Degradation Pathway Of Dye Research Articles

Efficient catalytic activity of BiVO4 nanostructures by crystal facet regulation for environmental remediation

Controlled growth of BiVO4 nanostructures along (121) and (040) crystal facets plays a crucial role in enhancing their catalytic performance. In this regard, the visible light active photocatalyst BiVO4 was synthesized concerning the effect of pH and surfactants by hydrothermal method. The morphology and size of BiVO4 are strongly dependent on the concentration of H+ and Bi3+ in the reaction system while varying the pH. Further, the significant role of cationic surfactant for obtaining the morphology of the spherical nanoparticles of BiVO4 powders with size 55 nm was analyzed. Adsorption behavior of as-synthesized samples was investigated through Langmuir isotherm model. The catalytic performance of BiVO4 photocatalyst with the degradation efficiency of 98.79% and 15.58% over the methylene blue (MB) and methyl orange (MO) dyes were noticed within 60 min of light irradiation respectively. The enhanced and declined catalytic activity was well correlated with the surface charge of BiVO4 photocatalyst towards the MB and MO dyes respectively. Further, the photocatalytic activity of mixed anionic and cationic dyes was performed. The degradation pathway of MB dye was analyzed by LC-MS for the identification of intermediate products. From the obtained results, the proposed possible photocatalytic mechanism reported.

Enhanced photocatalytic degradation of RhB dye from aqueous solution by biogenic catalyst Ag@ZnO

In the present work, ZnO and Ag@ZnO nanoparticles based photocatalyst were synthesized via green route by using the leaves extract of pecan nuts (Carya illinoinensis) for the first time. The phytochemicals present in leaf of extract pecan nuts (Carya illinoinensis) such as methyl gallate and kaempferol act as capping and reducing agents. The obtained photocatalyst were analyzed via various techniques such as XRD (X-ray diffraction), TEM (transmission electron microscopy), SEM (scanning electron microscopy), FTIR (Fourier transform infrared spectroscopy), PL (Photoluminescence spectroscopy), XPS (X-ray photoelectron spectroscopy) and UV (UV–visible spectroscopy). The activity of biogenic photocatalyst were investigated against RhB (Rhodamine B) dye and the results demonstrated that the catalytic properties become enhanced significantly after Ag doping as compared to bare ZnO. The effect of various parameters were also investigated such as pH, catalyst dose, initial concentration of dye. The obtained results showed highest efficacy of catalyst at pH 10, further the photo-degradation of Rhodamine B (RhB) dye followed pseudo first order kinetic model. The reusability test of biogenic photocatalyst revealed that the catalyst was an excellent option for practical use with high stability even after 5 cycles. The mechanism for, ZnO and Ag@ZnO synthesis and degradation pathway of RhB dye was proposed.

Analysis and effective separation of toxic pollutants from water resources using MBBR: Pathway prediction using alkaliphilic P. mendocina

Azo dyes are highly toxic, which acts as a notable mutagen and carcinogen. This has a significant effect on human health, plants, animals, aquatic and terrestrial environments. Thus, the degradation of the azo dyes is exclusively studied using the conventional methods of which biodegradation is an eco-friendly approach. Hence, the present study is focused on the elucidation of reactive mixed azo dye degradation pathway using MBBR and laccase enzyme produced by an alkaliphilic bacterium P. mendocina. Synthetic wastewater treatment performed using MBBR was very effective which reduced the COD and BOD to 90 mg/L and 460 mg/L. The potential degrader P. mendocina was isolated and laccase enzyme was screened. Finally, the degradation pathway was elucidated. The in silico toxicity analysis predicted Reactive Red and Reactive Brown as developmental toxicants during Reactive Black as Developmental non-toxicant. Docking studies were performed to understand interaction of laccase with compounds evolved from dyes.

Metagenomic Insight of a Full Scale Eco-Friendly Treatment System of Textile Dye Wastewater Using Bioaugmentation of the Composite Culture CES-1.

Effects of bioaugmentation of the composite microbial culture CES-1 on a full scale textile dye wastewater treatment process were investigated in terms of water quality, sludge reduction, dynamics of microbial community structures and their functional genes responsible for degradation of azo dye, and other chemicals. The removal efficiencies for Chemical Oxygen Demand (COD), Total Nitrogen (T-N), Total Phosphorus (T-P), Suspended Solids (SS), and color intensity (96.4%, 78.4, 83.1, 84.4, and 92.0, respectively) 300–531 days after the augmentation were generally improved after bioaugmentation. The denitrification linked to T-N removal appeared to contribute to the concomitant COD removal that triggered a reduction of sludge (up to 22%) in the same period of augmentation. Azo dye and aromatic compound degradation and other downstream pathways were highly metabolically interrelated. Augmentation of CES-1 increased microbial diversity in the later stages of augmentation when a strong microbial community selection of Acinetobacter parvus, Acinetobacter johnsonii, Marinobacter manganoxydans, Verminephrobacter sp., and Arcobacter sp. occurred. Herein, there might be a possibility that the CES-1 augmentation could facilitate the indigenous microbial community successions so that the selected communities made the augmentation successful. The metagenomic analysis turned out to be a reasonable and powerful tool to provide with new insights and useful biomarkers for the complex environmental conditions, such as the full scale dye wastewater treatment system undergoing bioaugmentation.

Bimetallic Ag-Zn-BTC/GO composite as highly efficient photocatalyst in the photocatalytic degradation of reactive yellow 145 dye in water

Agx-Zn100−x-BTC/GO composites (BTC: benzene-1,3,5-tricarboxylic, GO: graphene oxide) with different Ag/Zn molar ratios were synthesized using microwave-assisted hydrothermal treatment. The Agx-Zn100−x-BTC/GO exhibited excellent photocatalytic performance in the reactive yellow 145 dye (RY-145) degradation under irradiation of visible light with nearly 100% of RY-145 removal after 35 min, as compared to Zn-BTC/GO and Ag-BTC/GO. Reactive oxygen species scavenging assays have shown that the holes (h+) and superoxide radical anion (O2−•) play a primary role in RY-145 degradation. Based on the band structure of materials, the Z-scheme photocatalytic mechanism was suggested. The effect of catalyst dosage, pH and dye concentration on the efficiency of photocatalytic activity of bimetallic Ag50-Zn50-BTC/GO was also investigated. The improvement in photocatalytic activity of bimetallic Ag50-Zn50-BTC/GO could be given by the synergism of (i) absorption of visible light confirmed by UV-Vis diffuse reflectance spectra; (ii) the increased lifetime as evidenced by photoluminescence spectra and transient photocurrent response; (iii) the increased oxygen vacancy defects as confirmed by X-ray photoelectron spectroscopy results. The degradation pathway of RY-145 dye was also predicted based on liquid chromatography-mass spectrometer analysis. The removed chemical oxygen demand, biological oxygen demand, total organic carbon outcomes indicated the high mineralization ability for RY-145 degradation over Ag50-Zn50-BTC/GO.

Coupling azo dye degradation and biodiesel production by manganese-dependent peroxidase producing oleaginous yeasts isolated from wood-feeding termite gut symbionts

BackgroundTextile industry represents one prevalent activity worldwide, generating large amounts of highly contaminated and rich in azo dyes wastewater, with severe effects on natural ecosystems and public health. However, an effective and environmentally friendly treatment method has not yet been implemented, while concurrently, the increasing demand of modern societies for adequate and sustainable energy supply still remains a global challenge. Under this scope, the purpose of the present study was to isolate promising species of yeasts inhabiting wood-feeding termite guts, for combined azo dyes and textile wastewater bioremediation, along with biodiesel production.ResultsThirty-eight yeast strains were isolated, molecularly identified and subsequently tested for desired enzymatic activity, lipid accumulation, and tolerance to lignin-derived metabolites. The most promising species were then used for construction of a novel yeast consortium, which was further evaluated for azo dyes degradation, under various culture conditions, dye levels, as well as upon the addition of heavy metals, different carbon and nitrogen sources, and lastly agro-waste as an inexpensive and environmentally friendly substrate alternative. The novel yeast consortium, NYC-1, which was constructed included the manganese-dependent peroxidase producing oleaginous strains Meyerozyma caribbica, Meyerozyma guilliermondii, Debaryomyces hansenii, and Vanrija humicola, and showed efficient azo dyes decolorization, which was further enhanced depending on the incubation conditions. Furthermore, enzymatic activity, fatty acid profile and biodiesel properties were thoroughly investigated. Lastly, a dye degradation pathway coupled to biodiesel production was proposed, including the formation of phenol-based products, instead of toxic aromatic amines.ConclusionIn total, this study might be the first to explore the application of MnP and lipid-accumulating yeasts for coupling dye degradation and biodiesel production.

Synthesis, characterization and photocatalytic dye degradation studies of novel defect pyrochlore, KHf0.5Te1.5O6

We report the solid-state synthesis of KHf0.5Te1.5O6 (KHTO), its characterization and employment as photocatalyst for methylene blue and methyl violet degradations in aqueous solution. The material was subjected to X-ray Diffraction (XRD), Field emission-scanning electron microscopy (FE-SEM), Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), N2 adsorption/desorption and XPS measurements. The material was crystallized in a cubic lattice with the space group. The bandgap energy of the KHTO is 2.60 eV. The photocatalytic methylene blue (MB) and methyl violet (MV) dyes degradation efficiency of KHTO was investigated under the visible light irradiation. The mechanistic dye degradation pathway of MB was studied. The radical quenching experiments reveal that the short-lived species O2●-, OH●, and h+ actively participate in the degradation of MV and MB dyes. An additional terephthalic acid experiment was carried out to establish the participation of OH● radicals in the dye degradation process. The stability and reusability of the KHTO catalyst were also studied.

Effect of substituents in hydroxyl radical-mediated degradation of azo pyridone dyes: Theoretical approaches on the reaction mechanism

Understanding the degradation behavior of azo dyes in photocatalytic wastewater treatment is of fundamental and practical importance for their application in textile-processing and other coloration industries. In this study, quantum chemistry, as density functional theory, was used to elucidate different degradation pathways of azo pyridone dyes in a hydroxyl radical (HO•)-initiated photocatalytic system. A series of substituted azo pyridone dyes were synthesized by changing the substituent group in the para position of the benzene moiety, ranging from strong electron-donating to strong electron-withdrawing groups. The effect of dye molecular structure on the photocatalytic degradation reaction mechanism was analyzed and quantification of substituent effects on the thermodynamic and kinetics parameters was performed. Potential energy surface analysis revealed the most susceptible reaction site for the HO• attack. The calculated reaction barriers are found to be strongly affected by the nature of substituent group with a good correlation using Hammett σp constants and experimentally determined reaction rates. The stability of pre-reaction complexes and transition state complexes were analyzed applying the distortion-interaction model. The increased stability of the transition state complexes with the distancing from the substituent group has been established.

Synthesis of nickel nanoparticles using Citrullus colocynthis stem extract for remediation of Reactive Yellow 160 dye.

In current years, pollution caused by synthetic dyes has become one of the most serious environmental issues. By rapidly developing industrial units, effluents having synthetic dyes are directly or indirectly being discharged into the environment. Bio-sorption is cost-effective way for the eradication of toxic dyes present in textile effluent. The present study involves the synthesis of nickel nanoparticles using Citrullus colocynthis stem extract. The characterization of synthesized nickel nanoparticles (Ni-NPs) was done by SEM. The synthesized Ni-NPs were used to degrade the Reactive Yellow 160 dye following the optimization of different experimental parameters. The maximum decolorization (91.4%) was obtained at 0.02% dye conc., 9 mg/L conc. of Ni-NPs, pH 7 at 40 °C. TOC and COD were used to assess the efficiency of this experiment. Percent reduction in COD and TOC was found to be 84.35% and 83.24% respectively. The degradation pathway of dye under study confirmed the formation of non-toxic end-products.

Hydrothermal synthesis of C-doped K2Al2Ti6O16 as a visible light–activated photocatalyst in the degradation of organic dyes

Hydrothermally synthesized C-doped K2Al2Ti6O16 (C-KATO) is reported as a novel photocatalysts for methylene blue (MB) and methyl orange (MO) degradation under visible light irradiation. Glucose is used as a carbon source. The structural, morphological, and optical properties are investigated using powder XRD, FE-SEM/EDS elemental mapping, TEM/HR-TEM, FT-IR, UV-Vis DRS, and XPS techniques. C-KATO sample crystallized in the tetragonal lattice with space group I4/m. The bandgap energy of C-KATO is found to be 2.59 eV whereas the bandgap energy of the parent KATO is 3.58 eV. FE-SEM elemental mapping and XPS results of C-KATO reveal the presence of carbon in the KATO lattice. The photocatalytic activities of the KATO and C-KATO oxides are evaluated for MB and MO degradation under visible light irradiation, and the results have been compared with those attained over P25 Degussa. It shows higher activity in comparison to P25. The mechanistic dye degradation pathway is studied using radical scavengers during photoreaction.

Fe2O3/TiO2 functionalized biochar as a heterogeneous catalyst for dyes degradation in water under Fenton processes

Functionalized biochar as a great potential purification material towards removal of contaminants form environment. Herein, Fe2O3/TiO2 functionalized biochar (Fe2O3/TiO2-BC) was fabricated through one-step pyrolysis of Fe2+–Ti4+ laden tea leaves biomass under air environment. The morphology, structure, and chemical state of Fe2O3/TiO2-BC were systematically characterized. Fe2O3/TiO2-BC exhibits higher degradation efficiency for dye pollutants via synergistic effect of sorption and oxidation in the Fenton system. The total organic carbon (TOC) removal efficiencies reached above 65 %. The degradation mechanisms and pathways of dyes (methylene blue (MB) selected as model), and the effects of the amount of H2O2, catalyst dosage, temperature, and initial pH value on the degradation processes were also studied. The electron spin resonance (ESR) and radicals quenching experimental results confirmed that the dominant radical species was hydroxyl radical. Additionally, Fe2O3/TiO2-BC could be easily regenerated by washing with water/ethanol mixture. Overall, these results indicate that the Fe2O3/TiO2-BC provides great potential for removing dye pollutants from water.

Microaerophilic biodegradation of raw textile effluent by synergistic activity of bacterial community DR4

Treatment of raw textile effluent (RTE) is very difficult, due to its inherent heterogeneous, low-biodegradable and toxic compositions. Pure and mixed microbial cultures have limited metabolic capabilities in effective mineralization of complex RTE. Therefore, in this study a novel bacterial community DR4 was enriched directly into a complex RTE consisting of 27 different dyes using textile dye polluted soil as an inoculum. The rigorous enrichment process resulted in acclimatization of a taxonomically distinct bacterial population, with an abundance of the genus Comamonas in the bacterial community DR4 as compared to the abundance of Pseudomonas in the RTE respectively, as revealed by high-throughput 16S rRNA gene (V3–V4 region) sequencing. Microaerophilic treatment of RTE by enriched bacterial community DR4, in the presence of optimized electron donor (sucrose) and nitrogen source (yeast extract) resulted in 88% of American Dye Manufacturer's Institute (ADMI) removal and 98% of Chemical oxygen demand (COD) reduction within 32 h at 37 °C. In silico prediction of the functional genes within bacterial community DR4 was made by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis. The PICRUSt analysis revealed high abundance of xenobiotic degradation and metabolism genes. The predicted functional genes and textile dye degradation pathways were further validated using Ultraviolet–visible spectroscopy (UV–Vis), Fourier transform infrared (FTIR) spectroscopy and High Resolution Liquid Chromatography coupled with Mass Spectrometry (HR-LCMS) based characterization of textile dye degradation metabolites. The activity of azoreductases in the cell-free extracts (CFE) of the enriched bacterial community DR4 was induced by 1.83–7.81 folds in the presence of representative textile dyes as compared to uninduced samples, which confirmed their role in textile effluent decolourization. The degradation of four representative azo dyes present in RTE such as Disperse orange 30, Reactive red 152, Direct blue 2 and Acid brown 15 depicted symmetric degradation of azo bonds by bacterial community DR4.

Facile Synthesis of Ce–Doped SnO2 Nanoparticles: A Promising Photocatalyst for Hydrogen Evolution and Dyes Degradation

AbstractThis report discussed the efficient hydrogen generation via water splitting and fast dye degradation pathway using Ce doped SnO2 nanoparticles. One pot synthesis of Ce doped SnO2 nanoparticles was carried out by a simple, convenient wet chemical method using H2O2 and the product obtained was characterized using array of physico‐chemical techniques. Powder X‐ray diffraction confirmed the presence of rutile phase. Band gap for Ce:SnO2 was found out to be 3.80 eV which is more than the pure SnO2 (3.71 eV) and it is due to Moss‐Burstein effect. EDAX analysis and elemental mapping support uniform distribution of 5% Ce and the SEM imaging depicts irregular shape of nanocrystallites. The doping of 5% Ce into the interstitial and lattice positions of SnO2 nanoparticles was also confirmed by the X‐ray photoelectron spectroscopy analysis. Raman measurement and photoluminescence analysis showed the presence of oxygen vacancies and disorderness in the nanoparticles. Photocatalytic water splitting proficiency was investigated using Ce doped SnO2 nanomaterials in the presence of NiO as co‐catalyst and other different sacrificial reagents such as methanol, Na2S‐Na2SO3, EDTA ions, triethanolamine and in combinations. It was found that the evolution of H2 is maximum i. e. 25 μmol/g/h in presence of as‐synthesized catalyst, NiO (co‐catalyst) along with EDTA and methanol as scavengers under UV light irradiation. Further, the degradation of methylene blue and methyl orange dyes was investigated under UV‐Visible irradiation using Ce:SnO2 NPs.

Photocatalytic Behavior of SILAR-Grown Nano-flaked CdS

An undemanding and cost-effective low-temperature sequential ionic layer adsorption reaction process has been used to synthesize cadmium sulfide (CdS) thin films on glass substrates. The as-deposited films were photoconductive in nature with a photosensitivity of ~ 10, and their sensitivity could be improved using a post-deposition annealing process sequence to ~ 650. We have grown nano-flaked CdS and tested their efficacy for the photo-catalytic degradation of Rhodamine B dye molecules. We report that the nano-flaked CdS has an inherent Rhodamine B dye decay pathway which is active even in the absence of visible radiation. We also report on the Rhodamine B dye decay by the nano-flaked CdS under direct sunlight illumination. Our results prove that the kinetics of the photocatalysis is directly related to the photoconductive nature of the films. The highly photosensitive nature of the nano-flaked CdS films leads to alternate dye degradation pathways which enhance the kinetics of the reaction.

Mapping degradation pathways of natural and synthetic dyes with LC-MS: Influence of solvent on degradation mechanisms

Abstract To help conserve the vast array of (combinations of) dyestuffs and pigments encountered in cultural-heritage objects and application materials, a rapid and convenient method for dye-degradation research is required. In-solution degradation studies of dyes in a strong solvent, such as the commonly used dimethyl sulfoxide (DMSO), are potentially of interest, in addition to studies involving other solvents, such as water. The degradation of eosin and carminic acid under the influence of light was investigated in two solvents, i.e. in a mixture of DMSO and acetonitrile and in pure water. A liquid chromatography – mass spectrometry (LC-MS) method was developed for analysis of the degraded samples and identification of the individual components. The presence of DMSO generally facilitated faster degradation, which, in combination with its universal solvating properties are advantageous. However, different products were formed in the presence of DMSO. Degradation pathways for eosin and carminic acid in these solvents are proposed.

Fe complex immobilized on waste polypropylene fibers for fast degradation of Reactive Red 195 via enhanced activation of persulfate under LED visible irradiation

To develop a low cost, environmental care and high effective activation system for persulfate used for remediation of contaminated water, Fe complex was immobilized on waste polypropylene (PP) fibers through surface graft polymerization and coordination and then characterized for enhancing the activation of Na2S2O8 in the degradation of an organic dye, Reactive Red 195 in water under LED visible irradiation. It was found that Fe complex could activate Na2S2O8 in the dark, and LED irradiation enhanced the activation effect of Fe complexes on Na2S2O8, thus leading to a fast dye degradation. High Fe content in the complex or strong irradiation highly accelerated the dye decomposition in the pH range of 2–10. Hydroxyl radical as the main free oxygen radical could more significantly resulted in the dye decomposition than sulfate radicals. Dye degradation pathway in this system was elucidated. The high toxic intermediates were detected after short irradiation, and dramatically reduced by further oxidation of Na2S2O8 activated with Fe complex after long irradiation.

Color and nitrogen removal from synthetic dye wastewater in an integrated mesophilic hydrolysis/acidification and multiple anoxic/aerobic process

Dye wastewater is one kind of refractory pollutant and it is commonly treated by the integrated anaerobic and aerobic process. A new integrated hydrolysis/acidification and multiple anoxic/aerobic (AO) process was proposed for the removal of color and nitrogen from azo dye wastewater. System performance, the degradation pathway of azo dye and nitrogen metabolic pathway were investigated with quadrupole-time-of-flight and metagenomic analyses. The proposed process removed color and nitrogen efficiently, with the removal percentages of 89.4% and 54.0%, respectively. A colorful intermediate C16H11N3O7S2 during the degradation of azo dye was detected. Controlling a low dissolved oxygen concentration in the multiple AO process could enhance nitrogen removal. The detected bacteria possessing azoreductase for the azo dye degradation included Desulfovibrio aminophilus, Thermoanaerobacter, Lactococcus raffinolactis, Ruminiclostridium and Rhodopirellula. The nitrifying genes of amo and hao were mainly detected in Nitrosomonas, while the denitrifying genes were detected in Thauera, Candidatus Accumulibacter and Rhodothermus marinus.

Congo Red Decolorization and Detoxification by Aspergillus niger: Removal Mechanisms and Dye Degradation Pathway.

Congo red is one of the best known and used azo dyes which has two azo bonds (-N=N-) chromophore in its molecular structure. Its structural stability makes it highly toxic and resistant to biodegradation. The objective of this study was to assess the congo red biodegradation and detoxification by Aspergillus niger. The effects of pH, initial dye concentration, temperature, and shaking speed on the decolorization rate and enzymes production were studied. The maximum decolorization was correlated with lignin peroxidase and manganese peroxidase production. Above 97% were obtained when 2 g mycelia were incubated at pH 5, in presence of 200 mg/L of dye during 6 days at 28°C and under 120 to 150 rpm shaking speed. The degraded metabolites were characterized by using LC-MS/MS analyses and the biodegradation mechanism was also studied. Congo red bioconversion formed degradation metabolites mainly by peroxidases activities, i.e., the sodium naphthalene sulfonate (m/z = 227) and the cycloheptadienylium (m/z = 91). Phytotoxicity and microtoxicity tests confirmed that degradation metabolites were less toxic than original dye.

Enhanced azo dye Reactive Red 2 degradation in anaerobic reactors by dosing conductive material of ferroferric oxide

Effect of dosing ferroferric oxide (Fe3O4) on the anaerobic treatment of azo dye Reactive Red 2 (RR2) was investigated in two anaerobic sequencing batch reactors (ASBRs). System performance, dye degradation pathways, and microbial activities and structure were examined. The addition of Fe3O4 significantly improved treatment efficiency, with the removal efficiency of RR2 increased by 116%, the maximum methane (CH4) yield potential and the peak CH4 production rate improved by 7.7% and 22.3%, and the lag phase shortened by 39.6%, respectively. The activity of the electron transport system was significantly enhanced by dosing Fe3O4, with the maximum value increased by 77% and conductivity of the anaerobic sludge increased by 178%. According to the proposed pathway for the degradation of RR2, the degradation products from complete cleavage of the NN bond in RR2 were obtained at the presence of Fe3O4, while were absent without Fe3O4. At high initial dye concentrations, the dosage of Fe3O4 alleviated the inhibition to microbes by RR2, and high degradation rate and removal efficiency were maintained. The microbial community structure changed during the long-term acclimation with the dosage of Fe3O4. Paludibacter, Trichococcus and Methanosarcina were predominant and their relative abundances increased with the addition of Fe3O4.

Azo dye degradation pathway and bacterial community structure in biofilm electrode reactors

In this study, the degradation pathway of the azo dye X-3B was explored in biofilm electrode reactors (BERs). The X-3B and chemical oxygen demand (COD) removal efficiencies were evaluated under different voltages, salinities, and temperatures. The removal efficiencies increased with increasing voltage. Additionally, the BER achieved maximum X-3B removal efficiencies of 66.26% and 75.27% at a NaCl concentration of 0.33 g L−1 and temperature of 32 °C, respectively; it achieved a COD removal efficiency of 75.64% at a NaCl concentration of 0.330 g L−1. Fourier transform infrared spectrometry and gas chromatography–mass spectrometry analysis indicated that the X-3B biodegradation process first involved the interruption of the conjugated double-bond, resulting in aniline, benzodiazepine substance, triazine, and naphthalene ring formation. These compounds were further degraded into lower-molecular-weight products. From this, the degradation pathway of the azo dye X-3B was proposed in BERs. The relative abundances of the microbial community at the phylum and genus levels were affected by temperature, the presence of electrons, and an anaerobic environment in the BERs. To achieve better removal efficiencies, further studies on the functions of the microorganisms are needed.