Nitrobenzene Concentration Research Articles

Catalytic Membrane Microreactors with an Ultrathin Freestanding Membrane for Nitrobenzene Hydrogenation.

A catalytic membrane microreactor is a potential tool for the application in multiphase catalytic reactions. Currently, the installation of a permeable ultrathin membrane to separate the reactants with different phases and the grafting of a catalyst layer on the membrane in a microreactor remain challenging. In this work, a catalytic ultrathin membrane microreactor with an ultrathin freestanding supporting membrane was developed for nitrobenzene hydrogenation, which was formed by the interfacial polycondensation reaction with parallel laminar flow in a microchannel, followed by catalyst layer immobilization on one side of the ultrathin membrane surface using the layer-by-layer self-assembly technique and in situ reduction. The ultrathin freestanding membrane ensured a stable gas/liquid contact interface and good hydrogen permeability. The developed membrane microreactor could exhibit high catalytic performance under mild conditions, demonstrating its superior mass transport. In addition, the effects of the thickness of the ultrathin freestanding membrane, flow rates, and inlet nitrobenzene concentration were investigated to obtain the optimum operating conditions. The experimental results demonstrate that this newly developed membrane microreactor is a promising candidate for multiphase catalytic reactions.

Synthesis and characterization of magnetite nanoparticles for photocatalysis of nitrobenzene

The present work shows the photocatalytic degradation of nitrobenzene (NB) using Fe3O4 magnetic nanoparticles (MNP) as a photocatalyst in the presence of UV light. The MNP were synthesized by an ultrasonic-assisted reverse co-precipitation (US-RP) method using FeSO4, FeCl3 and NH4OH as precursors. The prepared nanoparticles were characterized by UV–vis spectroscopy, attenuated total reflectance Fourier transformed infrared spectroscopy (ATR FT-IR), Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Dynamic light scattering (DLS), Zeta potential, Vibrating sample magnetometer (VSM) and Magnetic thermogravimetric analysis (MTGA). The successive decrement in the absorbance at 265 nm shows the effective decrease in NB concentration measured by UV–vis spectroscopy. The reaction intermediates detected by gas chromatography/mass spectrum (GC/MS) were 2-nitrophenol (2-NPh), 3-nitrophenol (3-NPh) and 4-nitrophenol (4-NPh). The prepared MNP showed an optimal NB degradation at an initial pH of 2 and 100 ppm of the photocatalyst.

Evaluation of Limiting Sensitivity of the One-Color Laser Fragmentation/Laser-Induced Fluorescence Method in Detection of Nitrobenzene and Nitrotoluene Vapors in the Atmosphere

The paper presents the results of a numerical evaluation of limiting sensitivity of the method for detecting vapors of nitrocompounds in the atmosphere based on one-color laser fragmentation (LF)/laser-induced fluorescence (LIF) of NO fragments via A2Σ+ (v′ = 0) ← X2Π (v″ = 2) transition. The calculations were performed using the developed kinetic model of the one-color LF/LIF process under consideration. The calculations take into account the influence of ambient nitrogen dioxide as a limiter of the sensitivity of the method when operating in a real atmosphere. It is shown that if the nitrogen dioxide concentration in the atmosphere does not exceed a value of 10 ppb, the maximum detectable vapor concentrations of nitrobenzene and o-nitrotoluene are several ppb. It is also shown that the method of single-frequency one-color excitation usually used for the detection of nitrocompounds does not allow achieving the maximum efficiency of the LF/LIF process.

Catalytic Reduction of Nitrobenzene Using Silver Nanoparticles Embedded Calcium Alginate Film.

Synthesis of silver nanoparticles embedded on calcium alginate film and the catalytic property of this film in the reduction of nitrobenzene with sodium borohydride are demonstrated in this work. Natural polymer alginate acts as effective reducing and stabilizing agent in synthesis of silver nanoparticles. Effect of different parameters on the preparation of silver nanoparticles, such as, temperature, concentration of silver precursor and heating time was investigated. As-prepared silver nanoparticles were characterized by transmission electron microscopy, scanning electron microscopy, UV-Vis spectrometry, and atomic absorption spectrometry. Transmission electron microscopy analysis con-firms the formation of silver nanoparticles with particles size range of 3-19 nm and average particle size was found to be 10±4 nm. Effect of concentration of nitrobenzene and sodium borohydride, catalyst loading and temperature on the catalytic reduction of nitrobenzene was studied. Reusability of catalyst was examined in this reduction reaction and the catalyst shows good activity up to 10th run.

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.

Eu(III) doped zinc metal organic framework material and its sensing detection for nitrobenzene

An Eu(III) doped zinc metal-organic framework (MOF), i.e., Zn3(BTC)2: Eu(III), was synthesized by the solvothermal method. The crystal structure, morphology, compositions and photoluminescence properties of Zn3(BTC)2: Eu(III) were studied by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and optical spectroscopic technique, respectively. The sensing detection for different nitrobenzene concentrations is performed at room temperature. The results show that Zn3(BTC)2: Eu(III) is successfully synthesized, and 4% Eu(III) doped Zn3(BTC)2 exhibits the excellent fluorescence. The photoluminescence properties of activate Zn3(BTC)2: 4% Eu(III) in different solvents have been investigated in detail, and the results show that it has obvious fluorescence quenching behavior towards nitrobenzene (NB) in the range of 0-250 ppm, and the fluorescence intensity decreases exponentially when the NB concentration increases. According to the Stern-Volmer equation, the quenching constant KSV = 0.03873 ppm−1 (i.e., KSV = 3.957 × 103 M−1) can be obtained and the limit of detection is 0.97 ppm. The sensing mechanism is also discussed. The MOF sample shows rapid response, high sensitivity, good selectivity, good repeatability to NB, and may be used as a potential NB probe in liquid environment.

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.

Nanoscale zero-valent iron supported on biochar for the highly efficient removal of nitrobenzene

The application of nanoscale zero-valent iron (nZVI) in the remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation and iron leaching. To address this issue, nZVI was distributed on oak sawdust-derived biochar (BC) to obtain the nZVI/BC composite for the highly efficient reduction of nitrobenzene (NB). nZVI, BC and nZVI/BC were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). For nZVI/BC, nZVI particles were uniformly dispersed on BC. nZVI/BC exhibited higher removal efficiency for NB than the simple summation of bare nZVI and BC. The removal mechanism was investigated through the analyses of UV-Visible spectra, mass balance and XPS. NB was quickly adsorbed on the surface of nZVI/BC, and then gradually reduced to aniline (AN), accompanied by the oxidation of nZVI to magnetite. The effects of several reaction parameters, e.g., NB concentration, reaction pH and nZVI/BC aging time, on the removal of NB were also studied. In addition to high reactivity, the loading of nZVI on biochar significantly alleviated Fe leaching and enhanced the durability of nZVI.

Gas consumption characteristics determined by gas-liquid two-phase flow coupled with catalytic reaction in a gas-liquid-solid microreactor

In this work, the gas consumption characteristics were investigated by gas-liquid two-phase flow in a capillary microreactor using the catalytic hydrogenation of nitrobenzene as a reference gas-liquid reaction. Image processing technique was used to measure the gas consumption from the variation in the gas phase through the recorded images. The influence of the inlet nitrobenzene concentration and both the gas and liquid flow rates on the gas consumption and the microreactor performance was investigated. The experimental results showed that there existed a discrete hydrogen consumption process, i.e. the waiting stage and inburst stage. Hydrogen consumption was mainly attributed to the waiting stage in each bubble formation cycle. Minimal hydrogen was consumed in the inburst stage. In addition, there was a clear difference between the H2 consumption rates under each operating condition. As the gas flow rate and nitrobenzene concentration increased, the H2 consumption rate was gradually decreased with each successive formation cycle. Although the consumption rate was gradually reduced with each successive formation cycle with increasing liquid flow rate, the downward trend became increasingly gradual and clearly stabilized at 20 μL/min. The microreactor performances under different operating conditions were also investigated. The results showed that the nitrobenzene conversion was first increased and then gradually decreased with increasing the gas flow rate, whereas it was gradually decreased with increasing both the liquid flow rate and nitrobenzene concentration. The results obtained in this work are beneficial for not only understanding process intensification but also promoting the use of microreactor technology in additional industrial applications.

Chemical Detection Using a Metal-Organic Framework Single Crystal Coupled to an Optical Fiber.

The quantitative detection and real-time monitoring of target chemicals in the liquid phase are made possible by combining the tailored adsorption properties of metal-organic framework (MOF) material and the precise measuring capabilities of an optical fiber (OF) Fabry-Pérot interferometer (FPI) device. As the single-crystal MOF host adsorbs target analyte guests from the environment, its dielectric properties change causing the reflection spectrum derived from the FPI device to shift. A single crystal of HKUST-1 was attached to the end-face of an OF to form the sensor OF∪MOF (∪, union). The sensor's response curve was accurately measured using low concentrations of the target analyte nitrobenzene, an explosive simulant. Additionally, the uptake rate of nitrobenzene into the MOF single crystal was characterized. The experimental results show that the sensor achieved quantitative and real-time adsorption measurements of a target analyte.

Designed of bifunctional Z-scheme CuSnO3@Cu2O heterojunctions film for photoelectrochemical catalytic reduction and ultrasensitive sensing nitrobenzene

A direct Z-scheme CuSnO3@Cu2O heterojunctions photo-electroactive material were reasonably designed and fabricated by electrodeposited Cu2O on fluoride doped tin oxide (FTO) substrate followed anchoring 3D CuSnO3 microspheres onto Cu2O film. The novel 3D architectures can favor the mass transfer, provide multiple active sites and improve light absorption during the photoelectrocatalytic reactions. The artificial heterogeneous Z-scheme photoelectrochemical (PEC) system further prolong electrons path, promote the separation of photogenerated charge carriers and maintain high redox ability. As expected, the constructed Z-scheme CuSnO3@Cu2O as the photocathode show excellent dual functional properties which can not only detect the trace nitrobenzene (NB) but also undergo catalytic reduction of NB to less toxic species (aniline, AN) under visible light irradiation. Based on CuSnO3@Cu2O photocathode, the photocurrent was linearly proportional to the concentration of NB ranging from 0.5 nmol L−1 to 100 μmol L−1, and the detection limit (S/N = 3) was 0.43 nmol L−1. The fabricated sensor was successfully used to sensing the trace NB in real samples and it showed excellent anti-interference ability, good reproducibility and high stability. Besides, CuSnO3@Cu2O exhibited high PEC activity for NB reduction, 85.70% reduction efficiency was achieved within irradiation for 2.5 h. Thus, this study may provide insights into designing advanced photoeletrocatalysts for energy conversion and render a tunable platform in photoelectrochemistry for the monitor and clean-ups of environmental pollutants.

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.

Effect of nitrobenzene on the performance and bacterial community in an expanded granular sludge bed reactor treating high-sulfate organic wastewater

Nitrobenzene (NB) is frequently found in wastewaters containing sulfate and may affect biological sulfate reduction process, but information is limited on the responses of sulfate reduction efficiency and microbial community to the increased NB contents. In this study, a laboratory-scale expanded granular sludge bed reactor was operated continuously to treat high-sulfate organic wastewater with increased NB contents. Results successfully demonstrated that the presence of more than 50 mg/L NB depressed sulfate reduction and such inhibition was partly reversible. Bath experiments showed that the maximum specific desulfuration activity (SDA) decreased from 135.80 mg SO42‒/gVSS/d to 30.78 mg SO42‒/gVSS/d when the NB contents increased from none to 400 mg/L. High-throughput sequencing showed that NB also greatly affected bacterial community structure. Bacteroidetes dominated in the bioreactor. The abundance of Proteobacteria increased with NB addition while Firmicutes presented an opposite trend. Proteobacteria gradually replaced Firmicutes for the dominance in response to the increase of influent NB concentrations. The genus Desulfovibrio was the dominant sulfate-reducing bacteria (SRB) with absence or presence of NB, but was inhibited under high content of NB. The results provided better understanding for the biological sulfate reduction under NB stress.

Pre-magnetized Fe0 activated persulphate for the degradation of nitrobenzene in groundwater

Nitrobenzene (NB) is toxic and resistant to biodegradation and widespread in surface water and groundwater. The persulfate (PS) system has been employed for the NB degradation and proved to be effective. Zero-valent iron (Fe0) has been used for the activation of PS (Fe0/PS) recently. However, the process exhibits a significant drawback of slow release of Fe2+ from Fe0, resulting in low efficiency of the approach as Fe2+ is the primary species for the PS activation. In this study, a weak magnetic field was utilized to pre-treat Fe0 for PS activation (pre-Fe0/PS) based on the magnetic memory of iron. The efficiency of the pre-Fe0/PS process was tested on the degradation of NB in simulated groundwater under anoxic conditions. The NB removal in the pre-Fe0/PS process was significantly enhanced compared with that in the Fe0/PS process. The effect of Fe0, PS, and NB concentration on the NB degradation was investigated. The influence of single inorganic ions, anion couples and humic acids as ubiquitous species in groundwater on the NB removal in the pre-Fe0/PS and Fe0/PS processes were studied and discussed. A column filled with pre-Fe0 was designed to test the NB removal in the pre-Fe0/PS process in a continuous-flow mode. The experimental results indicated that pre-Fe0/PS is a promising approach for the remediation of groundwater with high NB concentration.

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.

Role of dissolved iron ions in nanoparticulate zero-valent iron/H2O2 Fenton-like system

Nanoparticulate zero-valent iron (nZVI) was proved as an efficient Fenton-like catalyst and dissolved iron ions were more or less released into the studied water, but the role of these ions and its primary mechanisms in nZVI/H2O2 Fenton-like reaction process were little known. To address these issues, batch tests were conducted with nitrobenzene (NB) as a probe compound for comparing reaction efficiencies. It was found that, all the initial parameters included the initial concentrations of NB, H2O2 and dissolved oxygen (DO), pH, and nZVI dose-affected NB degradation in the nZVI/H2O2 system, and their optimum values were determined as 40.0 mg/L, 4.0, 340.0 mg/L, 112.0 mg/L, and 5.0 mg/L, respectively. Interestingly, each parameter worked at its optimum value, while the concentration of the iron ions was approximately 1.13 mg/L in all the studied systems at the reaction time of 180 min. The influences of these ions on the generation of the reactive oxygen species like hydroxyl radical (HO∙), oxygen anion radical (O2−∙), and perhydroxyl radical (HO2−∙) depended on the concentration. When the concentration was lower than 1.13 mg/L, HO∙ generating was enhanced, otherwise, HO∙ was inhibited and more O2−∙ and HO2−∙ were generation. These ions initiated homogeneous and heterogeneous reactions to degrade NB, shortened the time from about 120 min to 60 min to the NB degradation maximum rate, and the direct contribution of the former reaction was more than 20.0%. Therefore, adjusting the dissolved iron ions concentration close to its optimal value via controlling DO to no less than 5.0 mg/L is a practical way to the maximum efficiency of nZVI/H2O2 system.

Study of the structure and lattice distortion on the sensing properties of hierarchical rutile TiO2 nanoarchitectures

In this paper, we report the hydrothermal synthesis of 3D hierarchical rutile TiO2 nanorod microspheres in an acid medium with controlled morphology. Four different controlled hierarchical rutile TiO2 architectures (HRTA) characterized by X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM) were tested as an electrochemical sensor to quantify nitrobenzene (NB) in aqueous solution. Based on the characterization results, we found the open hierarchical nanorod microspheres with flower-like appearance showing a higher distortion of the octahedral structure and higher performance as an electrochemical sensor reaching NB concentrations below the parts per billion. The findings of this study have several valuable implications for future studies of volatile organic compound (COV) monitoring in aqueous solution using flower-like hierarchical rutile TiO2 nanorod microspheres clusters.

Tube-in-tube hollow fiber catalytic membrane microreactor for the hydrogenation of nitrobenzene

The miniaturization of membrane reactors aims to improve the mass transfer efficiency. A tube-in-tube hollow fiber catalytic membrane microreactor that contains dual characteristics of a catalytic membrane reactor and a microreactor was developed in this study. For a gas-liquid-solid (G-L-S) reactor, the immobilization of solid catalysts on a hollow fiber membrane (HFM) via layer-by-layer (LBL) self-assembly enables the model reaction of nitrobenzene hydrogenation to occur. The unique structure of the novel catalytic membrane microreactor separates the gas and liquid reactants and shortens the transfer distance. The experimental results showed that the nitrobenzene conversion was high during 30 h of continuous operation. The effects of the flow rates and inlet nitrobenzene concentration were also investigated. At a given gas flow rate, the nitrobenzene conversion and concentration of the product aniline decreased with increasing the liquid flow rate. Meanwhile, at a given liquid flow rate, an increase in the gas flow rate led to an increase in the pressure of the gas phase. Sufficient hydrogen promoted the reaction, increasing the nitrobenzene conversion and aniline concentration. In addition, the inlet nitrobenzene concentration affected the conversion. Higher concentration not only enhanced the reaction rate but also caused catalyst poisoning. Based on these results, the newly designed catalytic membrane microreactor is feasible to improve the performance towards multiphase reaction.

Nanostructured carbon materials for enhanced nitrobenzene adsorption: Physical vs. chemical surface properties

The influence of physical and chemical surface properties on the adsorption of nitrobenzene, a major organic contaminant in wastewater, was investigated using a wide range of graphene-based materials. These included carbon blacks and activated carbons as well as nanostructured materials such as graphitic nanoribbons (GNRs) and graphene-like structures derived from rice husk (RHC). The surface of GNRs was also modified by oxidation with hydrogen peroxide under UV irradiation (yielding Ox-GNRs). For the understanding of the importance of electrostatic and dispersive interactions, the uptake of nitrobenzene was measured in solutions at controlled pH conditions. The Langmuir and Freundlich parameters were found to be dependent on both surface physics and chemistry. To elucidate this influence, the adsorption of H2O/D2O was performed on selected samples. The edge surfaces of nanoporous carbons appear to exert dominant interactions with polar molecules such as nitrobenzene. At the same time, while the presence of micropores is the most important factor for adsorption at low concentration, the meso- and macropores become more important at higher nitrobenzene concentrations. The novelty of this study resides in the use of complementary techniques to understand the adsorption on traditional carbon materials as a guide for the optimization of novel, graphene-like nanostructured adsorbents.

Degradation of nitrobenzene wastewater in an acidic environment by Ti(IV)/H2O2/O3 in a rotating packed bed.

The rotating packed bed (RPB) as a continuous flow reactor performs very well in degradation of nitrobenzene wastewater. In this study, acidic nitrobenzene wastewater was degraded using ozone (O3) combined with hydrogen peroxide and titanium ions (Ti(IV)/H2O2/O3) or using only H2O2/O3 in a RPB. The degradation efficiency of nitrobenzene by Ti(IV)/H2O2/O3 is roughly 16.84% higher than that by H2O2/O3, and it reaches as high as 94.64% in 30min at a H2O2/O3 molar ratio of 0.48. It is also found that the degradation efficiency of nitrobenzene is significantly affected by the high gravity factor, H2O2/O3 molar ratio, and Ti(IV) concentration, and it reaches a maximum at a high gravity factor of 40, a Ti(IV) concentration of 0.50mmol/L, a pH of 4.0, a H2O2/O3 molar ratio of 0.48, a liquid flow rate of 120L/h, and an initial nitrobenzene concentration of 1.22mmol/L. Both direct ozonation and indirect ozonation are involved in the reaction of O3 with organic pollutants. The indirect ozonation due to the addition of different amounts of tert-butanol (·OH scavenger) in the system accounts for 84.31% of the degradation efficiency of nitrobenzene, indicating that the nitrobenzene is dominantly oxidized by ·OH generated in the RPB-Ti(IV)/H2O2/O3 process. Furthermore, the possible oxidative degradation mechanisms are also proposed to better understand the role of RPB in the removal of pollutants. Graphical abstract ᅟ.