Pore-Matched Sponge for Microorganisms Pushes Electron Extraction Limit in Microbial Fuel Cells.

Microbial fuel cells (MFCs) are of great potential for wastewater remediation and chemical energy recovery. Nevertheless, limited by inefficient electron transfer between microorganisms and electrode, the remediation capacity and output power density of MFCs are still far away from the demand of practical application. Herein, a pore-matching strategy is reported to develop uniform electroactive biofilms by inoculating microorganisms inside a pore-matched sponge, which is assembled of core-shell polyaniline@carbon nanotube (PANI@CNT). The maximum power density achieved by the PANI@CNT bioanode is 7549.4 ± 27.6 mW m-2 , which is higher than the excellent MFCs with proton exchange membrane reported to date, while the coulombic efficiency also attains a considerable 91.7 ± 1.2%. The PANI@CNT sponge enriches the exoelectrogen Geobacter significantly, and is proved to play the role of conductive pili in direct electron transfer as it down-regulates the gene encoding pilA. This work exemplifies a practicable strategy to develop excellent bioanode to boost electron extraction in MFCs and provides in-depth insights into the enhancement mechanism.

A deep learning-enabled smartphone platform for rapid and sensitive colorimetric detection of dimethoate pesticide.

A novel deep learning-enabled smartphone platform is developed to assist a colorimetric aptamer biosensor for fast and highly sensitive detection of dimethoate. The colorimetric determination of dimethoate is based on the specific binding of dimethoate and aptamer, which leads to the aggregation of AuNPs in high-concentration NaCl solution, resulting in an obvious color change from red to blue. This color change provides sufficient data for self-learning enabled by a convolutional neural network (CNN) model, which is established to predict dimethoate concentration based on images acquired from a smartphone. To enhance user-friendliness for non-experts, the CNN model is then embedded into a smartphone app, enabling offline detection of dimethoate pesticide in real environments within just 15 min using a pre-configured colorimetric probe. The developed platform exhibits superior performance, achieving a regression coefficient of 0.9992 in the concentration range of 0-10 µM. Moreover, the app's performance is found to be consistent with the ELISA kit. These remarkable findings demonstrate the potential of combining colorimetric biosensors with smartphone-based deep learning methods for the development of portable and affordable tools for pesticide detection.

A supplementary assessment system of AQI-V for comprehensive management and control of air quality in chemical industrial parks.

Volatile organic compounds (VOCs) are the dominant pollutants in industrial parks. However, they are not generally considered as part of the air quality index (AQI) system, which leads to a biased assessment of pollution in industrial parks. In this study, a supplementary assessment system of AQI-V was established by analyzing VOCs characteristics with vehicle-mounted PTR-TOFMS instrument, correlation analysis and the standards analysis. Three hourly and daily scenarios were considered, and the hierarchical parameter setting was further optimized by field application. The hourly and daily assessments revealed the evaluation factors for the discriminability of different air quality levels, practiced value for regional air quality improvement, and the reservation of general dominant pollutants. Finally, the universality testing in ZPIP successfully recognized most of the peaks, with 54.76%, 38.39% and 6.85% for O3, VOCs and NO2 as the dominant pollutant, and reflected the daily ambient air quality condition, together with the dominant pollutant. The AQI-V system with VOCs sub-index is essential for air quality evaluation in industrial parks, which can further provide scientific support to control the pollution of VOCs and the secondary pollutant, therefore significantly improve the air quality in local industrial parks.

A novel approach for VOC source apportionment combining characteristic factor and pattern recognition technology in a Chinese industrial area.

Volatile organic compound (VOC) emission control and source apportionment in small-scale industrial areas have become key topics of air pollution control in China. This study proposed a novel characteristic factor and pattern recognition (CF-PR) model for VOC source apportionment based on the similarity of characteristic factors between sources and receptors. A simulation was carried out in a typical industrial area with the CF-PR model involving simulated receptor samples. Refined and accurate source profiles were constructed through in situ sampling and analysis, covering rubber, chemicals, coating, electronics, plastics, printing, incubation and medical treatment industries. Characteristic factors of n-undecane, styrene, o-xylene and propane were identified. The source apportionment simulation results indicated that the predicted contribution rate was basically consistent with the real contribution rate. Compared to traditional receptor models, this method achieves notable advantages in terms of refinement and timeliness at similar accuracy, which is more suitable for VOC source identification and apportionment in small-scale industrial areas.

A Novel Dual-Stage Phase Separation Process for CO2 Absorption into a Biphasic Solvent with Low Energy Penalty.

An amine-based biphasic solvent is promising to cut down the energy penalty of CO2 capture. However, the high viscosity of the CO2-enriched solvent retards its industrial application. This work proposed a novel dual-stage phase separation process using a triethylenetetramine and 2-(diethylamino)ethanol blend as a biphasic solvent, which separates a certain proportion of CO2-enriched phase during CO2 absorption to reduce its viscosity. Experimental results showed that the proposed dual-stage phase separation process improved the phase separation behavior and effectively enhanced the absorption rate by 49% at 50 °C, when 50 vol % CO2-enriched phase was separated at 0.3 mol mol-1. Kinetic analysis showed that the absorption rate was mainly controlled by liquid-side mass transfer. The regeneration heat of the dual-stage phase separation process cut down the energy penalty by 33% compared with the monoethanolamine-based process. Compared with the conventional biphasic solvent-based process, the heat duty was further declined by 8%. The 1H nuclear magnetic resonance analysis showed that the dual-stage phase separation process could effectively control the generation of absorption products and intensify the interphase migration of tertiary amines.

A Biophysicochemical Model for NO Removal by the Chemical Absorption-Biological Reduction Integrated Process.

The chemical absorption-biological reduction (CABR) integrated process is regarded as a promising technology for NOx removal from flue gas. To advance the scale-up of the CABR process, a mathematic model based on mass transfer with reaction in the gas, liquid, and biofilm was developed to simulate and predict the NOx removal by the CABR system in a biotrickling filter. The developed model was validated by the experimental results and subsequently was used to predict the system performance under different operating conditions, such as NO and O2 concentration and gas and liquid flow rate. NO distribution in the gas phase along the biotrickling filter was also modeled and predicted. On the basis of the modeling results, the liquid flow rate and total iron concentration were optimized to achieve >90% NO removal efficiency. Furthermore, sensitivity analysis of the model revealed that the performance of the CABR process was controlled by the bioreduction activity of Fe(III)EDTA. This work will provide the guideline for the design and operation of the CABR process in the industrial application.

Bioelectrochemical Reduction of Fe(II)EDTA-NO in a Biofilm Electrode Reactor: Performance, Mechanism, and Kinetics.

A biofilm electrode reactor (BER) is proposed to effectively regenerate Fe(II)EDTA, a solvent for NOx removal from flue gas, from Fe(II)EDTA-NO, a spent solution. In this study, the performance, mechanism, and kinetics of the bioelectrochemical reduction of Fe(II)EDTA-NO were investigated. The pathways of Fe(II)EDTA-NO reduction were investigated via determination of nitrogen element balance in the BER and an abiotic electrode reactor. The experimental results indicate that the chelated NO (Fe(II)EDTA-NO) is reduced to N2 with N2O as an intermediate. However, the oxidation of NO occurred in the absence of Fe(II)EDTA in abiotic reactors. Furthermore, the accumulation of N2O was suppressed with the help of electricity. The preponderant electron donor for reduction of Fe(II)EDTA-NO was also confirmed via analysis of the electron conservation. About 87% of Fe(II)EDTA-NO was reduced using Fe(II)EDTA as the electron donor in the presence of both glucose and cathode electrons while the cathode electrons were utilized for the reduction of Fe(III)EDTA to Fe(II)EDTA. Michaelis-Menten kinetic constants of bioelectrochemical reduction of Fe(II)EDTA-NO were also calculated. The maximum reduction rate of Fe(II)EDTA-NO was 13.04 mol m(-3) h(-1), which is 50% higher than that in a conventional biofilter.

Generation, utilization, and transformation of cathode electrons for bioreduction of Fe(III)EDTA in a biofilm electrode reactor related to NOx removal from flue gas.

A chemical absorption-biological reduction (CABR) integrated system, which employs iron chelate as a solvent, is under development for NOx removal from flue gas. Biofilm electrode reactor (BER) is deemed as a promising bioreactor to regenerate the iron chelate. Although it has been proved that BER can significantly enhance the bioreduction of Fe(III)EDTA, the bioelectrochemistry mechanism involved in the bioreduction of Fe(III)EDTA remains unknown. This work aims to explore this mechanism via the analysis of the generation, utilization, and transformation of cathode electrons in the BER. The results indicate that the generation of cathode electrons follows Faraday's law. The generated cathode electrons were used to produce H2 and directly reduce Fe(III)EDTA in the BER. Meanwhile, the produced H2 served as an electron donor for bioreduction of Fe(III)EDTA. The excess H2 product was transformed to simple organics, e.g., methanol by the hydrogen autotrophy of Pseudomonas under the inorganic and anaerobic conditions. Overall, this work revealed that the reduction of Fe(III)EDTA in the BER was enhanced by both direct electrochemical reduction and indirect bioreduction using H2 as an intermediate. It is also interesting that the excess H2 product was transformed to methanol for microbial metabolism and energy storage in the BER.

Re-acclimation performance and microbial characteristics of a thermophilic biofilter for NOx removal from flue gas.

Currently, a novel chemical absorption-biological reduction (CABR) integrated process, employing Fe(II)EDTA as a solvent, is being under development to reduce the cost of NOx removal from flue gas. In this work, the NO removal profile, re-acclimation performance, and microbial characteristics in a thermophilic biofilter were investigated at the conditions typical to CABR process. The biofilter comprised of four layers of packing material with a surface area of 1200 m(2) m(-3). Experimental results revealed that the biofilter could remove 95 % of the fed NO at typical flue gas conditions. As the gas residence time varied from 90 to 15 s, the NO removal efficiency decreased from 100 to 56.5 % due to the NO mass transfer limitation. The longer period of the biofilter shutdown required more time for its re-acclimation. For example, after 8-day shutdown, the biofilter was re-acclimated in 32 h. Denaturing gradient gel electrophoresis analysis of PCR-amplified product showed that Pseudomonas, a group of denitrifier, was dominant in the biofilter. Because the Pseudomonas was abundant at the bottom layer of packed-bed, the bottom layer contributed to 60-70 % of the total NO removal. In addition, Pseudomonas gradually faded away along the gas flow path from the bottom to the top of biofilter, resulting in a significant decrease in NO removal at the other three packed-bed layers. These observed results will provide the process engineering and scale-up data with respect to the biofilter operations to help advance the CABR process to pilot-scale testing.

Metagenomics revealing biomolecular insights into the enhanced toluene removal and electricity generation in PANI@CNT bioanode.

Microbial fuel cells (MFCs) have significant potential for environmental remediation and energy recycling directly from refractory aromatic hydrocarbons. To boost the capacities of toluene removal and the electricity production in MFCs, this study constructed a polyaniline@carbon nanotube (PANI@CNT) bioanode with a three-dimensional framework structure. Compared with the control bioanode based on graphite sheet, the PANI@CNT bioanode increased the output voltage and toluene degradation kinetics by 2.27-fold and 1.40-fold to 0.399 V and 0.60 h-1, respectively. Metagenomic analysis revealed that the PANI@CNT bioanode promoted the selective enrichment of Pseudomonas, with the dual functions of degrading toluene and generating exogenous electrons. Additionally, compelling genomic evidence elucidating the relationship between functional genes and microorganisms was found. It was interesting that the genes derived from Pseudomonas related to extracellular electron transfer, tricarboxylic acid cycle, and toluene degradation were upregulated due to the existence of PANI@CNT. This study provided biomolecular insights into key genes and related microorganisms that effectively facilitated the organic pollutant degradation and energy recovery in MFCs, offering a novel alternative for high-performance bioanode.

Enhanced 1,2-dichloroethane removal using g-C3N4/Blue TiO2 nanotube array photoanode in microbial photoelectrochemical cells.

The compound 1,2-dichloroethane (1,2-DCA), a persistent and ubiquitous pollutant, is often found in groundwater and can strongly affect the ecological environment. However, the extreme bio-impedance of C-Cl bonds means that a high energy input is needed to drive biological dechlorination. Biotechnology techniques based on microbial photoelectrochemical cell (MPEC) could potentially convert solar energy into electricity and significantly reduce the external energy inputs currently needed to treat 1,2-DCA. However, low electricity-generating efficiency at the anode and sluggish bioreaction kinetics at the cathode limit the application of MPEC. In this study, a g-C3N4/Blue TiO2-NTA photoanode was fabricated and incorporated into an MPEC for 1,2-DCA removal. Optimal performance was achieved when Blue TiO2 nanotube arrays (Blue TiO2-NTA) were loaded with graphitic carbon nitride (g-C3N4) 10 times. The photocurrent density of the g-C3N4/Blue TiO2-NTA composite electrode was 2.48-fold higher than that of the pure Blue TiO2-NTA electrode under light irradiation. Furthermore, the MPEC equipped with g-C3N4/Blue TiO2-NTA improved 1,2-DCA removal efficiency by 45.21% compared to the Blue TiO2-NTA alone, which is comparable to that of a microbial electrolysis cell. In the modified MPEC, the current efficiency reached 69.07% when the light intensity was 150 mW cm-2 and the 1,2-DCA concentration was 4.4 mM. The excellent performance of the novel MPEC was attributed to the efficient direct electron transfer process and the abundant dechlorinators and electroactive bacteria. These results provide a sustainable and cost-effective strategy to improve 1,2-DCA treatment using a biocathode driven by a photoanode.

Efficient biodechlorination at the Fe3O4-based silicone powder modified chlorobenzene-affinity anode.

The treatment of chlorinated volatile organic compounds faces challenges of secondary pollution and less-efficiency due to the substitution of chlorine. Microbial fuel cells (MFCs) provide a promising opportunity for its abatement. In this study, a novel Fe3O4 nanoparticles and silicone-based powder (SP) were integrated and immobilized on carbon felt (CF+Fe3O4@SP), which was further used as anode in the chlorobenzene (CB) powered MFC. Owing to the cooperation between SP and Fe3O4, the anode exhibited excellent performance for both biodechlorination and power generation. The results indicated that the CF+Fe3O4@SP anode loaded MFC achieved 98.5% removal of 200 mg/L CB within 28 h, and the maximum power density was 675.9 mW/m3, which was a 45.6% increase compared to that of the bare CF anode. Microbial community analysis indicated that the genera Comamonadaceae, Pandoraea, Obscuribacteraceae, and Truepera were dominated, especially, the Comamonadaceae and Obscuribacteraceae showed outstanding affinity for Fe3O4 and SP, respectively. Moreover, the proportion of live bacteria, secretion of extracellular polymer substances, and protein content in the extracellular polymer substances were significantly increased by modifying Fe3O4@SP onto the carbon-based anode. Thus, this study provides new insights into the development of MFCs for refractory and hydrophobic volatile organic compounds removal.

BiOI-SnO2 Heterojunction Design to Boost Visible-Light-Driven Photocatalytic NO Purification.

The efficient, stable, and selective photocatalytic conversion of nitric oxide (NO) into harmless products such as nitrate (NO3-) is greatly desired but remains an enormous challenge. In this work, a series of BiOI/SnO2 heterojunctions (denoted as X%B-S, where X% is the mass portion of BiOI compared with the mass of SnO2) were synthesized for the efficient transformation of NO into harmless NO3-. The best performance was achieved by the 30%B-S catalyst, whose NO removal efficiency was 96.3% and 47.2% higher than that of 15%B-S and 75%B-S, respectively. Moreover, 30%B-S also exhibited good stability and recyclability. This enhanced performance was mainly caused by the heterojunction structure, which facilitated charge transport and electron-hole separation. Under visible light irradiation, the electrons gathered in SnO2 transformed O2 to ·O2- and ·OH, while the holes generated in BiOI oxidized H2O to produce ·OH. The abundantly generated ·OH, ·O2-, and 1O2 species effectively converted NO to NO- and NO2-, thus promoting the oxidation of NO to NO3-. Overall, the heterojunction formation between p-type BiOI and n-type SnO2 significantly reduced the recombination of photo-induced electron-hole pairs and promoted the photocatalytic activity. This work reveals the critical role of heterojunctions during photocatalytic degradation and provides some insight into NO removal.

Dibenzothiophene Removal from Fuel Oil by Metal-Organic Frameworks: Performance and Kinetics.

Desulfurization of organic sulfur in the fuel oil is essential to cut down the emission of sulfur dioxide, which is a major precursor of the acid rain and PM2.5. Currently, hydrodesulfurization is regarded as a state-of-art technology for the desulfurization of fuel oil. However, due to the stringent legislation of the fuel oil, the deep desulfurization technology is urgent to be developed. Adsorptive desulfurization method is promising due to the high selectivity and easy operation. The development of efficient adsorbent is important to advance this technology into industrial application. In this work, the five types of metal-organic frameworks (MOFs), including Cu-BTC, UMCM-150, MIL-101(Cr), UIO-66, and Cu-ABTC were synthesized for the adsorption of dibenzothiophene (DBT), a typical organic sulfur compound in the fuel oil. The experimental results revealed that the adsorption capacity of the five MOFs followed the order of Cu-ABTC, UMCM-150, Cu-BTC, MIL-101(Cr), and UIO-66, which adsorption capacities were 46.2, 34.2, 28.3, 26.3, and 22.0 mgS/g, respectively. The three types of Cu-based MOFs such as Cu-ABTC, UMCM-150, and Cu-BTC outperformed the Cr-based MOFs, MIL-101, and Zr-based MOFs, UIO-66. Since the surface area and pore volumes of the Cu-based MOFs were not the greatest among the tested five MOFs, the physical properties of the MOFs were not the only limited factor for the DBT adsorption. The π-complexation between DBT and linkers/metal in the MOFs was also important. Kinetic analysis showed that the DBT adsorption onto the five tested MOFs follows the pseudo-second-order kinetics, confirming that the chemical π-complexation was also contributed to the DBT adsorption. Furthermore, the operation parameters such as oil-adsorbent ratio, initial sulfur concentration and adsorption temperature for the DBT adsorption onto Cu-ABTC were optimized to be 100:1 g/g, 1000 mgS/L and 30 °C, respectively. This work can provide some insights into the development of efficient adsorbent for the organic sulfur adsorption.

Exploring ozone formation rules and concentration response to the change of precursors based on artificial neural network simulation in a typical industrial park.

Industrial parks have more complex O3 formation mechanisms due to a higher concentration and more dense emission of precursors. This study establishes an artificial neural network (ANN) model with good performance by expanding the moment and concentration changes of pollutants into general variables of meteorological factors and concentrations of pollutants. Finally, the O3 formation rules and concentration response to the changes of volatile organic compounds (VOCs) and nitrogen oxides (NOx) was explored. The results showed that the studied area belonged to the NOx-sensitive regime and the sensitivity was strongly affected by relative humidity (RH) and pressure (P). The concentration of O3 tends to decrease with a higher P, lower temperature (Temp), and medium to low RH when nitric oxide (NO) is added. Conversely, at medium P, high Temp, and high RH, the addition of nitrogen dioxide (NO2) leads to a larger decrease capacity in O3 concentration. More importantly, there is a local reachable maximum incremental reactivity (MIRL) at each certain VOCs concentration level which linearly increased with VOCs. The general maximum incremental reactivity (MIR) may lead to a significant overestimation of the attainable O3 concentration in NOx-sensitive regimes. The results can significantly support the local management strategies for O3 and the precursors control.

Superior dimethyl disulfide degradation in a microbial fuel cell: Extracellular electron transfer and hybrid metabolism pathways.

To enhance the biological degradation of volatile organic sulfur compounds, a microbial fuel cell (MFC) system with superior activity is developed for dimethyl disulfide (DMDS) degradation. The MFC achieves a removal efficiency near 100% within 6 h (initial concentration: 90 mg L-1) and a maximum biodegradation rate constant of 0.743 mM h-1. The DMDS removal load attains 2.684 mmol h-1 L-1, which is 6.18-2440 times the loads of conventional biodegradation processes reported. Meanwhile, the maximum power density output and corresponding current density output are 5.40 W m-3 and 40.6 A m-3, respectively. The main mechanism of extracellular electron transfer is classified as mediated electron transfer, supplemented by direct transfer. Furthermore, the mass balance analysis indicates that methanethiol, S0, S2-, SO42-, HCHO, and CO2 are the main intermediate and end products involved in the hybrid metabolism pathway of DMDS. Overall, these findings may offer basic information for bioelectrochemical degradation of DMDS and facilitate the application of MFC in waste gas treatment. ENVIRONMENTAL IMPLICATION: Dimethyl disulfide (DMDS), which features poor solubility, odorous smell, and refractory property, is a typical pollutant emitted from the petrochemical industry. For the first time, we develop an MFC system for DMDS degradation. The superior DMDS removal load per unit reactor volume is 6.18-2440 times those of conventional biodegradation processes in literature. Both the electron transfer route and the hybrid metabolism pathway of DMDS are cleared in this work. Overall, these findings give an in-depth understanding of the bioelectrochemical DMDS degradation mechanism and provide an efficient alternative for DMDS removal.

A nanocubicle-like 3D adsorbent fabricated by in situ growth of 2D heterostructures for removal of aromatic contaminants in water.

Focusing on the emergence of organic pollutants in aqueous environments, attempts to assemble two-dimensional (2D) materials into three-dimensional (3D) structures are expected to improve their pollution control performance. However, most 3D heterostructural nanomaterials are constructed by mechanical mixing methods, which result in structures that are randomly arranged and prone to collapse. Two typical 2D carbon materials, reduced graphene oxide (rGO) and covalent triazine frameworks (CTFs), have exhibited excellent effects in the fields of contaminant adsorption and photocatalysis, respectively. However, their regular packing structure could not provide an interconnected pore network suitable for the diffusion or adsorption of pollutants. In this study, a series of heterostructures named rGCs were fabricated by direct growth of 2D CTFs with different ratios on the surface of rGO layers. The rGCs were designed to remove trace concentrations of naphthalene (NAP) and benzophenone (BP) from water, which can be regenerated under sunlight. rGC-20, in which nanocubicle-like 3D heterostructures were successfully constructed, not only adsorbed NAP and BP with superb normalized adsorption capacities (5000-5300 µmol/g) but also could be regenerated with an exceptional percentage recovery of 90-95% in the 4th cycle. The microenvironment created in nanocubicle-like 3D heterostructures enhances the adsorption of pollutants, the excitation of electrons and utilization of radicals, which further promotes the adsorption and photocatalysis of rGCs. This work provides a promising adsorbent with outstanding adsorption-regeneration ability for aromatic contaminant removal from water. DATA AVAILABILITY: The main data that support the findings of this study are available from the article and its Supplementary Information. Extra data are available from the corresponding author on request.

Roles of Oxygen Species in Low-Temperature Catalytic o-Xylene Oxidation on MOF-Derived Bouquetlike CeO2.

To realize efficient low-temperature catalytic o-xylene oxidation, MOF-derived CeO2-X catalysts were prepared via the pyrolysis of MOF precursors with different ratios of cerium nitrate to trimesic acid. Among the synthesized catalysts, the bouquet like CeO2-1 exhibited the best activity with T50 and T90 of 156 and 198 °C and the lowest activation energy of 60.67 kJ·mol-1 (WHSV= 48 000 mL·g-1·h-1, o-xylene concentration = 500 ppm). o-Xylene was completely mineralized, and no change in conversion efficiency or CO2 yield was found at 5 vol % H2O for over 50 h. The rich active oxygen species (XPS: Osur/Olatt = 0.69) and abundant oxygen vacancies (Raman: ID/IF2g = 0.036) of CeO2-1 made crucial contribution to its superior catalytic activity. The O2-TPD and H2-TPR results confirmed that CeO2-1 had more surface active oxygen and better mobility of bulk oxygen. Moreover, the reaction routes under different atmospheres were probed through in situ DRIFTS, in which oxygen vacancy played a key role in promoting the adsorption and activation of molecular oxygen and facilitating the migration of the bulk lattice oxygen.

Engineering multiscale polypyrrole/carbon nanotubes interface to boost electron utilization in a bioelectrochemical system coupled with chemical absorption for NO removal.

The chemical absorption-bioelectrochemical reduction (CABER) integrated system provides an alternative of good potential for NO removal. The efficient utilization of cathode electrons directly determines the system performance and operating cost. Herein, we synthesize a polypyrrole/carbon nanotubes (PPy/CNTs) composite to engineer a micro-and nanoscale interface with low resistance and high biocompatibility between the cathode and biofilms in the CABER system. The resulting PPy/CNTs biocathodes exhibit 36.4% increase in biomass density, 40.7%-302.6% increase in Faraday efficiency along Fe(III)EDTA reduction, and 204% increase in Fe(II)EDTA-NO reduction rate. The enrichment of functional microorganisms is validated to be a key strengthening factor, as the proportion of which increased from 57.9% to 84.6%. Moreover, for efficient electron transfer and utilization, a low-resistance electron transfer route, "electrode substrate → PPy (→ CNTs) → microbial cells → Fe(III)EDTA or Fe(II)EDTA-NO", is realized in the multiscale conductive networks constructed of PPy/CNTs composite and microbial nanowires.

Combined experimental and theoretical study of o-xylene elimination on Fe-Mn oxides catalysts.

The development of low-cost and easily accessible catalysts to realize the practical applications of catalytic combustion of volatile organic compounds remains a challenge. In this work, a series of Fe-Mn oxides catalysts were prepared via a facile redox-precipitation route for the elimination of o-xylene. Among the synthesized catalysts, Fe3Mn1-RP exhibited excellent activity for o-xylene elimination with a T50 and T90 of 223 °C and 236 °C, respectively (o-xylene concentration = 500 ppm, WHSV = 36,000 mL g-1 h-1). Characterization results demonstrated that superior catalytic activity could be achieved from large specific surface area, good reducibility and high proportion of Mn4+. Besides, high Fe contents proved beneficial in generating additional oxygen vacancies, thereby improving the performance of the catalyst. The stable crystal structures and surface electron density distributions of the catalysts, and adsorption sites of o-xylene on the catalyst surface, were also determined through density functional theory (DFT) calculations to provide an in-depth mechanism on how the o-xylene oxidation occurred. Moreover, analysis of the energy barrier during the oxidation process proved that the ring-opening reaction on the surface of Fe3Mn1-RP with an activation energy as low as 2.46 eV would more likely occur via oxygen vacancies.