Geobacter sulfurreducens promoted the biosynthesis of reduced graphene oxide and coupled it for nitrobenzene reduction

In order to explore an efficient and green method to deal with nitrobenzene (NB) pollutant, reduced graphene oxide (rGO) as an electron shuttle was applied to enhance the extracellular electron transfer (EET) process of Geobacter sulfurreducens, which was a typical electrochemically active bacteria (EAB). In this study, rGO biosynthesis was achieved via the reduction of graphene oxide (GO) by G. sulfurreducens PCA within 3 days. Also, the rGO-PCA combining system completely reduced 50-200 µmol/L of NB to aniline as end product within one day. SEM characterization revealed that PCA cells were partly wrapped by rGO, and therefore the distance of electron transfer between strain PCA and rGO material was reduced. Beside, the ID/IG of GO, rGO, and rGO-PCA combining system were 0.990, 1.293 and 1.31, respectively. Moreover, highest currents were observed in rGO-PCA-NB as 12.950 µA/-12.560 µA at -408 mV/156 mV, attributing to the faster electron transfer efficiency in EET process. Therefore, the NB reduction was mainly due to: (I) direct EET process from G. sulfurreducens PCA to NB; (II) rGO served as electron shuttle and accelerated electron transfer to NB, which was the main degradation pathway. Overall, the biosynthesis of rGO via GO reduction by Geobacter promoted the NB removal process, which provided a facile strategy to alleviate the problematic nitroaromatic pollution in the environment.

Fluorescence-quenching mechanisms of novel isomorphic Zn/Cd coordination polymers for selective nitrobenzene detection

Nitroaromatic compounds in aqueous undermine environmental sustainability and affect human health. The development of a fluorescent sensor capable of efficiently and selectively detecting trace amounts of nitroaromatic compounds presents a considerable challenge. This study introduced Zn/Cd isomeric coordination polymers (Zn-H2CIA-1/Cd-H2CIA-2), which are synthesized using 5-((4-carboxybenzyl)oxy)isophthalic acid (5-H3CIA) and 1,10-phenanthroline (Phen). The polymers have zero-dimensional discrete crystal structure with a six-coordinated scissor-like shape. The two coordination polymers can be used as fluorescent sensors for detecting nitrobenzene (NB) and demonstrated favorable sensitivity, with detection limits of 1.95 × 10-8 and 4.66 × 10-7 mol/L, respectively. Zn-H2CIA-1 exhibited stronger fluorescence and a more sensitive response to NB compared with Cd-H2CIA-2. To elucidate their fluorescence-quenching mechanisms, we analyzed Zn-H2CIA-1 by performing DFT and TD-DFT calculations. The pore structure, density of states, excitation energy, hole-electron distribution, and orbital composition were analyzed. The suitable size of pores in Zn-H2CIA-1 is the main reason for its high NB selectivity. Moreover, intermolecular π-π stacking interactions result in an orbital overlap between Zn-H2CIA-1 and NB, enabling the transfer of electrons from Zn-H2CIA-1 to NB. This electron transfer is identified as the fundamental cause of fluorescence quenching in Zn-H2CIA-1.

An extensive experimental and DFT studies on highly selective detection of nitrobenzene through deferasirox based new fluorescent sensor

A deferasirox based substituted triazole amine sensor TAD has been synthesized for the highly selective detection of nitrobenzene in real samples. Sensor TAD exhibited selective quenching response against nitrobenzene among the other nitroaromatic compounds (NACs). Photoinduced electron transfer (PET) process was devised as plausible sensing mechanisms which was supported via UV-visible and fluorescence spectroscopy, 1H NMR titration experiment, density functional theory (DFT) analysis and Job's plot. Non-covalent interaction (NCI) analysis and Bader's quantum theory of atoms in molecules (QTAIM) analysis were performed to investigate the presence of non-covalent interactions and symmetry perturbation theory (SAPT0) was performed for energy decomposition and quantitative analysis of interaction energies between sensor TAD and NB. Furthermore, sensor TAD was practically applied for the identification of NB in real samples.

Molecular toxicity of nitrobenzene derivatives to tetrahymena pyriformis based on SMILES descriptors using Monte Carlo, docking, and MD simulations

It is challenging to model the toxicity of nitroaromatic compounds due to limited experimental data. Nitrobenzene derivatives are commonly used in industry and can lead to environmental contamination. Extensive research, including several QSPR studies, has been conducted to understand their toxicity. Predictive QSPR models can help improve chemical safety, but their limitations must be considered, and the molecular factors affecting toxicity should be carefully investigated. The latest QSPR methods, molecular modeling techniques, machine learning algorithms, and computational chemistry tools are essential for developing accurate and robust models. In this work, we used these methods to study a series of fifty compounds derived from nitrobenzene. The Monte Carlo approach was used for QSPR modeling by applying the SMILES molecular structure representation and optimal molecular descriptors. The correlation ideality index (CII) and correlation contradiction index (CCI) were further introduced as validation parameters to estimate the developed models' predictive ability. The statistical quality of the CII models was better than those without CII. The best QSPR model with the following statistical parameters (Split-3): (R2 = 0.968, CCC = 0.984, IIC = 0.861, CII = 0.979, Q2 = 0.954, QF12 = 0.946, QF22 = 0.938, QF32 = 0.947, Rm2 = 0.878, RMSE = 0.187, MAE = 0.151, FTraining = 390, FInvisible = 218, FCalibration = 240, RTest2 = 0.905) was selected to generate the studied promoters with increasing and decreasing activity.

Evaluating the inhibitory effects of Nitrobenzene short-term stress on denitrification performance: Electron behaviors, bacterial and fungal community

Denitrifying system is a feasible way to remove nitro-aromatic compounds (NACs) in wastewater. However, the toxicity and mechanisms of NACs to denitrification remain unknown. This study investigated effects of nitrobenzene (NB, a typical NAC) on denitrification in short term. Results showed that NB in 10-50 mg/L groups decreased NO3--N removal efficiency by 9%-24%, but increased nitrous oxide (N2O) generation by 6-17fold. Mechanistic research indicated that NB could deteriorate electron behaviors and disturbed enzyme activities of microbial metabolism and denitrification, leading to a decline in denitrification performance. Structural equation modeling revealed that N2O reductase activity was the core factor in predicting denitrification performance at exposure of NB, with the indirect effects of NADH and electron transport system activity. High-throughput sequencing analysis demonstrated that NB had made an alteration on both bacterial and fungal community structure, as well as their interactions.

Phytotoxicity of nitrobenzene bioaccumulation in rice seedlings: Nitrobenzene inhibits growth, induces oxidative stress, and reduces photosynthetic pigment synthesis

Nitrobenzene (NB) has been used in numerous industrial and agricultural fields as an organic compound intermediate. NB has mutagenicity and acute toxicity, and is typically a toxic pollutant in industrial wastewater worldwide. To evaluate its phytotoxicity, we treated rice (Oryza sativa) with different concentrations of NB (0, 5, 25, 50, 75, and 100 mg L-1). NB inhibited growth indices of rice (shoot and root length, fresh shoot and root weight, and dry shoot and root weight) as NB treatment concentrations increased. High concentrations (>25 mg L-1) of NB significantly inhibited rice root and shoot growth; root growth was more susceptible to NB. NB treatment could damage the structure and reduce the activity of rice seedling roots. The result of high performance liquid chromatography (HPLC) indicated that the bioaccumulation of NB in rice seedlings had a dose-dependent effect on the growth inhibition. NB reduced the photosynthetic pigment content and the expression levels of chlorophyll synthesis genes. NB treatment increased active oxygen radicals, electrical conductivity, malondialdehyde (MDA), proline, and soluble sugar contents. The expressions of antioxidant enzyme genes were induced by NB stress, and exhibited a phenomenon of initial increase followed by decrease. When the NB concentration was higher than 50 mg L-1, the gene expression levels decreased rapidly. This study provides insight into the association between exposure to NB and its phytotoxic effects on rice seedlings, and assesses the potential risk of NB bioaccumulation for crops that require a large amount of irrigation water.

Mechanism of quinone mediators modified polyurethane foam for enhanced nitrobenzene reduction and denitrification

The nitrobenzene (NB) reduction and denitrification performance of the immobilized biofilm (I-BF) reactors based on 9,10-anthraquinone-2-sulfonyl chloride (ASC) modified polyurethane foam (PUF-ASC) carriers were investigated. Experiments demonstrated that the quinone mediators enhanced NB reduction and denitrification performance. The NB reduction rates increased by 1.46, while the NO3--N removal rates increased by 1.55 times in the PUF-0.1ASC system. The quinone mediators promote extracellular polymeric substances (EPS) secretion. Electrochemical tests indicated that quinone mediators enhanced the electron transfer of biofilm systems. NADH generation was accelerated and microbial electron transport system activity (ETSA) was promoted. The abundance of genera with electrochemical activity, NB degradation and denitrification ability (Pseudomonas sp., Diaphorobate sp., and Acinetobacter sp.) increased. Metabolic pathways relating to NO3--N and NB reduction were uploaded. In conclusion, electron acquisition by NO3--N and NB was facilitated, bacterial community structure and metabolic pathways were affected by the quinone mediators.

Research on the electrochemical treatment of nitrobenzene wastewater: The effects of process parameters and the mechanism of distinct degradation pathways

Nitrobenzene is a typical organic pollutant of petroleum pollutant, which is a synthetic chemical not found naturally in the environment. Nitrobenzene in environment can cause toxic liver disease and respiratory failure in humans. Electrochemical technology provides an effective and efficient method for degrading nitrobenzene. This study, the effects of process parameter (e.g., electrolyte solution type, electrolyte concentration, current density and pH) and distinct reaction pathways for electrochemical treatment of nitrobenzene were investigated. As a result, available chlorine dominates the electrochemical oxidation process compared with hydroxyl radical, thus the electrolyte of NaCl is more suitable for the degradation of nitrobenzene than that of Na2SO4. The concentration and the existence form of available chlorine were mainly controlled by electrolyte concentration, current density and pH, which directly affect the removal of nitrobenzene. Cyclic voltammetry and mass spectrometric analyses suggested that electrochemical degradation of nitrobenzene included two important ways. Firstly, single oxidation: nitrobenzene → other forms of aromatic compounds→ NO-x + organic acids + mineralization products. Secondly, coordination of reduction and oxidation: nitrobenzene → aniline→ N2 + NO-x + organic acid + mineralization products. The results of this study will encourage us to further understand the electrochemical degradation mechanism of nitrobenzene and develop the efficient processes for nitrobenzene treatment.

Optical Sensing Capability Evaluation for Methylammonium Based Perovskites for Explosive

Here, we have synthesized methylammonium based two metal halide perovskites (MHP) such as MAPbBr3, and MAPbI3 using methylammonium bromide, methylammonium iodide, lead bromide, respective at room temperature under certain experimental conditions. All synthesized MHPs have been confirmed through X-ray diffraction technique (XRD), scanning electron microscope (SEM), Fourier transform infra-red (FTIR) and photoluminescence (PL) analysis. Afterward, comparative evaluation on optical sensing capability has been made for both MHPs using PL in different solvents. Importantly, we find out that MAPbBr3 exhibit an excellent optical feature over MAPbI3 in hexane only. Afterward, MAPbBr3 has also been explored to know the sensing capability for nitrobenzene sensing. Our model study confirms that MAPbBr3 is an excellent sensing material with R square (0.87), selectivity (16.9%) and Stern Volmer constant (Ksv=10- 2 × 0.464) for nitrobenzene in hexane.

AIEE active J-aggregates of naphthalimide based fluorescent probe for detection of Nitrobenzene: Combined experimental and theoretical approaches for Non-covalent interaction analysis

A new naphthalimide-based fluorescent probe NS with exceptional J-aggregates based aggregation-induced emission enhancement (AIEE) properties was rationally synthesized through a single-step imidation reaction. Probe NS exhibited excellent AIEE properties in aqueous media through the formation of J-aggregates with remarkable red-shift. The AIEE active probe NS was used for selective and sensitive detection of nitrobenzene (NB) based on fluorescence quenching response. Formation of J-aggregates was assessed through fluorescence titration. These J-aggregates contributed significantly to produce favorable interaction between probe NS and NB. The highly selective fluorescence detection of NB was accredited to the adjustable smaller size of NB that can easily penetrate into interstitial spaces of probe molecules. Ability of sensor to detect NB in solid state was also accomplished through solid state fluorescence spectroscopy. Nature of interaction and sensitivity of probe NS for NB has also been investigated through ¹H NMR titration and density functional theory (DFT) including non-covalent interaction (NCI), quantum theory of atom in molecule (QTAIM), electron density differences (EDD), frontier molecular orbitals (FMO) and density of states (DOS) analysis. Advantageously, probe exhibited colorimetric and vapor phase detection of NB. Moreover, probe was quite sensitive for the trace detection of NB in real samples.

Graphene Encapsulated Low-Load Nitrogen-Doped Bimetallic Magnetic Pd/Fe@N/C Catalyst for the Reductive Amination of Nitroarene Under Mild Conditions

Aniline is a group of important platform molecules that has been widely used in the synthesis of other high-value chemicals and pharmaceutical products. How to produce high-value anilines as the high-value chemical intermediates more efficiently and environmentally has always been a research topic in the industry. Catalytic hydrogenation is an environmentally friendly method for preparing halogenated anilines. Traditional noble metal catalysts face the problems of cost and noble metals residue. To improve the purity of the product as well as the activity and recyclability of the catalyst, we prepared a Pd/Fe magnetic bimetallic catalyst supported on N-doped carbon materials to reduce nitrobenzene to aniline under mild conditions. The catalyst has a low Pd loading of 2.35%. And the prepared bimetallic Pd/Fe@N/C catalyst showed excellent catalytic reactivity with the nitrobenzene conversion rate of 99%, and the aniline selectivity of 99% under mild reaction conditions of 0.8 MPa H2 and 40 °C. A variety of halogenated and aliphatic nitro compounds were well tolerated and had been transformed to the corresponding target amine products with excellent selectivity. In addition, the novel N-doped graphene-encapsulated bimetallic magnetic Pd/Fe@N/C catalyst not only had magnetic physical properties, which was easy to separate, recover, and used for the recycling of the catalyst without metal leaching but also catalyzed highly selective reductive amination of aromatics was a green, economical and environmentally friendly reaction with the only by-product of H2O.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s10562-023-04273-7.

Surfactant-enhanced reduction of soil-adsorbed nitrobenzene by carbon-coated nZVI: Enhanced desorption and mechanism

The reduction process of pollutants by nano zero-valent iron (nZVI) is limited by mass transfer and its effective utilization, and previous studies have ignored the electron loss caused by its oxidative passivation. The carbon-coated structure can effectively inhibit the oxidation of nZVI, but the effectiveness of carbon-coated nZVI (Fe⁰@C) as a reducing agent in soil remediation is unclear. Therefore, in this study, the Fe⁰@C/surfactant system was used to remove soil-adsorbed nitrobenzene (NB) to simultaneously enhance the mass transfer process and effective utilization of nZVI. The results showed that the use of surfactants effectively promoted the desorption of NB adsorbed by the soil, and the desorption process was affected by factors such as the type and concentration of surfactants, water-soil ratio, and soil organic matter (SOM) content. The enhanced desorption of NB by the surfactant in the soil system promoted the effective contact between the composite and NB, thereby enhancing the reduction of NB by the composite. In addition, Fe⁰@C exhibited excellent performance for the reduction of soil-adsorbed NB compared with the conventional nZVI, and this advantage was more obvious in the potting soil system. However, the composite will be gradually passivated due to the alkaline environment during the reduction process, and this phenomenon was especially obvious in the campus soil system. When the pH value decreased from 9 to 3, the proportion of aniline (AN) generated in the campus soil system increased from 19.37 % to 69.29 %. In addition, in potting soil systems with high SOM content, the adsorption of soil particles to the composite and the high dissolved organic matter (DOM) content resulting from the high SOM content also negatively affected the reduction process. The conclusions of this study demonstrate the great potential of the Fe⁰@C/surfactant system for in-situ contaminated site remediation applications.

A Luminescent Cu(II)-MOF with Lewis Basic Schiff Base Sites for the Highly Selective and Sensitive Detection of Fe3+ Ions and Nitrobenzene

A Schiff base functionalized Cu(II)-based metal-organic framework (MOF) denoted as Cu-L, was developed via a solvothermal method using low-cost starting material, i.e., Schiff base linker, 4,4'-(hydrazine-1,2-diylidenedimethylylidene)dibenzoic acid (L). Good crystallinity and thermal stability of synthesized Cu-L was confirmed by the crystallographic and thermogravimetric studies. An excellent photoluminescent properties of Cu-L ensure their suitability for the ultrafast detection of Fe³⁺ ions and nitrobenzene via a turn-off quenching response. The remarkable sensitivity of Cu-L towards Fe³⁺ ions and nitrobenzene was certified by the low limit of detection (LOD) of 47 ppb and 0.004 ppm, respectively. With incorporated free azine groups, this MOF could selectively capture Fe³⁺ ions and nitrobenzene in aqueous solution. The plausible mechanistic pathway for the quenching in the fluorescence intensity of the Cu-L in the presence of Fe³⁺ ions and nitrobenzene have been explained in detail through the density functional theory calculations, photo-induced electron transfer (PET), fluorescence resonance energy transfer (FRET), and competitive energy adsorption. This present study open a new avenue to synthesize novel crystalline MOF-based sensing materials from cheap Schiff base linkers for fast sensing of toxic pollutants.

Effect of sulfidation on nitrobenzene removal from groundwater by microscale zero-valent iron: Insights into reactivity, reaction sites and removal pathways

While it has been recognized that sulfidation can effectively improve the reactivity of microscale zero valent iron (mZVI), there is limited understanding of nitrobenzene (ArNO₂) removal by sulfidated mZVI. To understand the reduction capacity and pathway of ArNO₂ by sulfidated mZVI, ball-milling sulfidated mZVI (S-mZVI^bm) with different S/Fe molar ratios (0-0.2) was used to conduct this experiment. The results showed that sulfidation could efficiently enhance ArNO₂ removal under iron-limited and iron excess conditions, which was attributed to the presence of FeS_x sites that could provide higher Fe(0) utilization efficiency and stronger passivation resisting for S-mZVI^bm. The optimum ArNO₂ reduction could be obtained by S-mZVI^bm with S/Fe molar ratio at 0.1, which could completely transform ArNO₂ to aniline (ArNH₂) with a rate constant of 4.36 × 10^-2 min^-1 during 120-min reaction. FeS_x phase could act as electron transfer sites for ArNO₂ reduction and it could still be reserved in S-mZVI^bm after reduction reaction. The product distribution indicated that sulfidation did not change the types of reduction products, while the removal of ArNO₂ by S-mZVI^bm was a step-by-step reduction progress along with the adsorption of ArNH₂. In addition, a faster reduction of ArNO₂ in groundwater/soil system further demonstrated the feasibility of S-mZVI^bm in the real field remediation.

The chemical adsorption effect of surface enhanced Raman spectroscopy of nitrobenzene and aniline using the density functional theory

Nitrobenzene and Aniline are representatives of the nitro or amino compounds of benzene, mainly used in the manufacture of dyes, spices, medicines, and so on. Extensive use of Nitrobenzene and Aniline may cause pesticide residue pollution and have carcinogenic effects on organisms. In this paper, the Nitrobenzene and Aniline single molecules and their complexes with gold nanoparticles are studied theoretically by Raman spectroscopy, the surface-enhanced Raman spectroscopy (SERS) and the density functional theory (DFT) simulations. Selective binding of gold nanoparticles (AuNPs) to the analyte was used to study the molecular electrostatic potential (MEP), frontier molecular orbital (FMO) and the Raman activity spectra of Nitrobenzene and Aniline, as well as the Raman activity spectrum of the complexes. The most electronegative sites of Nitrobenzene and Aniline are found in the MEP and the hypothesis that these sites might be the adsorption sites of Nitrobenzene/Aniline molecules at the gold surface. At the same time, the MEP of the Nitrobenzene/Aniline complexes also prove the existence of the charge transfer effect between Nitrobenzene/Aniline and Au. The FMO energy gap of Nitrobenzene/Aniline is 0.18983 eV and 0.18953 eV, respectively, and which, after adding the Au₃ clusters, change to 0.03376 eV and 0.0797 eV, respectively, indicating that the Nitrobenzene/Aniline-Au₃ complexes have stronger chemical activities and are more prone to the charge transfer effects. The electrophilic indices of Nitrobenzene (0.17921 eV) and Aniline (0.05635 eV) are calculated and analyzed, as well as that of Nitrobenzene/Aniline-Au₃ complexes after adding the Au₃ atomic clusters, 0.80819 eV and 0.19819 eV, respectively. The obvious increasing trend in the electrophilic indices of the Nitrobenzene/Aniline-Au₃ complexes indicate their stronger biological activities and more prone to chemical reactions. The chemisorption of Nitrobenzene/Aniline and gold nanoparticles complexes is studied by the SERS, and the Raman formation of the complexes at different binding sites of Nitrobenzene/Aniline and Nitrobenzene/Aniline-Au₃ is well explained by the surface selection rule. The reason for the selective enhancement of the spectral peaks presented in the Raman activity spectrum is calculated, and the enhancement factor of the chemical enhancement due to the charge transfer effect is calculated as well. The reason for the peak offset in the SERS spectrum to the conventional Raman spectrum is explained.

Effects of different modifiers on the sorption and structural properties of biochar derived from wheat stalk

Nitrobenzene is a widespread contaminant in water. Biochar (BC) is a promising material for removing organic pollutants, but the adsorption capacity of pristine BC is low. Chemical modification is often used to improve the adsorption performance, but information on the sorption of nitrobenzene by modified BC is rare. In this study, BCs pyrolyzed at 300, 500, and 700 °C were modified by hydrochloric acid (HCl), sulfuric acid (H2SO4), sodium hydroxide (NaOH), hydrogen peroxide (H2O2), and nitric acid (HNO3), respectively. The properties, nitrobenzene sorption behaviors, and sorption mechanisms of different BCs were analyzed. The results showed that chemical modification decreased the sorption of nitrobenzene on BCs pyrolyzed at 300 °C, possibly due to the loss of the partition phase and the increase in polarity after modification. Regarding BCs pyrolyzed at 500 and 700 °C, the NaOH and HCl modifications significantly increased the sorption capacity by 19% and 60%, 18%, and 41%, respectively, possibly due to the increase in surface area, available pores, and aromaticity, while HNO3 modification decreased the sorption capacity by 41% and 31%. Two reasons were probably responsible for the decrease: one was the decrease in surface area after HNO3 modification due to the destruction of pore walls and the continuity of holes; the other was the strong repulsion between the nitro groups formed on the surface of BC and the nitro groups of nitrobenzene that drove nitrobenzene molecules away from the surface. A principal component-based comprehensive evaluation of the BC properties, which were significantly correlated with the sorption isotherm parameters, was used to evaluate the nitrobenzene sorption performance of the modified BC. Overall, BC pyrolyzed at 700 °C modified with NaOH or HCl were proposed as effective sorption materials for the removal of nitrobenzene in environment, which also provided a chemical modified method of biochar derived from agricultural waste.

Enhanced nitrobenzene removal in soil by biochar supported sulfidated nano zerovalent iron: Solubilization effect and mechanism

Sulfidated nano zerovalent iron (S-nZVI) is reported to be effective in removal of aqueous organic contaminants. However, little is known about its potential use in reductive degradation of soil-sorbed contaminants. In this study, biochar (BC) supported S-nZVI (S-nZVI@BC) was successfully synthesized through sulfidation and carbon loading modification, which effectively combined the solubilization characteristics of BC and high reduction characteristics of S-nZVI. Transmission electron microscopy (TEM) with an energy-dispersive X-ray spectroscopy (EDS) analysis suggested that sulfur and iron were evenly distributed throughout BC matrix. The degradation of nitrobenzene (NB) in soil was achieved more efficiently with the as-synthesized S-nZVI@BC composites. Results indicated that S-nZVI@BC with S-nZVI/BC mass ratio of 3:1, dosage of 10 mg/g exhibited superior NB removal (98%) and aniline (AN) formation (90%) efficiency within 24 h without formation of other intermediates, higher than those of S-nZVI. Meanwhile, the surface FeS_X layer enhanced the antioxidant capacity of S-nZVI@BC and participated in the reduction of NB. The soil-sorbed NB decreased from 14% to 1.4%, indicating that the addition of BC played an important role in solubilization of NB from soil. Solubilization-reduction was the dominant mechanism for NB removal. This research indicated that S-nZVI@BC held the potential to enhance in-situ remediation of NB-contaminated soil.

Effects of Nitrobenzene's mass transfer at water-air interface

As a volatile organic compound, nitrobenzene has high vapor pressure and low boiling point, and it is very volatile when it enters the water body and enters the air. The mass transfer of VOCs at the water-air interface is a complex process of transboundary transport. In this paper, the effects of water temperature, interface turbulence, surfactant concentration, and humic acid concentration on the volatilization of nitrobenzene at the water-air interface were investigated. Under the influence of temperature, the volatilization of nitrobenzene accorded with the first-order kinetic equation. When the temperature increased from 5 ℃ to 25 ℃, the volatilization rate of nitrobenzene increased by 2.03 times. Temperature for volatilization rate constant was in accordance with the Arrhenius equation. The water-gas distribution of volatile organic compounds was in accordance with the Boltzman equation. Under the same temperature conditions, when the agitating intensity increased from 0 r/min to 250 r/min, the volatilization rate constant of nitrobenzene increased by 1.51 times. When the surfactant is greater than the critical micelle concentration, the volatilization rate constant of nitrobenzene decreases with the increase of surfactant. When the concentration of humic acid increased from 100 mg/L to 500 mg/L, the half-life increased by 1.14 h, and the volatilization rate decreased by 1.14 h, reduced by 17%. The results showed that the increase of temperature and the intensification of stirring had a significant promoting effect on the volatilization of nitrobenzene, while the surfactant and humic acid both played an inhibitory effect on the volatilization of nitrobenzene.

Facile fabrication of Tb3+-functionalized COF mixed-matrix membrane as a highly sensitive platform for the sequential detection of oxolinic acid and nitrobenzene

A novel Tb³⁺-functionalized covalent organic framework-based polymer mixed-matrix membrane (Tb³⁺@COF MMM) has been successfully fabricated by incorporating the highly stable Tb³⁺@PI-COF as filler into polyvinylidene fluoride (PVDF) solution. Compared with pure COF membrane, MMM exhibits its good flexibility, processability and high detection sensitivity. The obtained Tb³⁺@COF-MMM (M) can be employed as a highly sensitive sensing platform for the sequential detection of oxolinic acid (OA) and nitrobenzene (NB) based on a "off-on-off" process. M has performed its great selectivity, high sensitivity, and low detection limit for detecting OA with "turn-on" mechanism. Moreover, owing to the good chemical stability and anti-interference of M sensor, it is prospective to efficiently detect residues of OA in serum or river water. After the detection of M-15 toward OA, the obtained fluorescent M-15/OA exhibits the rapid quenching, facile manipulation, cycling utility and low detection limits for sensing NB solution and vapor. This work has proposed a typical case of developing flexible Ln³⁺-functionalized COF-based polymer mixed-matrix membrane as a highly sensitive sensing platform for detecting OA and NB, simultaneously revealed the applied potentiality of M for monitoring animal health and environmental pollution.

Information encryption, highly sensitive detection of nitrobenzene, tetracycline based on a stable luminescent Cd-MOF

A stable luminescent Cd-MOF, formulated as [Cd(L)_0.5(4, 4'-bpy)_0.5]·H₂O (1), (H₄L = 1, 1'-ethylbiphenyl -3, 3', 5, 5'- tetracarboxylic acid, 4, 4' -bpy = 4, 4'-bipyridine), is acquired under solvothermal conditions. 1 exhibits stability in the pH range from 1.5 to 12.2 and in different organic solvents. 1 can detect tetracycline and nitrobenzene by fluorescence quenching with high sensitivity and selectivity. The detection limits are 0.14 μM and 14 nM, respectively. Interestingly, 1 can encapsulate Tb³⁺ and sensitize its characteristic peaks. Moreover, the fluorescent ink is prepared by using the luminescent properties of the Tb³⁺@Cd-MOF. The light of the fluorescent ink disappears in an acid gas HCl atmosphere and then reappears in an alkaline gas ammonia atmosphere. This phenomenon can be repeated and the reason for this phenomenon is also explained in the article. Therefore, Tb³⁺@Cd-MOF has huge application potential in information encryption.

Rapid and sensitive determination of nitrobenzene in solutions and commercial honey samples using a screen-printed electrode modified by 1,3-/1,4-diazines

In this work, a screen-printed electrode (SPE) modified by 1,3/1,4-diazines was prepared for the rapid and sensitive determination of nitrobenzene (NB). The obtained results indicated enhanced cathodic currents of direct NB reduction into hydroxylaminophenol on the diazine-modified SPEs. The enhanced effect was most likely due to the combination of complexation and collisional processes of diazines towards nitroaromatic compounds and also the diazine-modified electrodes' increased electroconductivity. The best electrochemical responses were obtained in square wave voltammetry mode by using the carbazolyl substituted diazines as a component of the sensitive layer, which was assembled by co-electropolymerization with the unsubstituted carbazole on the electrode during 5 cycles. The low detection limit estimated as 0.107 μM and wide linear range (1-1000 µM) enables NB in water and food samples to be determined. The developed modified electrode was applied in the analysis of commercial honey samples.

Aquifer flushing using a SDS/1-butanol based in-situ microemulsion: Performance and mechanism for the remediation of nitrobenzene contamination

In-situ microemulsion flushing is an effective remediation technology for the removal of dense non-aqueous phase liquids (DNAPLs) from aquifers. Nitrobenzene (NB) is a typical DNAPL pollutant that is responsible for the serious contamination of many groundwater systems, while its removal using the flushing method has rarely been studied. In this study, bench scale, 1-D column and 2-D tank experiments were conducted to establish an efficient salt-free sodium dodecyl sulfate (SDS)/1-butanol based in-situ microemulsion flushing system for NB contaminated aquifers. Results showed that the NB/SDS/1-butanol/water microemulsion increased dissolved NB concentrations by more than 15-fold compared to the SDS-only solution. The formulation also presented good solubilization capacity at low temperature (5 ℃) and with clay media. NB was effectively removed from the aquifer by solubilization and mobilization via the formation of the microemulsion with the injected SDS/1-butanol solution. The flushing system also reduced the tailing phenomenon in later remediation stages, and exhibited weak reagent adsorption onto aquifer media. Furthermore, the vertical DNAPL migration to deeper aquifer was effectively controlled. Therefore, the constructed in-situ microemulsion flushing system is a highly efficient treatment method for NB contaminated aquifers, with this study providing valuable reference information on the optimal reagent parameters and the remediation mechanism.

Selective activation of TRPA1 ion channels by nitrobenzene skin sensitizers DNFB and DNCB

2, 4-dinitrofluorobenzene (DNFB) and 2, 4-dinitrochlorobenzene (DNCB) are well known as skin sensitizers that can cause dermatitis. DNFB has shown to more potently sensitize skin; however, how DNFB and DNCB cause skin inflammation at a molecular level and why this difference in their sensitization ability is observed remains unknown. In this study, we aimed to identify the molecular targets and mechanisms on which DNFB and DNCB act. We used a fluorescent calcium imaging plate reader in an initial screening assay before patch-clamp recordings for validation. Molecular docking in combination with site-directed mutagenesis was then carried out to investigate DNFB and DNCB binding sites in the TRPA1 ion channel that may be selectively activated by these tow sensitizers. We found that DNFB and DNCB selectively activated TRPA1 channel with EC₅₀ values of 2.3 ± 0.7 μM μM and 42.4 ± 20.9 μM, respectively. Single-channel recordings revealed that DNFB and DNCB increase the probability of channel opening and acts on three residues (C621, E625 and Y658) critical for TRPA1 activation. Our findings may not only help explain the molecular mechanism underlying the dermatitis and pruritus caused by chemicals like DNFB and DNCB, but also provide a molecular tool 7.5-fold more potent than the current TRPA1 activator allyl isothiocyanate (AITC) used for investigating TRPA1 channel pharmacology and pathology.

An in-situ bio-remediation of nitrobenzene in stimulated aquifer using emulsified vegetable oil

Widespread nitrobenzene (NB) contamination in groundwater requires an economical and effective remediation technology. In situ microbial reactive zone enhanced by injecting emulsified vegetable oil (EVO) is an effective method for remediating NB-contaminated groundwater, which can be reduced to aniline (AN) effectively in the reactive zone. However, the bio-mechanism of NB remediation in a real contaminated site is still unclear. Thus, a 3-D tank was established to conduct a pilot-scale experiment and the bacterial communities in the tank were analyzed by 16S rDNA high-throughput sequencing. The results suggested that the injection of EVO can stimulate some certain microorganisms to grow, and reduce NB though biological and biochemical processes. There were three degradation pathways of NB: (1) direct oxidation by Pseudomonas; (2) direct mineralization by Clostridium sensu stricto; and (3) coupled reduction of NB through microbial dissimilatory iron reduction by Geobacter and Arthrobacter. Among these pathways, the coupled reduction process is the main degradation pathway.

Heterogeneous UV-Switchable Au nanoparticles decorated tungstophosphoric acid/TiO2 for efficient photocatalytic degradation process

In the present study, gold nanoparticles were locally well-decorated on the surface of TiO₂ using the tungstophosphoric acid (HPW), as UV-switchable reducing intermediate linkers. The prepared Au NPs/HPW/TiO₂ nanostructure was characterized using FTIR, XRD, EDS, SEM and TEM, which confirmed the successful attachment of quasi-spherical Au NPs in the range of 20-30 nm on the surface of HPW modified TiO₂. Also, the FTIR results show that the Au NPs were binded to TiO₂ through the terminal the oxygen atoms HPW. The photocatalytic performance of prepared nanostructures was assessed in degradation of nitrobenzene. The nitrobenzene photodegradation kinetic study revealed that it well followed the Langmuir-Hinshelwood kinetic model with the apparent rate constant of 0.001 min^-1 using anatase TiO₂, 0.0004 min^-1 using HPW, 0.0014 using HPW/TiO₂, while it was obtained 0.0065 min^-1 using Au NPs@HPW/TiO₂ nanostructure. It shows that the photocatalytic rate of the prepared nanocomposites increased by 6.5- and 4.6-fold compared to photoactivity of anatase TiO₂ and HPW/TiO₂ respectively. Also, the photocatalytic mechanism of process was proposed. Moreover, the reusability study confirmed that its photocatalytic activity still remained high after three cycles.

Role of the biochar modified with ZnCl2 and FeCl3 on the electrochemical degradation of nitrobenzene

The Zn/Fe-modified biochar on nitrobenzene (NB) removal during the electrolysis was investigated in this study. Both the Fe and Zn-modified biochar enhanced the NB adsorption compared with the un-modified biochar due to their greater specific surface area and more abundant surface function groups, respectively. The electrolysis under 2-11 V with the assist of both Fe/Zn-modified biochar achieved effective NB removal (>93%). The removal rate under 2 V using Zn/Fe-modified biochar (∼94%) was higher than that of the un-modified biochar (∼80%), whereas the removal was similar for those under 5, 8 and 11 V. The NB removal under 2 and 5 V was attributed to both adsorption and electrochemical decomposition of NB molecules. Electrolysis under 5 V by Fe-modified biochar had a higher degree of NB mineralisation than that using un-modified and Zn-modified biochar. This was likely that the Fe-modified biochar exhibited higher electrocatalytic properties, facilitating the further NB mineralisation. The ∙OH played significant roles in the degradation of NB by Fe-modified and un-modified biochar but did not significantly participated for the test using Zn-modified biochar. This was possibly because the Zn-modified biochar could adsorb greater amounts of ∙OH into the inner pores of Zn-modified biochar via its greater porosity and specific surface area, which may prevent the contact between ∙OH and NB molecules.

Carbon coating enhances single-electron oxygen reduction reaction on nZVI surface for oxidative degradation of nitrobenzene

Research on the in-situ generation of hydrogen peroxide (H₂O₂) using nano zero-valent iron (nZVI) has received more and more attention in recent years. However, the low utilization rate of nZVI, strict production conditions, and high energy consumption limit the application of this technology in actual environmental pollution remediation. In this study, carbon-coated nZVI (Fe⁰@C) was used to synthesize H₂O₂ in situ and realize the mineralization of nitrobenzene (NB). The results showed that the composite removed 91% of NB through adsorption, reduction, and oxidation within 120 min, of which oxidation accounts for 42.92%. Not only that, the composite material could achieve effective mineralization of NB under the wide pH range of 3-7. Quantitative experiments of hydroxyl radicals (HO) showed that the composite could generate 185.64 μM HO in 120 min without any extra energy consumption. The carbon-coated structure effectively inhibits the formation of the passivation layer on the surface of the nZVI, thereby ensuring the high activity of the Fe⁰. In addition, the carbon coating strengthens the sequential single-electron transfer process by changing the oxygen reduction pathway on the surface of the nZVI, so that the Fe⁰ can efficiently generate HO through the superoxide radical (O₂^-) pathway under neutral conditions. This study provides a fundamental understanding of the in-situ synthesis of H₂O₂ to mineralize NB by carbon-coated nZVI.

Production of copper nanoparticles exhibiting various morphologies via pulsed laser ablation in different solvents and their catalytic activity for reduction of toxic nitroaromatic compounds

Comparative experiments were conducted to determine the effects of various solvents (i.e., deionized water, methanol, ethanol, 1-propanol, butanol, ethylene glycol, hexane, and acetonitrile) on the final compositions, morphologies, and catalytic activities of copper-based nanoparticles (NPs). The NPs were effectively synthesized by pulsed laser ablation (PLA) using a copper plate as the target. The obtained copper NPs were characterized utilizing various analytical techniques. It was established that the developed methodology allows for the production of NPs with different morphologies and compositions in a safe and simple manner. When laser ablation of a solid copper plate was performed in acetonitrile, the formation of copper(I) cyanide cubes was observed. On the other hand, in deionized water and methanol, spherical and rod-like particles of copper(I) and copper(II) oxide were detected, respectively. The catalytic activity of the prepared copper NPs in the reduction of aromatic nitro compounds, such as 4-nitrophenol and nitrobenzene, was also evaluated. A high k value was determined for the reduction over the copper(II) oxide NPs produced in methanol. Moreover, particles with graphitic carbon (GC) layers exhibited superior catalytic performance in the reduction of a hydrophobic substance, i.e., nitrobenzene, over the reduction of 4-nitrophenol. The enhanced catalytic activity of this catalyst may be due its unique surface morphology and the synergistic effects between the copper nanostructure and the GC layer. Lastly, a detailed reduction pathway mechanism for the catalytic reduction of 4-nitrophenol and nitrobenzene has been proposed.

Photocatalytic degradation of nitrobenzene in wastewater by persulfate integrated with Ag/Pb3O4 semiconductor under visible light irradiation

Nitrobenzene oxidation was executed utilizing an innovative method, in which Ag/Pb3O4 semiconductors irradiated by visible light were used for activation of persulfate into sulfate radicals. Batch mode experiments were accomplished to elucidate the effect of persulfate concentrations and Ag/Pb3O4 dosages on the nitrobenzene oxidation behaviors. The physicochemical properties of original and reacted Ag/Pb3O4 were illustrated by X-ray diffraction analyses, UV-Vis diffuse reflectance spectra, FE-SEM images, EDS analyses, photoluminescence spectra and X-ray photoelectron spectra, respectively. The main oxidant was hypothesized to be sulfate radicals, induced from persulfate caused by photocatalysis of Ag/Pb3O4. It was clearly reflected on the scavenging experiments with addition of benzene, ethanol and methanol individually. As far as degradation pathways concerned, nitrobenzene was essentially transformed into hydroxycyclohexadienyl radicals, and sequentially converted to 2-nitrophenol, 3-nitrophenol or 4-nitrophenol simultaneously. Denitration of nitrophenols gave rise to synthesis of phenol, followed with generation of hydroquinone and p-benzoquinone.

An ultra-sensitive electrochemical sensor of Ni/Fe-LDH toward nitrobenzene with the assistance of surface functionalization engineering

Hypersensitive detection of organic pollutions with high toxicity in drinking water always keeps its challenge in electroanalysis due to their low concentration and electrochemical redox inert. In this work, a novel nanomaterial modified electrode for the sensitive detection of nitrobenzene (NB) is presented, based on environmental friendly and cost-effective Ni/Fe layered double hydroxides functionalized with sodium dodecyl sulfate (Ni/Fe(SDS)-LDH). Such 2D layered composites were prepared and used to improve the sensitivity for NB detection, due to its good catalytic activity for NB reduction. Besides, the proposed electrode shows a remarkably promoted sensitivity to NB compared to Ni/Fe-LDHs modified one. It is because that the surface modifier SDS can provide more adsorption sites to significantly improve the adsorption of NB, which has been confirmed by the adsorption experiment and the characterization of Fourier transform infrared spectroscopy (FTIR). As a result, an impressive sensing behaviour is achieved at the proposed Ni/Fe(SDS)-LDHs modified electrode with a sensitivity of 15.79 μA μM^-1 cm^-2. This work provides a promising way to build more advanced nanomaterials to electrochemical detection of organic pollution based on energetically synergizing of adsorption by surface functionalization engineering.

The removal mechanism of nitrobenzene by the Cu-Fe/Carbon material under different aeration conditions

Zero-valent Cu-Fe bimetallic porous carbon materials were successfully applied to remediate organic wastewater. In this work, we successfully recycled the layered double hydroxides (LDHs) adsorbed with Orange II (OII) to form a zero-valent Cu-Fe bimetallic porous carbon material (CuFe/Carbon). The characterization results showed that CuFe/Carbon was a zero-valent Cu-Fe bimetallic porous graphene-like carbon material. In the course of the experiment, we found that aeration condition had a great influence on the activity of CuFe/Carbon. The removal efficiency of nitrobenzene (NB) was 100 % in nitrogen system and 48 % in air system. The active species of O₂^- and OH was formed under air condition, while there was no active species under nitrogen condition. NB was reduced to aniline directly under nitrogen condition. We proposed there were reduction and oxidation mechanisms under different aeration conditions. This work mainly investigated the conversion process of a novel material under different reaction conditions, which provided theoretical support for the removal of organic matters.

Quantifying bond strengths via a Coulombic force model: application to the impact sensitivity of nitrobenzene, nitrogen-rich nitroazole, and non-aromatic nitramine molecules

The quantification of bond strengths is a useful and general concept in chemistry. In this work, a Coulombic force model based on atomic electric charges computed using the accurate distributed multipole analysis (DMA) partition of the molecular charge density was employed to quantify the weakest N-NO₂ and C-NO₂ bond strengths of 19 nitrobenzene, 11 nitroazole, and 10 nitramine molecules. These bonds are known as trigger linkages because they are usually related to the initiation of an explosive. The three families of explosives combine different types of molecular properties and structures ranging from essentially aromatic molecules (nitrobenzenes) to others with moderate aromaticity (nitroazoles) and non-aromatic molecules with cyclic and acyclic skeletons (nitramines). We used the results to investigate the impact sensitivity of the corresponding explosives employing the trigger linkage concept. For this purpose, the computed Coulombic bond strength of the trigger linkages was used to build four sensitivity models that lead to an overall good agreement between the predicted values and available experimental sensitivity values even when the model included the three chemical families simultaneously. We discussed the role of the trigger linkages for determining the sensitivity of the explosives and rationalized eventual discrepancies in the models by examining alternative decomposition mechanisms and features of the molecular structures.

Performance of nitrobenzene and its intermediate aniline removal by constructed wetlands coupled with the micro-electric field

The degradation of nitrobenzene and its intermediate aniline from wastewater by constructed wetlands coupled with the micro-electric field (CW-MEF) technology was studied. The results showed that the CW-MEF system had good degradation. With the increase of influent concentration of nitrobenzene, the removal rate of the anode was excellent which remained above 86%, but the degradation of CW-MEF for COD decreased. In different stages, the power generation capacity was different. In the second stage, the power generation voltage reached 430 V and the average power density was 85.07 MW m^-3, while the maximum reached 87.47 MW m^-3. Through high-throughput sequencing analysis, the A1 sludge layer contained 36% of thick-walled bacteria and 20% of bacteroides, the A2 contained about 20% of campylobacter green, and the A3 contained 10% of green campylobacter, pachyphyte and bacteroides.

Eco-friendly synthesis of lignin mediated silver nanoparticles as a selective sensor and their catalytic removal of aromatic toxic nitro compounds

The development of an eco-friendly and reliable process for the production of nanomaterials is essential to overcome the toxicity and exorbitant cost of conventional methods. As such, a facile and green synthesis method is introduced for the preparation of lignin mediated silver nanoparticles (L-Ag NPs). This is produced by reducing Ag precursors using lignin biopolymers which are formulated by pulsed laser irradiation and an ultrasonication process. Lignin operates as both a reducing and stabilizing agent. The various analytical techniques of ultraviolet-visible spectroscopy, transmission electron microscope and X-ray diffractometer studies were employed to verify the formation of non-aggregated spherical L-Ag NPs with an average size as small as 7-8 nm. The selective sensing capability of the synthesized L-Ag NPs was examined for the detection of hydrogen peroxide and mercury ions in an aqueous environment. Furthermore, the superior catalytic performance of L-Ag NPs was demonstrated by the rapid conversion of toxic 4-nitrophenol and nitrobenzene as targeted pollutants to the corresponding amino compounds. A plausible catalytic reduction mechanism for the removal of toxic nitro-organic pollutants over L-Ag NPs is proposed. This research coincides with existing studies and affirms that L-Ag NPs are an effective sensor that be applied as a catalytic material within environmental remediation and also alternative biomedical applications.

Sulfide-induced reduction of nitrobenzene mediated by different size fractions of rice straw-derived black carbon: A key role played by reactive polysulfide species

Here we investigated the mediation efficiency of different size fractions of rice straw-derived black carbon (BC) using sulfide-induced nitrobenzene reduction as a model system. The bulk BC was divided into three size fractions: dissolved BC (size <0.45 μm), colloidal BC (0.45 μm < size < 1 μm), and particulate BC (size > 1 μm). With the presence of BC fractions (250 mg/L) nitrobenzene reduction by Na₂S was significantly facilitated, wherein the mediation efficiency was positively correlated with the BC fraction's oxygen group content in an order of particulate BC < colloidal BC ≪ dissolved BC. Consistently, the oxidation treatment of particulate BC with O₃ or HNO₃ improved the mediation efficiency, whereas the reduction treatment with NaBH₄ reduced the mediation efficiency. The supernatant collected with dialysis or filtration of suspension of BC materials pre-reacted with Na₂S could effectively reduce nitrobenzene, suggesting that reactive reducing sulfur species were produced in aqueous solutions by reacting sulfide only with BC materials. This was evidenced by the fact that polysulfides and polysulfide radicals were both detected in the supernatant. As demonstrated by electron paramagnetic resonance analysis, the quinone moieties at the surface of BC materials accepted electrons from sulfide and turned into semiquinone free radicals, consequently leading to formation of reactive reducing sulfur species and thus enhanced nitrobenzene reduction. The strong mediation efficiency on redox reactions observed for colloidal BC and dissolved BC combined with their significant mobility in subsurface environments indicate that these carbonaceous materials may play an important role in the fate process of organic contaminants as both carriers and catalysts. CAPSULE: The surface quinone moieties of BC induce the formation of reactive reducing sulfur species by acting as one-electron acceptors and facilitate nitrobenzene reduction by sulfide.

Neuroprotective mechanism of Vernonia amygdalina in a rat model of neurodegenerative diseases

The global upsurge in the prevalence of neurodegenerative diseases in recent years has been associated with increase in toxic chemical exposure and release into the biosystem, having over 46.8 million people suffer dementia worldwide. This study focused on elucidating the neuroprotective mechanism of methanol leaf extract of Vernonia amygdalina (MLVA) in nitrobenzene-induced neurodegenerative disease in rats. Thirty aged male rats were sorted into five groups of six rats each. Group A received distilled water while 100 mg/kg bw of nitrobenzene was orally administered to groups (B to E) to induce neurodegeneration. Group B (disease control) was untreated, while Group C and D were treated with oral administration of 200 and 400 mg/kg bw of MLVA respectively and group E with vitamin E for 14 days. Locomotor behaviour was analysed using video-tracking software while the midbrain, cerebrum and cerebellum of the rats were processed for biochemical analyses. Results showed that treatment of nitrobenzene-induced neurodegenerative rats with MLVA significantly (p < 0.05) increase dopamine, GSH, antioxidant enzymes levels; and decrease acetylcholinesterase activity, biomarkers of inflammatory and oxidative stress level. Also, MLVA enhanced neurobehavioural and locomotor activities in all markers assessed. Taken together, neuroprotective mechanisms of MLVA can be linked to its antioxidant, acetylcholinesterase suppression, lipid peroxidation inhibition, anti-inflammatory and neurobehavioural restoring abilities.

Management of nitrobenzene poisoning with oral methylene blue and vitamin C in a resource limited setting: A case report

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Though intravenous methylene blue is a well established treatment modality for methhaemoglobinemia, there is limited experience with oral preparation.

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Oral methylene blue was used successfully in a case of nitrobenzene poisoning since intravenous preparation was not available in our setting.

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An oral dose of 2 mg/kg has been found to be safe and effective for other disease conditions. We too successfully managed the patient with this oral dose.

Nitrobenzene can cause life threatening methaemoglobinemia. Its management includes the use of intravenous methylene blue to reduce the iron moiety from its ferric to ferrous state. Due to unavailability of intravenous preparation, enteral methylene blue was used in our case. This case report is to highlight that even oral preparations can be successfully used in a resource limited setting where often intravenous preparations are unavailable.

Optimization ofS/Fe ratio for enhanced nitrobenzene biological removal in anaerobicSystem amended withSulfide-modified nanoscale zerovalent iron

Anaerobic reduction of nitrobenzene (NB) can be efficiently enhanced bySupplementing withSulfide-modified nanoscale zerovalent iron (S-nZVI). In thisStudy,S/Fe ratio ofS-nZVI was further optimized for enhancing biological NB removal in anaerobicSystem amended withS-nZVI and inoculated by anaerobicSludge. The results indicated that the performance andStability of the coupled anaerobicSystem for NB reduction and aniline formation were remarkably improved byS-nZVI atS/Fe molar ratio of 0.3 (0.3S-nZVI). TheSecretion of extracellular polymericSubstances (EPS), transformation of volatile fatty acids (VFAs), yield of methane and activity ofSeveral key enzymes could be efficiently improved by 0.3S-nZVI. Furthermore,Species related to NB reduction, fermentation, electroactivity and methanogenesis could be enriched in 0.3S-nZVI coupled anaerobicSystem, with remarkable improvement in the biodiversity observed. ThisStudy demonstrated thatSulfidation would be a promising method to improve the performance of nZVI in coupled anaerobicSystems for the removal of recalcitrant nitroaromatic compounds from wastewater.

Rapid aerobic visible-light-driven photo-reduction of nitrobenzene

Many strategies have been proposed to treat wastewater containing toxic contaminants, such as nitrobenzene, prior to discharge. Most of these degradation processes, especially biodegradation, undergo a limited step of nitrobenzene reduction into aniline and a subsequent fast step of aniline mineralization. The low efficiency of nitrobenzene reduction and the requirement of an anaerobic atmosphere limit the overall degradation performance. In this communication, eosin Y is reported as a potential homogeneous catalyst for the rapid photoreduction of nitrobenzene under aerobic conditions. As a result, a conversion (~10 min) of nitrobenzene (25 mg/L) into aniline driven by visible light was achieved. The reduction rate constants under aerobic conditions (0.30 min^-1) were even slightly higher than those under anaerobic conditions (0.28 min^-1), and the lifetime of the catalytic system was extended. Furthermore, the mechanism of nitrobenzene transformation was speculated based on the identification of intermediate products. To provide guidance for the practical application of this pretreatment strategy, the impact of pH value and widely existing heavy metal ions on photoreduction were also demonstrated. The results from this work provide a novel insight into the integrated control of organic pollutants produced in chemical industries.

Facile sonochemical synthesis of Ag2O-guar gum nanocomposite as a visible light photocatalyst for the organic transformation reactions

Silver Oxide (Ag₂O)-Guar gum nanocomposite was fabricated via a simple sonochemical co-precipitation method. The obtained photocatalyst was characterized with various techniques such as X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, UV-vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, scanning electron microscopy and transmission electron microscopy along with energy dispersion X-ray spectroscopy. The findings have demonstrated that Ag₂O nanoparticles are spherical of 5-20 nm and were dispersed on the surface of polysaccharide guar gum to form Ag₂O-guar gum nanocomposite. The as-synthesized nanocomposite was enacted as a competent photocatalyst for the reduction of nitrobenzene and oxidation of benzyl alchohol. The conversion efficiency for the reduction of nitrobenzene was 96 % with the addition of sodium borohydride, and the conversion of benzyl alcohol was 98 %. The highly efficient photocatalytic activity was due to the exceedingly dispersed Ag₂O-guar gum nanocomposite where effective separation rate of energy driven electron-hole pairs and stronger light absorption occurs. The possible mechanism of the reactions was implicated in understanding the active species involved in the photocatalytic study.

A dual mode photoelectrochemical sensor for nitrobenzene and L-cysteine based on 3D flower-like Cu2SnS3@SnS2 double interfacial heterojunction photoelectrode

In this work, 3D hierarchical Cu₂SnS₃@SnS₂ flower assembled from nanopetals with sandwich-like Cu₂SnS₃-SnS₂-Cu₂SnS₃ double interfacial heterojunction was successfully designed and synthesized on fluoride doped tin oxide (FTO) for photoelectrochemical (PEC) sensor by in situ electrodeposition p-type Cu₂SnS₃ nanoparticles on both inner and outer surfaces of n-type SnS₂ nanopetals. The unique double interfacial heterojunction simultaneously combines 3D flower-like architectures to drastically increase the light trapping and absorption in visible-near infrared range (Vis-NIR), and dramatically inhibites the charge carrier recombination, which is crucial for boosting the PEC activity. Benefitting from the shape and compositional merits, the Cu₂SnS₃@SnS₂ heterojunction possess dual-mode signal by controlling the electrodeposition time to manipulate the composition ratio of Cu₂SnS₃ and SnS₂. The Cu₂SnS₃@SnS₂/FTO electrode not only exhibits excellent photoeletro-reduction capacity for ultra-sensitive sensing trace persistent organic pollutant (nitrobenzene, NB), but also presents photoeletro-oxidization activity for high selective detection of L-cysteine (L-Cys) without any auxiliary enzyme under the light illumination. Dual mode sensor displayed superb performance for the detection of NB/L-Cys, showing a wide linear range from 100 pM to 300 μM/10 nM to 100 μM and a low detection limit (3S/N) of 68 pM/8.5 nM, respectively. Such a tunable double interfacial heterojunction design opened up new avenue for constructing multifunction PEC sensing platform.

Enhancing nitrobenzene biodegradation in aquatic systems: Feasibility of using plain soil as an inoculant and effects of adding ascorbic acid and peptone

Nitrobenzene (NB) is recalcitrant to microbial biodegradation due to the electron-deficient character of the nitro group (NO^2-). Prior work has found that the reductant could enhance NB biodegradation by providing excess electron donors. However, the existing theory couldn't explain the increase-and-decrease pattern of the NB biodegradation rate with an increase in a reductant concentration. Our results suggest that the reductant affects NB biodegradation by two mechanisms: the available electron donors and the stimulation or inhibition of biomass growth, which are linked by a pseudo-first-order reaction kinetics. In addition, the results showed that directly inoculating the plain soil into the aquatic system and then allowing the synergistic effect of the organic reductant (ascorbic acid) and the substrate (peptone) enhance NB biodegradation. Employing the new method, 200 mg L^-1 NB was transformed in 72 h. GC-MS analysis detected two novel intermediate metabolites, indicating that NB was degraded into aniline and further transformed into acetanilide and 9-octadecenamide before its mineralization. This study sheds light on how to exploit the synergistic effects of the availability of excess electron donors and biomass growth by controlling the reductant and a substrate in the right concentration range (e.g., ascorbic acid < 0.8 mgL^-1 + peptone).

Enhanced nitrobenzene reduction by modified biochar supported sulfidated nano zerovalent iron: Comparison of surface modification methods

In our previous study, biochar (BC) supported sulfidated nano zerovalent iron (S-nZVI@BC) was prepared for nitrobenzene (NB) reduction. In this study, in order to further improve the reduction performance of S-nZVI@BC, BC was modified before the loading of S-nZVI through three methods: oxidant (H₂O₂) pretreatment, alkali (NaOH) pretreatment and acid (HCl) pretreatment. The results indicated that S-nZVI could be evenly distributed onto HCl-BC due to increased surface area, negative surface charge and increased acidic functional groups on HCl-BC. At an initial concentration of 200 mg L^-1, NB could be completely removed by S-nZVI@HCl-BC within a reaction time as short as 60 min, indicating rather excellent performance of S-nZVI@HCl-BC. NB reduction performance followed the order: S-nZVI@HCl-BC > S-nZVI@NaOH-BC > S-nZVI@BC > S-nZVI@H₂O₂-BC. The mass ratio of S-nZVI and HCl-BC was optimized in terms of NB removal efficiency, with 3:1 being identified as the best mass ratio. Furthermore, the mechanism involved in the enhanced NB reduction by S-nZVI@HCl-BC was proposed. This study demonstrated that S-nZVI@HCl-BC is a promising alternative for efficient NB removal from wastewater.

In situ anodic induction of low-valence copper in electro-Fenton system for effective nitrobenzene degradation

To achieve superior advanced oxidation processes (AOPs), transitional state activators are of great significance for the production of active radicals by H₂O₂, while instability limits their activation efficiency. In this study, density functional theory calculation (DFT) results showed that Cu⁺ exhibits excellent H₂O₂ activation performance, with Gibbs free energy change (ΔG) of 33.66 kcal/mol, two times less than that of Cu²⁺ (77.83 kcal/mol). Meanwhile, an electro-Fenton system using Cu plate as an anode was proposed for in situ generation of Cu⁺. The released Cu with low-valence state can be well-confined on the surface of the exciting electrode, which was confirmed by X-ray photoelectron spectroscopy (XPS), Raman, and UV-vis spectroscopy. The hydroxyl radicals in this Cu-based electro-Fenton system were determined by the electron spin resonance (ESR). The nitrobenzene degradation ratio was greatly increased by 43.90% with the introduction of the proposed in situ electrochemical Cu⁺ generation process. Various characterization results indicated that the production of Cu⁺ was the key factor in the highly efficient Cu-based electro-Fenton reaction.

Substantially enhanced anaerobic reduction of nitrobenzene by biochar stabilized sulfide-modified nanoscale zero-valent iron: Process and mechanisms

Nanoscale zero-valent iron (nZVI), although being increasingly used in anaerobic systems for strengthening the removal of various refractory pollutants, is limited by various inherent drawbacks, such as easy precipitation, passivation, poor mass and electron transfer. To address the above issues, biochar stabilized sulfide-modified nZVI (S-nZVI@BC) was added into an up-flow anaerobic sludge blanket (UASB) to investigate the enhancement of anaerobic biodegradation of nitrobenzene (NB) and its impacts on microbial community structure. The results demonstrated that both NB reduction and aniline formation could be substantially facilitated in S-nZVI@BC coupled system compared to other anaerobic ones coupled with nZVI or S-nZVI. The dosage of S-nZVI@BC resulted in the formation of densely packed aggregates, evidently increased the extracellular polymeric substances content, promoted the volatile fatty acids transformation and stimulated the methane yield. Furthermore, species related to fermentation (Bacteroides and Longilinea), methanogenesis (Methanosarcina and Methanomethylovorans), electroactivity (Pelobacter, Thiobacillus and Phaselicystis) as well as reduction (Desulfovibrio) were considerably enriched in S-nZVI@BC coupled system. The activities of electron transport, total adenosine triphosphate, nitroreductase and NAD(P)H, which were closely related to microbial activity and NB transformation, were increased noticeably in S-nZVI@BC coupled anaerobic system. This study demonstrated the promising potential for long-term operation and full-scale application of S-nZVI@BC coupled system for the treatment of NB containing wastewater.

Sorption behaviors of phenanthrene, nitrobenzene, and naphthalene on mesoplastics and microplastics

The occurrence of plastic particles in aquatic environment has led to enormous concern in the past few years. The sorption behaviors of harmful organic compounds by plastic particles can increase their concentrations by several orders of magnitude influencing their global transport in the marine environment. Five types of mesoplastics (5-20 mm) and five types of microplastics (< 5 mm) were selected to investigate the sorption behaviors of three typical organic compounds (phenanthrene, nitrobenzene, and naphthalene). For phenanthrene, most microplastics have stronger sorption ability than that of mesoplastics due to the higher specific surface area (SSA). However, the sorption ability of nitrobenzene on low-density polyethylene (LDPE) mesoplastics was higher than that on LDPE microplastics, and the sorption ability of naphthalene on polyvinyl chloride (PVC) mesoplastics was higher than that on PVC microplastics, which were attributed to the presence of functional groups on the surface of mesoplastics, induced by adding slip agents, lubricant, plasticizer, stabilizer, etc. during film production. Talcum-filled polypropylene (PP) microplastics had strongest sorption ability to nitrobenzene and naphthalene due to the presence of talcum and high SSA. For unmodified microplastics, the sorption abilities of phenanthrene, nitrobenzene, and naphthalene were all followed the order of high-density polyethylene (HDPE) > polystyrene (PS) > LDPE > PVC after SSA normalization. Thus, SSA and the functional groups on the surface of plastic particles should be considered when the sorption behaviors of harmful organic compounds on plastic particles are studied.

Effects of glucose and starch on the toxicity of nitrobenzene to plants and microbes in constructed wetlands

Photosynthetic pigment content, antioxidant enzyme activities of plants, microbial enzyme activities and community structure were analyzed to investigate the effects of glucose and starch on the toxicity of nitrobenzene (NB) to plants and microbes in constructed wetlands (CWs). As the influent NB concentration increased from 10 mg/L to 100 mg/L, the NB removal efficiency of the blank group decreased from 97.1% to 75.02%. However, the NB removal efficiencies of the external carbon source groups were maintained at nearly 100%. External carbon sources accelerated the transformation process of NB to aniline (AN), thus decreasing NB toxicity to the microbes and plants. When the influent NB concentration reached 100 mg/L, the NB removal rates and NB reductase activities of the external carbon source groups were 2.4 times and 4 times higher, respectively, than those of the blank group. Most of the dominant genera found in the three CWs could reduce nitroaromatics to the corresponding aromatic amines according to the results of high-throughput sequencing. The performance of NB removal in the CWs indicated the potential of CWs for NB treatment and the necessity of external carbon sources under high NB concentrations.

Degradation of nitrobenzene by synchronistic oxidation and reduction in an internal circulation microelectrolysis reactor

The degradation of nitrobenzene by synchronistic oxidation and reduction was investigated using an internal circulation microelectrolysis (ICE) reactor with an active volume of 0.018 m³. Compared with a conventional fixed bed reactor with and without aeration, the ICE reactor exhibited a markedly higher nitrobenzene degradation efficiency. The effects of various operational parameters such as reaction time, aeration rate, initial nitrobenzene concentration, initial pH, and a volume ratio of iron and carbon (Fe/C) were also investigated. The optimal operating conditions (reaction time = 60 min, aeration rate = 5 × 10^-4 m³/s, initial concentration of nitrobenzene = 300 mg/L, pH = 3.0, Fe/C = 1:1) gave removal efficiencies of nitrobenzene and chemical oxygen demand of 98.2% and 58%, respectively. The biodegradability index of the treated nitrobenzene solution was 0.45, which is 22 times that of the original solution. The reaction intermediates were identified through high-performance liquid chromatography, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, and ion chromatography. The primary intermediates were determined to be aniline, phenol, and carboxylic acids, indicating that nitrobenzene was synchronously oxidized and reduced in the ICE reactor. Based on the identified intermediates, a possible pathway for nitrobenzene degradation in the ICE reactor is proposed.

Effective degradation of refractory nitrobenzene in water by the natural 4-hydroxycoumarin under solar illumination

In this study, nitrobenzene (NB) as typical refractory organic pollutants was effectively degraded by a new green approach, which was achieved by the chemical effect of natural organic matters (NOMs) under solar illumination as a potential natural degradation process. 4-hydroxycoumarin (4HC), which is natural compound and can be extracted from many plants, was found as an efficient photosensitizer to promote the photoreduction of NB to 4-aminophenol under the solar illumination. The reaction products were definitely identified by LC-MS/MS and ¹H NMR. The response spectrum of 4HC excited state (4H-chromene-2,4-diol radical, S₁) as key intermediate was also obtained by transient absorption spectroscopy (TAS) measurements, which showed that the decay time of S₁ was around 250 ps. Then, the measurements of electron paramagnetic resonance (EPR) confirmed the existence of OH. As a result, the reaction mechanism between 4HC and NB was proposed. In addition, the influence parameters such as light sources, gas surroundings, solvents, pH values were investigated to further reveal the reaction process.

Photoelectrocatalytic reduction of nitrobenzene on Bi-doped CuGaS2 films

Nitrobenzene, a toxic nitroaromatic, a feedstock compound to the production of many commercially relevant chemicals were photoelectrocatalytically reduced into aniline on a photoelectrode comprised by a bismuth-doped CuGaS₂ nanocrystallyne thin films on molybdenum. The activity of the photoelectrodes were compared to the reaction performed on undoped-CuGaS₂ films, and they were carried out under illumination with an applied bias potential at 0.9 V. Aniline was highly selectively obtained with 83% of conversion for reaction times of 100 min when using Bi-doped CuGaS₂, representing higher conversion of nitrobenzene and yield to aniline than the undoped photoelectrode. The catalytic performance of the doped films remained stable for a set of 5 consecutive experiments. These results indicate Bi-doped CuGaS₂ as a promising material to be applied in the photoelectrocatalytic reduction of nitrobenzene into aniline through the direct pathway mechanism, using solar light illumination.