Nitrobenzene In Aqueous Solution Research Articles

Unraveling the Ultrafast Photochemical Dynamics of Nitrobenzene in Aqueous Solution.

Nitroaromatic compounds are major constituents of the brown carbon aerosol particles in the troposphere that absorb near-ultraviolet (UV) and visible solar radiation and have a profound effect on the Earth's climate. The primary sources of brown carbon include biomass burning, forest fires, and residential burning of biofuels, and an important secondary source is photochemistry in aqueous cloud and fog droplets. Nitrobenzene is the smallest nitroaromatic molecule and a model for the photochemical behavior of larger nitroaromatic compounds. Despite the obvious importance of its droplet photochemistry to the atmospheric environment, there have not been any detailed studies of the ultrafast photochemical dynamics of nitrobenzene in aqueous solution. Here, we combine femtosecond transient absorption spectroscopy, time-resolved infrared spectroscopy, and quantum chemistry calculations to investigate the primary steps following the near-UV (λ ≥ 340 nm) photoexcitation of aqueous nitrobenzene. To understand the role of the surrounding water molecules in the photochemical dynamics of nitrobenzene, we compare the results of these investigations with analogous measurements in solutions of methanol, acetonitrile, and cyclohexane. We find that vibrational energy transfer to the aqueous environment quenches internal excitation, and therefore, unlike the gas phase, we do not observe any evidence for formation of photoproducts on timescales up to 500 ns. We also find that hydrogen bonding between nitrobenzene and surrounding water molecules slows the S1/S0 internal conversion process.

Four novel coordination compounds based on N-acetyl-L-phenylalanine: Synthesis, characterization and fluorescence properties

Four novel d10 transition metal chiral coordination compounds Cd(L-acphe)2(H2O)2 (1), {[Cd(L-acphe)2(bpe)(H2O)]·2·5H2O}n (2), {[Cd(L-acphe)2 (4,4′-bipy)(H2O)]·H2O}n (3), {[Zn2(L-acphe)2(bpp)2(OH)]NO3·2H2O}n (4) (L-Hacphe = N-acetyl-l-phenylalanine, 4,4′-bipy = 4,4′-bipyridine, bpe = 1,2-bis (4-pyridyl)ethane, bpp = 1,3-bis(4-pyridyl)propane) have been synthesized by changing central metal ions and N-containing auxiliary ligands. Their structures were determined by single crystal X-ray diffraction analysis and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction and circular dichroism. The structures of compounds 1–3 with cadmium(Ⅱ) as the center metal ion change from 0D, 1D to 2D, ultimately compound 1 generates a 2D supramolecular structure via hydrogen bonding, while compounds 2 and 3 expand to 3D supramolecular structures through hydrogen bonding. The compound 4 with zinc(Ⅱ) as the center metal ion feature 1D chain structures, and 3D supramolecular structure of compound 4 is formed by hydrogen bonding. The present results indicate that selecting central metals with different electronic structures and introducing different N-containing auxiliary ligands could achieve the regulation of the structures of compounds. In addition, the fluorescence recognition properties of compounds 3 and 4 demonstrate that they can highly selectively detect Fe3+ and nitrobenzene in aqueous solutions through fluorescence quenching, indicating that compounds 3 and 4 are expected to become bifunctional fluorescence recognition sensors for the detection of Fe3+ ions and nitrobenzene.

MOF-Conductive polymer composite electrode as electrochemical sensor of nitrobenzene

A metal-organic framework (MOF)-conductive polymer composite film modified electrode was constructed by drop casting using PCN-222(Fe) and p3HT-p3TPA copolymer. The composite materials were characterized by diffraction, spectroscopic and electron microscopic techniques, showing the uniform distribution of MOF particles in the polymer matrix with the original MOF structure maintained. Introduction of carboxylate groups to the polymer matrix enhances interaction between polymer and MOF particles, leading to enhanced electron transfer and better water stability. The modified electrode was used for electrochemical detection of nitrobenzene in aqueous solution with the wide linear detection ranges of 0.05μM-1.00μM (0.6572 μAμM-1) and 1.00μM-100μM (0.03304 μAμM-1) as well as a low detection limit of 0.047μM.

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 47ppb and 0.004ppm, 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.

A sensitive and selective fluorescent probe for nitrobenzene based on Europium(III) post-functionalized Al(III)-based MOF

A post-functionalized Eu 3+ @MIL-121 MOF was prepared through a facile hydrothermal approach and developed as a highly selective luminescent probe for detecting NB in aqueous solution. • A new MOF Eu 3+ @MIL-121 is designed and prepared. • A novel fluorescent strategy is proposed to specifically identify nitrobenzene in nitro-aromatic interferents in aqueous solution. • A new MOF fluorescent probe with the lower LOD for nitrobenzene compared to previous literature. Nitrobenzene (NB) is a substance with potential and possible hazards, which is widely used in industry field. In the current study, Europium(III) post-functionalized Al(III)-based metal–organic framework (Eu 3+ @MIL-121) was synthesized and utilized as an independently luminescent probe for the purpose of sensing NB. The red luminescence of Eu(III) could be quenched by NB through a process called fluorescence resonance energy transfer (FRET), and thus it could be used as a fluorescence off switch for NB, leading to its recognition. Eu 3+ @MIL-121 has its advantages of high sensitivity, selectivity, fast response time and wide response window. Compared with other MOFs, Eu 3+ @MIL-121 can specifically detect NB in aqueous solution, avoid secondary contamination by organic solvents, and has excellent linear range and LOD (limit of detection). Under the optimal conditions, the newly constructed Eu 3+ @MIL-121 fluorescent probe showed a satisfactory linear detection range of 0.005 to 20.000 μM, with a detection limit of 1.56 nM. Furthermore, the probe has been successfully applied to detect NB in real water samples.

Photocatalytic Decomposition of Nitrobenzene in Aqueous Solution by Ag/Cu2O Assisted with Persulfate under Visible Light Irradiation

The mineralization of nitrobenzene was executed using an innovative method, wherein Ag/Cu2O semiconductors stimulated by visible light irradiation were supported with persulfate anions. Batch-wise experiments were performed for the evaluation of effects of silver metal contents impregnated, persulfate concentrations and Ag/Cu2O dosages on the nitrobenzene removal efficiency. The physicochemical properties of fresh and reacted Ag/Cu2O were illustrated by X-ray diffraction analyses, FE-SEM images, EDS Mapping analyses, UV–Vis diffuse reflectance spectra, transient photocurrent analyses and X-ray photoelectron spectra, respectively. Because of intense scavenging effects caused by benzene, 1-propanol and methanol individually, the predominant oxidant was considered to be sulfate radicals, originated from persulfate anions via the photocatalysis of Ag/Cu2O. As regards oxidation pathways, nitrobenzene was initially transformed into hydroxycyclohexadienyl radicals, followed with the production of 2-nitrophenol, 3-nitrophenol or 4-nitrophenol. Afterwards, phenol compounds descended from denitration of nitrophenols were converted into hydroquinone and p-benzoquinone.

Highly sensitive detection of nitrobenzene by a series of fluorescent 2D zinc(ii) metal-organic frameworks with a flexible triangular ligand.

Four fluorescent zinc(ii) metal–organic frameworks, namely [Zn(HCIA)(4,4′-bipy)] (1), [Zn2(CIA)(OH)(1,4-bibz)1.5]·H2O (2), [Zn(CIA)(OH) (4,4′-bbpy)] (3), and [Zn2(HCIA) (4,4′-bimp)]·H2O (4), were prepared hydrothermally with a flexible triangular ligand (H3CIA) and a series of linear N-donor ligands (H3CIA = 5-(2-carboxybenzyloxy) isophthalic acid, 4,4′-bipy = 4,4′-bipydine, 1,4-bibz = 1,4-bis(1-imidazoly)benzene; 4,4′-bbpy = 4,4′-bis (imidazolyl) biphenyl; 4,4′-bimp = 4,4′-bis (imidazole-1-ylethyl) biphenyl). Structural analyses revealed that complex 1 exhibited a 2D brick-like network structure based on the basic bimetallic ring, 2 was also a 2D interspersed structure from the 1D tubular structure, compound 3 possessed a 2D (4,4) network with 4,4′-bbpy occupying the holes, and complex 4 displayed a 2D network from the 1D ladder-like chain. The thermal stabilities and fluorescent properties of these complexes were investigated in the solid state. The fluorescent sensing experiments revealed that all Zn-MOFs could highly sensitively detect nitrobenzene in aqueous solution, which indicated that these materials can be used as fluorescent probes for the detection of nitrobenzene.

Electrochemical sensor for determination of nitrobenzene in aqueous solution based on nanostructures of TiO2/GO

We synthesized polymer nanocomposites (PNCs) based on nanostructures of flower-like hierarchical rutile-phase TiO2 nanorod microspheres that were grow on oxide graphene sheets (GO). The synthesis parameters were modified to obtain desired morphologies (flower-like and cauliflower). The two PNC of TiO2/GO were characterized by scanning and transmission electron microscopy, dispersive energy spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TGA), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The modified graphite electrodes with TiO2/GO were evaluated as an electrochemical sensor in the determination of nitrobenzene (NB) using CV. The physicochemical characterization techniques confirmed the growth of the rutile-phase TiO2 nanoarchitecture on the GO sheets surface. The sensitivity and the detection interval of the sensor increase with the increasing amount of GO, reaching concentrations of the parts per billion. The TiO2/GO sensors shows an acceptable repeatability, reproducibility and stability in the detection of nitrobenzene (NB), and the recovery results in synthetic wastewater samples are excellent.

Apparent kinetics of the ozone oxidation of nitrobenzene in aqueous solution enhanced by high gravity technology

This study investigated the apparent reaction kinetics and degradation pathways of nitrobenzene by ozone enhanced by high gravity technology in the presence of tert-butyl alcohol, a radical scavenger. A promoted effect of ozone and high gravity technology was observed in the degradation of nitrobenzene due to the enhanced mass transfer of ozone into water by unique characteristics of high gravity technology. The second order rate constant was obtained varied from 0.732 L/(mol·s) to 5.267L/(mol·s) at different operation parameters (temperature, initial pH value, high-gravity factor, initial nitrobenzene concentration and ozone dosage). A kinetic empirical model was established to reflect the effects of different operating parameters on the apparent rate constants of ozone and nitrobenzene, which showed that rate constants varied strongly with initial nitrobenzene concentration and high-gravity factor. The reaction was proved in the slow kinetics of gas-liquid reaction. Furthermore, the results of Gas Chromatography-Mass Spectrometer showed that nitrobenzene could only be degraded into intermediate products with unopened benzene ring (p-benzoquinone, phenol, catechol and hydroquinone) by ozone alone.

Experimental study of nitrobenzene degradation in water by strong ionization dielectric barrier discharge

ABSTRACT Nitrobenzene (NB) is toxic and carcinogenic aromatic compound widely used in several industries which is ultimately found in their effluents. In this work, dielectric barrier discharge (DBD) reactor was employed for the degradation of nitrobenzene in aqueous solution. Active species like O3 and •OH produced by DBD reactor were mixed with water which degraded the NB. The results indicated that the lower NB concentrations slightly acidic conditions and high voltage ranges showed the optimum efficiencies. Moreover, the impacts of active species inhibitors isopropyl alcohol (IPA), tert-butanol (TBA), inorganic ions for instance sulfates (), bicarbonates (), nitrates (), carbonates () and chlorides (Cl−) on the degradation of NB were examined. This analysis showed that the hydroxyl radical was captured by the addition of these inhibitors and resulted in the decrease in efficiencies. Byproducts produced during the degradation of nitrobenzene were assessed by analytical techniques of high-performance liquid chromatography (HPLC), liquid chromatography–mass spectrometry (LC–MS), UV–visible spectroscopy and total organic carbon (TOC) analysis. Main intermediate products were nitrophenols and low molecular weight organic acids including oxalic acid and acetic acid that were eventually mineralized to CO2 and H2O. The dielectric barrier discharge technology was found productive for the degradation of nitroaromatic compounds.

Catalytic ozonation by Si-doped α-Fe2O3 for the removal of nitrobenzene in aqueous solution

Si-doped α-Fe2O3 by controlling the atom ratio of Si/Fe was synthesized for catalytic ozonation of nitrobenzene in aqueous solution. Basing on the results of batch oxidation experiments, the catalysts in Si/Fe ratios of 0.1, 0.5, 1.0, and 2.0 showed various activities for ozone decomposition into hydroxyl radical (OH), which obviously enhanced the removal efficiency of nitrobenzene in aqueous solution compared with sole ozonation. The best Si/Fe ratio was 0.5 in present study. The dose of the catalyst, solution pH and reaction temperature can significantly affect the removal efficiency of nitrobenzene. Moreover, the catalyst was composed of Si–Fe binary oxides and α-Fe2O3. With the increase of Si/Fe ratio, the surface relative content of Si-Fe binary oxides increases and the relative content of α-Fe2O3 decreases, which promotes the ozone adsorption-desorption on the surface of the catalyst. The generation of hydroxyl radical in catalytic ozonation was dependent on the synergy of ozone adsorption-desorption by Si–Fe binary oxides and ozone decomposition by α-Fe2O3 on the surface of the catalyst.

A New Route to Cyclohexanone using H2CO3 as a Molecular Catalytic Ligand to Boost the Thorough Hydrogenation of Nitroarenes over Pd Nanocatalysts

AbstractCarbon dioxide has been important in green chemistry, especially in catalytic and chemical engineering applications. While exploring CO2 to produce cyclohexanone for nylon or nylon 66 that is currently produced with low yields using harsh catalytic methods, we made the exciting discovery that carbonic acid, generated from dissolved CO2 in water, was utilized as molecular catalytic ligand to produce cyclohexanone via the hydrogenation of nitrobenzene in aqueous solution that uses Pd catalysts with a total yield higher than 90 %. Importantly, the gaseous nature of catalytic ligand H2CO3 profoundly simplifies post‐catalysis cleanup unlike liquid or solid catalysts. This new green catalysis strategy demonstrated the universality for hydrogenation of aromatic compounds like aniline and N‐methylaniline and could be broadly applicable in other catalytic field like artificial photosynthesis and electrocatalytic organic synthesis.

Influencing investigation of metal ions on heterogeneous catalytic ozonation by ceramic honeycomb for the degradation of nitrobenzene in aqueous solution with neutral pH

Abstract Influence of metal ions on heterogeneous catalytic ozonation by ceramic honeycomb for degradation of nitrobenzene in aqueous solution was investigated through the semi-continuous batch experiments to compare apparent reaction rate constant (kapp) and hydroxyl radical ( OH) formation rate ( k · OH ) in the presence of different metal ions including monovalent (Na+, K+ and Ag+), divalent (Zn2+, Ni2+, Co2+, Mn2+, Ca2+, Fe2+, Cu2+ and Mg2+) and trivalent ions (Fe3+, Al3+ and Cr3+). Each metal ion can increase kapp and k · OH in the process of ozonation alone under the present experimental conditions. Except for the positive influence of Mn2+, the others all show the early enhancement effect and the latter inhibition effect on kapp and k · OH , namely existing a critical maximum concentration of metal ion for catalytic ozonation. The ratio of OH initiation from heterogeneous and homogeneous systems decreases with the increasing concentration of metal ion, indicating that the contribution of OH initiation derived from heterogeneous catalytic system decreases. Results confirm that the increasing concentration of metal ion causes the decrease in density of surface hydroxyl groups on ceramic honeycomb, and a novel correlation is established between the density decrease rates of surface hydroxyl group and the standard reduction potentials of metal ions.

Fabrication of a hydrophobic SDBS-PbO2 anode for electrochemical degradation of nitrobenzene in aqueous solution

In present work, a hydrophobic PbO2 electrode modified by sodium dodecyl benzene sulfonate (SDBS-PbO2) was fabricated using electrodeposition method. The effect of SDBS concentration in electroplating bath on the surface morphology, structure, electrochemical properties, hydrophilicity, OH generation ability and stability of SDBS-PbO2 electrodes was studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), water contact angle, fluorescence probe technique, and accelerated life test, respectively. Results showed that SDBS modification not only increased the electro-catalytic activity, but also prolonged the service life of PbO2 electrode. The electrode prepared from the electroplating bath containing 10 mg/L SDBS (SDBS-PbO2-10 mg/L) showed the highest electrocatalytic activity and the longest service life. The electrochemical degradation of nitrobenzene (NB) in simulated wastewater was used to evaluate the potential application of SDBS-PbO2 electrodes for wastewater treatment. The highest NB removal efficiency and total organic carbon (TOC) removal efficiency of 89.35% and 52.62% were both obtained by SDBS-PbO2-10 mg/L anode. Thus, the SDBS-PbO2-10 mg/L anode was used to systematically investigate the effects of applied current density, initial NB concentration, temperature, and pH value on the reaction kinetics and mineralization current efficiency (MCE) of NB degradation. It was found that the increase of applied current density and the reduction of initial NB concentration exerted a prominent effect on the degradation of NB, but caused the decrease of MCE, while high temperature and low pH value improved both NB degradation rate and MCE. These results show that the SDBS-PbO2-10 mg/L electrode may become a promising anode for organic pollutant degradation.

Improvement of zinc substitution in the reactivity of magnetite coupled with aqueous Fe(II) towards nitrobenzene reduction

The reduction of nitrobenzene (NB) by Zn-substituted magnetite coupled with aqueous Fe(II) was studied. A series of Zn-substituted magnetites (Fe3−xZnxO4, x = 0, 0.25, 0.49, 0.74, and 0.99) were synthesized by a coprecipitation method followed by systematic analysis of the variation in structure and physicochemical properties of magnetite using XRD, TEM, TG, BET and XAFS. All of the samples had a spinel structure by Zn substitution. Zn2+ primarily occupied the tetrahedral sites, but a portion of them moved to the octahedral sites at higher Zn level. Zn substitution increased the BET specific surface area and surface hydroxyl amount. The electron balance indicated that the NB reduction was primarily through the heterogeneous reaction by Fe3−xZnxO4 and adsorbed Fe(II), where NB in aqueous solution was reduced by structural Fe2+ in magnetite recharged by adsorbed Fe(II). Various factors, such as aqueous Fe(II) concentration, magnetite stoichiometry and Zn level, were investigated to illustrate their effects on the reduction processes. Both the rate constant kobs and electron transfer amount illustrated that Zn substitution generally improved the reduction activity of the Fe3−xZnxO4/Fe(II) system, while overdose of Zn retarded the process. This issue was attributed to the variation in electron conductivity of Fe3−xZnxO4 and Zn2+ occupancy.

A luminescent coordination polymer for selective, sensitive, and recyclable sensing of nitrobenzene in aqueous solution

A luminescent coordination polymer, [Cd(H2biim)2SO4]·3H2O (JLNU-1, JLNU=Jilin Normal University); H2Biim=2,2′-biimidazole, has been prepared by hydrothermal method and characterized by corresponding analytical tools. JLNU-1 exhibits outstanding chemical stability in aqueous solution and solvent-dependent luminescent behaviour. In particular, stable suspension of JLNU-1 in nitrobenzene showed highest quenching. The emission spectra were nearly completely quenched at a concentration of 100ppm nitrobenzene in aqueous solution. JLNU-1 can be regenerative for 6cycles by centrifugation of the solution after use and washing several times with H2O. Therefore, JLNU-1 can be used as a fluorescent probe for sensitive and recyclable sensing of small-molecule pollutant nitrobenzene in aqueous solution.

A novel Ag(i)-calix[4]arene coordination polymer for the sensitive detection and efficient photodegradation of nitrobenzene in aqueous solution.

Nitrobenzene (NB) is a widespread and highly toxic organic pollutant in water, and consequently its detection and removal have attracted considerable attention. In the present study, we designed and synthesized a novel coordination polymer, [AgL0.5(NO3)]n (1), {L = 25,26,27,28-tetra[(3-pyridylmethyl)oxy]calix[4]arene}, from AgNO3 and a tetra-pyridyl-functionalized calix[4]arene ligand, which possessed a 2D network based on [Ag4L(NO3)4] units. The 1-modified glassy carbon electrode (1/GCE) exhibited good electrocatalytic activity toward the reduction of NB, offering the selective detection of NB in a wide linear range (1-2450 μM) and a low detection limit (0.62 μM). Furthermore, it displayed excellent photocatalytic activity for the degradation of NB in aqueous solution under UV light. The kinetics of the catalytic degradation reaction and the stability of the catalyst were also studied. These results indicated that compound 1 is a favorable material for the effective determination and degradation of NB, which makes it a promising candidate in both monitoring water quality and treating wastewater.

Novel hydrophobic cotton fibers adsorbent for the removal of nitrobenzene in aqueous solution

In order to improve the superhydrophobic and oil-wet properties of raw cotton fibers come from Jiangsu province, China. A novel adsorbent, hydrophobic cotton fibers (HCF) with an excellent superhydrophobic and larger length was synthesized via modified sol–gel method and examined for the removal of nitrobenzene in aqueous solution. Results show that the treated raw cotton fibers exhibited outstanding non-wettability with the WCA of 152° and the larger length of 0.2–0.4cm, which offers an opportunity to separation in for the removal of nitrobenzene. It was found that adsorption isotherm and kinetics of nitrobenzene onto HCF were well described by the Freundlich and pseudo-second-order kinetic models, respectively. The thermodynamic data showed that the nitrobenzene adsorption onto HCF was a spontaneous, endothermic and physisorption reaction. The monolayer adsorption capacity of nitrobenzene was found to be 16.85mg/g at 30°C.

Preparation of Magnetic Graphene Nanocomposites for Fast Detection of Nitrobenzene in Environmental Water Samples by GC–MS

In this work, magnetic graphene nanocomposites were synthesized via hydrothermal reaction and used as an effective adsorbent to extract and concentrate nitrobenzene in water samples, followed by analysis using gas chromatography-mass spectrometry. The properties of the magnetic nanocomposites were characterized by Fourier transform infrared analysis, transmission electron microscopy, and scanning electron microscopy. The nanocomposites have a distinct structure with the magnetite particles scattered over the surface of the graphene. Due to the unique structure, they not only adsorb the target compound strongly, but also have excellent magnetic response that allows fast separation from water. All the experimental parameters affecting the extraction efficiency, including the amounts of sorbents, eluting solvents and volume, adsorption and desorption time were investigated and optimized. Under the optimum conditions, validation experiments showed a good linearity (r 2 = 0.9999) at the range of 5–1,000 μg/L, satisfactory precision (RSD of intra-day = 3.3 % and RSD of inter-day = 3.9 %), high recovery of 77.3 % for 500 μg/L and 82.5 % for 100 μg/L and 84.7 % for 50 μg/L, respectively, and low detection limit of 0.01 μg/L for nitrobenzene in aqueous solutions. Finally, the magnetic graphene nanocomposites were successfully applied to detect nitrobenzene in real-world water samples and showed promising results.

Relationship between acceleration of hydroxyl radical initiation and increase of multiple-ultrasonic field amount in the process of ultrasound catalytic ozonation for degradation of nitrobenzene in aqueous solution

The synergetic effect between ozone and ultrasound can enhance the degradation of nitrobenzene and removal efficiency of TOC in aqueous solution, and the degradation of nitrobenzene follows the mechanism of hydroxyl radical (OH) oxidation. Under the same total ultrasonic power input condition, the degradation rate of nitrobenzene (kNB), the volumetric mass transfer coefficient of ozone (kLa), and the initiation rate of OH (kOH) increases with introduction of additional ultrasonic field (1–4) in the process of ozone/ultrasound. The increasing amount of ultrasonic fields accelerates the decomposition of ozone, leading to the rapid appearance of the maximum equilibrium value and the decrease in the accumulation concentration of ozone in aqueous solution with the increasing reaction time. The increase in mass transfer of gaseous ozone dissolved into aqueous solution and the acceleration in the decomposition of ozone in aqueous solution synchronously contribute to the increase of kLa. The investigation of mechanism confirms that the increasing amount of ultrasonic fields yields the increase in cavitation activity that improves the mass transfer and decomposition of ozone, resulting in acceleration of OH initiation, which determines the degradation of nitrobenzene in aqueous solution.