Formation Of Aniline Research Articles

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 FeSX 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.

Evaluation of Nitrobenzene Hydrogenation Kinetic Particularities over Mono and Bimetallic Ni Containing Hypercrosslinked Polystyrene

Nitrobenzene hydrogenation is a widely used process applied for aniline production. Nitrobenzene hydrogenation kinetics greatly depends on catalyst properties and structure therefore, its study can shed light on process particularities and catalyst properties. The article is devoted to study of nitrobenzene hydrogenation kinetics for monometallic Ni (18.4 wt.%) containing hypercrosslinked polystyrene and bimetallic Pd(0.5 wt.%), Ni(17.9 wt.%) containing hypercrosslinked polystyrene. Nitrobenzene concentration and hydrogen partial pressure influence was studied in a variety of conditions. Nitrobenzene hydrogenation over monometallic sample shows the formation of essential amounts of side products - nitrozobenzene and phenylhydroxylamine while for bimetallic sample direct formation of aniline was noticed. Langmuir–Hinshelwood model was used to study reaction kinetics. A complex model including azobenzene, phenylhydrohylamine and aniline formation steps was developed for monometallic catalyst. The reaction model for bimetallic Ni, Pd catalyst contains only direct aniline formation reaction due to high process selectivity. Values of adsorption and reaction constants are higher for bimetallic catalyst that can explain its enhanced nitrobenzene hydrogenation rate.

Updated yields of nitrogenated species in flames of ammonia/benzene via introducing an aniline sub-mechanism

Ammonia and cyclic aromatic compounds are principal products from combustion of various fractions of biomass. Yet, kinetic mechanistic models on formation of NOx from biomass de-couple the oxidation mechanism of ammonia from that of aromatic molecules. Literature kinetic models do not consider a plausible formation of aniline as the initial product from the interaction of amine radicals and benzene molecules (as the simplest aromatic molecule). Such reaction acts a sink for NH2 radicals, and thus may alter the yields of NOx and HCN. To fill in this gap, this study reports production pathways of aniline from NH2 + benzene reactions, maps out unimolecular decomposition pathways of aniline and its derived anilino radical into, and explores the effect of the title reaction on the yields of small nitrogenated species from co-combustion of ammonia and benzene. We find that anilino radical to preferentially decompose into iso-HNC and a cyclopentadienyl radical. The resonance-stabilized structure of the anilino radical enables it to undergo bimolecular reaction with the aniline molecule to generate N-analogous compounds of dioxins, namely diphenylamine, carbazole, and phenazine. Detail kinetic modeling discloses that decomposition of aniline initiates at 1100 K with ammonia and HCN signify the most abundant N-bearing species at intermediates and high temperatures, respectively. Introducing the newly constructed aniline sub-mechanism in NOx + benzene kinetic model from the literature (i.e., CERCK model) alters predicted concentrations of principal N species within factors of 1.2- 2 between 1100–1300 K. It is hoped that reaction rate constants and mechanistic pathways presented herein to improve the predictive performance of kinetic models that address NOx and HCN emission from flames of ammonia and aromatic-containing fuels in general.

Visible‐Light Driven Ni‐Incorporated CdS Photocatalytic Activities for Azo‐Bond Cleavages with Hydrogenation Reaction

AbstractNi‐incorporated CdS (Ni‐CdS) photocatalysts with different amounts of Ni dopant have been synthesized, characterized, and examined toward azo‐bond cleavages in visible‐light illuminated conditions. The optimum performance was achieved with a relatively low amount of Ni dopant (2 % atomic mass). The azo bonds of azobenzene (AB) and methyl orange (MO) compounds were hydrogenated with the in‐situ generated hydrogen on Ni‐CdS catalyst surfaces. The hydrogen evolution reaction was proved and measured with GC measurement during the photocatalytic session with an incandescent halogen lamp. Furthermore, the experimental data of UV‐vis spectra analyses suggested the formation of aniline or sodium sulfanilate and p‐aminodimethylaniline with the emerged peaks at ∼240 nm, indicating azo‐bond has been cleaved in AB or MO compounds, respectively. The catalytic performances of 2 % Ni‐CdS are also supported with electrical and photoresponse analyses. To demonstrate the possibility of industrial application, Ni‐CdS catalyst stability is also tested for several runs in reusability experiments and examined with cyclic voltammetry for 100 cycles without any significant degradation. The cleavage mechanisms of azo bonds in AB and MO compounds were discussed and proposed in this work.

Изучение кинетических особенностей синтеза анилина на Ni-содержащем сверхсшитом полистироле

This paper presents a study of the kinetics of catalytic hydrogenation of nitrobenzene to aniline in the presence of Ni-containing catalysts based on super-crosslinked polystyrene. Aniline hydrogenation is a complex multi-stage process accompanied by the formation of a large number of both intermediate and by-products, including azobenzene, azoxybenzene, nitrosobenzene, phenylhydroxylamine and other substances. Therefor the study of the process kinetics is an important scientific and technical task necessary to increase the yield of the target product — aniline. The hydrogenation reaction of nitrobenzene was carried out in a six-cell high-pressure reactor Parr instruments, Series 5000. The products were analyzed by chromatography using a gas chromatograph Kristallux-4000M (Russia, Meta–Chrom). The effect of temperature, pressure, and concentration of the catalyst was studied; optimal reaction conditions were selected that ensure the maximum yield of aniline. Investigation of the effect of the nitrobenzene initial concentration on the rate of its transformation shows that increase of catalyst to nitrobenzene ratio from 0.2 to 0.6 kg (Cat)/kg (NB) leads to a linear increase in the rate of transformation of nitrobenzene from 0.0002 kg (NB) / (kg (Cat)*s ) to 0.0028 kg(NB)/(kg(Cat)*s), a further increase in the ratio of catalyst concentration to nitrobenzene concentration to 1.2 kg (Cat)/kg(NB) leads to stabilization of the nitrobenzene transformation rate at the level of 0.003 kg(NB)/(kg(Cat)*s). An increase in the temperature of the reaction from 90 to 160 °C contributes to a significant increase in the nitrobenzene transformation rate. The constructed dependences made it possible to calculate the apparent activation energy of the process, which amounted to be 50.4 kJ/mol and the preexponential factor, which amounted to be 15821.1 1/s. The applicability of the Langmuir–Henschelwood model to describe the basic kinetic laws of the reaction of catalytic nitrobenzene hydrogenation with the formation of aniline is studied. Numerical methods in the Matlab software allows to determine the values of preexponential factors and activation energies of the nitrobenzene hydrogenation processes, adsorption of nitrobenzene and adsorption of hydrogen, which made it possible to establish the optimal area of nitrobenzene hydrogenation process of hydrogenation of Pн2 = 15–18 atm, C(NB) = 1.2 kg(NB)/kg(Cat), t =115–120 °C providing maximum speed.

One‐Pot Generation of Benzynes from Phenols: Formation of Primary Anilines by the Deoxyamination of Phenols

Benzynes were selectively generated in-situ from phenols and trapped regioselectively by potassium hexamethyldisilazide to form primary anilines following acidic workup. The direct conversion of a phenolic hydroxyl group to a free amino group is a useful method for the preparation of primary aryl amines that are hard to synthesize using coupling reactions involving phenol derivatives with ammonia. While reactions of ortho - and meta -substituted phenols produced meta-substituted anilines exclusively, those of para -substituted phenols provided ortho -silylanilines.

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.

Sonication-assisted synthesis of a new heterostructured schiff base ligand Silver-Guar gum encapsulated nanocomposite as a visible light photocatalyst

A heterostructured Schiff base ligand (Benzildiethylenetriamine)-Silver-Guar gum encapsulated nanocomposites was intended to prepare by simple sonication assisted reflux method. Appropriate composition of purified guar gum, Schiff base ligand and silver nitrate were used for the synthesis. The synthesised nanocomposites were characterised by photoluminescence spectrum, UV-vis diffuse reflectance spectrophotometer, Fourier transform infra-red spectroscopy, X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. The crystalline peaks of XRD and FTIR reveals that Schiff base ligand and guar gum forms metal-organic matrix. Morphology studies have confirmed the organic framework structure and metallic silver nanoparticles are embedded on the organic framework. The efficiency of nanocomposites depends on adsorption capacity and silver nanoparticles that are encapsulated thereby increasing the visible light absorption through surface plasma resonance. The nanocomposite was proved to be highly selective in hydrogenation reaction which favoured the formation of aniline from nitrobenzene as single product with short reaction time and 90% conversion.

Mechanism of Current Oscillation during Simultaneous Reduction of Tin(II) Ions, Nitrate, and Nitrobenzene at Au Electrode

It has been reported [1] that the interfacial energy, or the interfacial tension, at Au electrode surface in H2SO4 solution increases when Sn2+ are reduced (Sn2+ + 2e- → Sn), i.e., when Sn is electrodeposited on the electrode surface. The increase in the interfacial energy was attributed to the reaction intermediates of the electrodeposition (namely, Sn adatoms on the surface), and induced a lateral motion of a nitrobenzene (NB) droplet that was put on the electrode (see Figure 1a). The driving force inducing the droplet motion was an imbalance of the interfacial tension acting on the droplet, and the droplet spontaneously moved toward the area where the interfacial tension was relatively high. In our previous work [2], we showed that one of the factors creating the imbalance was the occurrence of hydrogen evolution reaction near the rear side of the droplet. When the reduction of Sn2+ was conducted in HNO3 solution, the NB droplet moved on the surface in a different manner, namely, it moved like an amoeba, because a liquid flow was induced by a decrease in the interfacial tension at nitrobenzene/electrolyte interface [3]. The flow, known as the Marangoni effect, was attributed to the simultaneous reduction of NO3 - and NB at the electrode. The nitrate reduction occurred on the Sn atoms deposited on the Au surface, whereas the NB reduction (C6H5NO2 + 6H+ + 6 e- → C6H5NH2 + 2H2O), i.e., the formation of aniline (AN), occurred in the vicinty of the NB droplet. Although the NB reduction was not the main current-producing reaction, it played an important role in the Marangoni effect because the AN produced by the reduction decreased the interfacial tension at the NB droplet/HNO3 solution interface. Interestingly, the reduction current oscillated spontaneously during the simultaneous reduction of Sn2+, NO3 -, and NB. Figure 1b shows a waveform of the current oscillation which was observed when the electrolyte solution was 1.1 M HNO3 + 5 mM SnSO4. In general, most of electrochemical oscillations require the existence of an N-shaped negative differential resistance (N-NDR) characteristic. The mechanism of oscillation, or its oscillatory instability, can be explained by a combination of positive and negative feedback mechanisms. The positive one is atrributed to an N-NDR and the negative one involves a slow process such as the surface concentration of an electroactive species and the surface coverage of an adsorbed species. In this present work, we study the mechanism of the current oscillation observed during the simultaneous reduction. An N-NDR characteristic was observed in a current (I) – potential (E) curve when the 1.1 M HNO3 + 5 mM SnSO4 solution contained 1mM NB (the blue curve in Figure 1c). We thus propose that the adsorption of NB (and/or AN) induced the N-NDR characteristic. The reduction current was mainly produced by the nitrate reduction, and hence we can suggest that the concentration of nitrate ions at the electrode surface is the slow process. This electrochemical system, which shows the droplet motions as well as the spontaneous current oscillation, is of considerable intereset from the viewpoint of dynamic self-organization of molecular systems. REFERENCES [1] S. Nakanishi, T. Nagai, D. Ihara, Y. Nakato, Chemphyschem, 9 (2008) 2302-2304. [2] Y. Mukouyama, T. Shiono, J. Electrochem. Soc., 163 (2016) H36-H41. [3] Y. Mukouyama, Y. Ishibashia, Y. Fukuda, T. Kuge, Y. Yamada, S. Nakanishi, S. Yae, J. Electrochem. Soc., 165 (2018) H473-H480. FIGURE CAPTION Figure 1. (a) Schematic of Au film electrode. The film was produced on a Si wafer by electroless plating. A nitrobenzene (NB) droplet with a volume of 5 mL was put on the film surface before electrolysis. (b) Time course of current at -0.66 V vs. SHE. The working electrode was the Au film electrode. (c) Current (I) – potential (E) curves for an Au-wire electrode. The black curve was obtained in the absence of NB, whereas the blue curve, which shows an N-NDR characteristic, was obtained in the presence of NB. Figure 1

Beneficial role of the nitrogen-doped carbon nanotubes in the synthesis of the active palladium supported catalyst

The use of nitrogen doped carbon nanotubes (N-CNTs) as a palladium catalyst support resulted in the formation of isolated palladium ions and metal nanoparticles, depending on the Pd content. It was found that the formation of isolated palladium ions is due to the presence of pyridinic nitrogen centers in the N-CNTs and does not depend on the method of palladium deposition (impregnation or reductive deposition). These ions possess high thermal stability in hydrogen atmosphere, poorly adsorb CO even at subambient temperature and are low active in catalytic hydrogenation of nitrobenzene to aniline. The beneficial role of the N-CNTs was found to be in the stabilization by graphitic nitrogen of the metallic Pd nanoparticles of ~1.5 nm size showing high activity towards aniline formation at atmospheric pressure. The possibility of the tailored synthesis of different metal species by means of the N-CNTs as a support opens a wide room for use of these carbon nanomaterials in various catalytic applications.

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.

Изучение реакции Бухвальда-Хартвига с катализаторами на основе одновалентной меди

Many natural substances and drugs includes N-aryl-substituted heterocycles. These substances can be synthesized in various conditions, one of which is the amination of Buchwald-Hartwig. In this reaction formation of N-substituted anilines was observed as the resalt of the interaction between aryl halides and tin amides in palladium catalysis condition. It was discovered by Buchwald and Hartwig in 1994. In 1996, toxic amides of tin and P(o-Tol)3 were replaced by amines and chelating diphosphines. Due to high yields and good reproducibility, Buchwald-Hartwig amination is the attractive method for producing aromatic amines. Currently, this amination is carried out with triphenylphosphine palladium complexes. The main drawback of these catalysts is the high cost and toxicity. In this regard, work is underway to replace these catalysts on copper containing. Currently using complexes of monovalent copper with the following chelating agents: diamines, amino acids, 1,10-phenanthroline, diols. In this work, we studied the reaction of C-N cross-combination using a catalytic system based on a complex of monovalent copper and 1-ethylbenzimidazole. The efficiency of this catalytic system is compared with the copper – L proline system described in the literature. It is shown that the use of copper – 1-ethyl-benzimidazole system can reduce the synthesis time from forty hours to twelve. It is established that the presence of the acceptor substituent in the substrate increase the yield of the product in the Buchwald-Hartwig reaction. Indole was used as a substrate. Arylation was carried out by iodobenzene, o-iodotoluene and p-iodnitrobenzen.

Supercritical water oxidation of octol – containing wastewater

<p>This study investigated optimum operating conditions of supercritical water oxidation (SCWO) for octol and compared the degradation of its components TNT (2,4,6-trinitrotoluene) and HMX (octahydro-1,3,5,7- tetranitro-1,3,5,7-tetrazocine, octogen) under the same conditions. Pilot scale experiments were conducted at various temperatures, reaction times and oxidant amounts. Removal efficiency, by-product analysis and toxicity tests were selected as the performance criteria for the SCWO. Optimum conditions were determined as a temperature of 500 C, 120 s of oxidation time and an oxidant ratio of 150%. Removal of octol was achieved at a rate of 99.99%, while TNT and HMX were removed individually at a rate of ~85% when they existed in the wastewater. No toxicity was observed at the end of the octol oxidation, whereas toxicity was found in the TNT and HMX oxidation due to the formation of TNT isomer and aniline. Higher initial organic material concentrations promoted the removal rates. These results demonstrated that SCWO can be effectively used for the degradation of ammunition wastewater even when concentrations are high.</p>

On the nature of spillover hydrogen species on platinum/nitrogen-doped mesoporous carbon composites: A temperature-programmed nitrobenzene desorption study

Spillover hydrogen species were generated by dissociative H2 adsorption on Pt nanoparticles supported on nitrogen-doped mesoporous carbon. The spillover hydrogen species on the support can migrate back to the Pt nanoparticles and hydrogenate subsequently adsorbed nitrobenzene to aniline at 80 °C, which was detected during temperature-programmed desorption experiments from 80 to 300 °C in pure He. The amount of spillover hydrogen can be tuned mainly by the pre-reduction temperature rather than by other parameters. The absence of aniline formation during nitrobenzene desorption experiments in the presence of CO indicates that hydrogenation occurs exclusively on Pt and that the spillover hydrogen species are present on the carbon support in a chemically inactive state. Most likely, spillover hydrogen is reversibly stored on the carbon support as adsorbed protons on the surface and as electrons in the bulk. These findings provide a new perspective on Pt/C-based hydrogen storage materials and fuel cell catalysts.

Reductive Denitration of Nitroarenes.

The Pd-catalyzed reductive denitration of nitroarenes has been achieved via a direct cleavage of the C-NO2 bonds. The catalytic conditions reported exhibit a broad substrate scope and good functional-group compatibility. Notably, the use of inexpensive propan-2-ol as a mild reductant suppresses the competitive formation of anilines, which are normally formed by other conventional reductions. Mechanistic studies have revealed that alcohols serve as efficient hydride donors in this reaction, possibly through β-hydride elimination from palladium alkoxides.

Self-Propelled Motion of a Nitrobenzene Droplet on Au Electrode during Sn Electrodeposition: Factors Creating Imbalance of Interfacial Tension and Marangoni Effect

A nitrobenzene droplet moves in a self-propelled manner on Au electrode surface during the Sn electrodeposition in H2SO4 solution because the interfacial tension of solid-water interface acting on the front side of the droplet is larger than that on the rear side. The electrodeposition, which increases the interfacial tension, is suppressed by a side reaction such as hydrogen evolution reaction and by adsorbed nitrobenzene molecules. If the electrode surface is non-uniform, the electrodeposition as well as the side reaction takes place non-uniformly on the electrode surface, leading to an initiation of the droplet motion. If the electrode surface is uniform, the motion is initiated when nitrobenzene molecules are adsorbed non-uniformly on the surface. Once the motion is initiated, the imbalance is created spontaneously: the electrodeposition occurs less efficiently at the rear side because it is suppressed by nitrobenzene molecules remaining on the surface. When the electrodeposition is performed in HNO3 solution, the formation of aniline by the reduction of the non-uniformly adsorbed nitrobenzene induces the Marangoni effect and consequently the droplet continually changes in shape and moves like an amoeba. This amoeba-like motion is also self-propelled because nitrobenzene molecules remaining on the rear side are reduced to form aniline molecules.

Rhodium-calix[4]pyrrole and rhodium-tetraphenyl porphyrin: preparation, surface grafting and their catalytic application in nitro-benzene reduction.

Rhodium containing macromolecules calix[4]pyrrole (RhCP) and tetraphenyl porphyrin (RhTPP) were prepared and grafted on the surface of functionalised molecular sieve materials. 1H and 13C NMR, CHNS and mass spectral analyses were used for the structural elucidation of homogeneous organometallic complexes.1H NMR and CHNS analyses confirm the formation of calix[4]pyrrole (CP) and tetraphenyl porphyrin (TPP). The introduction of rhodium ions into the macromolecule is well evident from the disappearance of the 1H NMR signal characteristic of N-H proton (7.1 ppm in CP and -2.74 ppm in TPP). Furthermore the formation of RhCP and RhTPP complexes is confirmed using CHNS and mass spectral analysis; the data are in line with theoretically calculated values. The grafting of RhCP and RhTPP on a diamino functionalised SBA-15 support was confirmed through low angle XRD, 13C MAS-NMR and SEM-EDAX analysis. Both homogeneous and heterogeneous catalysts were utilized for nitrobenzene reduction. RhCP and RhTPP heterogenized on SBA-15-F showed complete conversion of nitrobenzene with exclusive formation of aniline as a product. The catalytic activities were retained in both the systems even after several runs.

Cobalt nanocomposites on N-doped hierarchical porous carbon for highly selective formation of anilines and imines from nitroarenes

A heterogeneous, active, and non-noble cobalt nanocomposite for selective synthesis of aniline derivatives and imines from nitroarenes is reported.

Green synthesized iron nanoparticles supported on pH responsive polymeric membrane for nitrobenzene reduction and fluoride rejection study: Optimization approach

Iron nanoparticles (NPs) were prepared via Clove extract mediated green synthesis. Iron NPs were immobilized in flat asymmetric polymeric pH responsive PVDF-co-HFP membranes prepared by blending of Polyethylene glycol methyl ether (PEGME)(Mw = 5000 g/mol) and Humic acid (HA). Iron NPs dispersed in pH responsive polymeric membrane in different weight percentage (0.01, 0.1 and 1) imparted catalytic effect in reducing nitrobenzene to aniline as well as enhanced fluoride rejection by dead end filtration experiment. Both the process of NB reduction and fluoride rejection was dependent on pH responsiveness of the membrane. High performance liquid chromatography (HPLC) analysed formation of aniline and nitrobenzene at different ultra-filtration time. Aniline formation of 15 ppm was found to be highest at pH3 and lowest of 12.8 ppm at pH7 for 0.01 wt% iron NPs impregnated membrane at end of 50 min. Aniline formation increased for pH12 than pH7 due to pH responsiveness. Fluoride rejection was studied on optimized wt% of iron NPs from NB reduction experiments with different pH of fluoride solutions. In order to maximize the Aniline formation and Nitrobenzene reduction, the variables (time, pH and wt% of NPs) was optimized using Design expert software 9.0 TRIAL through ANOVA (analysis of variance) using the combination of response surface methodology (RSM) and central composite design (CCD). The optimization study showed negligible error with experimentally obtained values at optimized conditions for maximizing NB reduction (error 3.37%) and aniline formation (error 3.93%).

Reduction of nitrobenzene in aqueous and soil phases using carboxymethyl cellulose stabilized zero-valent iron nanoparticles

Zero valent iron (ZVI) has been extensively studied for reductive degradation of a host of organic pollutants including nitrobenzene (NB) in the water phase. However, little is known about the effectiveness for degrading soil-adsorbed NB, for which stabilized ZVI nanoparticles are often required to facilitate delivery of the reactive materials into contaminated soil. In this study, stabilized ZVI nanoparticles were prepared using a food-grade and low-cost polysugar, carboxymethyl cellulose (CMC), as a stabilizer; and the nanoparticles were tested for reductive degradation of NB in both water and soil phases. Compared to non-stabilized ZVI, CMC-stabilized ZVI nanoparticles degraded NB 3.7 times faster based on the apparent pseudo-first order reaction rate constant (0.643min−1 for stabilized ZVI). Nearly 90% of electrons donated by ZVI were effectively used for NB reduction according to the reaction stoichiometry. Dissolved organic matter at 10–50mg/Las TOC had little effect on NB conversion into nitrosobenzene, but decreased aniline formation rate by 30–58%; and higher pH (>8) favored the NB reduction. Based on the reduction intermediates and computational chemistry analysis, the reaction pathway was determined, showing that CMC-stabilized ZVI nanoparticles rapidly converted NB to nitrosobenzene, but the subsequent conversion of the intermediates (nitrosobenzene→phenylhydroxylamine→aniline) was relatively slower. When tested for reductive degradation of NB pre-sorbed on a model soil, CMC-stabilized ZVI nanoparticles could completely reduce the soil-sorbed NB (0.01mmol/g) at a ZVI dosage of 0.6g/L, and the reaction was limited by available electrons rather than desorption. The findings indicate that CMC-stabilized ZVI nanoparticles hold the potential to facilitate in-situ remediation of NB-contaminated soil and groundwater.