Aromatic Intermediates Research Articles

Molecular-growth pathways in premixed flames of benzene and toluene doped with propyne

In a combined experimental and modeling effort, we investigated the molecular-growth pathways in propyne-doped low-pressure premixed flames of benzene and toluene. We determined the chemical structures of these two flames with flame-sampling molecular-beam mass spectrometry. The mole fraction profiles of the aromatic intermediates served as validation targets for two chemically detailed mechanisms that were independently developed at the German Aerospace Center (DLR) and at the Lawrence Livermore National Laboratory (LLNL). Reaction path analyses reveal the important pathways for indene, naphthalene, and phenanthrene. There is no appreciable fuel-structure effect and molecular growth was observed to be driven by radical-radical recombination reactions, and ring-closure and ring-enlargement reactions with little contribution from the classical HACA mechanism. Indene is formed in both flames through the reactions of the phenyl and propargyl radicals. The benzyl radical plays only a very minor role in the formation of indene through the reaction with acetylene. Reactions of the propargyl radical with fulvenallenyl, a C7H5 isomer, contribute significantly to naphthalene formation in both flames investigated here. Benzyl radicals contribute to naphthalene formation via reactions with propargyl radical through formation of phenyl-substituted butadienyl and vinylacetylene isomers. Ring-enlargement reactions converting indene's five-membered ring into naphthalene's six-membered ring also contribute in small amounts to naphthalene. Fulvenallenyl radicals also contribute substantially to phenanthrene formation.

A local QSAR model based on the stability of nitrenium ions to support the ICH M7 expert review on the mutagenicity of primary aromatic amines

BackgroundAromatic amines, often used as intermediates for pharmaceutical synthesis, may be mutagenic and therefore pose a challenge as metabolites or impurities in drug development. However, predicting the mutagenicity of aromatic amines using commercially available, quantitative structure–activity relationship (QSAR) tools is difficult and often requires expert review. In this study, we developed a shareable QSAR tool based on nitrenium ion stability.ResultsThe evaluation using in-house aromatic amine intermediates revealed that our model has prediction accuracy of aromatic amine mutagenicity comparable to that of commercial QSAR tools. The effect of changing the number and position of substituents on the mutagenicity of aromatic amines was successfully explained by the change in the nitrenium ion stability. Furthermore, case studies showed that our QSAR tool can support the expert review with quantitative indicators.ConclusionsThis local QSAR tool will be useful as a quantitative support tool to explain the substituent effects on the mutagenicity of primary aromatic amines. By further refinement through method sharing and standardization, our tool can support the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) M7 expert review with quantitative indicators.

Demonstration of a plant-microbe integrated system for treatment of real-time textile industry wastewater

The real-time textile dyes wastewater contains hazardous and recalcitrant chemicals that are difficult to degrade by conventional methods. Such pollutants, when released without proper treatment into the environment, impact water quality and usage. Hence, the textile dye effluent is considered a severe environmental pollutant. It contains mixed contaminants like dyes, sodium bicarbonate, acetic acid. The physico-chemical treatment of these wastewaters produces a large amount of sludge and costly. Acceptance of technology by the industry mandates that it should be efficient, cost-effective and the treated water is safe for reuse. A sequential anaerobic-aerobic plant-microbe system with acclimatized microorganisms and vetiver plants, was evaluated at a pilot-scale on-site. At the end of the sequential process, decolorization and total aromatic amine (TAA) removal were 78.8% and 69.2% respectively. Analysis of the treated water at various stages using Fourier Transform Infrared (FTIR), High Performance Liquid Chromatography (HPLC)) Gas Chromatography-Mass Spectrometry (GC-MS) Liquid Chromatography-Mass Spectrometry (LC-MS) indicated that the dyes were decolourized and the aromatic amine intermediates formed were degraded to give aliphatic compounds. Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM) analysis showed interaction of microbe with the roots of vetiver plants. Toxicity analysis with zebrafish indicated the removal of toxins and teratogens.

Effective degradation of Direct Red 81 using FeS-activated persulfate process

As a burgeoning advanced oxidation process (AOP), heterogeneous activation of persulfate (PS) for synthetic refractory contaminants decontamination has recently received much attention. In this study, FeS was selected as a heterogeneous PS activator to facilitate the degradation of a typical recalcitrant contaminant of diazo dye Direct Red 81 (DR 81). The results showed that approximately 95% of 0.03 mM DR 81 was removed within 60 min with FeS and PS doses of 1.5 × 10−3 M. The efficient decomposition of DR 81 by the FeS/PS system was assumed to be mainly attributed to the highly reactive SO4−• and •OH, which was related to PS cleavage by both dissolved Fe2+ leached from FeS and Fe2+ bound on the FeS surface. Except for strongly alkaline conditions, DR 81 decolorations by FeS/PS were insignificantly affected by operational parameters such as temperature, initial solution pH, and rotate speed. Meanwhile, the presence of five inorganic anions being studied had distinct impacts on DR 81 degradation and followed a strict order of NO3− < Cl− < SO42− < CO32− < PO43−. However, FeS/PS system was highly adaptable, and FeS, which is used as a PS activator was more stable. GC/MS and TOC data revealed that thorough mineralization of DR 81 by PS/FeS in an initial fast reaction phase to transform DR 81 to aromatic intermediates, followed by a slow reaction phase that mineralized these organic intermediates into carboxylic acids and carbon dioxide through further oxidation.

Investigation on n-pentylbenzene combustion at various pressures: Insight into effects of side-chain length on alkylbenzene combustion

This work investigated the flow reactor pyrolysis of n-pentylbenzene using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) at 0.04 and 1 atm, and measured the laminar burning velocities (LBVs) of n-pentylbenzene in a high-pressure constant-volume cylindrical combustion vessel at 473 K, 1–10 atm and equivalence ratios (ϕ) of 0.7–1.5. A kinetic model of n-pentylbenzene combustion was developed from our previous models of n-butylbenzene and validated against the present experimental data. The unimolecular decomposition reactions and H-abstraction reactions are the dominant consumption pathways of n-pentylbenzene under pyrolysis conditions. Aromatic intermediates with unsaturated side-chains play crucial roles in indene and naphthalene formation, while phenyl and benzyl are precursors of unfused polycyclic aromatic hydrocarbons (PAHs) which in turn convert to fused tricyclic PAHs. In the laminar flame propagation, small species reactions are crucial under lean conditions, while chain-termination reactions, especially fuel-specific reactions, show important inhibition effects on the laminar flame propagation under rich conditions. Furthermore, the effects of side-chain length on the pyrolysis and laminar flame propagation of alkylbenzenes were also investigated for toluene, ethylbenzene, n-propylbenzene, n-butylbenzene and n-pentylbenzene. It is concluded that alkylbenzene smaller than n-butylbenzene tends to decompose at low temperature as the side-chain length increases, while n-butylbenzene and n-pentylbenzene have very close decomposition temperature regions. For indene and naphthalene formation, decomposition/cyclization reaction sequences of C9 and C10 alkenylbenzenes have rapidly increasing importance in the pyrolysis of large alkylbenzenes. Benzyl is concluded to play an important role in inhibiting laminar flame propagation of alkylbenzenes, which is an important reason for the observations that toluene and ethylbenzene have the lowest and highest LBVs, respectively.

Three-Dimensional PbO2-Modified Carbon Felt Electrode for Efficient Electrocatalytic Oxidation of Phenol Characterized with In Situ ATR-FTIR

A three-dimensional (3D) electrode was successfully fabricated by coating carbon felt substrate with PbO2 using an electrodeposition method. Compared with the conventional planar Ti/SnO2–Sb/PbO2 electrode, the CF/PbO2 electrode displayed superior electrocatalytic performance for the degradation of phenol, with an 11.2 times higher rate constant. The improved performance was due to its larger active surface area, enrichment of phenol on the surface due to adsorption, and enhanced mass transfer with the porous 3D structure. It also exhibited an 11.4 times higher current efficiency and a 9.1 times lower energy consumption due to the superior electrocatalytic activity and a higher oxidation potential to hinder oxygen evolution. Moreover, the generation rate of •OH from CF/PbO2 was 1.3 times higher than that of the Ti/SnO2–Sb/PbO2 electrode. The surface chemistry on the CF/PbO2 electrode during phenol degradation was explored by in situ attenuated total reflection–Fourier transform infrared (ATR-FTIR) characterization, with aromatic intermediates and carboxylic acids identified as key reaction intermediates. This composite electrode also presented excellent long-term stability and durability and negligible leaching of Pb cation, demonstrating as a promising electrode for the electrocatalytic degradation of refractory pollution in wastewater treatment.

Degradation and Mineralization Study of Promecarb by Electro Fenton Process

Organic substances as pesticides, especially aromatic compounds are a major environmental concern. In the present work, solutions of Promecarb or 3-isopropyl-5-methylphenyl-N-methylcarbamate of pH = 3 have been degraded by electro Fenton process, using a volumic electrochemical reactor filled with carbon graphite. Effects of nature of material of cathode, initial concentration of insecticide and applied current on the kinetics of oxidative degradation and mineralization efficiency have been investigated. Kinetic analysis showed that the oxidation of Promecarb by hydroxyl radicals follows a reaction kinetic of pseudo first order. The absolute rate constant for Promecarb oxidation by hydroxyl radicals was determined as 10.88 × 10⁹ L mol^-1 s^-1 by competitive kinetics method and benzoic acid was used as reference compound. Mineralization of this pesticide by hydroxyl radicals consists in its transformation to mineral products. The evolution of the mineralization during Promecarb treatment by electro Fenton process was followed by analysis of Total Organic Carbon TOC. Thus, after 3 hours of electrolysis and at I = 800 mA, more than 50% of the organic carbon present in the solution is mineralized. Several degradation products were formed during its electro Fenton treatment. These intermediates were identified using High Performance Liquid Chromatography HPLC, Ionic Chromatography IC and Liquid Chromatography - Mass Spectrometry LC-MS. Based on identification of aromatic intermediates and carboxylic acids, a plausible Promecarb mineralization pathway is proposed. Also, we realized the measurement of the Biochemical Oxygen Demand BOD₅ of insecticide solution after treatment by electro Fenton process, to evaluate its biodegradability.

Performance deterioration of Sb-SnO2/C membrane anode treating phenolic wastewater and anode regeneration: Adsorption and physicochemical change of catalysts

• The removal performance of Sb-SnO 2 /C for phenol deteriorated with time. • The adsorption of benzoquinone had a significant impact on phenol degradation. • Sn(OH) 4 and decreased crystallinity of SnO 2 also led to performance deterioration. • The degradation performance was fully restored after cleaning and recalcination. Stability of anodes is the core of electrochemical oxidation (EO), but there still lacks systematic investigation on the stability of anodes under the conditions of long-term wastewater treatment. Sb-SnO 2 anode was selected for investigation in this study due to its outstanding electrocatalytic activity. The sol–gel method was utilized to coat the Sb-SnO 2 onto a carbon membrane to form the Sb-SnO 2 /C membrane anode, and its stability during long-term treatment of phenol was studied in an electrocatalytic membrane reactor. The results showed that the COD removal efficiency of Sb-SnO 2 /C dropped from 80.6% to 41.3% after 6 days. Carbonaceous intermediates were found to be adsorbed onto Sb-SnO 2 /C, mainly including aromatic intermediates and fatty acids. The adsorption of benzoquinone had a significant adverse impact on the phenol degradation of Sb-SnO 2 /C, leading to a decreased COD removal efficiency. The formation of Sn(OH) 4 , decreased crystallinity of Sb-SnO 2 , and the reduced Sb/Sn of the used Sb-SnO 2 /C were also proposed to lead to the performance deterioration. NaOH cleaning (pH = 11.9) was able to remove the adsorbed carbonaceous intermediates and improved the COD removal from 41.3% to 64.3%. Recalcination after chemical cleaning could further improve the COD removal efficiency to 89.7%, close to the initial value.

Selective catalytic synthesis of bio-based terephthalic acid from lignocellulose biomass

_Efficient synthesis of bio-based chemicals from renewable lignocellulosic biomass is of great significance to promote the sustainable development of chemical industry. This work aims to demonstrate that terephthalic acid, a bulk high value chemical in petrochemical industry, can be synthesized using biomass. This novel controllable transformation process was started with the selective catalytic pyrolysis of sawdust biomass to form p-xylene intermediate. The high p-xylene yield of 23.4% was obtained using the Ga2O3/SiO2/HZSM-5 catalyst under the optimized reaction condition. Subsequently, the selective oxidation of the biomass-derived aromatic intermediates to terephthalic acid was realized with the metal oxide catalysts. The highest terephthalic acid yield of 72.8% with the terephthalic acid selectivity of 82.3% was achieved using the CoMn2O4@SiO2@Fe3O4 catalyst. Based on the study of the catalytic conversion of the model compounds and the catalyst characterizations, the reaction pathways and possible reaction mechanism have been proposed.

An appraisal on valorization of lignin: A byproduct from biorefineries and paper industries

Lignocellulose based processes consist of technology platforms for production of materials and products for developing a bio-based, sustainable economy. Production of sugar streams and ethanol from cellulose is a mature technology, and its deployment results in increased lignin availability. Although lignin is used for low-value applications, its high-value utilization needs to be explored and developed. The aromatic intermediates from lignin can be transformed into high-value products. The unique structural/chemical properties of lignin offer possibilities for valorization, which can be achieved through thermochemical or biological transformation platforms, each route having its pros and cons. Lignin degrading oragnisms hold promise for biovalorization. In this work, different categories of organisms (fungi and bacteria) capable of degrading lignin, possessing unique repertoires of enzymes have been discussed. Under natural niches consortium of organisms decay lignin as a single organism does not possess all the activities. The constraints in biological processing can be addressed by using a combination of processes for lignin depolymerization to aromatic intermediates, followed by their conversion to target products. The recent devised metabolic engineering strategies to tackle these challenges are reviewed. Ultimately, the success of biorefineries will be dictated by the technical feasibility of bioconversions, robustness of engineered organisms, and their ability to produce the desired products in high titers with relatively high purity, scalability, and overall economics.

Asymmetric Addition and Cycloaddition Reactions with Ylidene‐Five‐Membered Heterocycles

AbstractFive‐membered heterocycles bearing an exocyclic double bond have been successfully used as substrates in asymmetric addition and cycloaddition reactions. Ylidene‐heterocycles are attractive substrates due to their high functionalization and the presence of an electrophilic conjugated exocyclic double bound that can participate in nucleophilic addition reactions as well as cycloaddition reactions, which may be triggered by the formation of aromatic intermediates or products in many cases. During the last decades, catalytic methodologies have been developed using ylidene‐heterocycles as substrates in order to synthesize useful optically active heterocyclic derivatives. 4‐Ylidene‐pyrazol‐5‐ones, isoxazolin‐5‐ones, 2,3‐dioxopyrrolidines, rhodanines, oxazolidindiones, Erlenmeyer‐Ploch azlactones and 5‐ylidene‐thiazolones have been successfully used as substrates in asymmetric reactions. This review collects the powerful research in asymmetric addition and cycloaddition reactions where ylidene‐five‐membered heterocycles have been used.magnified image

Simultaneous energy generation, decolorization, and detoxification of the azo dye Procion Red MX-5B in a microbial fuel cell

Microbial fuel cells (MFCs) are sustainable technologies that can effectively treat wastewater with simultaneous electricity generation. The present study investigated the performance of an MFC highly specific for decolorizing and degrading the azo dye Procion Red MX-5B (PRMX), which eliminates the toxicity of the solution while generating electricity. The MFC anode biofilm was formed from mining sediment after acclimatization in sodium acetate (1 g L-1), followed by the addition of 100 mg L-1 PRMX. The system was totally decolorized, and the color removal occurred fast during the first 70 h of the MFC feed cycle. Total mineralization occurred after 172 h of the feed cycle of the MFC system. Complete degradation of the aromatic intermediates generated after PRMX degradation reduced the toxic potential of the PRMX solution against A. salina larvae and L. sativa seeds to near zero. PRMX supply into the anode increased the voltage output from 360 mV (1 g L-1 sodium acetate - SA) to 520 mV (PRMX/SA 100 mg L-1: 0.25 g L-1). The maximum power density of 156 mW m-2 obtained herein was higher than most values reported for dye remediation in similar devices. Assessment of the microbial community showed that PRMX addition to the acetate diminished the microbial diversity in the bioanode. Pseudomonas and Dysgonomonas accounted for 87% of the biofilm. Therefore, both genera are most probably responsible for external electron transfer and PRMX degradation.

Solution-phase conversion of glucose into semiconductive carbonaceous nanosheet photocatalysts for enhanced environmental applications

Two-dimensional (2D) materials are important materials in environmental science and engineering. They have been widely used in environmental treatments. However, most of the 2D materials are obtained and synthesized from minerals. The sources are not very environmental-friendly. In this regard, it is a sustainable strategy to fabricate 2D materials by renewable precursors like glucose in biomasses. However, synthesis of 2D materials from glucose in water is still a great challenge mainly because of isotropy growth. Herein, we achieve an aqueous solution-phase synthesis of semiconductive 2D nanosheets by using renewable carbohydrates via hydrothermal method. Previously, glucose tend to form irregular or spherical particles in hydrothermal solution due to isotropy growth. In this work, the carbohydrate of glucose can be converted into hydrothermal carbonation carbon (HTCC) nanosheets in the presence of ethylenediamine and Fe3+/Fe2+/Co2+/Ni2+ ions in water. Firstly, a Maillard reaction occurs to activate sp3-sp2 conversion of carbon to form aromatic intermediates. Then, the metal ions will trigger the formation of the HTCC nanosheets. The thickness of the nanosheets is c.a. 2–8 nm. Compared with bulk HTCC, the nanosheets exhibit dramatical enhancement. The pure bulk HTCC suffers from very poor charge transfer efficiency, which does not has obvious activiity in photocatalytic disinfection and pollution degradation. By contrast, as a 2D materials, the HTCC nanosheet exhibits excellent charge transfer efficiency at the direction perpendicular to its surface, which exhibits remarkable activity in photocatalytic disinfection, pollution degradation, and Cr(IV) adsorption and reduction. As a new method for the synthesis of 2D material in water, this method will lead to the development of a new generation of carbon-based 2D materials.

Towards a more realistic heterogeneous electro-Fenton

• Mechanical design of the cell as a key issue in the scale-up. • Successful scaling-up of the heterogeneous electro-Fenton process. • Clofibric acid abatement was achieved regardless of the cell. • Higher hydrogen peroxide production & clofibric acid removal with improved design. With the aim of bringing the heterogeneous electro-Fenton (EF) treatment one step closer to a more realistic operation, the scaling-up of that technology was evaluated. Assays were performed firstly at lab scale in a stirred-tank reactor and then at bench scale in a flow setup including a jet aerator and a microfluidic flow-through electrochemical cell. A fluidized-bed reactor was added to the bench-scale installation in order to retain the solid catalyst, iron-containing alginate beads. To the best of the authors’ knowledge, there are no precedent studies reporting a heterogeneous EF treatment in a similar bench scale-configuration. Hydrogen peroxide generation and clofibric acid removal were assessed at both scales at current intensities of 0.12 and 0.25 A. Results showed that the scaled-up treatment was more efficient and cost-effective: at bench scale 18 times more volume was treated, the mass production of hydrogen peroxide was 28 higher and the specific cost for the removal of clofibric acid was cut by more than half. The most efficient treatment turned out to be the EF performed at 0.12 A at bench scale. Those results highlighted the importance of the reactor design in the scaling-up process. Additionally, aromatic intermediates were detected by liquid chromatography-mass spectrometry (LC-MS) and a degradation route was suggested. Carboxylic acids were also measured by HPLC confirming that the pollutant is mineralizing.

Lignin Aromatics to PHA Polymers: Nitrogen and Oxygen Are the Key Factors for Pseudomonas

Many wild type Pseudomonas strains have the potential to contribute to the valorization of lignin in future biorefineries. Through a robust aromatic catabolism, i.e., biofunneling capacity, they can ease the inherent aromatic heterogeneity found in lignin hydrolysates and accumulate naturally marketable biopolymers like mcl-polyhydroxyalkanoate (mcl-PHA) under nitrogen limitation. Besides a comparative strain evaluation, we present fundamental research on the funneling of aromatic mixtures under specific bioprocess conditions to improve biocatalytic lignin valorization. For the most robust and best performing strain, P. putida KT2440, we improve the mcl-PHA accumulation from a defined aromatic mixture of p-coumarate, ferulate, and benzoate under technically relevant conditions by up to 40% by tailoring the nitrogen and oxygen supply. The highest mcl-PHA concentration (582 ± 41 mg L–1) was obtained for a C/N ratio of 60 for oxygen-unlimited conditions (oxygen transfer rate >20 mmol L–1 h–1). In contrast, aromatic intermediates accumulated under oxygen-limited conditions at oxygen transfer rates below 10 mmol L–1 h–1. The experimental conditions were scalable into a 1L stirred tank bioreactor. This study contributes to deepening our understanding of the biocatalytic capability of promising Pseudomonas strains toward downstream microbial conversions of lignin aromatics for future biorefinery applications.

Efficacy of a novel electrochemical membrane-aerated biofilm reactor for removal of antibiotics from micro-polluted surface water and suppression of antibiotic resistance genes

An electrochemical membrane-aerated biofilm reactor (EMABR) was developed for removing sulfamethoxazole (SMX) and trimethoprim (TMP) from contaminated water. The exertion of electric field greatly enhanced the degradation of SMX and TMP in the EMABR (~60%) compared to membrane-aerated biofilm reactor (MABR, < 10%), due to the synergistic effects of the electro-oxidation (the generation of reactive oxygen species) and biological degradation. Microbial community analyses demonstrated that the EMABR enriched the genus of Xanthobacter, which was potentially capable of degrading aromatic intermediates. Moreover, the EMABR had a lower relative abundance of antibiotic resistance genes (ARGs) (0.23) compared to the MABR (0.56), suggesting the suppression of ARGs in the EMABR. Further, the SMX and TMP degradation pathways were proposed based on the detection of key intermediate products. This study demonstrated the potential of EMABR as an effective technology for removing antibiotics from micro-polluted surface water and suppressing the development of ARGs.

Conserved Metabolic and Evolutionary Themes in Microbial Degradation of Carbamate Pesticides.

Carbamate pesticides are widely used as insecticides, nematicides, acaricides, herbicides and fungicides in the agriculture, food and public health sector. However, only a minor fraction of the applied quantity reaches the target organisms. The majority of it persists in the environment, impacting the non-target biota, leading to ecological disturbance. The toxicity of these compounds to biota is mediated through cholinergic and non-cholinergic routes, thereby making their clean-up cardinal. Microbes, specifically bacteria, have adapted to the presence of these compounds by evolving degradation pathways and thus play a major role in their removal from the biosphere. Over the past few decades, various genetic, metabolic and biochemical analyses exploring carbamate degradation in bacteria have revealed certain conserved themes in metabolic pathways like the enzymatic hydrolysis of the carbamate ester or amide linkage, funnelling of aryl carbamates into respective dihydroxy aromatic intermediates, C1 metabolism and nitrogen assimilation. Further, genomic and functional analyses have provided insights on mechanisms like horizontal gene transfer and enzyme promiscuity, which drive the evolution of degradation phenotype. Compartmentalisation of metabolic pathway enzymes serves as an additional strategy that further aids in optimising the degradation efficiency. This review highlights and discusses the conclusions drawn from various analyses over the past few decades; and provides a comprehensive view of the environmental fate, toxicity, metabolic routes, related genes and enzymes as well as evolutionary mechanisms associated with the degradation of widely employed carbamate pesticides. Additionally, various strategies like application of consortia for efficient degradation, metabolic engineering and adaptive laboratory evolution, which aid in improvising remediation efficiency and overcoming the challenges associated with in situ bioremediation are discussed.

Ultrasound-assisted decomposition of metronidazole by synthesized TiO2/Fe3O4 nanocatalyst: Influencing factors and mechanisms

This study focused on the facile preparation of TiO2/Fe3O4 catalyst prepared by the sol-gel approach as an efficient catalyst for decomposition and mineralization of metronidazole (MTN) in TiO2/Fe3O4/US process. FE-SEM, EDX, VSM, FTIR and XRD analyses were used to characterize the catalyst. The results confirmed the formation of TiO2/Fe3O4 catalyst with the average crystallite size of 32.4 nm. The influence of various factors such as solution pH, catalyst dose, initial MTN concentration and ultrasonic (US) power was examined on MTN decomposition. Also, the effect of various scavengers and inorganic anions was evaluated. In addition, mineralization of MTN, intermediates, reusability and stability tests of catalyst was also investigated. The removal efficiency of MTN by TiO2/Fe3O4 assisted ultrasonic was higher than of pure TiO2 and Fe3O4 nanoparticles. Under the optimal conditions (TiO2/Fe3O4 dosage = 1.0 g L−1, pH = 5.0, initial MTN content = 10 mg L−1, US power = 40 W and time = 90 min), 97.5% of MTN was removed. The scavenging studies expressed that •OH radicals were the main active species in the process. The GC–MS analysis showed that MTN was firstly decomposed into aromatic and aliphatic intermediates in the first stage of the reactions and then mineralized to CO2, H2O and inorganic ions. The removal efficiency of 91.2% for COD and 73.6% for TOC approved the efficient mineralization of MTN solution. The low leakage value of Fe and high reusability of the catalyst (within six consecutive cycles) indicated that TiO2/Fe3O4 had a high stability and reusability and makes it a promising catalyst for efficient degradation of antibiotics in the practical applications.

Effects of polyurethane foam carrier addition on anoxic/aerobic membrane bioreactor (A/O-MBR) for coal gasification wastewater (CGW) treatment: Performance and microbial community structure

Coal gasification wastewater (CGW) is a typical toxic and refractory industrial wastewater with abundant phenols contained. Two identical anoxic/aerobic membrane bioreactors (with (R2) and without (R1) polyurethane (PU) foam) were carried out in parallel to investigate the role of PU foam addition in enhancing pollutants removal in CGW. Results showed that both systems exhibited effective removal of chemical oxygen demand (>93%) and total phenols (>97%) but poor ammonia nitrogen removal (<35%) constrained by ammonia oxidation process. GC–MS analysis revealed that aromatic and other refractory intermediates were dramatically reduced in R2. Moreover, the PU addition had negligible influence on the total soluble microbial products and extracellular polymeric substances contents but significantly alleviated membrane fouling with the operating time 33% prolonged. Microbial community revealed that Flavobacterium, Holophaga, and Geobacter were enriched on PU. Influent type might be a main driver for microbial community succession.

Palladium-catalyzed carbonylative synthesis of quinazolines: Silane act as better nucleophile than amidine

Abstract A palladium-catalyzed reductive carbonylation reaction has been developed for the synthesis of quinazolines. With N-(2-iodophenyl)benzimidamide as starting materials, a series of quinazolines were obtained through the aromatic aldehyde intermediates in moderate to good yields with good functional group compatibilities. In this system, silane act as better nucleophile than amidine.