Exploring the decolorization efficiency and biodegradation mechanisms of different functional textile azo dyes by Streptomyces albidoflavus 3MGH.

Efficiently mitigating and managing environmental pollution caused by the improper disposal of dyes and effluents from the textile industry is of great importance. This study evaluated the effectiveness of Streptomyces albidoflavus 3MGH in decolorizing and degrading three different azo dyes, namely Reactive Orange 122 (RO 122), Direct Blue 15 (DB 15), and Direct Black 38 (DB 38). Various analytical techniques, such as Fourier Transform Infrared (FTIR) spectroscopy, High-Performance Liquid Chromatography (HPLC), and Gas Chromatography-Mass Spectrometry (GC-MS) were used to analyze the degraded byproducts of the dyes. S. albidoflavus 3MGH demonstrated a strong capability to decolorize RO 122, DB 15, and DB 38, achieving up to 60.74%, 61.38%, and 53.43% decolorization within 5 days at a concentration of 0.3 g/L, respectively. The optimal conditions for the maximum decolorization of these azo dyes were found to be a temperature of 35 °C, a pH of 6, sucrose as a carbon source, and beef extract as a nitrogen source. Additionally, after optimization of the decolorization process, treatment with S. albidoflavus 3MGH resulted in significant reductions of 94.4%, 86.3%, and 68.2% in the total organic carbon of RO 122, DB 15, and DB 38, respectively. After the treatment process, we found the specific activity of the laccase enzyme, one of the mediating enzymes of the degradation mechanism, to be 5.96 U/mg. FT-IR spectroscopy analysis of the degraded metabolites showed specific changes and shifts in peaks compared to the control samples. GC-MS analysis revealed the presence of metabolites such as benzene, biphenyl, and naphthalene derivatives. Overall, this study demonstrated the potential of S. albidoflavus 3MGH for the effective decolorization and degradation of different azo dyes. The findings were validated through various analytical techniques, shedding light on the biodegradation mechanism employed by this strain.

Screening different solid supports for Pseudomonas aeruginosa biofilm formation and determining its efficiency for decolorization and degradation of congo red.

A global water crisis is emerging due to increasing levels of contaminated water and decreasing clean water supply on Earth. This study aims to address the removal of azo dye from wastewater to enable its reuse. Recently, utilizing microorganisms has been proven to be a practical choice for the remediation of azo dyes in wastewater. Hence, in this study, we employed a preformed biofilm of Pseudomonas aeruginosa on a solid support (called substrate) to degrade azo dyes. This process offers several advantages, such as stability, substrate portability, more biofilm production in less time, and efficient utilization of enzymes for remediation. From 50 ppm of initial Congo Red concentration, 75.74% decolorization was achieved within ten h using a preformed biofilm on a coverslip. A maximum of 52.27% decolorization was achieved using biofilm during its formation after 72 h of incubation. The Fourier-transform infrared (FTIR) spectroscopic analysis of Congo Red dye before and after remediation revealed a significant change in peak intensity, indicating dye degradation. Phytotoxicity studies performed by seed germination with Vigna radiata revealed that, after 5-7 days, almost 40% more seeds with longer root and shoot lengths were germinated in the presence of treated dye compared to the untreated one. This data indicated that the harmful Congo Red was successfully degraded to a non-toxic product by Pseudomonas aeruginosa biofilm grown on a glass substrate.

Kinetic studies on optimized extracellular laccase from Trichoderma harzianum PP389612 and its capabilities for azo dye removal.

BACKGROUND: Azo dyes represent a common textile dye preferred for its high stability on fabrics in various harsh conditions. Although these dyes pose high-risk levels for all biological forms, fungal laccase is known as a green catalyst for its ability to oxidize numerous dyes. METHODS: Trichoderma isolates were identified and tested for laccase production. Laccase production was optimized using Plackett-Burman Design. Laccase molecular weight and the kinetic properties of the enzyme, including Km and Vmax, pH, temperature, and ionic strength, were detected. Azo dye removal efficiency by laccase enzyme was detected for Congo red, methylene blue, and methyl orange. RESULTS: Eight out of nine Trichoderma isolates were laccase producers. Laccase production efficiency was optimized by the superior strain T. harzianum PP389612, increasing production from 1.6 to 2.89 U/ml. In SDS-PAGE, purified laccases appear as a single protein band with a molecular weight of 41.00 kDa. Km and Vmax values were 146.12 µmol guaiacol and 3.82 µmol guaiacol/min. Its activity was stable in the pH range of 5-7, with an optimum temperature range of 40 to 50 °C, optimum ionic strength of 50 mM NaCl, and thermostability properties up to 90 °C. The decolorization efficiency of laccase was increased by increasing the time and reached its maximum after 72 h. The highest efficiency was achieved in Congo red decolorization, which reached 99% after 72 h, followed by methylene blue at 72%, while methyl orange decolorization efficiency was 68.5%. CONCLUSION: Trichoderma laccase can be used as an effective natural bio-agent for dye removal because it is stable and removes colors very well.

Physiological and biomolecular interventions in the bio-decolorization of Methylene blue dye by Salvinia molesta D. Mitch.

Methylene blue, a cationic dye as a pollutant is discharged from industrial effluent into aquatic bodies. The dye is biomagnified through the food chain and is detrimental to the sustainability of aquatic flora. Despite of number of physico-chemical techniques of dye removal, the use of aquatic flora for bio-adsorption is encouraged. Thus, we used Salvinia molesta D. Mitch in bio-reduction of methylene blue on concentrations of 0, 10, 20, and 30 mg L-1 through 5 days with biosorption kinetics. The dye removal was concentration-dependent, maximized at 2 days with 30 mg L-1 which altered the relative growth rate (44%) of plants. Biosorption recorded 71% capacity at optimum pH (8.0), 24 h reducing major bond energies of amide, hydroxyl groups, etc. Bioaccumulation of dye changed potassium content (446%) under maximum dye concentration modifying tissues for dye sequestration. Reactive oxygen species were altered on dye reduction by oxidase (33%) with redox homeostasis by enzymes. Plants altered the metabolism with over accumulation of polyamines (51%), abscisic acids (448%), and phosphoenolpyruvate carboxylase (83%) on dye reduction. Thus, this study is rationalized with a sustainable approach where aquatic ecosystems can be decontaminated from dye toxicity with the exercise of bioresources like Salvinia molesta D. Mitch as herein.

Azo dyes as industrial effluents are more hazardous with their high solubility in water causing inhibition of life processes in aquatic ecosystem. Methylene blue as a dye, in the aquatic environment deteriorates the ecosystem by increasing a chemical oxygen demand, impairing light harnessing mechanism, inhibiting growth of microflora, recalcitrance, bioaccumulation, mutagenicity of the whole environment. Aquatic weed like Salvinia molesta D. Mitch is evident as an effective bio-adsorbent, bio-decolorization, finally dye removing material to reduce water pollution as an alternative strategy for environmental remediation.

Voltammetric Sensor Based on the Combination of Tin and Cerium Dioxide Nanoparticles with Surfactants for Quantification of Sunset Yellow FCF.

Sunset Yellow FCF (SY FCF) is one of the widely used synthetic azo dyes in the food industry whose content has to be controlled for safety reasons. Electrochemical sensors are a promising tool for this type of task. A voltammetric sensor based on a combination of tin and cerium dioxide nanoparticles (SnO2-CeO2 NPs) with surfactants has been developed for SY FCF determination. The synergetic effect of both types of NPs has been confirmed. Surfactants of various natures (sodium lauryl sulfate (SLS), Brij® 35, and hexadecylpyridinium bromide (HDPB)) have been tested as dispersive media. The best effects, i.e., the highest oxidation currents of SY FCF, have been observed in the case of HDPB. The sensor demonstrates a 4.5-fold-higher electroactive surface area and a 38-fold-higher electron transfer rate compared to the bare glassy carbon electrode (GCE). The electrooxidation of SY FCF is an irreversible, two-electron, diffusion-driven process involving proton transfer. In differential pulse mode in Britton-Robinson buffer (BRB) pH 2.0, the sensor gives a linear response to SY FCF from 0.010 to 1.0 µM and from 1.0 to 100 µM with an 8.0 nM detection limit. The absence of an interferent effect from other typical food components and colorants has been shown. The sensor has been tested on soft drinks and validated with the standard chromatographic method.

Kinetic Study of Coprinus cinereus Peroxidase-Catalyzed Oxidation of 2,2'-Dihydroxyazobenzene.

Azo dyes are of concern due to their harmful effects on the environment and human health. The oxidation of 2,2'-dihydroxyazobenzene (DHAB) catalyzed with recombinant Coprinus cinereus (rCiP) peroxidase was investigated. The kinetic measurements were performed using the spectrophotometric and fluorimetric methods. The dependences of the initial reaction rates on enzyme, substrate and hydrogen peroxide concentrations during DHAB oxidation were established, and bimolecular constants of enzyme interaction with DHAB were calculated. This research demonstrated that the initial biocatalytic oxidation rates of DHAB depend on the pH and the estimated pKa values of the active forms of rCip. This study's findings thus contribute to a more comprehensive understanding of the biocatalytic oxidation of DHAB, providing valuable data for assessing the long-term toxicity, carcinogenesis and epigenetic effects of azo dyes in the environment.

Efficient Decolorization of the Poly-Azo Dye Sirius Grey by Coriolopsis gallica Laccase-Mediator System: Process Optimization and Toxicity Assessment.

The textile industry produces high volumes of colored effluents that require multiple treatments to remove non-adsorbed dyes, which could be recalcitrant due to their complex chemical structure. Most of the studies have dealt with the biodegradation of mono or diazo dyes but rarely with poly-azo dyes. Therefore, the aim of this paper was to study the biodegradation of a four azo-bond dye (Sirius grey) and to optimize its decolorization conditions. Laccase-containing cell-free supernatant from the culture of a newly isolated fungal strain, Coriolopsis gallica strain BS9 was used in the presence of 1-hydroxybenzotriazol (HBT) to optimize the dye decolorization conditions. A Box-Benken design with four factors, namely pH, enzyme concentration, HBT concentration, and dye concentration, was performed to determine optimal conditions for the decolorization of Sirius grey. The optimal conditions were pH 5, 1 U/mL of laccase, 1 mM of HBT, and 50 mg/L of initial dye concentration, ensuring a decolorization yield and rate of 87.56% and 2.95%/min, respectively. The decolorized dye solution showed a decrease in its phytotoxicity (Germination index GI = 80%) compared to the non-treated solution (GI = 29%). This study suggests that the laccase-mediator system could be a promising alternative for dye removal from textile wastewater.

Synergistic Ag/g-C3N4 H2O2 System for Photocatalytic Degradation of Azo Dyes.

Graphitic carbon nitride (g-C3N4), known for being nontoxic, highly stable, and environmentally friendly, is extensively used in photocatalytic degradation technologies. Silver nanoparticles effectively capture the photogenerated electrons in g-C3N4, enhancing the photocatalytic efficiency. This study primarily focused on synthesizing graphitic carbon nitride via thermal polymerization and depositing noble metal silver onto g-C3N4 through photoreduction. Methyl orange (MO) and methylene blue (MB) were targeted as the pollutants in the photocatalytic experiments under visible light in conjunction with a H2O2 system. The characteristics peaks, structure, and morphology were analyzed using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). g-C3N4 loaded with 6% Ag exhibited superior photocatalytic performance; the photocatalytic fraction of the degraded materials of the MO and MB solutions reached 100% within 70 and 80 min, respectively, upon adding 1 mL and 2 mL of H2O2. ·OH and ·O2- were the primary active free radicals in the dye degradation process within the synergistic system. Stability tests also demonstrated that the photocatalyst maintained good reusability under the synergistic system.

Removal of Azo Dyes from Water Using Natural Luffa cylindrica as a Non-Conventional Adsorbent.

Reducing high concentrations of pollutants such as heavy metals, pesticides, drugs, and dyes from water is an emerging necessity. We evaluated the use of Luffa cylindrica (Lc) as a natural non-conventional adsorbent to remove azo dye mixture (ADM) from water. The capacity of Lc at three different doses (2.5, 5.0, and 10.0 g/L) was evaluated using three concentrations of azo dyes (0.125, 0.250, and 0.500 g/L). The removal percent (R%), maximum adsorption capacity (Qm), isotherm and kinetics adsorption models, and pH influence were evaluated, and Fourier-transform infrared spectroscopy and scanning electron microscopy were performed. The maximum R% was 70.8% for 10.0 g L-1Lc and 0.125 g L-1 ADM. The Qm of Lc was 161.29 mg g-1. Adsorption by Lc obeys a Langmuir isotherm and occurs through the pseudo-second-order kinetic model. Statistical analysis showed that the adsorbent dose, the azo dye concentration, and contact time significantly influenced R% and the adsorption capacity. These findings indicate that Lc could be used as a natural non-conventional adsorbent to reduce ADM in water, and it has a potential application in the pretreatment of wastewaters.

Textile azo dye, Sudan Black B, inducing hepatotoxicity demonstrated in in vivo zebrafish larval model.

Environmental pollution, particularly from textile industry effluents, raises concerns globally. The aim of this study is to investigate the hepatotoxicity of Sudan Black B (SBB), a commonly used textile azo dye, on embryonic zebrafish. SBB exposure led to concentration-dependent mortality, reaching 100% at 0.8 mM, accompanied by growth retardation and diverse malformations in zebrafish. Biochemical marker analysis indicated adaptive responses to SBB, including increased SOD, CAT, NO, and LDH, alongside decreased GSH levels. Liver morphology analysis unveiled significant alterations, impacting metabolism and detoxification. Also, glucose level was declined and lipid level elevated in SBB-exposed in vivo zebrafish. Inflammatory gene expressions (TNF-α, IL-10, and INOS) showcased a complex regulatory interplay, suggesting an organismal attempt to counteract pro-inflammatory states during SBB exposure. The increased apoptosis revealed a robust hepatic cellular response due to SBB, aligning with observed liver tissue damage and inflammatory events. This multidimensional study highlights the intricate web of responses due to SBB exposure, which is emphasizing the need for comprehensive understanding and targeted mitigation strategies. The findings bear the implications for both aquatic ecosystems and potentially parallels to human health, underscoring the imperative for sustained research in this critical domain.

Fungus mediated synthesis of biogenic palladium catalyst for degradation of azo dye.

Dyes are the coloured substances that are applied on different substrates such as textiles, leather and paper products, etc. Azo dyes release from the industries are toxic and recalcitrant wastewater pollutants, therefore it is necessary to degrade these pollutants from water. In this study, the palladium (0) nanoparticles (PdNPs) were generated through the biological process and exhibited for the catalytic degradation of azo dye. The palladium nanoparticles (PdNPs) were synthesized by using the cell-free approach i.e. extract of fungal strain Rhizopus sp. (SG-01), which significantly degrade the azo dye (methyl orange). The amount of catalyst was optimized by varying the concentration of PdNPs (1 mg/mL to 4 mg/mL) for 10 mL of 50 ppm methyl orange (MO) dye separately. The time dependent study demonstrates the biogenic PdNPs could effectively degrade the methyl orange dye up to 98.7% with minimum concentration (3 mg/mL) of PdNPs within 24 h of reaction. The long-term stability and effective catalytic potential up to five repeated cycles of biogenic PdNPs have good significance for acceleration the degradation of azo dyes. Thus, the use of biogenic palladium nanoparticles for dye degradation as outlined in the present study can provide an alternative and economical method for the synthesis of PdNPs as well as degradation of azo dyes present in wastewater and is helpful to efficiently remediate textile effluent.

Joining Two Switches in One Nano-Object: Photoacidity and Photoisomerization in Electrostatic Self-Assembly.

Multi-switchable supramolecular nano-objects that respond to irradiation of different wavelengths with changes in size and shape have been built from two different water-soluble molecular switches, joined by attachment to the same polyelectrolyte. Accordingly, two wavelength-specific reactions, namely the excited-state proton dissociation of a photoacid and the cis-trans isomerization of an azo dye, are combined in one supramolecular nano-object that is stable in aqueous solution. The concept has potential in the fields of sensors, molecular motors, and transport.

Analyte Detection: A Decade of Progress in the Development of Optical/Fluorescent Sensing Probes.

The development of selective and sensitive chemical sensors capable of detecting metal ions, anions, neutral species, explosives and hazardous substances, selectively and sensitively has attracted considerable interest of various research groups. The presence of such analytes within the permissible limits is often beneficial, but the excess amounts may lead to lethal effects to both the environment as well as the living organisms. Owing to the toxicity of the heavy metal ions, toxic anions and nitro-aromatics which are main constituents of explosives, the timely detection of these materials is most desirable to ensure safety and security of the mankind. In this personal account, we present several classes of molecular sensors that were specifically designed in our lab during the past decade for detecting several species in solutions, solid state as well as biological media. Modulation of the optical properties in response to the presence of guest species, led to selective and sensitive detection protocols, and was supported by the theoretical studies wherever possible. We have also extended the application of some of these probes for the on-site detection of analytes by developing the paper strips, glass slides and even the wool and cotton fabrics loaded with probes. One such development represents detection of palladium in human urine and blood samples collected from clinical samples. Additionally, the sensing events in some cases have successfully been reproduced in the live cancer cells. Based on the ease and cost-effective synthesis of the molecular probes, we hope that this account shall provide significant information to researchers in understanding the structure dependent sensing capabilities of the molecular probes.

Ultrasensitive and highly selective detection of nickel ion by two novel optical sensors.

Novel optical sensors for nickel determination by incorporation of 5-(2`-bromo-phenylazo)-6-hydroxypyrimidine-2,4-dione (I), 5-(2`,4`-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (II), dibutylphthalate (DBP) and sodium tetra-phenylborate (Na-TPB) to the plasticized polyvinyl chloride matrices were prepared. The introduction of DBP in the membrane substantially increased the ability of both ionophores I and II to function as chromo ionophores. The advantages of the reported sensors include great stability, reproducibility, and relatively long lifespan, as well as excellent selectivity for Ni2+ ion detection across a wide range of alkali, alkaline earth, transition, and heavy metal ions.Under optimized membrane compositions and experimental parameters, the response of both sensors was linear throughout a concentration range of 3.5 × 10-8 to 8.1 × 10-5 and 2.0 × 10-8 to 5.1 × 10-5 M for I and II, respectively. Sensor detection and quantification limits based on the definition that the concentration of the sample leads to a signal equal to the blank signal plus three and ten times its standard deviation were determined to be 1.15 × 10-8 and 3.45 × 10-8 M when utilizing I, whereas they were 0.61 × 10-8 and 1.95 × 10-8 M when utilizing II, respectively. The reaction time of optodes is defined as the period required achieving 95% of based sensors and found to be 8.0 and 5.0 min using I and II, respectively. Ni2+ ion concentrations in water, food, and environmental samples were effectively determined using the proposed optical sensors. Representative diagram for preparation of the sensing Ni2+ sensor.

Natural waste-derived nano photocatalysts for azo dye degradation.

Due to their widespread application in water purification, there is a significant interest in synthesising nanoscale photocatalysts. Nanophotocatalysts are primarily manufactured through chemical methods, which can lead to side effects like pollution, high-energy usage, and even health issues. To address these issues, "green synthesis" was developed, which involves using plant extracts as reductants or capping agents rather than industrial chemical agents. Green fabrication has the benefits of costs less, pollution reduction, environmental protection and human health safety, compared to the traditional methods. This article summarises recent advances in the environmentally friendly synthesis of various nanophotocatalysts employed in the degradation of azo dyes. This study compiles critical findings on natural and artificial methods to achieve the goal. Green synthesis is constrained by the time and place of production and issues with low purity and poor yield, reflecting the complexity of plants' geographical and seasonal distributions and their compositions. However, green photocatalyst synthesis provides additional growth opportunities and potential uses.

Magnetic porous Ag2O/Chitin nanostructure adsorbent for eco-friendly effective disposing azo dyes.

Water treatment is as much important as it is to satisfying 11 worldwide sustainable development goals out of 17. The removal of Azo is much important as they are toxic and their existence in water, air and food can easily affect humans by triggering allergies, forming tumours etc. Azo contained Dyes Production was banned in many countries. This research aims to synthesize composite Nanorods and Nanospheres and characterize and test to remove Azo dyes from the wastewater. This research used a previously reported method to rapidly synthesize chitin magnetite nanocomposites (ChM) by co-precipitation while irradiating with ultrasound (US). Detailed structural characterization of ChM revealed a crystalline phase analogous to magnetite and spherical morphologies; extending the reaction time to 8 min yielded a "nanorod" type morphology. Both the morphologies displayed a nanoscale limit with particles averaging between 5 and 30 nm in size, resulting the superparamagnetic performance and saturation magnetization values between 45 and 58 emu/g. The nitrogen adsorption-desorption isotherms showed that the surface modification of ChMs resulted in a rise of specific surface area and pore size. Anionic azo dyes (methyl orange (MO) and reactive black 5 (RB5)) adsorption on the surface of nanocomposites was also demonstrated to be pH-dependent, with the reaction favoured for surface-modified samples at pH 4 and unmodified samples at pH 8. Adsorption capacity studies showed that molecule size effect and electrostatic attraction were two distinct adsorption processes for unmodified and modified ChMs. Chitin Magnetite nanoparticles appear to be a substitute for traditional anionic dye adsorbents. Additionally, the two key materials sources, chitin, and magnetite are inexpensive and easily accessible.

Screening of regulated aromatic amines in clothing marketed in Brazil and Spain: Assessment of human health risks.

Azo dyes used in textile products contain aromatic amines (AAs), which may be released into the environment after skin bacteria cleavage the azo bond. In Europe, 22 carcinogenic AAs are regulated. Unfortunately, no information is available in many non-European countries, including Brazil. This study aimed to determine the concentrations of 20 regulated AAs in clothes marketed in Brazil and Spain. Generally, higher levels of regulated AAs were found in samples sold in Brazil than in Spain, which is linked to the lack of regulation. Sixteen AAs showed concentrations above 5 mg/kg in samples commercialized in Brazil, while 11 exceeded that threshold in Spain. Regulated AAs with levels above 5 mg/kg were more found in synthetic clothes of pink color. Concentrations in clothing were also used to evaluate the dermal exposure to AAs in 3 vulnerable population groups. The highest exposure corresponded to 2,4-diaminoanisole for toddlers in Brazil and 4,4-oxydianiline for newborns in Spain. Non-cancer risks associated with exposure to 4,4-benzidine by Brazilian toddlers was 14.5 (above the threshold). On the other hand, 3,3-dichlorobenzidine was associated with potential cancer risks for newborns and toddlers in Brazil. Given this topic's importance, we recommend conducting continuous studies to determine the co-occurrence of carcinogenic substances.

Light-driven biodegradation of azo dyes by Shewanella decolorationis-CdS biohybrid in wastewater lacking electron donors.

The lack of electron donors prevents the effective degradation of azo dyes by bacteria, which severely limits the practical application of conventional biological treatment. Herein, we innovatively designed a bio-photoelectric reduction degradation system composed of CdS and Shewanella decolorationis, which could effectively degrade amaranth in anaerobic conditions driven by light when electron donors were unavailable. Compared with bare S. decolorationis and S. decolorationis (heat-killed)-CdS biohybrid, S. decolorationis-CdS biohybrid had 39.36-fold and 3.82-fold higher first-order kinetic constants, respectively. The morphology, particle size, elemental composition, crystalline type, photovoltaic properties, and band structure of the nanoparticles synthesized by S. decolorationis were carefully examined and analyzed. Light-driven biodegradation experiments showed that amaranth was degraded by the synergy of CdS and S. decolorationis. Reductive degradation of amaranth by electrons was demonstrated by electron and hole trapping. The effect of potential coexisting contaminants, which might serve as hole scavengers, on the degradation of amaranth was evaluated. Membrane protein inhibition experiments also suggested that NADH dehydrogenase, menaquinone, and cytochrome P450 played an important role in electron transfer between CdS and Shewanella decolorationis. The cyclic conversion of NAD+/NADH was probably the most critical rate-limiting step. Electrochemical measurements suggested that faster electron transfer might facilitate the degradation of amaranth. Our findings might contribute to the degradation of azo dyes in wastewater lacking electron donors and deepen our recognition of the microbe-material interface. KEY POINTS: • A BPRDS was constructed with Shewanella decolorationis and CdS. • Amaranth was effectively degraded by BPRDS in anaerobic conditions driven by light. • NDH, MQ, and CYP450 were involved in electron transfer.

Preparation of 1,8-dichloroanthraquinone/graphene oxide/poly (vinylidene fluoride) (1,8-AQ/GO/PVDF) mediator membrane and its application to catalyzing biodegradation of azo dyes.

Anthraquinone is a redox mediator that can effectively catalyze the degradation of azo dyes by promoting the electron transfer. In this study, a mediator membrane with poly (vinylidene fluoride) (PVDF) as the membrane support and 1,8-dichloroanthraquinone (1,8-AQ) and graphene oxide (GO) as the additives was prepared and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), atomic force microscopy (AFM) and water contact angle. The introduction of GO increases the pure water flux of the membrane to 258.56±12.93 L/(m2·h). Its catalytic performances for the biodegradation of azo dyes were evaluated. Under the optimized conditions, the 1,8-AQ/GO/PVDF composite membrane is able to improve the dye degradation efficiency 2.2 times for reactive red X-3B and 1.1 times for acid red B, as compared with PVDF membrane. In addition, the mediator membrane maintains stable and high catalytic efficiency in the cyclic test and over 90 % dye degradation efficiency is still obtained after 5 cycles of decolorization. These results suggest the great application potentials of the 1,8-AQ/GO/PVDF membrane in the dye wastewater treatment.

Impact of immobilized algae and its consortium in biodegradation of the textile dyes.

In biological engineering, cell immobilization is a modern technique for immobilizing free cells in a small space. Disintegration and elimination of azo dyes [Reactive Orange 122 (orange 2RL) and Reactive Red 194 (Reactive Red M-2BF)] were investigated by using Chlorococcum sp. and Chlorococcum sp. mixed with Scenedesmus obliquus, respectively. After 7 days of incubation, the maximum decolorization was spotted at 40 ppm for Reactive Orange 122 and 20 ppm for Reactive Red 194 by Chlorococcum sp. and Chlorococcum sp. mixed with S. obliquus, respectively. The findings revealed that the best decolorization activity was found at pH 11 and 25 °C under aeration conditions. BG11 was considered the best medium for azo dye decolorization with a high decolorization percentage. Additionally, different concentrations of nitrogen and phosphorus show the high activity of decolorization of both dyes. Referring to vitamins (thiamin and Ascorbic acid), all studied concentrations showed high decolorization activity with immobilized Chlorococcum sp. mixed with S. obliquus; however, different concentrations (20, 40, and 60 mg/l) of thiamin showed completely decolorization of Reactive Red 194 after 3 days, and 60 mg/l of ascorbic acid showed completely decolorization of Reactive Orange 122 after 5 days of inoculation. FT-IR and GC-Ms analysis for azo dyes after and before treatment with Immobilization of Chlorococcum sp. and Chlorococcum sp. mixed with Scenedesmus obliquus were detected. Novelty statement: The natural carrier algae and its consortium combined with a suitable immobilization technique were considered in this study, which is non-toxic, enhanced their bioremediation potential for dyes, and allowed multiple uses of biocatalysts. The novel use of the immobilization and its consortium of algae on the degradation efficiency of azo dyes and studying the effect of physicochemical conditions on decolorization and degradation of azo dyes. Application of immobilization techniques using microalgae could be excellent bioremediation of wastewaters.