Removal Of Nitroaromatic Compounds Research Articles

Biological Treatment of Nitroaromatics in Wastewater

Nitroaromatic compounds (NACs), which are widely used in pesticides, explosives, dyes, and pharmaceuticals, include nitrobenzene, nitrotoluenes, nitrophenols, and nitrobenzoates. They are also significant industrial pollutants in the environment. These substances, as well as their derivatives, frequently have toxic or mutagenic properties. Wastewater containing nitroaromatic compounds can be effectively managed by using biological treatment methods that are accessible, cost-effective, and environmentally friendly. This review highlights the latest developments in biological treatment systems for removing NACs from wastewater. The large-scale implementation of biological treatment systems will be facilitated by future studies that focus on identifying the best operational methods and that determine how co-pollutants impact the removal of NACs from wastewater.

Graphene Oxide Decorated with Ag and CeO2 Nanoparticles as a Catalyst for Room-Temperature 4-Nitrophenol Reduction

Catalytic reduction of nitroaromatic compounds (NCs) into corresponding aminoaromatic compounds (ACs) addresses two challenges: enhancing of the manufacture scale of ACs as valuable chemical intermediates and removal of NCs as widespread wastewater pollutants. Among the noble metal catalysts that feature low-temperature activity, chemical stability, and nontoxicity, silver-containing catalysts are attractive as cost-efficient and easily prepared compositions. This paper is devoted to the design and study of efficient and environmentally benign Ag- and CeO2-containing NCs reduction catalysts supported on graphene oxide (GO). The silver- and/or ceria-containing catalysts are synthesized using deposition-precipitation onto GO prepared by oxidative treatment of graphite. The catalysts and support are characterized by XRD, XPS, TGA, N2 sorption, Raman spectroscopy, and UV–VIS spectrometry. The influence of state and the interaction of the active components on catalytic activity is thoroughly estimated in 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP) at ambient pressure and room temperature. Nanosized Ag and CeO2 particles with sizes up to 30 and 5 nm, respectively, in the GO structure are obtained. The co-deposition of Ag and CeO2 onto GO promotes the stabilization of silver in the catalyst. The Ag-CeO2/GO catalyst demonstrates superior activity in the synthesized series (kapp of 1.615 and 3.674 min−1 for as-prepared and pre-reduced samples). In addition, the Ag-CeO2/GO catalyst retains good stability and a low leaching degree of the active components that makes these compositions efficient in NCs’ reduction into corresponding ACs.

Unveiling the chemotactic response and mechanism of Shewanella oneidensis MR-1 to nitrobenzene

Bioreduction by electroactive bacteria (EAB) is considered as a potential and cost-effective approach for the removal of nitroaromatic compounds (NACs). However, little is known about how the widespread EAB sense and respond to slightly soluble NACs in aquatic environments. Here, the chemotactic behaviors of Shewanella oneidensis MR-1, a model EAB, toward several NACs were examined and their underlying molecular mechanism was elucidated. S. oneidensis MR-1 was found to exhibit a strong chemotactic response to nitrobenzene (NB), but not to other selected NACs under aerobic conditions. To sense NB, this bacterium requires both the histidine kinase (CheA-3)-involved chemotactic signal transduction pathway and an inner-membrane c-type cytochrome CymA. Such a chemotactic response is mediated by an energy taxis mechanism. Additionally, external riboflavin was shown to greatly enhance the Shewanella taxis toward NB, implying a feasible way to increase the bioavailability of NACs. The present study deepens our understanding of the role of microbial chemotaxis in the removal of NACs and provides more options for the bioremediation of NAC-contaminated sites.

Metal-organic framework for sorptive/catalytic removal and sensing applications against nitroaromatic compounds

Recently, the potential application of metal-organic frameworks (MOFs) has been recognized for removal and sensing of various organic pollutants (e.g., nitroaromatic compounds, pesticides, polycyclic aromatic compounds, and herbicides) due to their unique tunable and versatile properties. In this paper, we reviewed the recent experimental and computational efforts to develop MOFs for adsorption removal, catalytic conversion, and sensing of nitroaromatic compounds. To this end, we first classified nitroaromatic compounds in association with their toxicity. Then, we reviewed current advances made in the application of MOFs towards removal of nitroaromatic compounds (based on adsorption/catalysis) and their sensing applications. Furthermore, the discussion was made for the practical performance of MOFs for such applications. Finally, the future prospects for MOFs are described in the fields of adsorption removal, catalytic conversion, and sensing of nitroaromatic compounds.

Structures of nitroaromatic compounds induce Shewanella oneidensis MR-1 to adopt different electron transport pathways to reduce the contaminants

Nitroaromatic compounds (NACs) are one class of typical refractory biodegradable organic pollutants detected in various environmental media. The reductive transformation of NACs by the electrochemically active bacterium Shewanella oneidensis MR-1 is a possible and cost-effective option for the removal of NACs. However, little information on the respiratory pathway employed by S. oneidensis MR-1 to reduce NACs is available. In the present study, we investigated the reduction of NACs with different nitro or alkyl moieties by S. oneidensis MR-1 and eight constructed mutants with the deletion of the mtrA, mtrB, mtrC/omcA, cymA, napA, napB, nrfA, and nfnB genes to explore these key functional enzymes. The reduction of nitrobenzene, 4-nitrotoluene, 4-ethylnitrobenzene, 1-tert-butyl-4-nitrobenzene, 1,2-dinitrobenzene, 1,3-dinitrobenzene, 1,4-dinitrobenzene, 2,4-dinitrotoluene, 2,6-dinitrotoluene and 2,4,6-trinitrotoluene occurs via both the Mtr respiratory pathway and NfnB related pathway. However, 2,5-ditertbutyl-nitrobenzene, 2-nitrobiphenyl and 2,2′-dinitrobiphenyl are reduced only via the Mtr respiratory pathway. The van der Waals volume of NACs was the key factor in determining the reduction by S. oneidensis MR-1 according the correlation analysis. Our study provides new insights into the environmental adaption of S. oneidensis MR-1 and facilitates the bioremediation of NAC-related contamination.

Environmental persistence, hazard, and mitigation challenges of nitroaromatic compounds.

Nitroaromatic compounds (NACs) are extensively used in different industries and are synthesized in large quantity due to their heavy demand worldwide. The broad use of NACs poses a serious pollution threat. The treatment processes used for the removal of NACs are not effective and sustainable, leading to their release into the environment. The nitro group attached to benzene ring makes the compounds recalcitrant due to which they persist in the environment. Being hazardous to human as well as other living organisms, NACs are listed in the USEPA's priority pollutant group. This review provides updated information on the sources of NACs, prevalence in different environmental matrices, and recent developments in methods of their detection, with emphasis on current trends as well as future prospects. The harmful effects of NACs due to exposure through different routes are also highlighted. Further, the technologies reported for the treatment of NACs, including physico-chemical and biological methods, and the challenges faced for their effective implementation are discussed. Thus, the review discusses relevant issues in detail making suitable recommendations, which can be helpful in guiding further research in this subject.

Synthesis of MoS<sub>2</sub>/Graphene Hybrid for Electrochemical Detection and Catalytic Reduction of 4-Nitrophenol

Large amounts of nitroaromatic compounds are discharged into the natural environment, leading to environmental pollution. The detection and removal of nitroaromatic compounds are therefore important environmental issues. In this study, the hybrid of molybdenum disulfide (MoS2) and graphene (GR) was synthesized using a facile hydrothermal method. Sodium molybdate was selected as the precursors for MoS2. While thiourea was used as reductant and sulfur sources at the same time. Samples were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), N2 adsorption, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Raman microscope. Compared to pure MoS2, the obtained MoS2/GR hybrid showed improved activity for electrochemical detection and chemical reduction of 4-nitrophenol. The activity enhancement should be due to the addition of GR, which could improve the conductivity as well as provide more active sites. The MoS2/GR hybrid could therefore provide new multi-function catalyst for environment protection.

Synthesis of MoS2/graphene hybrid supported Au and Ag nanoparticles with multi-functional catalytic properties

The detection and removal of nitroaromatic compounds is an important issue for environmental protection. In this study, a hybrid of molybdenum disulfide (MoS2) and graphene (GR) was first synthesized using a facile hydrothermal method. Au and Ag nanoparticles were then deposited onto the surface of the MoS2/GR hybrid with sodium citrate as the stabilizer and reductant. Compared to using pure MoS2 as the support, the obtained Au (Ag)-MoS2/GR composites showed improved activity for electrochemical detection and chemical reduction of 4-nitrophenol. The activity enhancement appears to be due to the addition of GR, which could improve the conductivity as well as provide more active sites. The successful synthesis of Au (Ag)-MoS2/GR composites could provide new multi-function catalysts for environmental protection.

Removal of Nitro Aromatic Compounds from 2,4,6‐Trinitrotoluene Red Water Using 1,2‐Ethanediamine Modified Macroporous Polystyrene Microspheres

AbstractTo remove nitro aromatic compounds (NACs) from 2,4,6‐trinitrotoluene (TNT) red water, large‐pore‐size (pore size = 200 nm) polystyrene (PSt) microspheres were activated with chloroacetyl chloride followed by reaction with 1,2‐ethanediamine (EDA). Fourier transform IR analyses showed that the amino group was introduced onto PSt microspheres. Determination of the total amino group and primary amino densities suggested that the imino group was the functional group of EDA–PSt. Scanning electron microscope images and mercury porosimetry measurements indicated that the pore structure was well maintained during the reaction. After adsorption with EDA–PSt, 98.5% chemical oxygen demand and 99% acute toxicity of TNT red water was removed. As shown by HPLC and GC–MS, all the neutral and acid NACs in TNT red water were removed by EDA–PSt, while the basic NACs were not. The results showed that hydrogen bonding and electrostatic attraction were involved in adsorption. The adsorbed neutral and acid NACs were eluted using methanol and 0.1 mol L−1 NaOH, respectively.

Removal of nitro aromatic compounds and sulfite acid from distillate of 2,4,6‐trinitrotoluene red water using modified porous polystyrene microspheres

AbstractTo remove the nitro aromatic compounds (NACs) and SO32− from distillate of 2,4,6‐trinitrotoluene (TNT) red water, the carboxylated and aminated polystyrene (PSt) microspheres were used as adsorbents. GC‐MS and HPLC analysis were used to determine the types and concentrations of NACs before and after adsorption. The carboxylated PSt, which was prepared by modifying PSt with phthlandione (PA), could remove the neutral NACs including 2,6‐dinitrotoluene (2,6‐DNT), 2,4‐dinitrotoluene (2,4‐DNT), 1,3,5‐trinitrobenzene (1,3,5‐TNB), and 2,4,6‐trinitrotoluene (2,4,6‐TNT), with the acid 2,4‐dinitrophenol (2,4‐DNP) and SO32− remained in the distillate. The aminated PSt that was synthesized by activating PSt with chloroacetyl chloride follow by reaction with 1,2‐ethanediamine (EDA) could remove all the NACs and SO32−. The results suggested that EDA‐PSt adsorbed the NACs though multimode interactions, i.e., hydrogen bond and electrostatic attraction. After adsorption using EDA‐PSt, chemical oxygen demand (COD) was reduced from 86.1 to 11.2 mg L−1, and a colorless, transparent, and nontoxic solution with neutral pH value was obtained. Five grams of EDA‐PSt could purify 1600 cm3 of distillate of TNT red water, and the adsorbents could be recycled by elution with methanol to desorb the neutral NACs followed by elution with 0.1 mol L−1 NaOH to wash off 2,4‐DNP and SO32−. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Fluoroalkylated Polysilane Film as a Chemosensor for Explosive Nitroaromatic Compounds

The present paper reports a new type of polymer-based chemosensor made of stiff fluoroalkylated polysilane, poly(3,3,3-trifluoropropylmethylsilane) (1), which showed a remarkable sensitivity for explosive nitroaromatic compounds (NACs), such as 2,4,6-trinitrophenol (picric acid), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrotoluene (DNT), and m-dinitrobenzene (DNB), by a decrease in the photoluminescence (PL) intensity in the near-UV region with parts per million concentration of NACs in tetrahydrofuran (THF) solution and in the solid film in water. The PL intensity was completely reversible repeatedly after the removal of NACs from the thin film by rinsing with methanol (or water). A linear Stern−Volmer relationship was observed in all of the cases with high quenching constants. The PL quenching efficiency of 1 (Mn = 3.12 × 104, PDI = 3.6, K = 4.15 × 104 M-1) for picric acid is 198 times better than that of nonfluoroalkylpolysilane, poly(n-propylmethylsilane) (2) (Mn = 2.93 × 104, PDI = 2.1, K = 2.09 × 102 M-1). The weak noncovalent interaction between Si atoms of σ-conjugated polysilane and N and/or O atoms of electron-deficient NACs may be responsible for electron transfer from the excited state of the polysilane to the electron-deficient NACs, resulting in the PL quenching of 1 in solution and in the thin film by NACs.