Nitrobenzene Concentration Research Articles

Oxidation and degradation of nitrobenzene by ozone micro-nano bubbles

The remediation of ozone oxidation to nitrobenzene (NB) contaminated groundwater has limitations such as low ozone solubility and poor gas transmission capacity. In this paper, we combine the ozone oxidation and the micro-nano bubbles (MNBs) and investigate the oxidation of the degradation of NB using a semi-continuous experimental approach. The experimental results show that the degradation efficiency of NB by ozone MNBs system (98.69%) is significantly higher than that of traditional ozone oxidation. The presence of MNBs significantly increase the rate of ·OH, ·O2– and 1O2 production compared to large bubbles produced by ozone aeration. This is due to OH– adsorbed at the interface will accelerate the conversion of ozone to ·OH during bubble rupture. And conversion between O3,·OH, ·O2– and 1O2。 The degradation of NB in ozone MNBs could be described by quasi-first-order kinetics. The degradation kinetics of ozone MNBs are obviously affected by the initial concentration of NB, the initial pH of the reaction system, salinity, gas species and flow rate. Oxidative degradation products (p-benzoquinone, phenol, o-nitrophenol, p-nitrophenol, aniline, acetic acid, NO3–, etc.) have been identified by GC–MS, IC, UV–Vis. They show that the degradation results from the attack of the aromatic ring and –NO2 of NB through nitrification, free radicals and O3. This research introduces a novel approach for degrading NB and offers crucial insights into the degradation of organic substances using MNBs.

Sr(II) based one-dimensional coordination polymer as an efficient optical sensor for the detection of nitroaromatic explosives in aqueous medium

The detection of explosive materials holds significant importance due to their profound impact on various aspects such as environmental and biological systems, homeland security, and forensic investigations. Metal-organic frameworks (MOFs) and coordination polymers (CPs) have emerged as promising candidates for the selective and sensitive detection of small molecules. In this study, we synthesized a novel oxydiacetic acid functionalized strontium (II) coordination polymer, termed SDGA, using a cost-effective method known as the gel diffusion technique. The crystal structure, characterization, thermal stability, and photoluminescence properties of SDGA were thoroughly investigated by using single crystal X-ray diffraction, FTIR, UV–visible, TG/DTG, and fluorescence spectroscopy. The results revealed that SDGA crystallizes in a monoclinic crystal system with the P21/c space group. SDGA exhibits an emission peak at 340 nm under an excitation wavelength of 301 nm, attributed to the inter-ligand n-π* transition. Leveraging this photoluminescence behaviour, sensing experiments were conducted to detect nitrobenzene and p-nitrophenol within a concentration range of 0-10−20 M. The results indicate a decrease in fluorescence intensity with increasing concentrations of nitrobenzene and p-nitrophenol, indicative of a ‘turn-off’ mechanism.

Designing a three-dimensional CoFe2O4 cross-frame wrapped with carbon nanotubes for monitoring the environmental pollutant nitrobenzene

In this study, we employ a catalytic system derived from a zeolitic imidazolate framework (ZIF), comprising carbon nanotube-wrapped CoFe2O4 with a modified 3D cross morphology. The seamless transition between ionic valence states in CoFe2O4 contributes to enhanced material conductivity, illustrating a significant synergistic coupling effect. The 3D matrix has the capacity to generate a greater number of active sites and exhibit a high surface area. The generation of nanotubes provides additional channels for electron transport, thereby improving the charge transfer efficiency and enhancing the electrochemical sensing capability of the system. The synthesized material demonstrates outstanding electrochemical sensing capabilities for nitrobenzene, exhibiting impressive sensitivity with a remarkably low limit of detection at 0.013 μM and a broad linear response range (0.06–414.9 μM), heightened sensitivity, excellent repeatability, and superior selectivity. Furthermore, the quantification of trace nitrobenzene in water samples demonstrates a recovery rate within the range of 96.0 %–102.8 %. Consequently, this material presents itself as a promising catalyst for electrochemical analysis and introduces a novel approach for detecting low concentrations of nitrobenzene.

Assembly of three new triphenylamine functionalized MOFs for the fluorescent sensing of nitrobenzene

The detection of nitrobenzene (NB) is very important because it has a series of irreversible effects on human health. Metal-organic frameworks (MOFs) show potential applications in this field due to their tunable and porous structures. In this work, three new MOFs, namely [Mn3(TCA)2(DMF)4]·DMF (JOU-28), [Cd21(TCA)14(H2O)9]·21DMF·21H2O (JOU-29), and [Cd3Cl3(TCA)(DMF)2]·H2O (JOU-30), were successfully prepared by solvothermal method (H3TCA = 4,4′,4″-tricarboxytriphenylamine; DMF = N,N′-Dimethylformamide). Single crystal X-ray diffractions showed that JOU-28 was a 3D porous supramolecular structure based on 2D coordination networks, while both JOU-29 and JOU-30 were 3D porous structures based on 1D chains. Due to its strong fluorescence emission, JOU-29 was selected as a representative to study the NB sensing performance. A linear relationship between the NB concentration and the fluorescence emission intensity of JOU-29 could be obtained as I0/I = 0.952 + 8089[NB]. This result showed that JOU-29 can be used for quantitative detection of NB. Further studies revealed that the fluorescence quenching of JOU-29 may be due to the fluorescence resonance transfer effect and the competitive absorption. This work provides clues for the design and synthesis of fluorescent MOFs for NB detection.

Dynamic response of immobilized microbial denitrification reactor under long-term nitrobenzene stress

Denitrification is an effective method for the synergistic degradation of nitrate and nitrobenzene. In this study, microorganisms were cultured by gradually increasing the influent nitrobenzene concentration over 115 days, achieving efficient synergistic transformation of 50 mg/L nitrobenzene and 100 mg/L nitrate with removal efficiencies of 93.65 % and 98.50 %, respectively. It was studied that electrons flowing towards nitrate accounted for over 93.72 %, with that towards nitrobenzene for less than 6.28 %. Nitrobenzene promoted the enrichment growth of biofilm, significantly increased 64.1 % of the content of polysaccharides and 32.7 % of proteins on extracellular polymeric substance. Shannon index showed that nitrobenzene increased richness of bacteria and fungi by 47.6 % and 73.4 % and the dominant phyla were Proteobacteria and Ascomycota respectively. Metagenomic analysis uncovered a noteworthy surge in gene expression associated with carbon metabolism and nitrobenzene reduction, while the expression of denitrification genes exhibited no substantial alterations, elucidating the consistent denitrification efficiency and formidable nitrobenzene elimination capability of the system.

Two-dimensional VSe2 nanoflakes as a promising sensing electrocatalyst for nitrobenzene determination in water samples

Vanadium diselenide (VSe2) is an unprecedented transition metal dichalcogenide (TMD) with unusual characteristics in low dimensionality. Although theoretical studies suggest promising sensing features, its sensing applicability is yet unexplored. Herein, we propose the implementation of two-dimensional (2D) VSe2 nanoflakes for the voltammetric determination of nitrobenzene (NB); a highly toxic and hazardous compound that contaminates water sources due to increased industrial activity. Few-nanometers-thick VSe2 flakes were obtained through a simple and facile ultrasonication process followed by a centrifugation-based size selection step. Structural and morphological insights into the exfoliated material were obtained through various characterization techniques, including XRD, Raman, TGA, SEM-EDS, AFM, and XPS. The 2D-VSe2 modified glassy carbon electrode (VSe2/GCE) exhibits excellent electrocatalytic activity towards NB reduction, with a three-fold higher response compared to the unmodified electrode. The mechanism underlying the NB electrochemical reduction on the VSe2/GCE interface and the optimal sensing conditions are explored by voltammetric measurements. Under selected conditions, VSe2/GCE displays a linear relationship with the concentration of NB (R2=0.9993) over the range of 0.1–4 μM, with a limit of detection (S/N 3) as low as 0.03 μM. The sensor was successfully applied for the determination of nitrobenzene in untreated spiked water samples, with the recovery ranging from 93–96%.

Effect of nitrobenzene on the growth and yield of rice

A field experiment was conducted at two locations (Gazipur and Satkhira) during the Boro (dry) season in 2020 to study the performance of Nitrobenzene on the growth and yield of rice. Four different concentrations of Nitrobenzene (2.0 mL L-1, 2.5 mL L-1, 3.0 mL L-1 and 3.5 mL L-1) as foliar spray with recommended chemical fertilizer (RF) were tested on BRRI dhan89 under wetland condition. Application of Nitrobenzene at different concentrations with RF showed significant effect on rice growth and yield. At both locations, foliar application of Nitrobenzene (2 mL L-1) + RF gave higher number of tiller/m2, panicle/m2 and grain/panicle over RF. At Gazipur site, Nitrobenzene (2 mL L-1) + RF resulted in significant increase of grain and straw yield of BRRI dhan89 over the RF only whereas, at Satkhira site, no significant yield benefit with Nitrobenzene was found over RF. In terms of rice growth, yield and economic point of view, foliar application of Nitrobenzene at low concentration (2 mL L-1) with recommended fertilizer showed positive effect on the growth and yield of BRRI dhan89 in this study. However, since Nitrobenzene is a new type of plant stimulant, detailed studies on its mode of action, interaction with other plant growth hormones and environmental effects are required to get an insight on rice response to Nitrobenzene and its widespread application in rice cultivation. Bangladesh Rice J. 26 (2): 63-72, 2022

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.

Hydrogenation of Nitrobenzene in Trickle Bed Reactor over Ni/Sio2 Catalyst

Trickle bed reactor was used to study the hydrogenation of nitrobenzene over Ni/SiO2 catalyst. The catalyst was prepared using the Highly Dispersed Catalyst (HDC) technique. Porous silica particles (capped cylinders, 6x5.5 mm) were used as catalyst support. The catalyst was characterized by TPR, BET surface area and pore volume, X-ray diffraction, and Raman Spectra. The trickle bed reactor was packed with catalyst and diluted with fine glass beads in order to decrease the external effects such as mass transfer, heat transfer and wall effect. The catalyst bed dilution was found to double the liquid holdup, which increased the catalyst wetting and hence, the gas-liquid mass transfer rate. The main product of the hydrogenation reaction of nitrobenzene was aniline. Reaction operating conditions, i.e., temperature, liquid flow rate, and initial feed concentration were investigated to find their influences on the conversion and rate of nitrobenzene hydrogenation. Under normal conditions without bed dilution, the system was mass transfer controlled. In the diluted reactor, on the other hand, the resistance of mass transfer was nearly absent and the system became under surface kinetic control. The catalyst showed significant deactivation during the reaction period due to the adsorption of intermediate amine products on the surface of the catalyst. The kinetic study revealed that the reaction is zero order with respect to nitrobenzene concentration for the range of concentration between 0.58 to 1.17 mol/L while it was of positive order for the initial concentration less than 0.58 mol/L

Synthesis of carboxymethyl cellulose stabilized sulfidated nanoscale zero-valent iron (CMC-S-nZVI) for enhanced reduction of nitrobenzene

Sulfidated nanoscale zero-valent iron (S-nZVI) had been widely applied for in situ groundwater remediation, but it still suffered from aggregation, surface passivation, and low reactivity in the reaction system. Herein, sodium carboxymethyl cellulose (CMC) was used as a stabilizer, and the effects of the CMC on the physicochemical properties, reactivity, and reusability of S-nZVI on nitrobenzene (NB) degradation were investigated. The characterizations revealed that the CMC improved the degree of sulfidation and accumulated more FexSy phase on the particle surface. The NB degradation rate by Fe/CMC mass ratio of 0.25 was the highest, and its pseudo-first order degradation rate constant (0.203 min−1) was nearly 15 times higher than that of S-nZVI (0.014 min−1), mainly because CMC significantly inhibited the surface oxidation of S-nZVI, improved the hydrophobicity, and reduced the electron transfer resistance compared to S-nZVI. Meanwhile, CMC-S-nZVI exhibited superior reusability than S-nZVI on NB degradation. The product distribution indicated that almost all NB was reduced to aniline (AN) without accumulation of intermediate after reaction. Besides, the effects of initial NB concentration, initial pH, S/Fe molar ratio, and particles dosage on NB degradation by CMC-S-nZVI were also investigated systematically. These results suggested that CMC-S-nZVI provided better reactivity and reusability than S-nZVI, which can guide the optimal design of robust CMC-S-nZVI and display great potential for in situ remediation application.

Simultaneous spectrophotometric estimation of nitrobenzene, aniline, and phenol in a ternary mixture using genetic algorithm

In spectrophotometry, mixtures of chemical constituents cannot be determined simultaneously due to spectral interferences as well as the close λmax wavelength, the wavelength at which a substance absorbs the most photons. Since the spectra of individual components in a ternary mixture overlap, determining the concentration of individual components using the wavelength of maximum absorbance, λmax, can lead to a significant error. In this paper, the concentrations of individual components in ternary synthetic mixtures of nitrophenol, aniline, and phenol were estimated simultaneously using a model based on a genetic algorithm and partial least squares. The spectrophotometric data of ternary mixtures with almost identical spectra of nitrobenzene, aniline, and phenol were calibrated using partial least squares modeling without losing prediction capability, and a genetic algorithm method was used to select the appropriate wavelengths for partial least square calibration. The experimental calibration matrix of 27 samples containing a ternary mixture of nitrobenzene (1.0–20.0 mg L−1), aniline (1.0–15.0 mg L−1), and phenol (4.0–18.0 mg L−1) was designed by measuring the absorbance between 200 and 340 nm at a 1 nm wavelength intervals. The model was verified by using six different mixtures with varying concentrations of nitrobenzene, aniline, and phenol. The root mean square error in the prediction of nitrobenzene, aniline, and phenol was 0.1411, 0.1670, and 0.2861 with the genetic algorithm, and 0.3666, 0.6149, and 0.6279 without the genetic algorithm, respectively. This method can be successfully applied to estimate the components in synthetic mixtures accurately. Since this method is accurate and robust, it can be applied to actual industrial wastewater that contains a mixture of toxic chemicals. This eliminates the complications and costs related to separation and purification prior to the analysis using costly chromatographic methods.

Degradation of nitrobenzene in 3D stack Z-scheme photoelectrocatalytic system: Degradation condition, pathway analysis and synergistic mechanism

As a representative pollutant with carcinogenesis, mutagenicity and teratogenicity, nitrobenzene (NB) has devastating harm to human health. Herein, a unique three-dimensional (3D) stack Z-scheme photoelectrocatalytic (PEC) system was built by self-assembled different photoelectrodes for efficient NB removal. The effect of initial NB, bias potential, pH and electrolyte concentration on NB removal efficiency were investigated. The intermediates and oxygen-active radicals were determined and analyzed by high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), density functional theory (DFT) and electron paramagnetic resonance (EPR) to propose the NB degradation pathways and mechanism. The results showed that holes were utilized to produce ·OH to oxidize NB on the photoanode surface, the electrons excited from photocathode could reduce NB under UV irradiation; thereafter, the reduction product (aniline) was oxidized to phenol to achieve mineralization by the synergistic effect of anode (oxidation) and cathode (reduction). 3D stack Z-scheme PEC system exhibited a high NB degradation efficiency of 98.18% after 90 min reaction and a mineralization efficiency of 75.08% at 150 min. With ECOSAR software, the system toxicity was speculated. This study has advantages in NB removal and provides direction for other refractory organics.

Degradation of chlothianidin from Dantutso 50WG in electrochemical process: Kinetics and role of reactive species

The kinetic degradation of clothianidin (CLO) (in Dantuso 50 WG) during electrochemical oxidation (EO) process using sulfate- and chloride-supporting electrolytes was comprehensively investigated. The degradation of CLO was not due to direct electron oxidation, but was mainly due to •OH and other radicals generated from supporting electrolytes. The degradation of CLO was significantly inhibited when increasing the concentration of nitrobenzene (NB), methanol (MeOH) and benzoic acid (BA). The second-order rate constant of •OH toward CLO was determined to be 3.23×109 M-1 s-1 using competition kinetics method. When SO42- and Cl- were used as supporting electrolytes, the degradation of CLO by •OH was the same with kCLO = 0.0084 min-1. Meanwhile, the higher removal of CLO in SO42--supporting electrolyte was due to the contribution of (SO4•-/S2O82-) more than that of (Cl•/HClO/ClO-).

Synergistic effect of bioanode and biocathode on nitrobenzene removal: Microbial community structure and functions

This study aimed to reveal the synergistic effect of bioanode and biocathode on nitrobenzene (NB) removal with different microbial community structures and functions. Single-chamber bioelectrochemical reactors were constructed and operated with different initial concentrations of NB and glucose as the substrate. With the synergistic effect of biocathode and bioanode, NB was completely removed within 8 h at a kinetic rate constant of 0.8256 h−1, and high conversion rate from NB to AN (92%) was achieved within 18 h. The kinetic rate constant of NB removal was linearly correlated with the maximum current density and total coulombs (R2 > 0.95). Increase of glucose and NB concentrations had significantly positive and negative effects, respectively, on the NB removal kinetics (R2 > 0.97 and R2 > 0.93, respectively). Geobacter sp. and Enterococcus sp. dominated in the bioanode and biocathode, respectively. The presence of Klebsiella pneumoniae in the bioanode was beneficial for Geobacter species to produce electricity and to alleviate the NB inhibition. As one of the dominant species at the biocathode, Methanobacterium formicicum has the ability of nitroaromatics degradation according to KEGG analysis, which played a crucial role for NB reduction. Fermentative bacteria converted glucose into volatile fatty acids or H2, to provide energy sources to other species (e.g., Geobacter sulfurreducens and Methanobacterium formicicum). The information from this study is useful to optimize the bioelectrocatalytic system for nitroaromatic compound removal.

Residence time characteristic of Taylor reacting flow in a microchannel reactor

Herein, an in-situ visual method was developed to determine the residence time characteristic of a typical gas-liquid Taylor reacting flow in a microchannel reactor. Nitrobenzene hydrogenation was chosen as a reference heterogeneous reaction. The obtained results demonstrated the feasibility of the proposed in-situ visual method in determining the real residence time. The real residence time variation along with the flow distance is inherently related to the local nitrobenzene and hydrogen reactants consumption and mass transfer performance. The increase in residence time was initially accelerated due to rapid hydrogen consumption at the upstream. Then, ascribed to the gradually exhausted nitrobenzene, the deteriorated mass transfer resulted in the residence time being proceeded almost linearly increase along the flow direction at the downstream. Besides, the effects of both initial nitrobenzene concentration and liquid flow rate were also explored. This work reveals the intrinsic interaction between the residence time characteristic and catalytic reaction.

Effects of different permeable lenses on nitrobenzene transport during air sparging remediation in heterogeneous porous media

Air sparging (AS) is considered an effective remediation technology for groundwater contaminated by volatile organic compounds. However, the effects of AS remediation of heterogeneous aquifers with lenses of different permeability are still unclear, which limits the application of AS technology. In this study, the effects of different permeable lenses on nitrobenzene (NB) transport were quantitatively analysed by tracking the temporal and spatial evolutions of the NB concentration and using light transmission visualisation technology to observe airflow. Experimental results showed that the NB outside the airflow zone of the heterogeneous aquifer containing a gravel lens was rapidly removed, which is a special phenomenon. Through moisture content monitoring and colour tracer technology, the bubble-induced water circulation zone in a gravel lens was discovered during AS. At this time, the zone of influence (ZOI) included air flow zone and water circulation zone, while previous studies believed that the ZOI only contained the air flow zone. The presence of water circulation zone in the heterogeneous aquifer with a gravel lens increased the ZOI area and average contaminant removal flux by 5 and 2.3 times, respectively, compared with those in homogeneous aquifer. These findings have modified the conventional cognition about the ZOI and are conducive to an in-depth understanding of the remediation mechanisms and a better design of AS technology in heterogeneous aquifers with different permeable lenses.

Role of Pd in the Electrochemical Hydrogenation of Nitrobenzene Using CuPd Electrodes

AbstractInterest in the electrochemical reduction of organic compounds as an alternative to hydrogen electrosynthesis is driven, among other reasons, by the fact that the products obtained in this process may have more economic value than H2. Furthermore, the technique, coupled with renewable sources of electricity, may open the door for large volume green chemical synthesis. In the present article, the electrochemical reduction and hydrogenation of nitrobenzene to aniline at neutral pH is focused upon, using copper electrodes with and without palladium decoration. Both electrodes present good activity, with a decrease in the overpotential for nitrobenzene reduction and the competing hydrogen evolution reaction when Pd is deposited in the surface of the Cu electrode. It is observed that the rate and selectivity of nitrobenzene reduction to aniline improves at high concentrations, obtaining yields close to 70% for 30 × 10−3 m initial concentrations of nitrobenzene when using Pd decorated Cu electrodes. Impedance spectroscopy analysis reveals that the role of Pd in the decorated electrodes is to enhance the production of H* radicals, necessary for the nitrobenzene reduction process. This explains the increase in the selectivity toward aniline production by the incorporation of small amounts of Pd in the surface of the Cu electrode.

Effect of Nitrobenzene Concentrations with Application Methods on Plant Growth and Yield of Cucumber

The experiment was conducted in the Horticultural Farm of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh to investigate the effect of nitrobenzene concentrations with application methods on growth and yield of cucumber. The experiment consisted of two factors viz. i) concentration of nitrobenzene (F0= control, F1= Nitrobenzene @ 500ppm, F2= Nitrobenzene @ 600ppm, F3= Nitrobenzene @ 700ppm), ii) application method (T1= Foliar Application, T2= Soil Application, T3= Combined Application). In case of, different concentrations of nitrobenzene the maximum vine length (175.65 cm) at harvest was found in F2 treatment and minimum (124.44 cm) were found in F0 treatment. Nitrobenzene concentration of 600ppm showed better vine growth than concentration of 500ppm and 700ppm. However, the maximum number branches (12.02), female flower (25.61), fruit per plant (18.22), fruit weight (169.09 gm.) and yield (34.43 t/ha) were recorded from F2 and F3 treatment. The minimum values of the same parameters were observed in F0 treatment or control. The minimum yield (14.71 kg/plot) was found in T2 and maximum yield (16.16 kg/plot) was found in T3 treatment. In the combination of nitrobenzene concentration and application method, the maximum yield (36.90 t/ha) was found in F2T3 treatment and minimum yield (19.90 t/ha) was recorded in F0T3 treatment. The second highest (35.49 t/ha) yield was obtained from F3T3 treatment. The highest benefit cost ratio (2.632) was attained from the treatment combination of F2T3 (nitrobenzene @ 600ppm with combined application) treated plants.

Effects of temperature, pH, and salinity on the growth kinetics of Pseudomonas sp. NB-1, a newly isolated cold-tolerant, alkali-resistant, and high-efficiency nitrobenzene-degrading bacterium

Strain NB-1, which can efficiently degrade nitrobenzene, was identified as Pseudomonas frederiksbergensis. NB-1 was resistant to cold and alkali with the widest temperature (4°C–35°C) and pH (5–11) adaptive range, compared with other reported nitrobenzene-degrading microorganisms. Based on the Haldane-Andrews model, the real maximum specific growth rate μm’, specific affinity aA, and inhibition coefficient Ki were used in response surface methodology (RSM) simultaneously for the first time to guide NB-1 to treat nitrobenzene wastewater. According to the RSM model, the environmental factors (temperature, pH, salinity) corresponding to the optimal values of μm’, aA, and Ki were determined. By comparing the specific growth rates corresponding to the optimal values of μm’, aA, and Ki, respectively, the optimum growth conditions of NB-1 were determined under different nitrobenzene concentrations. The study of μm’, aA, and Ki by RSM provided a new approach for a more accurate optimization of biological wastewater treatment conditions.

Experimental Investigation on the Effects of Ethanol-Enhanced Steam Injection Remediation in Nitrobenzene-Contaminated Heterogeneous Aquifers

Steam injection is an effective technique for the remediation of aquifers polluted with volatile organic compounds. However, the application of steam injection technology requires a judicious selection of stratum media because the remediation effect of hot steam in heterogeneous layers with low permeability is not suitable. In this study, the removal effect of nitrobenzene in an aquifer was investigated through a series of two-dimensional sandbox experiments with different stratigraphic structures. Four types of alcohols were used during steam injection remediation to enhance the removal effect of nitrobenzene (NB)-contaminated heterogeneous aquifers. The principle of the removal mechanism of alcohol-enhanced organic compounds is that alcohols can reduce the surface tension of the contaminated water, resulting in Marangoni convection, thereby enhancing mass and heat transfer. The addition of alcohol may also reduce the azeotropic temperature of the system and enhance the volatility of organic compounds. The study revealed that all four alcohol types could reduce the surface tension from 72 mN/m to <30 mN/m. However, among these, only ethanol reduced the azeotropic temperature of NB by 15 °C, thereby reducing energy consumption and remediation costs. Therefore, ethanol was selected as an enhancing agent to reduce both surface tension and azeotropic temperature during steam injection. In the 2-D simulation tank, the interface between the low-and high-permeability strata in the layered heterogeneous aquifer had a blocking effect on steam transportation, which in turn caused a poor remediation effect in the upper low-permeability stratum. In the lens heterogeneous aquifer, steam flows around the lens, thereby weakening the remediation effect. After adding ethanol to the low-permeability zone, Marangoni convection was enhanced, which further enhanced the mass and heat transfer. In the layered and lens heterogeneous aquifers, the area affected by steam increased by 13% and 14%, respectively. Moreover, the average concentration of NB was reduced by 51% in layered heterogeneous aquifers and by 58% in low-permeability lenses by ethanol addition. These findings enhance the remediation effect of steam injection in heterogeneous porous media and contribute to improve the remediation efficiency of heterogeneous aquifers by steam injection.