen was able to degrade Ethylbenzene more efficiently in comparison with mono-doped TiO2@SiO2 nanocomposite under visible-light irradiation. The synergistic effects of Cu and N co-dopants were responsible for strong visible light absorption and effective separation of electron/hole.

Insights into gut microbiome and its functional pathways in asthma patients through high-throughput sequencing.

Aim: To describe gut microbiome and functional genes of asthma. Patients & methods: Fecal microbiome in controls, asthma patients with and without inhaled corticosteroid(ICS) treatment was determined. Results: Patients with ICS had lower abundance of Alloprevotella, unclassified_f_Lachnospiraceae and Lachnospiraceae_NC2004_group, higher abundance of Sutterella and Sphingomonas than patients without ICS. In all the asthma patients, there are microbial differences in aging distribution, different gender and different asthmatic phenotypes. Asthma patients without ICS treatment had more microbial genes related to geraniol degradation, ethylbenzene degradation and bladder cancer than controls; 15 pathways showed significant difference between asthma patients with and without ICS treatment. Conclusion: We found gut dysbiosis in asthma and different functional pathways associated with both asthma and ICS.

Photocatalytic ethylbenzene degradation associated with ozone (TiO2/UV/O3) under different percentages of catalytic coating area: Evaluation of process parameters

Over decades heterogeneous photocatalysis has been successfully applied to degrade a wide range of pollutants. Despite it, when aromatic volatile organic compounds (VOCs) are treated, generally, challenges such as low efficiency and photocatalyst deactivation are faced. In this scenario, the association between heterogeneous photocatalysis and ozone (TiO2/UV/O3) has emerged as an alternative to overcome such issues, although it has not yet been applied to ethylbenzene removal from gaseous streams. In this work, gas-phase ethylbenzene degradation (73 ppmv) by UV radiation, O3, UV/O3, TiO2, TiO2/UV, TiO2/O3, and TiO2/UV/O3 processes was evaluated. The influence of parameters such as relative humidity (26–80%), space-time (130, 74, 52, and 29 s), ozone concentration (3.6, 4.2, and 5.5%), and percentage of catalytic coating area (50, 70, 90, and 100%) on ethylbenzene removal was investigated. Relative humidity from 26 to 50% did not affect ethylbenzene degradation significantly and TiO2/UV/O3 enhanced its removal up to 87.7% and 22% when compared to the TiO2/UV and the UV/O3 processes, respectively. A maximum ethylbenzene conversion of 98% was also reached at 130 s, 70% of TiO2 coating area, and 5.5% of ozone. We found that, in the TiO2/UV/O3 system, reactions on the catalyst surface and in the gas bulk were both important, thus a 70% of TiO2 coating area was obtained as the best configuration. Furthermore, catalyst stability was assessed by a time-on-stream experiment and TiO2/UV/O3 maintained the average ethylbenzene conversion at 75% during 50 h. TGA/DTGA and FTIR analyses allowed the identification of possible compounds adsorbed on the catalyst surface after reactions.

Metagenome Analysis of a Hydrocarbon-Degrading Bacterial Consortium Reveals the Specific Roles of BTEX Biodegraders

Environmental contamination by petroleum hydrocarbons is of concern due to the carcinogenicity and neurotoxicity of these compounds. Successful bioremediation of organic contaminants requires bacterial populations with degradative capacity for these contaminants. Through successive enrichment of microorganisms from a petroleum-contaminated soil using diesel fuel as the sole carbon and energy source, we successfully isolated a bacterial consortium that can degrade diesel fuel hydrocarbons. Metagenome analysis revealed the specific roles of different microbial populations involved in the degradation of benzene, toluene, ethylbenzene and xylene (BTEX), and the metabolic pathways involved in these reactions. One hundred and five putative coding DNA sequences were identified as responsible for both the activation of BTEX and central metabolism (ring-cleavage) of catechol and alkylcatechols during BTEX degradation. The majority of the Coding DNA sequences (CDSs) were affiliated to Acidocella, which was also the dominant bacterial genus in the consortium. The inoculation of diesel fuel contaminated soils with the consortium resulted in approximately 70% hydrocarbon biodegradation, indicating the potential of the consortium for environmental remediation of petroleum hydrocarbons.

Anaerobic enrichment of &lt;i&gt;Bacillus&lt;/i&gt; alkylbenzene remedial consortia from waste biomass melanoid sources

&lt;abstract&gt; &lt;p&gt;Bioremediation of alkylbenzenes, including toluene, ethylbenzene and xylenes, was performed using fermentable aromatic sources and electron mediators by &lt;italic&gt;Bacillus cereus&lt;/italic&gt; 301 in a limited oxygen state. The fermentation of small fermentable aromatic melanoids from cow manure as soluble humus hydrolysates or sugarcane molasses as saccharine, glucose and limited basal medium was compared. Thus, an evaluation model of exponential decline against a control was incorporated for interpretation of remedial data. The significance of the present strategy for constructing multivariant effects of electron donors could be objectively judged by pattern comparison with the short-term data analyzed. Thus, grafted aromatics as methyl- or ethylbenzene require much more microbial reaction time, even with mixed aromatic donors or stronger electron donors such as methanol in the original reduced medium, as indicated in the scatter chart. However, completion of the remedial time was needed by the kinetic simulation, and even low, smooth data were expressed. Among the exponential decay curves indicated, the carbon sources in the mix were favorably expressed. The smooth pattern indicated that fermentations with glucose and molasses showed lower remedial activity than melanoids or the indole series. The vigor increase was better for melanoid carbon in the initial fermentation of 24 h, while molasses increased later at 72 h and was more quenched by amending indole acetic acid (IAA) or indole expression. The molecular interaction of the electron mediator indole acetic acid in most trials indicated a quenched effect on toluene and ethylbenzene degradation, even when mixed with the original reducing medium, but expressed better with molasses in both kinetic simulations and growth effects. Thus, combining electron mediators such as IAA for &lt;italic&gt;Bacillus&lt;/italic&gt; may offer a new degradation route for the metabolite alkylbenzene, which is worth further exploration for environmental aromatic waste remediation and combined restoration strategies.&lt;/p&gt; &lt;/abstract&gt;

Degradation of BTEXS with stable and pH-insensitive iron-manganese modified biochar from post pyrolysis

An efficient iron-manganese modified biochar (FMBC) was successfully synthesized as a heterogeneous Fenton-like catalyst through easy post-modification and applied for degradation of benzene, toluene, ethylbenzene, xylene isomers (ortho, para, and meta), and styrene (BTEXS) in the presence of H2O2. The catalyst was characterized by Brunauer–Emmett–Teller method, scanning electron microscopy, and X-ray photoelectron spectrometry. The effects of H2O2 concentration, FMBC dose, and initial pH on BTEXS degradation were also investigated. Results showed that degradation efficiency of FMBC for individual BTEXS varied from 83.05% to 94.12% in 3 h. Kinetic analysis showed that a first-order kinetic model with respect to BTEXS concentration could be used to explain the BTEXS degradation for FMBC/H2O2 system. The degradation reaction was more suitable in a wide pH range (3–10) than those in previous studies, thereby overcoming the low-efficiency problem of conventional Fenton reaction at high pH. Moreover, the doses of FMBC and H2O2 are a crucial factor affecting BTEXS degradation. Radical scavenger experiments revealed that ∙OH, ∙O2−, and 1O2 participated in the degradation process, and ∙OH was the major contributor. The synthesized catalyst is durable with stable BTEXS removal efficiency after seven consecutive cycles. The removal efficiency of BTEXS by FMBC in produced water reached 93.23% in 12 h, indicating FMBC has practical value.

α-Fe2O3/Ag/g-C3N4 Core-Discontinuous Shell Nanocomposite as an Indirect Z-Scheme Photocatalyst for Degradation of Ethylbenzene in the Air Under White LEDs Irradiation

A new class of α-Fe2O3/Ag/g-C3N4 composites with various metallic Ag contents were effectively synthesized, characterized and applied for photocatalytic degradation of ethylbenzene in continuous air flow. Compared with α-Fe2O3, g-C3N4 and α-Fe2O3/g-C3N4, an excellent visible light absorption, higher charge separation and photocatalytic activity were found for α-Fe2O3/Ag/g-C3N4. These findings were originated from an efficient Z-scheme charge transfer mechanism and a well-constructed core-discontinuous shell structure. To optimize the operational conditions for the practical application of the most efficient photocatalyst, a central composite design (CCD) based response surface method (RSM) was defined. This study showed that Fe2O3/Ag/g-C3N4 can stably remove the ethylbenzene from the air stream, without any byproduct generation.

Ultrasound-assisted heterogeneous activation of persulfate and peroxymonosulfate by asphaltenes for the degradation of BTEX in water

This study investigated – for the first time – the simultaneous degradation of benzene, toluene, ethylbenzene and o-xylene (BTEX) by persulfate (PS) and peroxymonosulfate (PMS) activated by asphaltenes (Asph) under ultrasound (US) irradiation. Advantageous properties such as high thermal stability, low production cost and extensive availability make asphaltenes as an appealing carbonaceous material for heterogeneous catalysis. The application of asphaltenes in PS/US increased the degradation of BTEXs from 31%, 34%, 35%, 32%–78%, 94%, 98% and 98%, while the removal of these compounds in PMS/US system was improved from 26%, 27%, 24%, 20%–76%, 91%, 97%, 97%, respectively. PS and PMS activation followed a typical sulfate-radical based advanced oxidation processes. In terms of activation of PS and PMS, the particles of asphaltenes intensified formation of reactive radicals by creating additional centers of cavitational events. Moreover, owing to π–π stacking interaction between asphaltenes and sp2-hybridized systems of BTEX, the contaminants undergo adsorption on the surface of asphaltenes and subsequent oxidation by formed radicals. The radical route of BTEX degradation in both PS/US/Asph and PMS/US/Asph systems was mainly contributed by sulfate (SO4•−) and hydroxyl radicals (HO•) and coexisting superoxide radical anions (O2•−) played a minor role.

Structure and Functions of Hydrocarbon-Degrading Microbial Communities in Bioelectrochemical Systems

Bioelectrochemical systems (BESs) exploit the interaction between microbes and electrodes. A field of application thereof is bioelectrochemical remediation, an effective strategy in environments where the absence of suitable electron acceptors limits classic bioremediation approaches. Understanding the microbial community structure and genetic potential of anode biofilms is of great interest to interpret the mechanisms occurring in BESs. In this study, by using a whole metagenome sequencing approach, taxonomic and functional diversity patterns in the inoculum and on the anodes of three continuous-flow BES for the removal of phenol, toluene, and BTEX were obtained. The genus Geobacter was highly enriched on the anodes and two reconstructed genomes were taxonomically related to the Geobacteraceae family. To functionally characterize the microbial community, the genes coding for the anaerobic degradation of toluene, ethylbenzene, and phenol were selected as genetic markers for the anaerobic degradation of the pollutants. The genes related with direct extracellular electron transfer (EET) were also analyzed. The inoculum carried the genetic baggage for the degradation of aromatics but lacked the capacity of EET while anodic bacterial communities were able to pursue both processes. The metagenomic approach provided useful insights into the ecology and complex functions within hydrocarbon-degrading electrogenic biofilms.

Nano-magnetite supported by biochar pyrolyzed at different temperatures as hydrogen peroxide activator: Synthesis mechanism and the effects on ethylbenzene removal

Nano-magnetite supported by biochar (nFe3O4/BC) pyrolyzed at temperatures of 300 °C–600 °C was developed to activate hydrogen peroxide (H2O2) for the efficient degradation of ethylbenzene in aqueous solution. It was revealed that the degradation efficiency of ethylbenzene and TOC removal were 96.9% and 36.2% respectively after the reaction for 40 min in the presence of initial concentration of 0.1 mmol L−1 ethylbenzene, 2.76 g L−1 nFe3O4/BC500 with the mass ratio of nFe3O4 to BC500 of 4:1 and 2.0 mmol L−1 H2O2 at pH 7.0. Based on electron paramagnetic resonance (EPR), quenching experiment and X-ray photoelectron spectroscopy (XPS) data, both OH and O2- radicals were generated in the nFe3O4/BC500 activated H2O2 system, and the OH radicals were the predominant species for the degradation of ethylbenzene. Through electron transfer process, mechanisms of Fe(II), phenolic hydroxyl group and persistent free radicals (PFRs) on BC surfaces accounted for the generation of OH radicals, and Fe(III) in nFe3O4 and formed from Fe(II) oxidation responsible for the generation of O2- radicals in the nFe3O4/BC activated H2O2 system were proposed.