Decolorization Rate Research Articles

Investigating the optimum conditions for azo dye (methyl orange and methyl red) decolorization from aqueous solution using oyster mushroom (Pleurotus ostreatus): a mycoremediation approach

Since conventional dye removal techniques require a substantial amount of energy and chemicals, this study evaluated the utilization of Pleurotus ostreatus, a species of fungus, in an environmentally beneficial mycoremediation approach to decolorize two azo dyes, methyl orange (MO) and methyl red (MR), in a liquid medium. Pleurotus ostreatus was utilized under standard circumstances in the solutions containing 0.05% (w/v) MO and 0.05% (w/v) MR, without undergoing any genetic modifications. By analyzing the effects of time (6, 12, and 18 days), temperature (15 °C to 40 °C), pH (4 to 7), and inoculum volume (1 to 25 mL) on the decolorization rate of P. ostreatus, the ideal environment for the decolorization of MO and MR was determined. The highest rate of decolorization was evident at 25 °C temperature, pH 7 within 18 days of incubation, P. ostreatus could decolorize 0.05 g MO up to 97% when added in 10 mL inoculum volume on the other hand 0.05 g MR up to 93% in 15 mL inoculum volume at pH 6. Furthermore, the dye uptake rate after 18 days for MO was 59.25% and MR was 53.97% which indicated that P. ostreatus had a better uptake efficiency for MO than MR. Based on its ability to decolorize both MO and MR under suitable circumstances, the study concludes that P. ostreatus offers an appreciable mycoremediation approach for removing dye pigments from industrial wastewater.

Enhanced performance of hydrothermally synthesized zinc vanadium oxide nanoparticles for supercapacitor and photocatalytic applications

Zinc(II) vanadium oxide (Zn2V2O7) nanoparticles (ZVONPs) were successfully synthesized by the hydrothermal technique. The sample's structure and morphology were examined by using the XRD and FESEM techniques. HRTEM microscopic analysis revealed the presence of tiniest particles which were self-assembled to create sphere-like morphology. The ZVONPs were evaluated using various electrochemical methods. ZVONPs showed good supercapacitor characteristics. The photocatalytic tests conducted to degrade the industrial pollutant Fast Orange Red (F-OR) dye show that a 98.4 % decolorization rate was attained after 120 min of UV light irradiation. The specific capacitance value for ZVONPs was found to be 364 Fg-1, with a retention rate of about 87 % after 2500 cycles. These aspects offers better insight into the material's properties and encourage the development of nanoparticles for energy and environmental applications.

Peroxydisulfate-based Non-radical Oxidation of Rhodamine B by Fe-Mn Doped Granular Activated Carbon: Kinetics and Mechanism Study.

While numerous persulfate-based advanced oxidation processes (AOPs) have been studied based on fancy catalysts, the practical combination of Fe or Mn modified granular activated carbon (GAC) has seldom been investigated. The present study focused on a green and readily synthesized Fe-Mn bimetallic oxide doped GAC (Fe-Mn@GAC), to uncover its catalytic kinetics and mechanism when used in the peroxydisulfate (PDS)-based oxidation process for degrading Rhodamine B (RhB), a representative xenobiotic dye. The synthesized Fe-Mn@GAC was characterized by SEM-EDS, XRD, ICP-OES and XPS analyses to confirm its physicochemical properties. The catalytic kinetics of Fe-Mn@GAC+PDS system were evaluated under varying conditions, including PDS and catalyst dosages, solution pH, and the presence of anions. It was found Fe-Mn@GAC exhibited robust catalytic performance, being insensitive to a wide pH range from 3 to 11, and the presence of anions such as Cl-, SO4 2-, NO3 - and CO3 2-. The catalytic mechanism was investigated by EPR and quenching experiments. The results indicated the catalytic system processed a non-radical oxidation pathway, dominated by direct electron transfer between RhB and Fe-Mn@GAC, with singlet oxygen (1O2) playing a secondary role. The catalytic system also managed to maintain a RhB removal above 81 % in successive 10 cycles, and recover to 89.5 % after simple DI water rinse, showing great reusability. The catalytic system was further challenged by real dye-containing wastewater, achieving a decolorization rate of 84.5 %. This work not only provides fresh insight into the kinetics and mechanism of the Fe-Mn@GAC+PDS catalytic system, but also demonstrates its potential in the practical application in real dye-containing wastewater treatment.

Economic and environmentally friendly anionic flocculant synthesized by starch-acrylic acid-itaconic acid grafting and efficient treatment of cationic dye wastewater

Starch-based flocculants are environmentally friendly and high-performance products, potentially applied in wastewater treatment with low operation cost and ecological risk. In this study, we successfully synthesized a ternary anionic copolymer of starch-acrylic acid-itaconic acid (SAI) through graft copolymerization. The synthesis conditions were optimized based on flocculation efficiency against cationic crystal violet (CV), and subsequent applicability was conducted under various environmental conditions. The results indicate that SAI exhibited outstanding decolorization efficiency under wide scopes of pH, temperature, and ionic strength. Most importantly, SAI achieved a remarkable decolorization rate of 91.2 % for 100 mg/L CV dye at a low concentration of 25 mg/L, accounting for one-fourth of the cost operated with commercial polyacrylamide. Compared to binary flocculants, SAI demonstrates superior flocculation performance too. The flocculation mechanism is primarily attributed to the combined effects of charge neutralization, bridging, and sweeping. SAI flocculants possess characteristics of high efficiency, environmental friendliness, and cost-effectiveness, thus presenting broad prospects for the treatment of dye wastewater.

Treatment of azo dye-containing wastewater in a combined UASB-EMBR system: Performance evaluation and membrane fouling study

This work investigated the treatment of azo dye-containing wastewater in an upflow anaerobic sludge blanket (UASB) reactor combined with an electro-membrane bioreactor (EMBR). Current densities of 20 A m−2 and electric current exposure mode of 6′ON/30′OFF were applied to compare the performance of the EMBR to a conventional membrane bioreactor (MBR). The results showed that dye (Drimaren Red CL-7B) removal occurred predominantly in the UASB reactor, which accounted for 57% of the total dye removal achieved by the combined system. When the MBR was assisted by electrocoagulation, the overall azo dye removal efficiency increased from 60.5 to 67.1%. Electrocoagulation batch tests revealed that higher decolorization rates could be obtained with a current density of 50 A m−2. Over the entire experimental period, the combined UASB-EMBR system exhibited excellent performance in terms of chemical oxygen demand (COD) and NH4+-N removal, with average efficiencies above 97%, while PO43--P was only consistently removed when the electrocoagulation was used. Likewise, a consistent reduction in the absorption spectrum of aromatic amines was observed when the MBR was electrochemically assisted. In addition to improving the pollutants removal, the use of electrocoagulation reduced the membrane fouling rate by 68% (0.25–0.08 kPa d−1), while requiring additional energy consumption and operational costs of 1.12 kWh m−3 and 0.32 USD m−3, respectively. Based on the results, it can be concluded that the combined UASB-EMBR system emerges as a promising technological approach for textile wastewater treatment.

Textile Dye Decolorization Potential of Bacillus pumilus and Staphylococcus saprophyticus Isolated From Textile Industry Effluents

Textile dyeing industries are usually chastised for being big polluters due to the poisonous nature of most dyes, which endangers all kinds of life, including people. In this study, dye degrading bacteria were isolated from water and soil samples contaminated with textile dye taken from Batik palli in Narayanganj and the ability of five isolated bacteria including Staphylococcus saprophyticus, Bacillus pumilus, Micrococcus endophyticus, Pseudomonas mendocina, and Acinetobacter baumannii, to decolorize crystal violet (CV) dye was investigated. Among these, Bacillus pumilus decolorized 58% of CV at 250 ppm, while Staphylococcus saprophyticus decolorized 48% of CV, after 3 days of incubation at 37°C. We examined multiple temperature and pH conditions to determine the best parameters for CV dye decolorization. Bacillus pumilus boosted decolorization rates by 65.39% at 37°C and at pH 7.0, while Staphylococcus saprophyticus increased decolorization rates by 58.73%, at 37°C and at pH 5.0. Furthermore, extending the incubation period to 6 days enhanced decolorization rate in both isolates, with Bacillus pumilus increased from 58% to 65% and Staphylococcus saprophyticus increased from 48% to 58%. Nevertheless, the inclusion of co-substrates such glucose and yeast extract further boosting decolorization rate for both isolates, approximately tripling it. As a result, this study discovered indigenous bacteria capable of decolorizing CV dye, implying that they could be employed in the treatment of textile wastewater effluents. Bangladesh J Microbiol, Volume 40, Number 2, December 2023, pp 50-54

Insights on kraft lignin degradation in an anaerobic environment

Lignin is an aromatic macromolecule and one of the main constituents of lignocellulosic materials. Kraft lignin is generated as a residual by-product of the lignocellulosic biomass industrial process, and it might be used as a feedstock to generate low molecular weight aromatic compounds. In this study, we seek to understand and explore the potential of ruminal bacteria in the degradation of kraft lignin. We established two consortia, KLY and KL, which demonstrated significant lignin-degrading capabilities. Both consortia reached maximum growth after two days, with KLY showing a higher growth and decolorization rate. Additionally, SEM analysis revealed morphological changes in the residual lignin from both consortia, indicating significant degradation. This was further supported by FTIR spectra, which showed new bands corresponding to the C-H vibrations of guaiacyl and syringyl units, suggesting structural transformations of the lignin. Taxonomic analysis showed enrichment of the microbial community with members of the Dickeya genus. Seven metabolic pathways related to lignin metabolism were predicted for the established consortia. Both consortia were capable of consuming aromatic compounds such as 4-hydroxybenzoic acid, syringaldehyde, acetovanillone, and syringic acid, highlighting their capacity to convert aromatic compounds into commercially valuable molecules presenting antifungal activity and used as food preservatives as 4-hydroxyphenylacetic, 3-phenylacetic, and phenylacetic acids. Therefore, the microbial consortia shown in the present work are models for understanding the process of lignin degradation and consumption in bacterial anaerobic communities and developing biological processes to add value to industrial processes based on lignocellulosic biomass as feedstock.

Hibiscus sabdariffa assisted green fabrication of reduced graphene oxide and its application for methyl orange removal: Optimization employing response surface methodology

Eco-friendly fabrication of reduced graphene oxide (rGO) is of paramount importance among various carbon nanostructures. In the current research, sustainable preparation of rGO via aqueous extract of Hibiscus sabdariffa L. calyces as the green reducer of graphene oxide (GO) without utilizing hazardous chemical agents was described. The structural characteristics of the GO and rGO were studied utilizing Fourier transform infrared (FT-IR) spectroscopy, UV–Visible spectrophotometry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The prepared nanostructure was applied as the potential adsorbent for effective methyl orange (MO) decolorization and degradation in aqueous solution. The effect of numerous independent parameters on the decolorization process involving rGO dosage, H2O2 volume, process time, and temperature were assessed and optimized via Box-Behnken design/response surface methodology BBD/RSM). A second-order model was proved to express the decolorization efficiency (D %) responses with high values of R2 and adjusted R2. Under optimal condition, the decolorization rate of MO using rGO was higher than 99 % in contact time of 31 min. The reusability of rGO for the MO removal manifested good efficiency in up to five cycles of recyclability. The findings of this research illustrate the feasibility of Hs based rGO as a suitable adsorbent for effective decolorization of MO dye from aqueous medium.

Cleaner reactive dyeing with the recycled dyeing wastewater

In order to recycle water and inorganic salts, sodium persulphate (SPS) was used to degrade the C.I. Reactive Red 195 (RR195) dyeing wastewater. The thermodynamic and kinetic relationships of RR195 dyeing in cleaner and conventional dyeing processes were analyzed and compared. The feasibility of the one-bath cyclic dyeing in the recycled dyeing wastewater was confirmed through the properties of dye utilization, color parameters and energy conservation. The appropriate conditions were 0.3 g/L of SPS and treatment at 95 °C for 30 min, which resulted in a decolorization rate of 99.7% for the dyeing wastewater, mainly due to the action of radical sulfate. When cotton fabric was dyed with the cleaner dyeing, the kinetic was pseudo-second-order and the thermodynamic was Freundlich adsorption. There was a 47.5% reduction in half dyeing time, a greater diffusion coefficient and standard affinity, and lower entropy and enthalpy values when dyeing in reused wastewater. Cotton fabrics were dyed with the proposed cleaner dyeing process, which reduced the amount of water and inorganic salt by 95.8% and 89.8%, respectively. The total organic carbon (TOC), biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) were 53.6%, 69.8% and 42.6% lower than the conventional dyeing process, respectively. The recommended technology not only reduces the amount of dyeing wastewater but also enables the recycling of inorganic salts and water, which makes great progress in the textile industry.

Decolorization of reactive dyes by the white rot fungus Phanerochaete velutina in presence of Zn and ZnO nanoparticles

AbstractReactive organic dyes are hazardous pollutants that should be removed from wastewater from the textile industry. A remediation of dye polluted wastewater can be achieved by using the oxidative properties of nanomaterials, such as ZnO nanoparticles, or by microorganisms and their dye degrading enzymes. Promising approaches are expected from hybrid strategies, which use more than one approach. However, ZnO nanoparticles are also reported to be an antimicrobial and antifungal agent, which may undermine the decolorization ability of potent organisms, such as white rot fungi. Therefore, in this study we investigated the effects of soluble Zn and ZnO nanoparticles on the decolorization behaviour of the white rot fungus Phanerochaete velutina on commonly used reactive dyes, Reactive Orange 16 and Reactive Green 19. Zn ions led to a low decolorized rate of both dyes at low concentrations and restored the rate at higher Zn concentrations. However, ZnO nanoparticles showed highest decolorization rates, but only in a narrow concentration range. Overall, no toxic or inhibitory effects for decolorization of the dyes were found at the applied concentration of up to 20 mg Zn l−1 indicating that tolerant P. velutina will be suitable for remediation of dyes in multi polluted waste waters.

Production of Camellia oleifera Abel Seed Oil for Injection: Extraction, Analysis, Deacidification, Decolorization, and Deodorization.

Camellia seed oil (CSO), as a nutrient-rich edible oil, is widely used in foods, cosmetics, and other fields. In this work, the extraction, deacidification, decolorization, and deodorization processes of CSO were respectively optimized for meeting injectable oil standards. The results showed that the CSO extraction rate reached the highest level of 94% at optimized conditions (ultrasonic time, 31.2 min; reaction pH, 9.2; and reaction time, 3.5 h). The physicochemical indexes of CSO and 10 other vegetable oils were evaluated by the principal component analysis method, and the overall scores of vegetable oils were ranked as camellia seed oil > olive oil > rice oil > peanut oil > sesame oil > corn oil > soybean oil > sunflower oil > rapeseed oil > walnut oil > flaxseed oil. The physicochemical indicators of CSO were the most ideal among the 11 vegetable oils, which means that CSO is suitable as an injectable oil. Through the optimized processes of the deacidification, decolorization, and deodorization, the CSO acid value was reduced to 0.0515 mg KOH/g, the decolorization rate reached a maximum of 93.86%, and the OD430 was 0.015, meeting the requirement (≤0.045 of OD430) of injectable oil. After the deodorization process, these parameters of the refractive index, acid value, saponification value, iodine value, absorbance, unsaponifiable, moisture and volatiles, fatty acid composition, and heavy metal limits all met the pharmacopoeia standards of injectable oil in many countries and regions. The possibility of CSO as an injectable oil was first verified through refining-process optimization and nutritional index analysis, providing an important technical reference for the high-value utilization of vegetable oil.

Exploring the improving role of MWCNTs on the electrochemical behavior of electrophoretically prepared Ti/nanoZnO metal oxide electrode: A comparative study

In recent years, a growing amount of attention has been paid to the investigation and modification of metal oxide anodes as a critical parameter in electrochemical removal. In this way, this research attempts to bring out an effective comparison between modified Ti/nanoZnO electrode by multi-walled carbon nanotubes (MWCNTs) and base Ti/nanoZnO electrode. The electrophoretic deposition (EPD) method was used to prepare electrodes. The morphological and chemical composition of the surface for both electrodes were obtained by using characterization tests including field emission scanning electron microscope - energy dispersive spectrometer (FESEM-EDS), elemental mapping, and X-ray diffraction (XRD). Furthermore, the electrochemical behavior of Ti/nanoZnO as well as Ti/nanoZnO-MWCNTs electrodes were compared using linear sweep voltammetry (LSV), chronopotentiometry (CP), and chronoamperometry (CA) analysis. In the final step, the chemical oxygen demand (COD) removal in addition to the decolorization rate of a dyes mixture was used to evaluate the electrochemical performance in the same conditions. Presented results in this study showed the importance of metal oxide anode modification by improved deposited coating properties of Ti/nanoZnO-MWCNTs electrode compared with base ZnO electrode.

Biodegradation of aniline blue dye by salt-tolerant Bacillus thuringiensis DHC4 isolated from soil-feeding termite guts

The existence of aniline blue in aquatic environments poses a large threat to aquatic organisms. Microbial degradation of aniline blue has been frequently used in remediation because of its effectiveness, low cost, and environmental friendliness. However, the mechanisms by which the dye can be biodegraded are not well understood. In this study, Bacillus thuringiensis DHC4 was isolated from the gut of a soil-feeding termite, and its ability to degrade aniline blue was investigated. The results showed that DHC4 was highly resistant to both aniline blue and salt, with the decolorization rate reaching 78% and 67% after 96 h of incubation at initial dye concentrations of 1 g/L and 7% salinity, respectively. Aniline blue degradation products were identified based on UV–vis, FTIR, and GC–MS analyses, and genome analysis confirmed that DHC4 contained many potential dye-degrading genes. Transcriptome analysis revealed significant up-regulation of methyltransferase, nitroreductase, arylamine N-acetyltransferase and oxidoreductase genes on exposure to aniline blue, indicating their active role in its biodegradation. A new degradation pathway of aniline blue by DHC4 is proposed, based on analysis of metabolites and differentially expressed genes. This mechanism involves cleavage of aniline blue by oxidoreductases into mono- and diphenyl ring molecules, followed by further methylation and alkylation through methyltransferases. The phytotoxicity results showed that aniline blue was degraded by DHC4 into less toxic metabolites. These results provide new insights into the mechanism of biodegradation of aniline blue by microorganisms.

Evaluation of the Adsorptive Performance of Rambutan-shaped γ-Al2O3 Micro-nanostructure against Wastewater Containing the Azo Dye: Methyl Orange

Aim: The aim of this study is to explore and evaluate the possibility of rambutan-shaped micro-nanostructured γ-Al2O3 material’s usage as an adsorbent in industrial wastewater processing. Background: Every year, more than 7 million tons of dyestuff-containing wastewater are produced in the industry. Although there are many adsorbents like fly ash and clays, the shortages limit their actual applications. It is still necessary to find a new cheaper adsorbent. Objective: The paper aimed to investigate the adsorption capacity and decolorization ability of rambutan- shaped γ-Al2O3 material synthesized via a composite soft template method. Methods: The rambutan-shaped γ-Al2O3 material was prepared and characterized via XRD, TEM, FE-SEM, and FT-IR (See our group’s published article in “Ming Shen*, et al., Acta Phys.-Chim. Sin. 2013, 29 (10), 2286-2294”). The methyl orange aqueous solution was selected as the model of industrial wastewater. The methyl orange solution (15.0 mg·L-1) with different pH (2~9) was exposed to a series of amounts of γ-Al2O3 powder ranging from 10.0 to 70.0 mg. Different concentrations of methyl orange solution, ranging from 5.0 to 200.0 mg·L-1 were also tested with the same amount of γ-Al2O3 powder (50.0 mg). The adsorption-calcination cycle analysis was performed with methyl orange solution (50.0 mg·L-1) and 500.0 mg of γ-Al2O3 powder at pH=3. Results: The γ-Al2O3 material exhibits excellent adsorption capacity (114.10 mg·g-1) towards acidic methyl orange aqueous solution. At the same time, the decolorization rate of the γ-Al2O3 material reaches about 88%. This material still keeps a 50% decolorization rate after 6 repeats of the adsorption- calcination cycle. Moreover, the excellent self-sedimentation ability of this material also provides an easy separation for future industrial applications. Conclusion: The γ-Al2O3 material with rambutan-like micro-nanostructure presents excellent adsorption capacity/decolorization ability and self-sedimentation ability. It can be used as a new type of adsorbent for wastewater processing. The rambutan-shaped micro-nanostructure plays an important role in maintaining the adsorption ability of the γ-Al2O3 material.

Sn-based precursors dependence for electrocatalytic degradation of organic pollutants on Ti/SnO2-Sb electrode

The utilization of SnO2-based coated electrodes prepared through thermal decomposition process for degrading organic pollutants is a prominent topic in the field of wastewater treatment. However, the impact of precursor salts on the structure and catalytic degradation activity of Sn oxide coatings still lacks research. This study examined the procedures for synthesizing SnO2 coatings by high-temperature oxidation of two common Sn chlorides with different valences. Through systematic characterization, it was revealed that the high boiling point of SnCl2 makes it less volatile during the high-temperature oxidation stage, allowing for maximum retention of Sn source on the substrate, thereby forming a dense and stable oxide coating structure (Ti/SnO2-Sb(II)). On the other hand, the low boiling point of SnCl4 makes it easily volatile during heating, resulting in a thin and loose structure coating (Ti/SnO2-Sb(IV)). Due to these factors that the electrical conductivity of Ti/SnO2-Sb(II) is significantly superior to Ti/SnO2-Sb(IV). Moreover, at 20 mA·cm−2, Ti/SnO2-Sb(II) can achieve almost complete decolorization of methylene Blue (MB) in just 40 minutes, while achieving the same decolorization rate with Ti/SnO2-Sb(IV) requires over 90 minutes. Furthermore, stability tests demonstrated that after 5 cycles of reaction, Ti/SnO2-Sb(II) showed no significant decrease in decolorization rate of MB, whereas Ti/SnO2-Sb(IV) exhibited a decline in decolorization performance towards MB starting from the 2nd cycle. This study revealed the crucial role of precursor salt boiling points in the formation of stable SnO2-based coated electrodes, providing a theoretical basis for the development of structurally stable and highly catalytic oxidation active coating electrodes.

Decolorization of anthraquinone dye by Brevibacillus laterosporus R81 via polysaccharides excreted

AbstractThe aim of this research was to assess the efficacy of different microbial strains in the decolorization of anthraquinone dyes. Strain R81 was obtained from a textile company's wastewater discharge for its remarkable ability to decolorize reactive blue 19 (RB19). By employing physiological and biochemical analyses, along with 16S rRNA gene sequencing, strain R81 was determined to be Brevibacillus laterosporus. After optimization, the decolorization rate achieved a peak of 86.24% over a 48‐h timeframe, utilizing an initial dye concentration of 100 mg L–1. The decolorization capacity of strain R81 was observed to be impeded by heightened levels of salt and temperature in culture solutions, yet remained unaltered when R81 cells were directly introduced into dye solutions. Furthermore, cells that were induced through prior cultivation in a medium containing RB19 demonstrated enhanced efficacy in decolorization compared to noninduced cells. Subsequent analysis indicated that the development of biofilms and the synthesis of polysaccharides by strain R81 were augmented in a concentration‐dependent fashion by RB19. Nevertheless, the decolorization efficacy of R81 was impeded by the existence of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), both of which possess the capacity to eliminate polysaccharides. The decolorization capabilities were reinstated by the SDS or CTAB eluent containing polysaccharides, suggesting a reliance on the presence of polysaccharides. The employment of stepwise diethylaminoethyl (DEAE)‐cellulose chromatography and decolorization experiments elucidated the importance of a specific polysaccharide in the decolorization process. This study proposes a bacteria‐derived polysaccharide as a promising remedy for treating dyeing wastewater contaminated with anthraquinones.

In Situ Utilization of Electron-Enhanced Degradation of Azo Dyes in a Constructed Wetland–Microbial Fuel Cell Coupling System

In this study, a constructed wetland was coupled with a microbial fuel cell to establish a coupled system known as the constructed wetland–microbial fuel cell (CW–MFC), utilized for the treatment of X-3B azo dye wastewater at varying concentrations. Experimental results indicated that the anodic region made the primary contributions to the discoloration of azo dyes and COD removal, with a contribution rate of 60.9–75.8% for COD removal and 57.8–83.0% for the effectiveness of discoloration. Additionally, the role of plants in the constructed wetland area could achieve the removal of small molecular substances and further discoloration. In comparison to open-circuit conditions, under closed-circuit conditions the CW–MFC effectively degraded X-3B azo dye wastewater. Under an external resistance of 2000 Ω, a maximum COD removal rate of 60.0% and a maximum discoloration rate of 85.8% were achieved for X-3B azo dye at a concentration of 100 mg/L. Improvements in the treatment efficiency of X-3B dye wastewater were achieved by altering the external resistance. Under an external resistance of 100 Ω and an influent concentration of X-3B of 800 mg/L, the COD removal rate reached 78.6%, and the decolorization rate reached 85.2%. At this point, the CW–MFC exhibited a maximum power density of 0.024 W/m3 and an internal resistance of 99.5 Ω. Spectral analysis and GC–MS results demonstrated the effective degradation of azo dyes within the system, indicating azo bond cleavage and the generation of numerous small molecular substances. Microbial analysis revealed the enrichment of electrogenic microorganisms under low external resistance conditions, where Geobacter and Trichococcus were dominant bacterial genera under an external resistance of 100 Ω, playing crucial roles in power generation and azo dye degradation within the system.

Efficient removal of Basic Violet 16 by a multistage oxygen enhanced liquid glow discharge plasma system: Mechanism and roles of reactive species quantified by machine learning

A multistage oxygen enhanced Liquid Glow Discharge Plasma reactor (LGDP/multistage oxygen, LGDP/M-O2) was designed to improve the removal efficiency of organic dyes in wastewater. As a result of the multistage oxygen system, the degradation rate constant of Basic Violet 16 (BV16) was enhanced by approximately 18 times, the decolorization rate of BV16 was 97.39 % in 4 min, and the removal rate of TOC was 33.32 % in 10 min. Detailed study of how the system works to help break down pollutants. The reactive species series of experiments showed that multistage oxygen injection strongly promoted reactive species production and utilization. Meanwhile, a machine learning model to quantify the contribution of reactants was proposed. Machine learning indicated the dominating contribution of reactive oxygen species (63.89 %) and reactive chlorine species (21.92 %) in the degradation of BV16. In addition, the transformation intermediates during the degradation of BV16 were monitored. Accordingly, three possible degradation pathways of BV16 in the LGDP/M-O2 system were proposed, i.e., benzene ring substitution of hydroxyl groups, hydroxyl addition of C=C double bond, and halogenation of benzene rings. This study demonstrates the importance of the LGDP/M-O2 system for organic dye removal from wastewater.

Preparation of Ti4O7/h‐BN self‐supported ceramic photoelectrode and its photoelectrocatalytic performance for water purification

AbstractThe construction of high‐efficiency self‐supported ceramic photoelectrode based on ideal semiconductor materials is essential for achieving effective degradation of pollutants by photoelectrocatalysis (PEC) technology. Herein, a Ti4O7/h‐BN composite ceramic photoelectrode with a unique microstructure was fabricated by a step‐by‐step calcination process and used in PEC water pollution remediation. The PEC activity of Ti4O7 ceramic photoelectrode could be enhanced by introducing hexagonal boron nitride (h‐BN) nanoparticles on the surface. The most optimized Ti4O7/h‐BN photoelectrode exhibited the decolorization rate of active brilliant blue KN‐R at about 97.79% in 30 min. The PEC activities could remain stable during five degradation cycles. The excellent photoelectrocatalytic performance of Ti4O7/h‐BN ceramic photoelectrode could be attributed to the low Tafel slope, low charge transfer resistance, large electrochemical active area, and excellent photo‐generated carrier separation efficiency. A type‐II heterojunction was formed between the Ti4O7 and h‐BN, which caused more effective carrier separation and enhanced the generation of dominant active species •O2− and h+. This work provided a mature synthesis strategy of Ti4O7/h‐BN self‐supported ceramic photoelectrodes with excellent practical application prospects to achieve superior PEC performance for water purification.

Biomineralization induced synthesis and self-assembly of photocatalyst-enzyme hybrid system for highly efficient environmental remediation

The photocatalyst-enzyme hybrid systems (PEHSs) provided a promising method for environmental remediation by simultaneously harnessing the power of solar-energy conversion and biocatalysis. However, the use of PEHSs for environmental remediation was restricted by a complicated synthesis and assembly process. This work explored a simple one-pot biomineralization approach to fabricate PEHS. It was found that the cytochrome enzyme could be directly self-assembled onto the biosynthesized CdS during biomineralization by Shewanella oneidensis MR-1. More strikingly, those attached cytochrome enzymes could efficiently receive the photoelectrons from the CdS and serve as the photoreduction center which formed a typical PEHS. Impressively, this bio-CdS-cytochrome PEHS exhibited an extremely high photocatalytic decolorization rate of 69.4 mg/g/min, which was the highest record ever reported for procion red H-E3B. This work provided a simple and facile approach for PEHSs fabrication, which would be promising for practical application in environmental remediation.