Microbial degradation of dyes: An overview

NADH flavin oxidoreductase and catalase-induced reactive oxygen species and key enzymes synergistically drive oxidative degradation of xanthene dye Rose Bengal in Aspergillus flavus A5P1

This study showed that Aspergillus flavus A5P1 efficiently degrades Rose Bengal dye through the synergistic action of extracellular reactive oxygen species (H₂O₂ and O₂-) and key enzymes (laccase, lignin peroxidase, and quinone reductase), confirmed by quenching and enzyme activity assays. An abnormal 90 % decreased in intracellular catalase activity, increased superoxide dismutase activity, and elevated superoxide anion content were observed under dye stress, but no detectable H₂O₂ accumulation was found, suggesting that intracellularly generated H₂O₂ and O₂- were transported extracellularly via transmembrane mechanisms. Genome and transcriptome analyses reveal a complete ROS generation and transport pathway, with upregulated genes for ROS production (e.g., NADH flavin oxidoreductase) and transmembrane transporters, while catalase genes are downregulated. Based on these findings, this study proposes a novel mechanism of " dye induction - intracellular ROS generation - transmembrane transport - intra- and extracellular synergistic degradation". Specifically, dye stress induces the production of H2O2 and O2- within cells. These ROS are subsequently transported to the extracellular environment via transmembrane systems, where they synergize with extracellular ROS and traditional key decolorization enzymes to achieve efficient dye degradation. This discovery provides a critical theoretical foundation for the development of ROS-enzyme synergistic dye bioremediation processes.

MOF-derived Cu@Cu2O nanoclusters for photothermally enhanced Fenton-like catalytic degradation of dye pollutants

This paper presents a synthesis method for a novel octahedral Cu@Cu2O nanocluster (NAs), which is prepared by calcining Cu-BTC (metal-organic framework, 1,3,5-benzenetricarboxylate) in air, resulting in a porous carbon structure. The obtained Cu@Cu2O nanoclusters exhibit heterogeneous interfaces between Cu and Cu2O, significantly enhancing their Fenton-like catalysis and photothermal properties. Using SEM, TEM, XPS, and XRD techniques, the Cu@Cu2O NAs were comprehensively characterized. Upon near-infrared irradiation, these nanoclusters rapidly heat to 45 °C, generating reactive oxygen species (•OH) that effectively catalyze the degradation of Rhodamine B (RhB) dye. Moreover, cellular and animal experiments demonstrated that Cu@Cu2O NAs possess good biocompatibility and exhibit excellent biological safety. Overall, this study offers a promising and biocompatible material option for environmental remediation, integrating Fenton-like reactions with photothermal effects.

Multiple regeneration of "high iron" alginate composite gel beads for rapid treatment of dye wastewater

Water pollution, particularly from dye contaminants, has become a critical global issue, driving the demand for efficient treatment technologies such as persulfate-based advanced oxidation processes. In our study, we developed a novel chitosan-modified calcium alginate gel as a scaffold for heterogeneous Fenton catalysis. Through grafting ethylenediaminetetraacetic acid onto the amino groups within the gel backbone and subsequent loading of Fe2+, we developed CASGMC, a "high iron" alginate gel capable of efficiently absorbing and releasing Fe2+. Additionally, 3D RGO@Cu2S-MoS2 was incorporated into the gel system to enhance catalytic efficiency and suppress Fe3+ accumulation, thereby extending the gel's service life. CASGMC exhibited excellent mechanical stability and structural integrity, achieving an impressive 98.8 % removal of rhodamine B within 15 min. Furthermore, its regeneration process was straightforward, with catalytic activity restored simply by immersion in an Fe2+ solution, allowing for up to ten cycles of reuse. Notably, even after 1032 h of continuous operation, a CASGMC-filled purification column maintained an 88.67 % removal efficiency of rhodamine B, demonstrating its long-term applicability. This study not only enhances the mechanical durability and reusability of alginate-based catalysts but also provides a promising strategy for sustainable wastewater treatment using iron-loaded gel materials.

Environmentally sustainable fabrication of SnO2/fly ash/biochar nanocomposite for enhanced photocatalytic performance for degradation of Ofloxacin and Rose Bengal

A ternary nanocomposite SnO2/FA/Biochar was synthesized using the sol-gel process to degrade Ofloxacin (Pharmaceutical) and Rose Bengal (RB) dye. Transmission electron microscopy, X-ray powder diffraction, Scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy and UV-Vis diffuse reflectance spectroscopy were used to characterize the prepared composite's structure, surface morphology, composition, and surface area. The SnO2/FA/Biochar nanocomposite, which was synthesized, has a particle size of 14.43 nm. The test results showed that SnO2 nanoparticles clustered together on the surface of Fly ash and Biochar. Under sun irradiation, the composite exhibited excellent photocatalytic efficacy in decomposing Rose Bengal and Ofloxacin. The maximum degradation rates of 99.12% and 88.08% were attained with catalyst doses of 0.01 g/L for RB dye and Ofloxacin, respectively, within 60 min each. The improved photocatalytic activity may be ascribed to the photocatalyst's reduced rate of charge recombination and lowered bandgap value. The synthesized SnO2/FA/Biochar nanocomposite has a direct band gap of 2.3 eV, as determined by Tauc's plot. The degradation of RB and Ofloxacin by exposure to light followed a reaction kinetics mechanism identified as pseudo-first-order, having rate constants of 0.0250 min- 1 and 0.0159 min- 1, respectively. The photocatalyst may be used for a maximum of five cycles while maintaining an efficiency above 75%. The impact of pH was also examined. The photodegradation activity of SnO2/FA/Biochar under visible light was investigated, resulting in efficient contamination removal from the water.

Simultaneous degradation of direct black BN dye wastewater and electricity generation by red soil microbial fuel cells

Azo dyes, widely used in industries, pose environmental challenges due to their recalcitrance and potential carcinogenicity. Microbial fuel cells (MFCs) offer a sustainable solution by coupling wastewater treatment with renewable energy production. However, research on polyazo dye treatment using MFCs remains limited. This study developed a novel MFC system using red soil as the anode substrate (RSMFC) to treat direct black BN wastewater, focusing on removal efficiency, power generation, and microbial community dynamics. The concentration of direct black BN influenced the RSMFC's performance, showing a "low promotion and high inhibition" effect on electricity generation. The system achieved a peak power density of 584.82 mW/m3. GC-MS analysis identified primary degradation products, including 13-Docosenamide, (Z)- and Bis(2-ethylhexyl) phthalate, revealing the degradation pathway of direct black BN. Microbial community analysis highlighted the roles of Bosea, Citrifermentans, Desulfosporosinus, and Pseudomonas in dye tolerance and degradation. Additionally, influent concentrations of 300 mgCOD/L, containing 99.7 mg/L direct black BN, significantly enriched electricigens such as Geobacter, Desulfovibrio, Pseudomonas, and Acinetobacter. Our findings provide essential groundwork for optimizing RSMFCs and advancing azo dye wastewater treatment technologies. The simultaneous removal of direct black BN and electricity generation in the RSMFC holds promise for sustainable environmental management.

Environmental Impact of Textile Materials: Challenges in Fiber-Dye Chemistry and Implication of Microbial Biodegradation

Synthetic and natural fibers are widely used in the textile industry. Natural fibers include cellulose-based materials like cotton, and regenerated fibers like viscose as well as protein-based fibers such as silk and wool. Synthetic fibers, on the other hand, include PET and polyamides (like nylon). Due to significant differences in their chemistry, distinct dyeing processes are required, each generating specific waste. For example, cellulose fibers exhibit chemical inertness toward dyes, necessitating chemical auxiliaries that contribute to wastewater contamination, whereas synthetic fibers are a major source of non-biodegradable microplastic emissions. Addressing the environmental impact of fiber processing requires a deep molecular-level understanding to enable informed decision-making. This manuscript emphasizes potential solutions, particularly through the biodegradation of textile materials and related chemical waste, aligning with the United Nations Sustainable Development Goal 6, which promotes clean water and sanitation. For instance, cost-effective methods using enzymes or microbes can aid in processing the fibers and their associated dyeing solutions while also addressing textile wastewater, which contains high concentrations of unreacted dyes, salts, and other highly water-soluble pollutants. This paper covers different aspects of fiber chemistry, dyeing, degradation mechanisms, and the chemical waste produced by the textile industry, while highlighting microbial-based strategies for waste mitigation. The integration of microbes not only offers a solution for managing large volumes of textile waste but also paves the way for sustainable technologies.

Adsorptive removal of Congo red dye from industrial effluent using cotton calyx iron oxide (CC-Fe3O4) composite

Environmental pollution is an emerging issue in the areas of South Asia and the burning of crop residues is one of the major contributors to smog/pollutants production. In recent work, the residues of cotton crop, i.e., cotton calyx (CC), have been converted into a valuable and eco-friendly adsorbent at zero cost for the refining of polluted waters. Furthermore, cotton calyx composite was synthesized with iron oxide (CC-Fe3O4) to improve its sorption potential for the mitigation of selected pollutants, i.e., Congo red (CR) dye. By using FTIR, SEM, TGA, and XRD, the newly synthesized biosorbents were characterized. SEM-EDX and FTIR analyses revealed that both biosorbents (CC and CC-Fe3O4) have a porous surface along with various functional groups, which is an indication of an ideal adsorbent for the sorptive removal of pollutants like dyes. The effect of the operating parameters (dye concentration, adsorbent dosage, temperature, contact time, and pH of the dye solution) on the sorption efficacy was studied to identify optimal conditions. The highest percentage of CR removal (99%) was achieved in an acidic medium using 0.6 g CC-Fe3O4 composite in 60 min at 20 °C. Isothermal modeling of the parameter's optimization data proved that the Langmuir model (R = 0.97-0.99) is more able to explain the sorption process than Freundlich indicates the monolayer sorption process. Adsorption kinetics professed that pseudo-second-order rate law effectively represented the ongoing adsorption system. The thermodynamic studies revealed that the sorption process was spontaneous at room temperature as ∆H° was negative. The maximal sorption capacity among the sorbents is 20.66 mg g-1 for CC-Fe3O4 composite, which is higher than CC. In conclusion, CC-Fe3O4 composite proved an efficient biosorbent for the mitigation of CR dye from wastewater.

Detection and selection of dye-degrading bacteria from surface waters with different degrees of contamination

Biodegradability and resistance from indigenous bacterial communities to dyes were tested using samples from both polluted and unpolluted surface waters in Buenos Aires. Five dyes were selected for the study: Acid Black 210, Direct Orange 39, Malachite Green, Gentian Violet, and Alizarin Red. Water quality was assessed by measuring chemical oxygen demand, biochemical oxygen demand, and both Escherichia coli and enterococci counts. Biodegradability was tested using a respirometric method, while resistance was assessed by determining the minimum inhibitory concentration (MIC). No bacterial strains capable of degrading the dyes as the sole carbon source were isolated from the respirometric tests. However, from the MIC tests, 28 strains capable of dye discolouration were identified, using nutrient broth as a supplement. Two of them were able to degrade Malachite Green and Acid Black 210 at a concentration of 50 mg L-1 in less than 24 h and with an efficiency greater than 87%. These strains were identified as Aeromonas sp. and Shewanella sp. through MALDI-TOF/MS and 16S rRNA gene sequencing. The determination of biodegradability and resistance can be used to enhance the characterization of watercourses. Furthermore, this methodology provides a means to isolate biodegrading bacteria that could be applied in effluent treatment processes.

Upconverting Luminescent MOF for Highly Sensitive Dual-Mode Recognition of Synthetic Dyes

Lanthanide-based luminescent materials hold promise in sensing applications due to their distinct optical properties. Though advancements in lanthanide-based metal-organic frameworks (MOFs) have enhanced downshifting luminescence, achieving upconversion remains challenging. In this effort, we prepared upconverting ytterbium-doped europium MOFs (x%Yb3+-EuMOFs; x = 10, 20, and 30) via the solvothermal method using 2,6-naphthalenedicarboxylic acid (NDC) as an organic linker. Upconversion (UC) luminescence studies revealed that 30%Yb3+-EuMOF (MOF-3) rapidly detects malachite green (MG, a textile dye) and brilliant green (BG, a food colorant) with excellent sensitivity (λex = 980 nm). Notably, UC luminescence offers a lower detection limit (MG: 36.33 nM, BG: 287.9 nM) compared to the downconverting sensing approach (λex 270 nm), while the related dual-mode luminescence minimizes the risk of false positives from interfering ultraviolet-visible (UV-vis) light-absorbing substances. Upconversion quenching has been linked to the FRET process, with its luminescence assay accurately detecting MG in fish, water, and soil samples under 980 nm excitation (98-105% recovery).

Enhancing the efficiency of PVDF-based piezoelectric catalysis through water-induced polarization and a micro-nano-composite strategy

Polyvinylidene fluoride (PVDF)-based piezoelectric catalysts show promise in mechanical force-driven catalysis due to their good biocompatibility, flexibility, and ease of fabrication. However, the catalytic activity of pristine PVDF is limited due to its low piezoelectric phase content (<20%), poor orientation, and low surface carrier concentration. Here, we introduce an efficient PVDF-based composite nano-catalyst (rGO/PVDF) with high piezoelectric catalytic performance. We achieve this by employing a composite strategy that combines nanoscale water-induced polarization with polar functional group-modified graphene (rGO) serving as a nanoelectrode. The nanoscale water polarization effect, together with the two-dimensional planar structure of PVDF and the modified graphene's polar functional groups, effectively induces orientation in the PVDF piezoelectric phase to increase the functional β phase content. As a result, the β phase content and crystallinity of rGO/PVDF reach 95% and 40%, respectively, which are 600% and 170% higher compared to those of pristine PVDF. This enhancement plays a crucial role in endowing the material with strong force-to-electricity conversion characteristics. Additionally, the surface-modified rGO also boosts PVDF's surface carrier concentration and provides active sites for catalysis on the rGO/PVDF composite. Notably, under optimized conditions, our catalyst achieves a ∼99.1% degradation rate of organic pollutants (10 mg L-1) after 12 minutes of sonication at 240 W and maintains a high efficiency of ∼93.7% even at a 10 times higher pollutant concentration (100 mg L-1). Our piezoelectric catalyst also demonstrates efficient H2O2 production at 95.8 mmol grGO-1 h-1, which is ∼9-fold and ∼134-fold higher than those of untreated PVDF and previously reported PVDF-based piezoelectric catalysts, respectively. This work paves the way for the development of highly efficient PVDF-based piezoelectric catalysts, thereby offering valuable insights for the advancement of mechanically driven catalysis in the environmental, energy, and chemical sectors.

A stable HOF-embedded alginate hydrogel membrane for selective adsorption of cationic dyes

Targeted at organic dye pollutants, a stable HOF was combined with an alginate (SA) hydrogel to enhance the affinity for cationic dyes. The as-obtained HOF@SA membrane (weight ratio: 1/1) shows a high adsorption capacity (729.21 mg g-1), adsorption selectivity and good recycling performance towards methylene blue.

Advanced BiVO4-deoxygenated lignocellulosic photocatalyst for effective degradation of organic and heavy metal pollutants in aqueous system

Bismuth vanadate (BiVO4) is a common photocatalyst for water remediation, yet its powder form renders difficult to disperse, recycle, and regenerate, limiting photodegradation efficiency. In this study, a lignocellulosic-templated BiVO4 photocatalyst was fabricated from BiVO4 precursor and lignocellulose using a simple vacuum impregnation (w/o heat treatment on wood template). Results showed that the modified template retained original hierarchical structure with an increased specific surface area and reduced hemicellulose content, leading to a promising template for uniform distribution of BiVO4. Moreover, compared to untreated, heat treatment cleaved acetyl groups in the hemicellulose chain, broke down fatty ether bonds, and oxidized lignin side chains, resulting in no disruption to the catalysis of BiVO4. The BiVO4-pyrolyzed lignocellulosic photocatalyst achieved remarkable degradation efficiencies of 90.03 % (approximately 7-fold increase compared to untreated) for RhB and complete degradation of Cr (VI) within 60 min. Furthermore, the efficiency remained >80 % after seven cycles. The mechanism was hypothesized that BiVO4 and template play distinct roles, as deoxygenated lignocellulosic template only acts as a carrier for BiVO4 growth, and BiVO4 serves as the photocatalyst. However, untreated template can react with BiVO4 and impair photocatalytic efficiency. The BiVO4-pyrolyzed lignocellulosic photocatalyst holds great promise for the remediation of aqueous contaminants.

Bioremediation technologies for remediation of dyes from wastewater

The colored dyes are extensively applied in diverse industrial setups such as textiles, paper, leather, and cosmetics. The unutilized dyes are released in the waste and pose a serious menace to the environment, ecological balance, and human health. Because of their chemical nature, they are extremely resistant to common methods of treatment and often persist in the aquatic environment. A sustainable and eco-friendly approach for treating dye-contaminated wastewater is "bioremediation." This manuscript aims to discuss the exclusive role of diversified microorganisms and plants, immobilized microbial cells/enzymes, microbial consortia, nanomaterials, and combination approaches in the bioremediation of dyes. It also provides a comprehensive understanding of different bio-remedial technologies used to remove dyes from wastewater. In addition, the underlying mechanisms affecting the efficacy of bio-remedial technologies, the latest breakthroughs, challenges, and potential solutions in scaling up, and prospects in this area are also explored. We also detail the noteworthiness of genetic engineering in different bioremediation technologies to solve the issues associated with dye contamination in wastewater and its removal from the environment.

An overview of recent advances in treatment of complex dye-containing wastewater and its techno-economic assessment

Industries such as textiles, polymers, pharmaceuticals, papers, and tanneries are the key contributors to the global economy. These industries utilize various types of synthetic dyes in their processes, leading to discharge of dyes-contaminated wastewater. The wastewater generally contains various types of dyes (such as methyl orange, congo red, malachite green, etc.), which have a detrimental impact on the ecosystem and human health due to their toxic, carcinogenic, and mutagenic nature. As the result, it is crucial to treat the dyes-contaminated wastewater to protect the environment and render it suitable for reuse, mitigating the escalating global demand for clean water. This review provides a comprehensive overview of dyes and their treatment technologies (i.e., physical, chemical, and biological treatment). Among various treatment methods, the biological treatment is widely employed due to its energy efficiency and eco-friendliness. However, biological treatment faces challenges such as slow processing rates and limited effectiveness in handling low-biodegradability pollutants (BOD5/COD <0.2). This review also highlighted recent advancements in treatment technologies and explored the emerging integrated treatment method that aims to achieve higher removal efficiency for a low biodegradability index dye-contaminated wastewater. Additionally, a techno-economic assessment is presented, analyzing the cost-effectiveness of the emerging technologies in real-world applications. Further, the critical research gaps and future outlooks are also discussed. Overall, the review aims to contribute to the ongoing efforts to improve wastewater treatment processes and promote sustainable water management practices.

Exploring performance and mechanism of modified metal-organic frameworks in calcium alginate/polyvinyl alcohol double-network hydrogels for effective dye wastewater treatment

To address the growing problem of dye wastewater pollution, a novel MOFs adsorbent calcium alginate/polyvinyl alcohol@UiO-66 was developed using environmentally friendly polymers, sodium alginate and polyvinyl alcohol creating gel spheres with a double-network structure through cross-linking. UiO-66 metal-organic frameworks are then grown onto the gel spheres, resulting in the final CA/PVA@UiO-66 adsorbent. This adsorbent boasts a high surface area (17.4 m2/g) and a mesoporous-nested microporous structure. It effectively removes MB from water, the actual maximum adsorption capacity was measured at 275.8 mg/g, which surpasses most existing adsorbents. Remarkably, the adsorbent retains 93.9 % of its initial capacity even after 10 reuse cycles. The adsorption process adhered to the Redlich-Peterson model and the PFO model. The N2-Sorption isotherm, actual Methylene blue (MB) adsorption experiments, and model analysis further suggest that the adsorption process is a complex heterogeneous diffusion process involving simultaneous chemical and physical adsorption. Additionally, the adsorption process is endothermic, indicating that it can occur spontaneously at 298 K. Increasing the temperature promotes the forward progress of the adsorption reaction, thereby enhancing the adsorption capacity. The gel adsorbent exhibited excellent dye wastewater purification capabilities, coupled with commendable reusability.

Adsorption of methyl orange and methylene blue from aqueous solutions on pure bentonite: statistical physical modeling provides an analytical interpretation

This study investigates the adsorption of methylene blue (MB) and methyl orange (MO) dyes from aqueous solutions using purified Moroccan bentonite, being mainly composed of silica and alumina, in the form of quartz and cristobalite. The temperature controls the adsorption capacity for the kinetics, increasing 5.08% (from 295.1 to 310.1 mg/g) for the MB and 55.47% (from 86.8 to 134.9 mg/g) for the MO. It was discovered that the pseudo-second-order model, with a low Bayesian criterion indicator of 12.72 and R2adj > 0.996, was the best suitable for explaining both systems. The adsorption isotherm, experimental data indicate that both systems follow the Langmuir isotherm. At lower temperatures, 298.15 K 1.22 molecules are adsorbed per site. However, at a higher temperature of 328.15 K, the number of molecules is less than a unit of 0.68. As for MO, the number of molecules remains above 1.4 per site for all the temperatures studied. The endothermic nature of the system is indicated by the observation that the adsorption energy tends to grow for both systems: for the MB, it increases from 18.85 to 21.26 kJ/mol, and for the MO, it increases from 14.83 to 19.01 kJ/mol. Last, thermodynamic functions indicate that maximum entropy is reached around the half-concentration saturation at 25 and 124 mg/L, which is the maximum energetic concentration of the system. The same results were obtained for Gibbs free energy, where the maximum energy found was - 5.39 × 10-18 kJ/mol for the MB and - 1.99 × 10-18 kJ/mol for the MO at 328.15 K.

Characterization and rational engineering of an alkaline-tolerant azoreductase derived from Roseibium sp. H3510 for enhanced decolorization of azo dyes

rAzoR2326, an azoreductase derived from Roseibium sp. H3510, functions as an FMN-dependent homodimer utilizing NADH as cofactor. It demonstrated maximum activity at 45 °C and retained moderate activity above 50 °C, exhibiting stability from pH 7-10. Evolution and structure guided rational design of wild-type rAzoR2326 (WT) efficiently yielded 6 single-point mutants with improved thermostability and activity from a 22-variant library. Further combinatorial mutation led to mutant M20 with substantially enhanced thermostability (15-fold longer half-life at 50 °C) and activity (3.24-fold higher kcat/Km). M20 exhibited superior catalytic properties for decolorizing Allura Red compared to WT. Specifically, its decolorization capacity at pH 10.0 was 4.26-fold higher than WT. Additionally, M20 demonstrated remarkable thermostability, retaining 76.83 % decolorization activity for Allura Red after 120 min at 50 °C, whereas WT nearly lost all catalytic activity under the same conditions. Molecular dynamics simulations revealed the structural changes in M20, such as improved hydrogen bonding and a new C-H···π interaction, led to a more compact and rigid enzyme structure. This resulted in a more stable FMN-binding pocket and substrate tunnel, thereby improving the catalytic stability and activity of M20. Given its enhanced dye decolorization ability and alkaline tolerance, M20 shows promise as a biocatalyst for treating azo dye effluents.

Synthesis and Dye Adsorption Dynamics of Chitosan-Polyvinylpolypyrrolidone (PVPP) Composite

One major environmental issue responsible for water pollution is the presence of dyes in the aquatic environment as a result of human activity, particularly the textile industry. Chitosan-Polyvinylpolypyrrolidone (PVPP) polymer composite beads were synthesized and explored for the adsorption of dyes (Bismarck brown (BB), orange G (OG), brilliant blue G (BBG), and indigo carmine (IC)) from dye solution. The CS-PVPP beads demonstrated high removal efficiency of BB (87%), OG (58%), BBG (42%), and IC (49%). The beads demonstrated a reasonable surface area of 2.203 m2/g and were negatively charged in the applicable operating pH ranges. TGA analysis showed that the polymer composite can withstand decomposition up to 400 °C, proving high stability in harsh conditions. FTIR analysis highlighted the presence of N-H amine, O-H alcohol, and S=O sulfo groups responsible for electrostatic interaction and hydrogen bonding with the dye molecules. A shift in the FTIR bands was observed on N-H and C-N stretching for the beads after dye adsorption, implying that adsorption was facilitated by hydrogen bonding and Van der Waals forces of attraction between the hydroxyl, amine, and carbonyl groups on the surface of the beads and the dye molecules. An increase in pH increased the adsorption capacity of the beads for BB while decreasing OG, BBG, and IC due to their cationic and anionic nature, respectively. While an increase in temperature did not affect the adsorption capacity of OG and BBG, it significantly improved the removal of BB and IC from the dye solution and the adsorption was thermodynamically favoured, as demonstrated by the negative Gibbs free energy at all temperatures. Adsorption of dye mixtures followed the characteristic adsorption nature of the individual dyes. The beads show great potential for applications in the treatment of dye wastewater.

Decolorization and detoxification of direct blue 5B by a Marinobacter-dominated halo-thermoalkalophilic consortium

Azo dye-containing sewage is commonly detected at high salinity, temperature and pH. In this study, a halo-thermoalkalophilic azo dye decolorization consortium was enriched and named "consortium HL". Consortium HL which was dominated by Marinobacter (84.30%), Desulfocurvibacter (1.89%), and Pseudomonas (1.85%), was able to completely decolorize Direct Blue 5B (DB5) during incubation with the material at 5% salinity, 50 °C, and pH 9 for 30 h. The decolorization mechanism was proposed based on combined metagenomic analysis, GC‒MS, and enzymatic activity detection. The action of the consortium HL showed great tolerance to variations in salinity, temperature and pH. A phytotoxicity study indicated that the metabolic intermediates showed no significant toxicity to the generation of Cucumis sativus and Oryza sativa seeds. This study, in which azo dye decolorization and degradation under high-salt, high-temperature and high-alkalinity conditions were investigated and deeply analyzed by metagenomic information, is the first report regarding the ability of Marinobacter to decolorize azo dyes at high temperatures.

Purification of aqueous orange II solution through adsorption and visible-light-induced photodegradation using ZnO-modified g-C3N4 composites

Semiconductor-based remediation enables environmentally friendly methods of removing aqueous pollutants. Simply fabricated ZnO modified g-C3N4 composites were utilized as bifunctional adsorptive photocatalysts for orange II removal from aqueous solution through adsorption and photocatalysis processes. The adsorption isotherm data of the g-C3N4 (g-CN) and ZnO modified g-C3N4 (ZCN) composites on orange II solution were better fitted with the Langmuir isotherm compared to the Freundlich isotherm. The maximum adsorption capacity for ZCN-2.5 was slightly higher than that of bare g-CN. According to the adsorption thermodynamics investigation of ZCN-2.5 in orange II solution, the positive values of Gibb's free energy change (ΔG0) suggested a non-spontaneous adsorption process. Furthermore, the negative values of entropy change (ΔS) and enthalpy change (ΔH) indicated the decrement of randomness and exothermic nature during the adsorption process, respectively. The photocatalytic degradation kinetics of g-CN and ZCN composites indicated that the degradation process follows the pseudo-first-order reaction kinetic. The degradation rate of orange II with the ZCN-2.5 composite was 6.67 times higher than that obtained with bare g-CN. Possible adsorption and photocatalytic mechanisms have been proposed.

Advances and challenges in the removal of organic pollutants via sulfate radical-based advanced oxidation processes by Fe-based metal-organic frameworks: A review

Organic contaminants, notorious for their complexity and resistance to degradation, are prevalent in aquatic environments, posing severe threats to ecosystems. Sulfate radical-based advanced oxidation processes (SR-AOPs), known for their stability and high effectiveness, have become a common choice for treating organic wastewater. Metal-organic framework materials (MOFs) have garnered substantial attention due to their facile chemical manipulation, unique structural configurations, and other favorable properties. Therefore, this article critically reviews recent advances in research involving the utilization of Fe-based MOFs (Fe-MOFs) and their derivatives in SR-AOPs. Specifically, it highlights the manipulation of influencing factors within the system to enhance the degradation of organic pollutants. The mechanisms and applications underlying the degradation of organic pollutants in the SR-AOPs system are also elucidated.

New insights on the decolorization of waste flows by Saccharomyces cerevisiae strain - A systematic review

One of the common causes of water pollution is the presence of toxic dye-based effluents, which can pose a serious threat to the ecosystem and human health. The application of Saccharomyces cerevisiae (S. cerevisiae) for wastewater decolorization has been widely investigated due to their efficient removal and eco-friendly treatments. This review attempts to create an awareness of different forms and methods of using Saccharomyces cerevisiae (S. cerevisiae) for wastewater decolorization through a systematic approach. Overall, some suggestions on classification of dyes and related environmental/health problems, and treatment methods are discussed. Besides, the mechanisms of dye removal by S. cerevisiae including biosorption, bioaccumulation, and biodegradation and cell immobilization methods such as adsorption, covalent binding, encapsulation, entrapment, and self-aggregation are discussed. This review would help to inspire the exploration of more creative methods for applications and modification of S. cerevisiae and its further practical applications.

Bacterial community structure analysis of sludge from Taozi lake and isolation of an efficient 17β-Estradiol (E2) degrading strain Sphingobacterium sp. GEMB-CSS-01

Environmental challenges arising from organic pollutants pose a significant problem for modern societies. Efficient microbial resources for the degradation of these pollutants are highly valuable. In this study, the bacterial community structure of sludge samples from Taozi Lake (polluted by urban sewage) was studied using 16S rRNA sequencing. The bacterial phyla Proteobacteria, Bacteroidetes, and Chloroflexi, which are potentially important in organic matter degradation by previous studies, were identified as the predominant phyla in our samples, with relative abundances of 48.5%, 8.3%, and 6.6%, respectively. Additionally, the FAPROTAX and co-occurrence network analysis suggested that the core microbial populations in the samples may be closely associated with organic matter metabolism. Subsequently, sludge samples from Taozi Lake were subjected to enrichment cultivation to isolate organic pollutant-degrading microorganisms. The strain Sphingobacterium sp. GEMB-CSS-01, tolerant to sulfanilamide, was successfully isolated. Subsequent investigations demonstrated that Sphingobacterium sp. GEMB-CSS-01 efficiently degraded the endocrine-disrupting compound 17β-Estradiol (E2). It achieved degradation efficiencies of 80.0% and 53.5% for E2 concentrations of 10 mg/L and 20 mg/L, respectively, within 10 days. Notably, despite a reduction in degradation efficiency, Sphingobacterium sp. GEMB-CSS-01 retained its ability to degrade E2 even in the presence of sulfanilamide concentrations ranging from 50 to 200 mg/L. The findings of this research identify potential microbial resources for environmental bioremediation, and concurrently provide valuable information about the microbial community structure and patterns within Taozi Lake.

Decolorization and detoxication of malachite green by engineered Saccharomyces cerevisiae expressing novel thermostable laccase from Trametes trogii

Malachite Green (MG) is a widely used industrial dye that is hazardous to health. Herein, the decolourisation and detoxification of MG were achieved using the engineered Saccharomyces cerevisiae expressing novel thermostable laccase lcc1 from Trametes trogii. The engineered strain RCL produced a high laccase activity of 121.83 U L-1. Lcc1 was stable at temperatures ranging from 20 ℃ to 60 ℃ and showed a high tolerance to organic solvents. Moreover, Lcc1 could decolorize different kinds of dyes (azo, anthraquinone and triphenylmethane), among which, the decolorization ability of MG is the highest, reaching 95.10 %, and the decolorization rate of other triphenylmethane dyes also over 50 %. The RCL decolorized about 95 % of 50 mg L-1 of MG dye in 10 h at 30 ℃. The MG degradation products were analyzed. The industrial application potential of the RCL was evaluated by treating industrial wastewater and the decolourisation rates were over 90 %.

Waste Biomass-Mediated Synthesis of TiO2/P, K-Containing Grapefruit Peel Biochar Composites with Enhanced Photocatalytic Activity

In this study, TiO2/P, K-containing grapefruit peel biochar (TiO2/P, K-PC) composites were synthesized in situ biomimetically using grapefruit peel as the bio-template and carbon source and tetrabutyl titanate as the titanium source. This was achieved using the two-step rotary impregnation-calcination method. Adjusting the calcination temperature of the sample in an air atmosphere could regulate the mass ratio of TiO2 to carbon. The prepared samples were subjected to an analysis of their compositions, structures, morphologies, and properties. It demonstrated that the prepared samples were complexes of anatase TiO2 and P, K-containing carbon, with the presence of graphitic carbon. They possessed a unique morphological structure with abundant pores and a large surface area. The grapefruit peel powder played a crucial role in the induction and assembly of TiO2/P, K-PC composites. The sample PCT-400-550 had the best photocatalytic activity, with the degradation rate of RhB, MO, and MB dye solutions reaching more than 99% within 30 min, with satisfactory cyclic stability. The outstanding photocatalytic activity can be credited to its unique morphology and the efficient collaboration between TiO2 and P, K-containing biochar.

Hues of risk: investigating genotoxicity and environmental impacts of azo textile dyes

The textile industry, with its extensive use of dyes and chemicals, stands out as a significant source of water pollution. Exposure to certain textile dyes, such as azo dyes and their breakdown products like aromatic amines, has been associated with health concerns like skin sensitization, allergic reactions, and even cancer in humans. Annually, the worldwide production of synthetic dyes approximates 7 × 107 tons, of which the textile industry accounts for over 10,000 tons. Inefficient dyeing procedures result in the discharge of 15-50% of azo dyes, which do not adequately bind to fibers, into wastewater. This review delves into the genotoxic impact of azo dyes, prevalent in the textile industry, on aquatic ecosystems and human health. Examining different families of textile dye which contain azo group in their structure such as Sudan I and Sudan III Sudan IV, Basic Red 51, Basic Violet 14, Disperse Yellow 7, Congo Red, Acid Red 26, and Acid Blue 113 reveals their carcinogenic potential, which may affect both industrial workers and aquatic life. Genotoxic and carcinogenic characteristics, chromosomal abnormalities, induced physiological and neurobehavioral changes, and disruptions to spermatogenesis are evident, underscoring the harmful effects of these dyes. The review calls for comprehensive investigations into the toxic profile of azo dyes, providing essential insights to safeguard the aquatic ecosystem and human well-being. The importance of effective effluent treatment systems is underscored to mitigate adverse impacts on agricultural lands, water resources, and the environment, particularly in regions heavily reliant on wastewater irrigation for food production.

Preparation of Novel Layered High Entropy Bismuth-Based Materials and their Photocatalytic Degradation Mechanism

We prepared BiOCl, BiO(ClBr), BiO(ClBrI), and BiO[ClBrI(CO3)0.5] materials using a simple coprecipitation method. It was found that adjusting the number of anions in the anion layer was conducive to adjusting the band structure of BiOX and could effectively promote the migration and separation of photogenerated carriers, thus improving the photocatalytic activity. We first selected methyl orange (MO) as the study pollutant and compared it with BiOCl, BiO(ClBr), and BiO(ClBrI). The first-order kinetic constants of MO degradation by BiO[ClBrI(CO3)0.5] increased by 90.3, 33.9, and 3.1 times, respectively. The photocatalytic degradation rate of methylene blue by BiO[ClBrI(CO3)0.5] was 89.5%, indicating the excellent photocatalytic performance of BiO[ClBrI(CO3)0.5]. The stability of BiO[ClBrI(CO3)0.5] was demonstrated through cyclic experiments and XRD analysis before and after the reaction. The photocatalytic degradation of MO by BiO[ClBrI(CO3)0.5] showed that h+ and 1O2 were the main active oxidizing species and •O2- was the secondary active substance. Overall, our work provides new ideas for the synthesis and degradation of organic pollutants by using two-dimensional anionic high-entropy materials.

Fenton reaction in the process of "Laser + Fe" mode excited plasma for Rhodamine B degradation

The spectral emission of laser-induced plasma in water has a broadband continuum containing ultraviolet light, which can be used as a novel light source for the degradation of organic compounds. We studied the degradation process of the organic dye Rhodamine B (RhB) using plasma light source excited by the "Laser + Fe" mode. Spectral analysis and reaction kinetics modelling were used to study the degradation mechanism. The degradation process using this light source could be divided into two stages. The initial stage was mainly photocatalytic degradation, where ultraviolet light broke the chemical bond of RhB, and then RhB was degraded by the strong oxidising ability of ·OH. As the iron and hydrogen ion concentrations increased, the synergistic effect of photocatalysis and the Fenton reaction further enhanced the degradation rate in the later stage. The plasma excited by the "Laser + Fe" mode achieved photodegradation by effectively enhancing the ultraviolet wavelength ratio of the emission spectrum and triggered the Fenton reaction to achieve rapid organic matter degradation. Our findings indicate that the participation of the Fenton reaction can increase the degradation rate by approximately 10 times. Besides, the impact of pH on degradation efficiency demonstrates that both acidic and alkaline environments have better degradation effects than neutral conditions; this is because acidic environments can enhance the Fenton reaction, while alkaline environments can provide more ·OH.

One-Step Synthesis of Polyethyleneimine-Grafted Styrene-Maleic Anhydride Copolymer Adsorbents for Effective Adsorption of Anionic Dyes

Wastewater containing organic dyes has become one of the important challenges in water treatment due to its high salt content and resistance to natural degradation. In this work, a novelty adsorbent, PEI-SMA, was prepared by grafting polyethyleneimine (PEI) onto styrene-maleic anhydride copolymer (SMA) through an amidation reaction. The various factors, such as pH, adsorbent dosage, contact time, dye concentration, and temperature, which may affect the adsorption of PEI-SMA for Reactive Black 5 (RB5), were systematically investigated by static adsorption experiments. The adsorption process of PEI-SMA for RB5 was more consistent with the Langmuir isotherm model and the pseudo-second-order model, suggesting a single-layer chemisorption. PEI-SMA exhibits excellent adsorption performance for RB5 dye, with a maximum adsorption capacity of 1749.19 mg g-1 at pH = 2. Additionally, PEI-SMA exhibited highly efficient RB5 competitive adsorption against coexisting Cl- and SO42- ions and cationic dyes. The adsorption mechanism was explored, and it can be explained as the synergistic effect of electrostatic interaction, hydrogen bonding and π-π interaction. This study demonstrates that PEI-SMA could act as a high performance and promising candidate for the effective adsorption of anionic dyes from aqueous solutions.

Viral community distribution, assembly mechanism, and associated hosts in an industrial park wastewater treatment plant

Viruses manipulate bacterial community composition and impact wastewater treatment efficiency. Some viruses pose threats to the environment and human populations through infection. Improving the efficiency of wastewater treatment and ensuring the health of the effluent and receptor pools requires an understanding of how viral communities assemble and interact with hosts in wastewater treatment plants (WWTPs). We used metagenomic analysis to study the distribution, assembly mechanism, and sensitive hosts for the viral communities in raw water, anaerobic tanks, and returned activated sludge units of a large-scale industrial park WWTP. Uroviricota (53.42% ± 0.14%) and Nucleocytoviricota (26.1% ± 0.19%) were dominant in all units. Viral community composition significantly differed between units, as measured by β diversity (P = 0.005). Compared to raw water, the relative viral abundance decreased by 29.8% in the anaerobic tank but increased by 9.9% in the activated sludge. Viral community assembly in raw water and anaerobic tanks was predominantly driven by deterministic processes (MST <0.5) versus stochastic processes (MST >0.5) in the activated sludge, indicating that differences in diffusion limits may fundamentally alter the assembly mechanisms of viral communities between the solid and liquid-phase environments. Acidobacteria was identified as the sensitive host contributing to viral abundance, exhibiting strong interactions and a mutual dependence (degree = 59). These results demonstrate the occurrence and prevalence of viruses in WWTPs, their different assembly mechanism, and sensitive hosts. These observations require further study of the mechanisms of viral community succession, ecological function, and roles in the successive wastewater treatment units.

Microorganism-mediated bioremediation of dyes from contaminated soil: Mechanisms, recent advances, and future perspectives

Many methods have been proposed for the remediation of dye-contaminated soils, a widespread form of environment pollution. Bioremediation, it is hoped, can combine ecological benefits with efficiency of dye decontamination. We review the types and sources of dye contaminants; their possible effects on plant, animal, and human health; and emerging strategies for microbial bioremediation. Challenges, limitations, recommendations for future research, and prospects for large-scale commercialization of microbial bioremediation are discussed.

pH-dependent and whole-cell catalytic decolorization of dyes using recombinant dye-decolorizing peroxidase from Rhodococcus jostii

Dyes in wastewater have adverse effects on the environment and human health. Dye-decolorizing peroxidase (DyP) is a promising biocatalyst to dyes degradation, but the decolorization rates varied greatly which influencing factors and mechanisms remain to be fully disclosed. To explore an effective decolorizing approach, we have studied a DyP from Rhodococcus jostii (RhDyPB) which was overexpressed in Escherichia coli to decolorize four kinds of dyes, Reactive blue 19, Eosin Y, Indigo carmine, and Malachite green. We found the decolorization rates of the dyes by purified RhDyPB were all pH-dependent and the highest one was 94.4% of Malachite green at pH 6.0. ESI-MS analysis of intermediates in the decolorization process of Reactive blue 19 proved the degradation was due to peroxidase catalysis. Molecular docking predicated the interaction of RhDyPB with dyes, and a radical transfer reaction. In addition, we performed decolorization of dyes with whole E. coli cell with and without expressing RhDyPB. It was found that decolorization of dyes by E. coli cell was due to both cell absorption and degradation, and RhDyPB expression improved the degradation rates towards Reactive blue 19, Indigo carmine and Malachite green. The effective decolorization of Malachite green and the successful application of whole DyP-overexpressed cells in dye decolorization is conducive to the bioremediation of dye-containing wastewaters by DyPs.

Expermental investigation on adsorption of methylene blue dye from waste water using corncob cellulose-based hydrogel

Hydrogel from corncob cellulose was synthesized in this investigation. The synthesized Hydrogel was characterized by SEM, XRD, and FTIR instruments. As the results indicate the synthesized hydrogel has required and important features, these suggest the suitability of hydrogel for the adsorption of methylene blue dye (MBD). Three important process variables (dosage, contact time, and initial concentration) with three levels were studied during the adsorption process at 30 °C and neutral pH. The efficiency of hydrogel for adsorption of MBD was determined in each experiment. The experimental results were statistically analyzed and interpreted. The maximum removal efficiency was achieved at 2.22 g/L of dosage, 80.36 min of contact time, and 74.54 mg/L of initial concentration. At this condition, 98.25% of MBD was achieved through experimental tests. Kinetics, isotherm, and thermodynamics studies were performed. Langmuir isotherm is more suitable to describe the adsorption process and the Pseudo second-order kinetic model fits this process. From the thermodynamics studies, all negative values of change in Gibbs free energy (ΔG°), and positive value of change in enthalpy (ΔH°), and change in entropy (ΔS°) indicate that the carried out experimental process is a spontaneous and endothermic. Moreover, the regeneration experiment for adsorbent was performed. The treatment of real textile industry waste water was conducted and the removal efficiency of hydrogel was 64.76%. This removal percentage reduction from sythetic aqueous solution is due to involvement of other pollutants in the real waste water. The synthesized hydrogel adsorbent is suitable up to the third cycle without significant loss in removal efficiency.

Wastewater Treatment Using Membrane Bioreactor Technologies: Removal of Phenolic Contaminants from Oil and Coal Refineries and Pharmaceutical Industries

Huge amounts of noxious chemicals from coal and petrochemical refineries and pharmaceutical industries are released into water bodies. These chemicals are highly toxic and cause adverse effects on both aquatic and terrestrial life. The removal of hazardous contaminants from industrial effluents is expensive and environmentally driven. The majority of the technologies applied nowadays for the removal of phenols and other contaminants are based on physio-chemical processes such as solvent extraction, chemical precipitation, and adsorption. The removal efficiency of toxic chemicals, especially phenols, is low with these technologies when the concentrations are very low. Furthermore, the major drawbacks of these technologies are the high operation costs and inadequate selectivity. To overcome these limitations, researchers are applying biological and membrane technologies together, which are gaining more attention because of their ease of use, high selectivity, and effectiveness. In the present review, the microbial degradation of phenolics in combination with intensified membrane bioreactors (MBRs) has been discussed. Important factors, including the origin and mode of phenols' biodegradation as well as the characteristics of the membrane bioreactors for the optimal removal of phenolic contaminants from industrial effluents are considered. The modifications of MBRs for the removal of phenols from various wastewater sources have also been addressed in this review article. The economic analysis on the cost and benefits of MBR technology compared with conventional wastewater treatments is discussed extensively.

Enzymatic dual-faced Janus structures based on the hierarchical organic-inorganic hybrid matrix for an effective bioremoval and detoxification of reactive blue-19

A novel, dual-faced, and hierarchical type of Janus hybrid structures (JHSs) was assembled through an in situ growing of lipase@cobalt phosphate sheets on the laccase@copper phosphate sponge-like structures. The chemical and structural information of prepared JHSs was investigated by Scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray diffraction analysis (XRD). The catalytic activity, storage stability, and reusability of JHSs were then investigated. The SEM-EDX analysis clearly confirmed the asymmetric morphology of the fabricated JHSs with two distinct metal distributions. Under optimized synthesis conditions, the prepared JHSs showed 97.8 % and 100 % of laccase and lipase activity, respectively. Compared to the free biocatalysts, the immobilization resulted in ~ a 2-fold increase in laccase and lipase stability at temperatures of >40 °C. The fabricated JHSs maintained 61 % and 90 % of their original laccase and lipase activity upon 12 successive repetition cycles. Up to 80 % of Reactive Blue-19 (RB-19), an anthraquinone-based vinyl sulphone dye, was removed after 5 h treatment with the prepared JHSs (50 % higher than the free forms of laccase and lipase). The dye removal data fitted very well on the pseudo-second-order kinetic model with a rate constant of 0.8 g mg-1 h-1. Following the bioremoval process, bacterial toxicity also decreased by about 70 %. Therefore, the prepared JHSs provide a facile and sustainable approach for the decolorization, biotransformation, and detoxification of RB-19 by integrating enzymatic oxidation and hydrolysis.

Synergistic molecular mechanism of degradation in dye wastewater by Rhodopseudomonas palustris intimately coupled carbon nanotube - Silver modified titanium dioxide photocatalytic composite with sodium alginate

The intimately coupled photocatalysis and biodegradation (ICPB), which combined the advantages of high oxidation capacity of photocatalysis and high mineralization rate of biodegradation, has demonstrated excellent removal performance in the degradation of azo dyes with highly toxic, refractory, mutagenic and carcinogenic. In order to explore the metagenomics mechanism of the ICPB system, a novel ICPB was prepared by coupling Rhodopseudomonas palustris (R. Palustris), carbon nanotube - silver modified titanium dioxide photocatalytic composite (CNT-Ag -TiO2, CAT) and sodium alginate (SA) (R. palustris/CAT@SA, R-CAT). Metagenomics sequencing was used to investigate the molecular mechanism of adaptation and degradation of dyes by photosynthetic microorganisms and the adaptive and synergistic interaction between photosynthetic microorganisms and photocatalyst. Experiments on the adaptability and degradability of photosynthetic microorganisms have proved that low concentration azo dyes could be utilized as carbon sources for growth of photosynthetic microorganisms. Metagenomics sequencing revealed that R. palustris was the main degrading bacterium in photosynthetic microorganisms and the functional genes related to carbohydrate metabolism, biological regulation and catalytic activity were abundant. It was found that the addition of photocatalyst significantly up-regulated the functional genes related to the catabolic process, electron transport, oxidoreductase activity and superoxide metabolism of organic matter in the photosynthetic microorganisms. Moreover, many key gene such as alpha-amylase, 1-acyl-sn-glycerol-3-phosphate acyltransferase, aldehyde dehydrogenase enrichment in microbial basal metabolism, such as enoyl-CoA hydratase, malate dehydrogenase, glutathione S-transferase enrichment in degrading azo dyes and electron transport, and many key gene such as undecaprenyl-diphosphatase, carbon storage regulator, DNA ligase enrichment in response to dyes and photocatalysts were discovered. These findings would contribute to a comprehensive understanding of the mechanism of degradation of dye wastewater by ICPB system, a series of genes was produced to adapt to environmental changes, and played synergistic role in terms of intermediate product degradation and electron transfer for degrading azo dyes. The photosynthetic microorganisms might be a promising microorganism for constructing ICPB system.

Decoration of viscose fibers with silver nanoparticle-based titanium-organic framework for use in environmental applications

To effectively remove pharmaceuticals, nitroaromatic compounds, and dyes from wastewater, an efficient multifunctional material was created based on silver nanoparticles (Ag) and MIL-125-NH2 (MOF) immobilized on viscose fibers (VF) as a support substrate. Firstly, silver nanoparticles (Ag) were immobilized on the surface of viscose fibers (VF) via in situ synthesis using trisodium citrate (TSC) as a reducing agent to create (VF-Ag). Then, VF and VF-Ag were decorated with the titanium metal-organic framework MIL-125-NH2 (MOF) to create VF-MOF and VF-Ag-MOF. The influence of VF-Ag, VF-MOF, and VF-Ag-MOF on the sonocatalytic or sonophotocatalytic degradation of sulfa drugs was investigated. The results show that VF-Ag-MOF showed excellent sonocatalytic and sonophotocatalytic activity towards the degradation of sulfa drugs compared to VF-Ag and VF-MOF. Furthermore, sonophotodegradation showed a dramatic enhancement in the efficiency of degradation of sulfa drugs compared to sonodegradation. The sonophotodegradation degradation percentage of sulfanilamide, sulfadiazine, and sulfamethazine drugs in the presence of VF-Ag-MOF was 65, 90, and 95 after 45 min of ultrasonic and visible light irradiation. The catalytic activity of VF-Ag, VF-MOF, and VF-Ag-MOF was evaluated through the conversion of p-nitrophenol (4-NP) to p-aminophenol (4-AP). The results demonstrate that VF-Ag-MOF had the highest catalytic activity, followed by VF-Ag and VF-MOF. The conversion percentage of 4-NP to 4-AP was 69%. The catalytic or photocatalytic effects of VF-Ag, VF-MOF, and VF-Ag-MOF on the elimination of methylene blue (MB) dye were investigated. The results demonstrate that VF-Ag-MOF showed high efficiency in removing the MB dye through the reduction (65%) or photodegradation (71%) after 60 min. VF-Ag-MOF composites structure-activity relationships represent that doping within silver NPs enhanced the photocatalytic activity of MIL-125-NH2, which could be explained as follows: (i) Due to the formation of a Schottky barrier at the junction between MIL-125-NH2 and Ag NPs, the photogenerated electrons in the conduction band of MIL-125-NH2 were supposed to be quickly transferred to the valence band of the Ag NPs, and subsequently, the electrons were transferred to the conduction band of Ag NPs. This considerable electron transferring process, which is reported as Z scheme heterojunction, can efficiently suppress the recombination of electron/hole pairs in VF-Ag-MIL-125-NH2 composites. (ii) Sufficient separation between the photogenerated charge carriers (holes and electrons) and avoiding their recombination enhanced the photocatalytic activity of composites.

Enzyme-triggered approach to reduce water bodies' contamination using peroxidase-immobilized ZnO/SnO2/alginate nanocomposite

Enzyme immobilization on solid support offers advantages over free enzymes by overcoming characteristic limitations. To synthesize new stable and hyperactive nano-biocatalysts (co-precipitation method), ginger peroxidase (GP) was surface immobilized (adsorption) on ZnO/SnO2 and ZnO/SnO2/SA nanocomposite with immobilization efficacy of 94 % and 99 %, respectively. Thereafter, catalytic and biochemical characteristics of free and immobilized GP were investigated by deploying various techniques, i.e., FTIR, PXRD, SEM, and PL. Diffraction peaks emerged at 2θ values of 26°, 33°, 37°, 51°, 31°, 34°, 36°, 56°, indicating the formation of SnO2 and ZnO. The OH stretching of the H2O molecules was attributed to broad peaks between 3200 and 3500 cm-1, whereas ZnO/SnO2 spikes occurred in the 1626-1637 cm-1 range. SnO stretching mode and ZnO terminal vibrational patterns have been verified at corresponding wavelengths of 625 cm-1 and 560 cm-1. Enzyme entrapment onto substrate was verified via interactions between GP and ZnO/SnO2/SA as corroborated by signals beneath 1100 cm-1. GP-immobilized fractions were optimally active at pH 5, 50 °C, and retained maximum activity after storage of 4 weeks at -4 °C. Kinetic parameters were determined by using a Lineweaver-Burk plot and Vmax for free GP, ZnO/SnO2/GP and ZnO/SnO2/SA/GP with guaiacol as a substrate, were found to be 322.58, 49.01 and 11.45 (μM/min) respectively. A decrease in values of Vmax and KM indicates strong adsorption of peroxidase on support and maximum affinity between nano support and enzyme, respectively. For environmental remediation, free ginger peroxidase (GP), ZnO/SnO2/GP and ZnO/SnO2/SA/GP fractions effectively eradicated highly intricate dye. Multiple scavengers had a significant impact on the depletion of the dye. In conclusion, ZnO/SnO2 and ZnO/SnO2/SA nanostructures comprise an ecologically acceptable and intriguing carrier for enzyme immobilization.

Sustainability analysis of orange peel biorefineries

Biorefineries are constantly evolving since new technological advances in enzyme and microbial processes are boosting research for producing new bio-based products. Nevertheless, the step towards real process implementation must overcome a series of stages based on process sustainability in the early design stages. Orange peel (OP) has been profiled as a potential raw material for producing different products. Few studies have estimated the sustainability of OP-based biorefineries considering the upstream influence on the final process performance. This research aims to perform the sustainability assessment of several OP valorization pathways based on experimental data applying the biorefinery concept. Steam distillation and polyphenolic compound extraction prior to saccharification and anaerobic digestion increase the process performance. A glucose concentration and biogas yield of 21.43 g/L (0.44 g/g OP, db) and 415 mL/g SV were obtained, respectively. An essential oil extraction yield of 1.17 g/100 g OP (db) with a d-limonene content of 91.62% was produced. Moreover, hesperidin, apigenin, and naringenin yields of 7.88 mg/g, 0.475 mg/g, and 0.675 mg/g were obtained. An OP-based biorefinery addressed to produce essential oil, polyphenolic compounds, and biogas with a processing 25 tons/day (wb) has a sustainability index of 66.88%, higher than the values obtained with lesser upstream stages. In conclusion, an integral OP upgrading leads to better enzymatic and anaerobic digestion performances, as well as, a high process sustainability.

Chitosan-based magnetic bioadsorbent beads from eucalyptus sawdust waste for the Direct Violet-51 dye remediation: Eco-friendly strategy and statistical optimization

In the present study, a new application was proposed for the eucalyptus sawdust waste, which is an environmental passive. Three adsorbent materials composed of chitosan (CS), sawdust (CSW), and magnetic beads (CSWF) were developed and used for the Direct Violet-51 remediation. The adsorption testes were optimized based on the variation of the adsorption parameters: (i) pH (2-12), (ii) contact time (5-60 min), (iii) initial dye concentration (10-60 mg L-1), (iv) adsorbent mass (10-100 mg) in 10 mL. The optimized conditions of the adsorption essays showed that the three synthesized adsorbents completely removed the dye from the aqueous medium, but under different experimental conditions. As the main findings in this study, we can highlight the excellent performance of CSW adsorbent material, which promoted maximum removal efficiency of Direct Violet-51 at neutral pH, which is of great importance for the industrial processes. On the other hand, CS and CSWF adsorbent materials exhibited a maximum adsorption efficiency at pH 2. Furthermore, the adsorbent materials were applied in the dye remediation in environmental water samples from the tap water, Marcela dam, and Poxim River, they did not suffer any major matrix interference, whose removal efficiency values varied between 99.8 and 100, 70.7-100, and 98.8-99.5 % for the CS, CSW, and CSWF, respectively. Finally, besides being materials produced from the waste, they can be reused more times, fitting into the concept of circular economy.

Efficient and rapid adsorption of methylene blue dyes by novel metal-organic frameworks and organic/inorganic hybrid alginate-based dual network gel composites

To address the limitations of gel-based adsorbents, such as inadequate mechanical strength, low adsorption capacity, and limited reusability, this study presents an innovative approach employing a dual network gel. The dual network consists of calcium alginate (CA) ionic crosslinked organic networks, and vinyl silica-based nanoparticles (VSNP) as crosslinking agents in acrylic acid (AA) free radical polymerization networks (denoted as P (AA-co-VSNP), abbreviated as PAV). After freeze-drying, ultimately yielding an organic/inorganic hybrid dual network gel (referred to as CA/P(AA-co-VSNP), abbreviated as CPAV), enriched with abundant functional groups, thereby enhancing material reusability. To further enhance the adsorption capacity, CPAV undergoes hydrothermal reactions to obtain metal-organic frameworks (MOFs) composite dual network gel adsorbent (UiO-66@CPAV). UiO-66@CPAV exhibited a density of 0.165 g/cm3 and showcased a unique pore structure with nested macropores and mesopores, featuring a uniform distribution of pore holes. Notably, the specific surface area was measured at 96.3 m2/g, and an average pore diameter was 17.9 nm. Most impressively, the actual maximum adsorption capacity reached 841.7 mg/g, and even after 10 cycles of use, the adsorption capacity remained 91.9 % of its initial value. Overall, this research introduced a novel methodology for the development of dual network MOFs@gel adsorbents, showcasing promising advancements in the field.

Laccase immobilized on nanocomposites for wastewater pollutants degradation: current status and future prospects

The bio-enzyme degradation technology is a promising approach to sustainably remove pollution in the water and laccase is one of the most widely used enzymes in this area. Nevertheless, the further industrial application of laccase is limited by low stability, short service, low reusability and high price. The immobilization technology can significantly improve the stability and reusability of enzymes and thus promoting their industrial applications. Nanocomposite materials have been developed and applied in the efficient immobilization of laccase due to their superior physical, chemical, and biological performance. This paper presents a comprehensive review of various nanocomposite immobilization methods for laccase and the consequent changes in enzymatic properties post-immobilization. Additionally, a comprehensive analysis is conducted on the factors that impact laccase immobilization and its water removal efficiency. Furthermore, this review examines the effectiveness of common contaminants' removal mechanisms while summarizing and discussing issues related to laccase immobilization on nanocomposite carriers. This review aims to provide valuable guidance for enhancing laccase immobilization efficiency and enzymatic water pollutant removal.

Synthesis of PVP-capped trimetallic nanoparticles and their efficient catalytic degradation of organic dyes

The study proposes a simple and efficient way to synthesize a heterogeneous catalyst that can be used for the degradation of organic dyes. A simple and fast chemical process was employed to synthesize Au: Ni: Co tri-metal nanohybrid structures, which were used as a catalyst to eliminate toxic organic dye contamination from wastewater in textile industries. The catalyst's performance was tested by degrading individual dyes as well as mixtures of dyes such as methylene blue (MB), methyl orange (MO), methyl red (MR), and Rose Bengal (RB) at various time intervals. The experimental results show the catalytic high degradation efficiency of different dyes achieving 72-90% rates in 29 s. Moreover, the material displayed excellent recycling stability, maintaining its degradation efficiency over four consecutive runs without any degradation in performance. Overall, the findings of the study suggest that these materials possess efficient catalytic properties, opening avenues toward their use in clean energy alternatives, environmental remediation, and other biological applications.

Simple ultrasonic integration of shapeable, rebuildable, and multifunctional MIL-53(Fe)@cellulose composite for remediation of aqueous contaminants

Metal-organic frames (MOFs) have been recognized as one of the best candidates in the remediation of aqueous contaminants, while the fragile powder shape restricts the practical implementation. In this work, a shapeable, rebuildable, and multifunctional MOF composite (MIL-53@CF) was prepared from MIL-53 (Fe) and cellulose fiber (CF) using a simple ultrasonic method for adsorption and photocatalytic degradation of organic pollutants in wastewater. The results showed MIL-53(Fe) crystals were uniformly growth on CF surfaces and bonded with surface nanofibrils of CF through physical crosslinking and hydrogen bonding. Because of the high bonding strength, the MIL-53@CF composite exhibited an excellent compressive strength (3.53 MPa). More importantly, the MIL-53@CF composite was rebuildable through mechanical destruction followed by re-ultrasonication, suggesting the excellent reusability of MIL-53@CF for water remediation. The MIL-53@CF composite also had high adsorption capacities for methyl orange (884.6 mg·g-1), methylene blue (198.3 mg·g-1), and tetracycline (106.4 mg·g-1). MIL-53@CF composite could degrade TC through photocatalysis. The photocatalytic degradation mechanism was attributed to the Fe(II)/Fe(III) transform cycle reaction of MIL-53 crystal located on MIL-53@CF. Furthermore, the mechanical property and remoldability of MIL-53@CF composite increased its practicability. Comprehensively, MIL-53@CF composite provided a possible strategy to practically apply MOF in the remediation of aqueous contaminants.

Enhanced Reactive Brilliant Blue Removal Using Chitosan-Biochar Hydrogel Beads

To address the challenges associated with the weak affinity and difficult separation of biochar, we developed chitosan-biochar hydrogel beads (CBHBs) as an efficient solution for removing reactive brilliant blue (RBB KN-R) from wastewater. The adsorption behavior and mechanism of RBB KN-R onto CBHBs were extensively studied. Notably, the adsorption capacity of RBB KN-R showed pH-dependence, and the highest adsorption capacity was observed at pH 2. The adsorption process was well fitted with the pseudo-second-order kinetic model and the intraparticle diffusion model. Film diffusion and intraparticle diffusion were both responsible for the adsorption of RBB KN-R onto CBHBs. At 298.15 K, the maximum adsorption capacity qm was determined to be 140.74 mg/g, with higher temperatures favoring the adsorption process. A complex mechanism involving π-π interactions, electrostatic attraction, hydrophobic interaction, and hydrogen bonding was found to contribute to the overall adsorption process. The experimental data discovered the coexisting substances and elevated ionic strength hindered the adsorption capacity. Significantly, after three cycles of adsorption-desorption, the CBHBs maintained an adsorption capacity above 95% for RBB KN-R. These promising results imply that CBHBs are a durable and cost-effective adsorbent for efficient removal of dyes from wastewater.

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.

The Defects, Physicochemical Properties, and Surface Charge of MIL-88A (Al) Crystal Were Regulated for Highly Efficient Removal of Anionic Dyes: Preparation, Characterization, and Adsorption Mechanism

In this paper, the physicochemical properties, surface charge, and crystal defects of MIL-88A (Al) were controlled by adjusting the ratio of metal ligands and temperature in the synthetic system without the addition of surfactants. The adsorption properties of different crystals for Congo red (CR) were studied. Among them, MIL-88A (Al)-130 and MIL-88A (Al)-d have the best adsorption properties. The maximum adsorption capacities are 600.8 and 1167 mg · g^-1, respectively. Compared with MIL-88A (Al)-130, the adsorption performance of MIL-88A (Al)-d was increased by 94.2%, and the adsorption rate was increased by about 4 times. It can be seen that increasing the proportion of metal ligands within a certain range will improve the adsorption capacity. The structure and morphology of the adsorbent were characterized by XRD, FTIR, SEM, EDS, TGA, BET, and zeta potential. The effects of time, temperature, pH, initial solution concentration, and dosage on CR adsorption properties were systematically discussed. The pseudo-second-order kinetic model and Langmuir isothermal model can well describe the adsorption process, which indicates that the adsorption process is a single-layer chemisorption occurring on a uniform surface. According to thermodynamics, this adsorption is an endothermic process. The mechanism of CR removal is proposed as the electrostatic attraction, hydrogen bond, metal coordination effect, π-π conjugation, crystal defect, and pore-filling effect. In addition, MIL-88A (Al)-d has good repeatability, indicating that it is a good material for treating anionic dye wastewater.

Core-Shell Composite MIL-101(Cr)@TiO2 for Organic Dye Pollutants and Vehicle Exhaust

MIL-101(Cr)@TiO₂ core-shell composite material was synthesized via the hydrothermal method, where MIL-101(Cr) served as the core and TiO₂ acted as the shell. SEM results revealed that the metal-organic framework core effectively prevented the aggregation of TiO₂ nanoparticles and facilitated their dispersion. Characterization techniques such as XRD, XPS, and TGA were utilized to confirm the successful loading of TiO₂ onto MIL-101(Cr) and its excellent thermal stability. MIL-101(Cr)@TiO₂ was employed in photocatalytic degradation of dye pollutants and vehicle exhaust, and the potential degradation mechanisms were investigated in detail. The results showed that MIL-101(Cr)@TiO₂ exhibited excellent photocatalytic degradation performance towards dye pollutants, with degradation efficiencies of 91.7% and 67.8% achieved for MB and RhB, respectively, under visible light irradiation for 90 min. Furthermore, the photocatalytic degradation of automobile exhaust revealed that the MIL-101(Cr)@TiO₂ composite material also exhibited degradation effects on NO_x, CO, and HC. The degradation efficiency for NO reached 24.2%, indicating its broader applicability.

Synergistic Promotion of Photocatalytic Degradation of Methyl Orange by Fluorine- and Silicon-Doped TiO2/AC Composite Material

The direct or indirect discharge of organic pollutants causes serious environmental problems and endangers human health. The high electron-hole recombination rate greatly limits the catalytic efficiency of traditional TiO2-based catalysts. Therefore, starting from low-cost activated carbon (AC), a photocatalyst (F-Si-TiO2/AC) comprising fluorine (F)- and silicon (Si)-doped TiO2 loaded on AC has been developed. F-Si-TiO2/AC has a porous structure. TiO2 nanoparticles were uniformly fixed on the surface or pores of AC, producing many catalytic sites. The band gap of F-Si-TiO2/AC is only 2.7 eV. In addition, F-Si-TiO2/AC exhibits an excellent adsorption capacity toward methyl orange (MO) (57%) in the dark after 60 min. Under the optimal preparation conditions, F-Si-TiO2/AC showed a significant photodegradation performance toward MO, reaching 97.7% after irradiation with visible light for 70 min. Even under the action of different anions and cations, its degradation efficiency is the lowest, at 64.0%, which has good prospects for practical application. At the same time, F-Si-TiO2/AC has long-term, stable, practical application potential and can be easily recovered from the solution. Therefore, this work provides new insights for the fabrication of low-cost, porous, activated, carbon-based photocatalysts, which can be used as high-performance photocatalysts for the degradation of organic pollutants.

Plant -microbe assisted emerging contaminants (ECs) removal and carbon cycling

Continuous increase in the level of atmospheric CO₂ and environmental contaminates has aggravated various threats resulting from environmental pollution and climate change. Research into plant -microbe interaction has been a central concern of ecology for over the year. However, despite the clear contribution of plant -microbe to the global carbon cycle, the role of plant -microbe interaction in carbon pools, fluxes and emerging contaminants (ECs) removal are still a poorly understood. The use of plant and microbes in ECs removal and carbon cycling is an attractive strategy because microbes operate as biocatalysts to remove contaminants and plant roots offer a rich niche for their growth and carbon cycling. However, bio-mitigation of CO₂ and removal of ECs is still under research phase because of the CO₂ capture and fixation efficiency is too low for industrial purposes and cutting-edge removal methods have not been created for such emerging contaminants.