Degradation Pathway Of Dye Research Articles

Green-synthesized BiFeO3 nanoparticles for efficient photocatalytic degradation of organic dyes, antibiotic and catalytic reduction of 4-nitrophenol

Green-synthesized nanoparticles have recently emerged as promising catalysts for the removal of toxic dyes from water bodies. In this article, Bismuth ferrite (BiFeO3) nanoparticles were synthesized by a simple and low-cost method using Couroupita guianensis plant leaf extract. The particles were used as photocatalysts for degrading RhB, MO dyes, and TC antibiotics, as well as for reducing toxic 4-NP to useful 4-AP. The synthesized nanoparticles were characterized using several state-of-the-art tools. The formation of perovskite structure and the presence of biomolecules on the surface of BiFeO3 nanoparticles was confirmed by FTIR analysis. Raman spectrum revealed a rhombohedral structure of BiFeO3 nanoparticles, corroborating the XRD analysis. FESEM micrograph demonstrated irregularly shaped agglomerated nanoparticles. The average hydrodynamic diameter was estimated to be 51 nm using the DLS technique. The optical energy bandgap of the bismuth ferrite was estimated using Tauc’s relation for direct bandgap semiconductors. SQUID measurements revealed that these nanoparticles exhibit a weak ferromagnetic ordering. Furthermore, these nanomaterials degraded the cationic and anionic dyes effectively because of the formation of hydroxyl radicals, confirmed by the scavenger test. The photocatalytic degradation pathway of RhB dye was investigated through LC-MS analysis, and the intermediate degradation products were identified. The prepared material also exhibited excellent catalytic efficiency in a short duration of time. This study proclaims that these nanoparticles can be used as potential catalysts for the purification of water.

Design of ternary GO@AgNPs@g-C3N4 membranes for efficient dye removals in integrated photocatalysis-filtration reactors

Photocatalytic composite membranes (PCMs), which integrate the high degradation efficiency of photocatalysts and the physical separation properties of membranes, have emerged as a promising technology for wastewater treatment. Herein, the ternary GO@AgNPs@g-C3N4 PCM was fabricated through a facile vacuum-filtration assembly of graphene oxide (GO), graphitic phase carbon nitride (g-C3N4), and silver nanoparticles (AgNPs) onto commercial mixed cellulose ester (MCE) substrates. The effects of g-C3N4 synthesized from different precursors and various metal nanoparticles on the performance of PCM were systematically investigated. Interestingly, results show the addition of AgNPs not only significantly improves the photocatalytic performance of PCMs but also enhances the mechanical adhesion between the active layer and the MCE substrate. The resultant PCMs exhibit outstanding photocatalytic performance, maintaining dye removal above 89% even after 25 consecutive cycles. Moreover, dye degradation pathways over the PCMs were investigated through free radical scavenging experiments and electron spin resonance characterizations. This simple assembly method results in a 3–12 times increase in flux compared to the layer-by-layer assembly method. Accordingly, our designed PCMs exhibit significant potential for wastewater treatment and water purification applications.

Study of Fe3O4 and Cu2+ doped modified Fe3O4 nano catalyst for photocatalytic degradation of methylene blue and eriochrome black-T dyes: Synthesis, characterization, and antimicrobial assessment

This study presents the synthesis and characterization of undoped Fe3O4 and 3% Cu-doped Fe3O4 nanoparticles via a cost-effective and environmentally friendly co-precipitation method. A comprehensive suite of nanomaterial characterization techniques, including energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS), was employed to confirm the elemental composition, structural parameters, and chemical states of the prepared materials. Additionally, fragmentation analysis using LC–MS illustrated the structural stability and breakdown of the nanoparticles under specific conditions. Both the materials were characterized by vibrating sample magnetometer (VSM), Brunauer-Emmett-Teller (BET) for investigating the magnetic, and surface characteristics respectively. Furthermore, the synthesized nanoparticles were evaluated for their photocatalytic degradation efficiency towards methylene blue and eriochrome black T dyes. A systematic investigation of various parameters, including the pH of the dye solution, dye concentration over time, catalyst dose, dye concentration versus degradation, catalyst reusability, and kinetic study, was conducted to understand the factors influencing the photocatalytic activity of both undoped and Cu-doped Fe3O4 nanoparticles. The LC-MS analysis predicted the probable degradation pathways of MB and EBT dyes. This work provides insights into the sustainable synthesis, comprehensive characterization, and practical application of Fe3O4-based nanoparticles for water treatment applications, highlighting their potential as efficient and environmentally benign Photocatalyst for wastewater remediation. An investigation was conducted to investigate the antimicrobial properties of both undoped and doped nanoparticles. The minimum inhibitory concentration (MIC) of the synthesized nanoparticles were determined against the bacterial strains E. coli, P. aeruginosa, S. aureus, and S. pyogenes, as well as the fungal strains C. albicans, A. niger, and A. clavatus.

Biodegradation of Malachite Green Dye by Novel Isolated Bacillus Species AAV from Garden Soil

Malachite green (MG) dye commonly use in textile and paper printing industry to a great extent. Textile effluent released from industries including dyes must be treated before release into the environment due to its toxic nature. In present study, newly isolated bacterial species was able to decolorize MG dye (100%) in 1 h at shaking condition and 94% at static condition. 16S rRNA analysis revealed an isolate as Bacillus sp. AAV. Lignin peroxidase, laccase and tyrosinase enzymes from Bacillus sp. AAV showed significant increased activity during decolourisation. There was 138, 369 and 164% trek in activity of LiP, laccase and tyrosinase after MG decolourization, respectively. Bacillus sp. AAV could decolourise MG efficiently at alkaline pH (8-10) and at 40°C temperature. Biodegradation was monitored by UV-VIS spectrophotometer. Gas chromatography-Mass spectroscopy data was used to propose the degradation pathway of MG dye. The newly isolated Bacillus sp. AAV was able to decolourise ten various types of dyes and textile dye effluent. Phytotoxicity test by using seeds of wheat and sorghum was also carried out to check toxicity of MG dye metabolites. The study reveals that there was no toxicity with respect to tested seeds. This study suggests that Bacillus sp. AAV could be a useful microorganism or its enzyme system for textile dyes and effluent treatment.

Exploring fungal-mediated solutions and its molecular mechanistic insights for textile dye decolorization

Decolorization of textile dyes and study of their intermediate compounds is necessary to comprehend the mechanism of dye degradation. In the present study, different fungal mediated solutions were explored to provide an alternative to treat the reactive dyes. Growing biomass of Pleurotus sajor caju showed 83% decolorization (249.99 mg L−1 removal) of Reactive Blue 13 (RB 13) and 63% decolorization (188.83 mg L−1) of Reactive Black 5 (RB 5) at 300 mg L−1 initial concentration on 8 d. Higher laccase activity was positively correlated with increase in decolorization. However, increasing dye concentration has inhibitory effect on fungal biomass due to increase in toxicity. In laccase mediated decolorization, laccase produced from P. sajor caju using carbon rich waste material as substrate showed 89% decolorization (276.36 mg L−1 removal) of RB 13 and 33% decolorization (105.37 mg L−1 removal) of RB 5 at 300 mg L−1 initial dye concentration in 100 min at 30 °C and pH 3.0’. Comparing the two methods, laccase-mediated decolorization shows better decolorization in less time and does not produce sludge. Further, the present work also attempted to study the dye degradation pathway for Reactive blue 13 via laccase mediated process. Fourier-transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC), and gas chromatography–mass spectrometry (GC-MS) were utilized to identify the degraded products. The GC-MS analysis showed the formation of naphthalene, naphthalene 2-ol, benzene,1–2, dicarboxylic acid, 4, amino, 6,chloro, 1-3-5, triazin-2-ol as the final degraded products after enzymatic degradation of RB 13. These findings provide in-depth study of laccase-mediated textile dye degradation mechanism.

Direct Z‐Scheme Xylan‐Based Carbon Dots@TiO2‐x Nanocomposites for Visible Light Driven Photocatalytic of Dye Degradation and Antibacterial

AbstractTiO2 photocatalysis has gained attention as a cost‐effective way of degrading contaminants. However, it relies on UV excitation and experiences rapid carrier recombination. To address these drawbacks, novel xylan‐based carbon dots@hydrogenated TiO2 (CDs@TiO2‐x) composited by direct Z‐scheme heterojunction is fabricated as a visible light‐driven photocatalytic material, which broadens the range of light absorption to visible light and suppresses the recombination of photogenerated carriers. The spindle‐shaped CDs@TiO2‐x has C/N/O/S groups, positive charges, and oxygen vacancies on its surface, and can degrade 89% of methylene blue and 87% of methyl orange within 90 min, and 99% of rhodamine B within 60 min in visible light. It also eradicates 99.9% of E. coli in 2 h and 97.1% of S. aureus in 2.5 h. These performances surpass CDs and TiO2‐x, and exhibit advantages in similar composite materials. The degradation pathways of dyes and the specific antibacterial processes induced by ROS are thoroughly investigated through LC‐MS testing and related enzyme activity assays. DFT calculations study the role of oxygen vacancies, heterojunction mechanism, and catalytic sites. This study has developed a novel nanocomposite with applications in both dye degradation and sterilization, offering insights for multifunctional materials based on photocatalysis and heterojunction.

Investigation of the Photocatalytic Performance, Mechanism, and Degradation Pathways of Rhodamine B with Bi2O3 Microrods under Visible-Light Irradiation.

In the present work, the photodegradation of Rhodamine B with different pH values by using Bi2O3 microrods under visible-light irradiation was studied in terms of the dye degradation efficiency, active species, degradation mechanism, and degradation pathway. X-ray diffractometry, polarized optical microscopy, scanning electron microscopy, fluorescence spectrophotometry, diffuse reflectance spectra, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, UV-visible spectrophotometry, total organic carbon, and liquid chromatography-mass spectroscopy analysis techniques were used to analyze the crystal structure, morphology, surface structures, band gap values, catalytic performance, and mechanistic pathway. The photoluminescence spectra and diffuse reflectance spectrum (the band gap values of the Bi2O3 microrods are 2.79 eV) reveals that the absorption spectrum extended to the visible region, which resulted in a high separation and low recombination rate of electron-hole pairs. The photodegradation results of Bi2O3 clearly indicated that Rhodamine B dye had removal efficiencies of about 97.2%, 90.6%, and 50.2% within 120 min at the pH values of 3.0, 5.0, and 7.0, respectively. In addition, the mineralization of RhB was evaluated by measuring the effect of Bi2O3 on chemical oxygen demand and total organic carbon at the pH value of 3.0. At the same time, quenching experiments were carried out to understand the core reaction species involved in the photodegradation of Rhodamine B solution at different pH values. The results of X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffractometer analysis of pre- and post-Bi2O3 degradation showed that BiOCl was formed on the surface of Bi2O3, and a BiOCl/Bi2O3 heterojunction was formed after acid photocatalytic degradation. Furthermore, the catalytic degradation of active substances and the possible mechanism of the photocatalytic degradation of Rhodamine B over Bi2O3 at different pH values were analyzed based on the results of X-ray diffractometry, radical capture, Fourier-transform infrared spectroscopy, total organic carbon analysis, and X-ray photoelectron spectroscopy. The degradation intermediates of Rhodamine B with the Bi2O3 photocatalyst in visible light were also identified with the assistance of liquid chromatography-mass spectroscopy.

Electron structure and photocatalytic properties of (Na/K)VMoO6 nanosuspensions

Electron structure features of nanopowders with composition of (Na/K)VMoO6 have been investigated both experimentally and theoretically. The dispositions of valence edge and conduction band were determined experimentally for vacuum condition by X-ray photoelectron spectroscopy, UV–visible and impedance spectroscopy and evaluated theoretically for water solutions. The additional absorbance band in the band gap has been found for both compounds, which leads to electron conductivity at low-temperature range (250–350 °C). Nanopowders have been prepared by sol-gel method with further ground in the planetary mill. Prepared powders in water solution have formed nanosuspension with size's particle up to 100 nm for NaVMoO6 and 400 nm for KVMoO6, which is hardly sedimentated. The highly effective photocatalytic ability under visible light irradiation of the prepared compounds was observed using methylene blue decomposition process. The almost full methylene blue (20 mg/L) degradation is observed during 30 min for 10 mg of the photocatalysts. The investigation of possible dye degradation pathway has showed the high depth of decomposition.

Photocatalytic degradation of multiple-organic-pollutant under visible light by graphene oxide modified composite: degradation pathway, DFT calculation and mechanism

Wastewater containing antibiotics, organic dyes, and waterborne bacteria is a severe threat to human health and the environment. Amoxicillin has a slow metabolism rate in humans. Methylene blue is mutagenic and carcinogenic. In addition, Salmonella causes serious diarrhea. In this study, an effective 2D/2D photocatalyst with excellent elimination of these pollutants was fabricated by combining graphene oxide (GO), Bi2WO6, BiPO4 and Ag species. GO was applied at varying loading contents (0.8, 1.6, 2.4, 3.2 wt%) to improve the properties of the photocatalyst toward the removal of representative pollutants. The chemical structures, morphology, light absorption and charge mobility were investigated by different GO loading samples. The results indicated that when the wt% of GO was 2.4%, the photocatalyst showed excellent photocatalytic properties and removal rates for typical pollutants. Amoxicillin and methylene blue were mineralized into CO2, H2O, and small molecules, while Salmonella was disinfected with excellent photocatalytic efficiency. Furthermore, the possible photodecomposition pathways of amoxicillin and methylene blue were proposed by DFT calculations and intermediates identified by LCMS. The mechanism of the photocatalytic process was investigated by radical trapping experiments, ESR spectroscopy, and Motty-Schottky plots. The free radicals could be produced constantly during the photocatalytic process, leading to mineralization of amoxicillin and methylene blue, and disinfection of Salmonella. In this work, a new perspective on GO modified Bi2WO6 with different loading contents and the degradation pathways of antibiotics and dyes was proposed.

A Potentially Practicable Halotolerant Yeast Meyerozyma guilliermondii A4 for Decolorizing and Detoxifying Azo Dyes and Its Possible Halotolerance Mechanisms.

In this study, a halotolerant yeast that is capable of efficiently decolorizing and detoxifying azo dyes was isolated, identified and characterized for coping with the treatment of azo-dye-containing wastewaters. A characterization of the yeast, including the optimization of its metabolism and growth conditions, its detoxification effectiveness and the degradation pathway of the target azo dye, as well as a determination of the key activities of the enzyme, was performed. Finally, the possible halotolerance mechanisms of the yeast were proposed through a comparative transcriptome analysis. The results show that a halotolerant yeast, A4, which could decolorize various azo dyes, was isolated from a marine environment and was identified as Meyerozyma guilliermondii. Its optimal conditions for dye decolorization were ≥1.0 g/L of sucrose, ≥0.2 g/L of (NH4)2SO4, 0.06 g/L of yeast extract, pH 6.0, a temperature of 35 °C and a rotation speed of ≥160 rpm. The yeast, A4, degraded and detoxified ARB through a series of steps, relying on the key enzymes that might be involved in the degradation of azo dye and aromatic compounds. The halotolerance of the yeast, A4, was mainly related to the regulation of the cell wall components and the excessive uptake of Na+/K+ and/or compatible organic solutes into the cells under different salinity conditions. The up-regulation of genes encoding Ca2+-ATPase and casein kinase II as well as the enrichment of KEGG pathways associated with proteasome and ribosome might also be responsible for its halotolerance.

Crystal Structure and Photocatalytic Properties of the CsV0.625Te1.375O6 Mixed‐Valence β‐Pyrochlore Compound

AbstractA new β‐pyrochlore compound with complex composition of Cs(V3+0.0625V5+0.5625Te4+0.34375Te6+1.03125)O6 has been synthesized by a solid‐state reaction and characterized by single‐crystal X‐ray diffraction and thermal analysis. The compound possesses the typical cubic symmetry with space group , however some of the oxygen atoms shift from the special position 48 f to the general crystallographic positions 32e, 96 g and 96 h. This shift is caused by complex B‐site composition with mixed‐valence vanadium and tellurium atoms, especially the presence of the large Te4+ ion. The locations of the valence band and conduction band edges were determined experimentally under vacuum conditions by X‐ray photoelectron spectroscopy, UV‐visible and impedance spectroscopy and evaluated theoretically for water solutions. The photocatalytic ability of the compound under visible light irradiation was determined using the methylene blue decomposition process as an example. The nature of the active radical species and possible dye degradation pathway were suggested according to experimental data.

Optimized photocatalytic performance of ZnS-SnO2 heterostructures for visible light driven mineralization of Acid violet 7 dye and inactivation of bacteria

The present study aims to decipher the defect-induced photocatalytic activity of ZnS-SnO2 heterostructure for visible light-assisted oxidative mineralization of Acid Violet 7 dye (AV7) and Escherichia coli (E. coli) bacterial disinfection. The prepared ZnS-SnO2 (60ZS) heterostructure/nanocomposite catalysts show improved optical and visible light absorption properties. Photoluminescence findings reveal the existence of defect energy levels/surface states associated with 60ZS heterostructure catalysts. Photo/Electrochemical studies show improved photocurrent response, high capacitance, lower charge transfer resistance, and improved charge-discharge behaviour in 60ZS heterostructure catalysts compared to individual components. The improved photocatalytic performance of 60ZS heterostructure is ascribed to the interactive effect of a reduction in the band gap, improved surface area, and enhanced lifetime of photogenerated charge carriers. The major reactive species that cause the degradation reaction have been identified, and a plausible AV7 dye degradation pathway has been proposed. The 60ZS heterostructure catalyst exhibits good stability and a recycled nature.

Bismuth-based nanostructured photocatalysts for the remediation of antibiotics and organic dyes.

A serious threat to human health and the environment worldwide, in addition to the global energy crisis, is the increasing water pollution caused by micropollutants such as antibiotics and persistent organic dyes. Nanostructured semiconductors in advanced oxidation processes using photocatalysis have recently attracted a lot of interest as a promising green and sustainable wastewater treatment method for a cleaner environment. Due to their narrow bandgaps, distinctive layered structures, plasmonic, piezoelectric and ferroelectric properties, and desirable physicochemical features, bismuth-based nanostructure photocatalysts have emerged as one of the most prominent study topics compared to the commonly used semiconductors (TiO2 and ZnO). In this review, the most recent developments in the use of photocatalysts based on bismuth (e.g., BiFeO3, Bi2MoO6, BiVO4, Bi2WO6, Bi2S3) to remove dyes and antibiotics from wastewater are thoroughly covered. The creation of Z-schemes, Schottky junctions, and heterojunctions, as well as morphological modifications, doping, and other processes are highlighted regarding the fabrication of bismuth-based photocatalysts with improved photocatalytic capabilities. A discussion of general photocatalytic mechanisms is included, along with potential antibiotic and dye degradation pathways in wastewater. Finally, areas that require additional study and attention regarding the usage of photocatalysts based on bismuth for removing pharmaceuticals and textile dyes from wastewater, particularly for real-world applications, are addressed.

Long-term photochemical stability of heteroaromatic dye-functionalised g-C3N4via covalent linkage for efficient photocatalytic hydrogen evolution

In this study, three typical D–π–A type heteroaromatic organic dyes containing carbazole (CBZ), phenothiazine (PTZ), and phenoxazine (POZ) moiety as electron donor cores and linked to g-C3N4 with amide covalent bonds were synthesized. Thereafter, we studied the long-term photochemical stability and degradation mechanism of the associated dye-sensitised g-C3N4 with covalent linkage or weak interaction. The results revealed that most of the dyes degraded and became unstable after absorption on g-C3N4 under light irradiation. Interestingly, after the target dyes were linked to g-C3N4 with amide covalent bonds, the photostability could be effectively promoted and improved to high levels of stability. For POZ-S dye covalent bond-linked sample g-C3N4/POZ-S, ∼90.5% percent of the dyes were reserved, whereas only ∼25.3% remained for the physically absorbed dye sample g-C3N4+POZ-S after 30 min of irradiation aging test. Moreover, the obtained g-C3N4/POZ-S sample exhibited enhanced H2 evolution activity with photocatalytic H2 production rates that were approximately 96- fold of that of pure g-C3N4. Then, we applied various instrumental analysis and DFT calculation to clarify the mechanism involved with dye photostability and degradation pathway. The typical decarboxylation process was confirmed, and such an unfavourable reaction process could be effectively inhibited if the target dye is linked to g-C3N4 with amide covalent bond instead of the weak interaction. Overall, the existed covalent bond is the key factor for enhancing both the photochemical stability and photocatalytic activity of organic dye-sensitised g-C3N4 for hydrogen evolution.

Degradation of Diazo Congo Red Dye by Using Synthesized Poly-Ferric-Silicate-Sulphate through Co-Polymerization Process.

The ability of poly-ferric-silicate-sulphate (PFSS) synthesized via a co-polymerization process has been applied for the removal of diazo Congo red dye. A novel degradation pathway of diazo Congo red dye by using PFSS is proposed based on LC-MS analysis. Diazo Congo red dye was successfully removed using synthesized PFSS at lower coagulant dosages and a wider pH range, i.e., 9 mg/L from pH 5 to 7, 11 mg/L at pH 9, and 50 mg/L at pH 11. The azo bond cleavage was verified by the UV-Vis spectra of diazo Congo red-loaded PFSS and FTIR spectra which showed disappearance of the peak at 1584 cm-1 for -N=N- stretching vibrations. The synchronized results of UV-Vis spectra, FTIR, and the LC-MS analysis in this study confirmed the significance of the Si and Fe bond in PFSS towards the degradation of diazo Congo red dye. The successfully synthesized PFSS coagulant was characterized by FTIR, SEM, TEM, and HRTEM analysis. From this analysis, it was proven that PFSS is a polycrystalline material which is favorable for the coagulation-flocculation process. Based on all these findings, it was established that synthesized PFSS can be employed as a highly efficient polymeric coagulant for the removal of dye from wastewater.

Double Z-Scheme ZnCo2O4/MnO2/FeS2 photocatalyst with enhanced photodegradation of organic compound: Insights into mechanisms, kinetics, pathway and toxicity studies

The present work highlights the preparation of double Z-scheme ZnCo2O4/MnO2/FeS2 nanocomposite (NCs) and investigated its photocatalytic activity against methyl orange (MO) dye degradation under visible light. An array of techniques was carried out to characterize the nanoparticles (NPs) in order to evaluate their morphological, structural, optical, and photocatalytic properties using FE-SEM, TEM, XRD, N2 adsorption and desorption studies, PL, UV–visible spectrophotometer, XPS, Raman, and UV–vis DRS analysis. The degradation efficiency of NCs was tested along with different parameter studies such as different pH, NCs concentration, dye concentration, reusability and structural stability. The NCs exhibited complete photodegradation of MO dye under visible light within 80 min at pH 4. The structural and compositional stability of the prepared NCs over 6 consecutive cycles was tested via XRD and XPS analysis. The results of active species trapping experiments showed that O2−• and OH• are responsible for the degradation of MO dye. The TOC analysis showed 95% of mineralization by the prepared NCs. The MO dye degradation pathway was determined using GC-MS/MS analysis and drafted all the intermediates involved. End product toxicity via seed germination and intermediate toxicity study using ECOSAR software results in less toxicity of end product compared to parent compound. Finally, the genotoxicity of the prepared NCs was evaluated using Allium cepa and showed its no causes of cytotoxicity & genotoxicity by the prepared NCs. ZnCo2O4/MnO2/FeS2 NCs exhibited its high photocatalytic activity and the toxicity studies confirms that there is no cause of any environmental impact.

Discerning the biodegradation of binary dyes in microbial fuel cell: Interactive effects of dyes, electron transport behaviour, autocatalytic mechanism, and degradation pathways

This research presented the first attempt to investigate the effect of biodegradation of binary Acid Orange 7 (AO7) and Reactive Green 19 (RG19) on the performances of wastewater treatment and bioelectricity generation, using anti-gravity flow microbial fuel cell (AGF-MFC) system. The influences of initial dye concentration, substrate loading, sulphate concentration and application of quinones on system performances were comprehensively evaluated. The decolourization efficiencies of AO7 were higher than RG19 in binary solutions, at every tested concentrations. The addition of higher concentration of RG19 in binary solution was also found to have increased the overall performances of MFC, owing to electron mediating characteristics of its decolourized intermediates. However, the power density declined with the addition in dye concentration. Further increase of substrate loading by 3-folds (2.43 g/L) improved the decolourization efficiency approximately by 7%, but deteriorated power performance by 42%, to 63.40 ± 0.07 mW/m2. Increasing sulphate concentration from 20 to 400 mg/L had resulted in a high decolourization extent of binary dyes ascribed to sulphide-mediated dye degradation, whereas the power generation was reduced. The increase of sulphate to 800 mg/L led to decrease in decolourization and power density of the system. These outcomes deciphered the competitions of electrons between different electron acceptors in the anodic compartment. Moreover, the autocatalytic mechanism of RG19 decolourized intermediates, 1-amino-2-naphthol-3,6-disulphonate (1A2N36S) as electronophore was thoroughly unearthed. Detailed degradation pathways of dyes were proposed based on UV-Visible spectra and gas chromatograph-mass spectrometer (GC-MS) analyses.

Enhanced Bioremediation Potential of Shewanella decolorationis RNA Polymerase Mutants and Evidence for Novel Azo Dye Biodegradation Pathways.

Bioremediation has been considered as a promising method for recovering chemical polluted environments. Here Shewanella decolorationis strain Ni1-3 showed versatile abilities in bioremediation. To improve the bioremediation activity, RNA polymerase (RNAP) mutations of strain Ni1-3 were screened. Eleven mutants were obtained, of which mutant #40 showed enhanced Amaranth (AMR) degradation capacity, while mutant #21 showed defected capacity in AMR degradation but greatly enhanced capacity in cathodic metal leaching which is three to four times faster than that of the wild-type (WT) strain Ni1-3, suggesting that different pathways were involved in these two processes. Transcriptional profiling and gene co-expression networks between the mutants (i.e., #40 and #22) and the WT strain disclosed that the non-CymA-Mtr but cytochrome b- and flavin-oxidoreductase-dominated azo dye degradation pathways existed in S. decolorationis, which involved key proteins TorC, TorA, YceJ, YceI, Sye4, etc. Furthermore, the involvement of TorA was verified by trimethylamine N-oxide reduction and molybdenum enzyme inhibitory experiments. This study clearly demonstrates that RNAP mutations are effective to screen active microbial candidates in bioremediation. Meanwhile, by clarifying the novel gene co-expression network of extracellular electron transfer pathways, this study provides new insights in azo dye degradation and broadens the application of Shewanella spp. in bioremediation as well.

Study on preparation methodology of zero-valent iron decorated on graphene oxide for highly efficient sonocatalytic dye degradation

Various preparation methodologies (stirring, hydrothermal, and high energy ball milling methods) were used to prepare zero-valent iron (ZVI) catalysts decorated on graphene oxide (GO) for highly efficient sonochemical dye degradation, and their dye degradation efficiencies were compared. For the effective activation of ZVI, N,S co-doped GO (N,S-GO) prepared by high-energy ball milling synthesis was also tested. According to the preparation methodologies, the ZVI catalysts showed different degrees of surface passivation, morphologies, and zeta-potentials because of the different degrees of aerial oxidation of ZVI, which are the key factors determining their activities in sonocatalytic dye degradation. The ZVI catalysts on GO prepared using the stirring and hydrothermal methods showed a high oxidation state with low sonocatalytic activity. In contrast, the ZVI catalysts on GO prepared using the high-energy ball milling method exhibited moderate sonocatalytic activity due to moderate passivation. The ZVI on N,S-GO prepared by stepwise high-energy ball milling synthesis showed the maximum activity (100% removal efficiency within 1 min) due to the minimum aerial oxidation. The rapid generation of •OH radicals by high-energy sonication, the existence of mixed-valence states of iron via activation, and N,S-doping facilitated electron transfer for the dye degradation process. The complete mineralization and degradation pathway of crystal violet dye was confirmed by electrospray ionization-mass spectrometry.

Green synthesized CuI as an adsorbent and a photocatalyst in the removal of aqueous reactive red 256 & reactive black 5 dyes

The extensive utilization of dyes in the industries and the consequent generation of their effluents in the water bodies have posed a major risk to the environment and mankind. Therefore, there is an increased necessity for waste water treatment in textile industries. The present study involves the utilization of highly versatile copper (I) iodide synthesized using Hibiscus rosa-sinensis L. flower extract (CuI-FE) in the removal of textile dyes. The synthesized material was characterized using XRD and found to be highly crystalline with an average crystallite size of 89.01 nm. The average particle size of the agglomerated CuI-FE was measured to be 492.7 nm using HR-SEM. The d-spacing calculated from HR-TEM was found to match with that from XRD. XPS analysis confirmed the oxidation state of Cu(+1) in CuI-FE. The purity of the syntheised CuI-FE was ascertained from its EDAX data. It was further characterized using BET, FTIR and UV-Visible spectroscopic techniques. Batch adsorption studies of Reactive Red 256 (RR) and Reactive Black 5 (RBL) were probed in the presence of CuI-FE and the respective adsorption capacity of RR and RBL were found to be 135.22 and 176.42 mg/g. LCMS data taken of the solution after Batch adsorption studies at the end of 24 h showed the presence of intermediates of low molecular weight that are environmentally benign confirming that the initial adsorption process was followed by degradation of dyes. A possible dye degradation pathway was proposed using LCMS data analysis.