Dye Decolorization Efficiency Research Articles

Enhanced bioremediation of saline azo dye effluents using PersiLac3: A thermo-halotolerant laccase from a tannery metagenome

Large quantities of recalcitrant azo dye wastewater represent an important environmental issue, owing to their toxicity and the difficulty of their treatment under hypersaline conditions. By maintaining high activity under salt-rich conditions, salt-tolerant laccases offer a promising solution for the effective breakdown of toxic azo dyes, making them indispensable for the sustainable treatment of industrial wastewater. This study explored the identification and application of a thermo-halotolerant laccase, PersiLac3, for bioremediation of azo dye wastewater under high-salt conditions typical of textile effluents. The broad substrate oxidation potential of PersiLac3 was assessed across diverse temperatures, pH levels, and challenging conditions, such as high salt levels, and in the presence of organic solvents and inhibitors. Remarkably, PersiLac3 showed enhanced activity (112.25 %) in 3 M NaCl, highlighting its superior ability to adapt to saline conditions. Kinetic studies of PersiLac3 indicated high efficiency and affinity for its substrate at saline concentrations ranging from 1 to 6 M NaCl. PersiLac3 effectively decolorized the Congo red dye (82.9 %) in highly concentrated solutions (5000 mg/L) within 15 min, and its performance was further improved in the presence of wastewater-relevant ions, achieving 92.3 % dye removal. Monitoring real wastewater treatments, PersiLac3 reduced optical density, underscoring its potential for application in the bioremediation of dye-laden and saline wastewater streams. The adaptability of PersiLac3 to harsh, high-salinity environments, coupled with its rapid dye decolorization efficiency, is an innovative and powerful tool for addressing environmental pollution challenges and advancing waste treatment methodologies.

Evaluation of blue textile dye decolorization by immobilized polyphenol oxidase using pumice stone under optimum conditions

Industrial dyes are major pollutants in wastewater and river water with an initial visible concentration of 1 mg/L. Recent studies have shown the possibility of using polyphenol oxidase in catalytic biological treatment due to its ability to oxidize a large number of dyes and pollutants in wastewater and the flexibility to work in wide ranges of temperature, pH and salinity. It is easy availability as well as the low economic cost resulting from its use in biological treatments, this enzyme polyphenol oxidase was used. The findings in this study showed that the extraction of polyphenol oxidase (PPO) from potato peel was homogenized with potassium phosphate buffer (0.1 M, pH 7) at a ratio of 1:10 (weight: volume) for two min. The result of enzyme purification by ion exchange chromatography showed that the yield of this step was 64 % and the specific activity was 6541.67 U/mg. The polyphenol oxidase was immobilized covalently on the functionalized pumice stone (25.2 U/gm) compared with other methods. The characterization results demonstrated that the optimum pH for immobilized and free enzyme activity was 6.0 while the pH range of free and immobilized polyphenol oxidase stability was from 4.5 -7.0 and 3.5 - 8.5 respectively. The better temperature for free and immobilized polyphenol oxidase activity was 25 ºC, whereas the free and immobilized polyphenol oxidase was stable at 15-35 and 15-50 °C respectively. The outcomes showed that the decolorization efficiency of blue textile dye employing immobilized polyphenol oxidase reached 99.85 % after 24 hr. for 100 mg/L concentration while for other concentrations 200, 300, 400, 500 and 1000 mg/L the decolorization efficiencies were 85.96, 76.15, 72.54, 66.94 and 63.5 % respectively. Based on the results, the immobilized polyphenol oxidase on pumice stone is highly efficient in removing textile dyes at large concentrations and in different environmental conditions.

Decolorization of anthraquinone dye (Reactive Blue 4) in the microbial fuel cell by Baker’s yeast: process optimization

The release of anthraquinone dyes in aquatic sources has a huge impact on the environment because of their turbidity, toxicity, mutagenicity, and carcinogenicity effects. Microbial Fuel Cell (MFC) is a hopeful technology for the decolorization of dyes. The goal of the present study is the decolorization of Reactive Blue 4 (RB4) as an anthraquinone dye from an aqueous solution by Baker’s yeast in MFC. The selection of three parameters (dye concentration, glucose concentration, and airflow rate) and optimization of dye decolorization and chemical oxygen demand (COD) removal are performed using response surface methodology (RSM). The results demonstrated that the interaction between parameters does not affect the dye decolorization efficiency, whereas the interaction between dye concentration and glucose concentration was found to be significant for COD removal. Accordingly, the optimum conditions for maximum dye decolorization and COD removal were obtained at a dye concentration of 50 mgL−1, a glucose concentration of 1 gL−1, and an airflow rate of 10 mLmin−1.

Degradation of bromothymol blue and methyl green from aqueous media by Photo-Fenton: comparison between UV-lamp and sun irradiation

Abstract The degradation of two textile dye molecules was studied using photochemical processes, both in the absence and presence of light. Various methods were employed, including photolysis/UV, combined H2O2/UV photolysis, Fe2+/UV treatment, Photo-Fenton/UV at 350 nm and Photo-Fenton with solar irradiation. The decolorization efficiency of dyes in aqueous solution was evaluated for two specific dyes: Bromothymol Blue (BTB) and Methyl Green (MG). These experiments were carried out in batch mode. The results demonstrated a synergy between light irradiation and the presence of Fenton’s reagents, such as hydrogen peroxide and divalent iron. In addition, it was demonstrated that direct solar irradiation can be used without specific devices to achieve high efficiency at low cost. In the first part, we checked the impact of the various operating parameters. Reaction efficiencies were compared for the same system in the dark and under the assistance of an artificial or solar light source. In the second part, we studied the parameters of the Photo-Fenton process, such as the initial pH of the solution, the initial concentrations of oxidant, iron catalyst, and dye under irradiation from either light source. Whereas the mere photolysis without Fenton’s reagents allowed decolorization yields below 26 %, addition of the oxidant (H2O2) or the catalyst (Fe(II) species amplified the treatment efficiency. However, the presence of both H2O2 and Fe(II) under light irradiation was shown synergetic with yields ranging from 72 to 85 % depending on the dye worked and the light source: because of its broader spectrum in the UV domain, solar irradiation led to the highest decolorization yields. The above results were obtained for well-defined proportions of dye and reagents: for a 20 mg/l dye solution, Fe(II) catalyst concentration equal to 10−3 M, peroxide concentration of 5.10−2 M and a pH of 3. These conditions allowed optimal production of OH· radicals, allowing high efficiency in systems using solar irradiation.

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.

Myco-remediation of synthetic dyes: a comprehensive review on contaminant alleviation mechanism, kinetic study and toxicity analysis

AbstractA strong economic foundation can be achieved by the growth of a number of businesses, including food, paper, clothes, leather, and textiles. However, because of improper waste management, industrialization and modernization have resulted in the massive disposal of water effluent laden with harmful substances like dyes and heavy metals, which has negatively impacted the ecosystem. A new green technology called myco-remediation has emerged to battle harmful toxins while promoting sustainable development effectively and economically. This review employed enzymatic degradation, biosorption, and their influencing parameters for optimization in order to highlight the invaluable potential of fungal bioremediation for dye degradation. Current perspectives on enzyme immobilization techniques and kinetic studies of dye removal have been reviewed, which can aid in the selection of quick and effective removal processes. This research offers new insight into a criterion that is often overlooked in favor of dye decolorization efficiency: the toxicity assessment of pure dye and post-process metabolites produced following myco-remediation. Our attention has been directed towards toxicity analysis at many levels, including genotoxicity, phytotoxicity, and zoo-toxicity. This is important to keep in mind when considering the extensive implications of myco-remediation for the recycling and reuse of industrial effluent. Enzyme engineering and omics technologies have been highlighted as potential future developments.

Controllable Cetrimide – Assisted Hydrothermal Synthesis of MoFe<sub>2</sub>O<sub>4</sub> and Coupling with Al<sub>2</sub>O<sub>3</sub> as an Effective Photocatalyst for Decolorization of Indigo Carmine Dye

This research focuses on the MoFe2O4 nanoparticles synthesized via the hydrothermal method in the presence of positive surfactant- Cetrimide (CT) as a template and stabilizer. This is vital to prevent the agglomeration and reducing its activity. The mean crystal sizes of MoFe2O4 and its composite with alumina system were observed to be 23.97 and 47.41 nm, respectively. The shapes of MoFe2O4 and its composite are nanoplate and like-popcorn nanoparticles. The EDX spectra demonstrated that the MoFe2O4 and its composite are truly synthesized with high purity. The FTIR proved the MoFe2O4 is normal spinel. Based on the Tauc equation, band gaps were measured and found to be 2.78 and 4.05 eV for MoFe2O4 and its nanocomposite. The photo decolorization efficiency (PDE) of indigo carmine dye (IC) using MoFe2O4 nanoparticles and its nanocomposite was discovered to be 90.84 and 91.50%, respectively, at pH 5.3, 10 °C for 50 min. This photoreaction obeys the pseudo-first order, exothermic, spontaneous, and negative activation energy, that attitude to the multi-step occurs in chain reactions. This behavior depends on the speed of the binding step of the dye with Fe3+, Mo6+, or Al3+ in the crystal lattice of MoFe2O4 nanoparticle and its nanocomposite.

Improved Laccase Encapsulation in Copper-Doped Zeolitic Imidazolate Framework-8 for Reactive Black 5 Decolorization

As the largest group of synthetic dyes, azo dyes can pose various health and environmental risks due to their widespread use and challenging degradation. Laccases are efficient green biocatalysts for the degradation of organic pollutants. Herein, we report the in situ packaging of laccase in copper-doped zeolitic imidazolate framework-8 (ZIF-8) for the decolorization of reactive black 5, which is a model azo dye. The immobilization support (Cu5/mZIF-8) was obtained via lowering the precursor ratio of ZIF-8 and incorporating copper ions during the synthesis process. Cu5/mZIF-8 were found to be nanospheres with an average diameter of around 150 nm. Laccase encapsulated in Cu5/mZIF-8 showed an activity recovery of 75.6%, which was 2.2 times higher than that of the laccase embedded in ZIF-8. Meanwhile, the immobilized laccase (Lac@Cu5/mZIF-8) showed a higher catalytic activity in organic solvents than that of the free enzyme. In the presence of a mediator, Lac@Cu5/mZIF-8 could remove 95.7% of reactive black 5 in 40 min. After four consecutive cycles, the dye decolorization efficiency declined to 28%. About four transformation products of reactive black 5 were identified via LC-MS analysis, and the potential decolorization mechanism was proposed. The results indicated that the immobilized laccase could be used as an efficient biocatalyst in dye decolorization.

Acid Red 17, Acid Yellow 11, Direct Yellow 12, Direct Blue 86 ve Mordant Violet 40 Boyalarının Karışımını İçeren Suyun Arıtılması İçin Gelişmiş Oksidasyon İşlemi

The removal of dyes from wastewater is one of the biggest problems in the textile industry for
 both environment and manufacturers. This study examined the possibility of applying ozone 
 (O3) and O3 in combination with ultraviolet (UV) to treat a mixture of synthetic wastewater 
 containing five different dyes (Acid Red 17, Acid Yellow 11, Direct Yellow 12, Direct Blue 86 
 and Mordant Violet 40) for the decolorization efficiency of dyes with different chromophore 
 and anchor groups. The contact time was studied in a batch reactor under the flow of O3 or 
 O3 combined with UV to achieve optimal operating conditions. The results showed that the 
 application of O3 was more effective than UV-assisted ozonation. The advanced oxidation of 
 each dye in this mixture was compared with the removal of the same dye in the solution 
 separately. The results proved that there is only a slight difference in the time required to 
 remove the dye from the mixture and the single dye in the water solution.

Fabrication of a SnO2–Sb electrode with TiO2 nanotube array as the middle layer for efficient electrochemical oxidation of amaranth dye

Efficient, stable, and easily producible electrodes are useful for treating dye wastewater through electrochemical oxidation. In this study, an Sb-doped SnO2 electrode with TiO2 nanotubes as the middle layer (TiO2-NTs/SnO2–Sb) was prepared through an optimized electrodeposition process. Analyses of the coating morphology, crystal structure, chemical state, and electrochemical properties revealed that tightly packed TiO2 clusters provided a larger surface area and more contact points, which is conducive to reinforcing the binding of SnO2–Sb coatings. Compared with a Ti/SnO2–Sb electrode without a TiO2-NT interlayer, the catalytic activity and stability of the TiO2-NTs/SnO2–Sb electrode significantly improved (P < 0.05), as reflected by the 21.8% increase in the amaranth dye decolorization efficiency and 200% increase in the service life. The effects of current density, pH, electrolyte concentration, initial amaranth concentration, and the interaction between various combinations of parameters on the electrolysis performance were investigated. Based on response surface optimization, the maximum decolorization efficiency of the amaranth dye could reach 96.2% within 120 min under the following set of optimized parameter values: 50 mg L−1 amaranth concentration, 20 mA cm−2 current density, and 5.0 pH. A potential degradation mechanism of the amaranth dye was proposed based on the experimental results of a quenching test, ultraviolet–visible spectroscopy, and high-performance liquid chromatography-mass spectrometry. This study provides a more sustainable method for fabricating SnO2–Sb electrodes with TiO2-NT interlayers to treat refractory dye wastewater.

Understanding the influence of additives on methyl orange degradation using adsorption/photocatalysis functioned materials

Dye wastewater has a severe influence on natural water environment. Using materials functioned by adsorption and/or photocatalysis to degrade dyes has received much attention due to high decolorization efficiency. However, there are a very limited knowledge on how co-existing additives influence dye degradation using the adsorption and/or photocatalysis materials. In this context, this study selected biochar-TiO2 composites to test whether different additives (anions, surfactants, thickeners and heavy metals) can affect the dye decolorization efficiency. The biochar-TiO2 composites, dye solution and selected additives were poured into a series of quartz tubes, which were put in a photochemical reactor equipped with a mercury lamp to simulate ultraviolet radiation. The outcomes showed that the biochar-TiO2 composites had a strong capacity of degrading eight dyes with different characteristics and structures. After 1-hour dark adsorption, the decolorization efficiency of the eight dyes were 40 %–99.89 % while after 1-hour photocatalytic reaction, the decolorization efficiency all reached nearly 100 %. In addition, taking methyl orange (MO) as a case study, it is found that the presence of different additive types had different influences on MO degradation via positively/negatively affecting dark adsorption and/or photocatalytic reaction. The influence mechanisms of different additives were also explored such as occupying adsorption sites (negative influence) and stimulating the creation of ·OH (positive influence). The research outcomes are expected to contribute the useful knowledge to effective dye wastewater treatment.

Enhanced UV assisted photocatalytic activity of doped and co-doped SnO2 nanostructured material

In the recent past, materials with unique properties were the versatile tools of modern technology. Metal oxide nanoparticles (NPs) are of incredible consideration because of their uncommon electrical, optical and attractive synergistic properties. One such metal oxide, tin oxide (SnO2), is widely applied and successfully researched as an n-type semiconductor in the field of electronics, as an optoelectronic sensor, as a gas sensor, as a transparent oxide in solar cells, etc. The success of these applications depends on the special qualities of SnO2 nanoparticles, which vary depending on size, manufacturing processes, dopants, etc. The present study illustrates the synthesis of pure, nickel (Ni), neodymium (Nd) doped, and Ni–Nd co-doped SnO2 NPs via low cost one step hydrothermal synthesis. X-ray diffraction study was utilized for the structural analysis and crystallite size measurement. A considerable decrease in crystallite size and band gap is obtained from the doped and co-doped samples. Scanning electron and transmission electron microscope images show an almost spherical particle with uniform size. The decolorization efficiency of methyl orange, rhodamine-6G, and eriochrome dyes was enhanced by the addition of dopants. The electrical properties of the proposed samples at various temperatures and frequencies were also reported.

Biodecolorization and degradation of textile azo dyes using Lysinibacillus sphaericus MTCC 9523

Wastewater discharges by textile industries constitute a major environmental concern as they exert grave human health dangers. Innovative, cost-effective and economical strategy aimed at ameliorating the effect of textile effluent in the environment is highly desirable. Hence, this study investigated the decolorization efficiency of selective reactive azo dyes by textile effluent non-adapted Lysinibacillus sphaericus MTCC 9523 in optimized operational conditions. Visual color changes with 96.30% and 92.71% decolorization for Reactive Yellow F3R (RYF3R) and Joyfix Red RB (JRRB) elucidated by UV-visible spectrophotometric analysis affirmed decolorization of the dyes. Meanwhile, Fourier Transform Infrared (FTIR) Spectroscopy of the metabolites obtained after degradation further revealed the functional groups and loss of peak for azo group indicated the breaking of azo bond. On High-Performance Liquid Chromatography (HPLC) analysis, difference in control dye’s retention time compared to treated sample with peaks at 2.413 and 2.895 min for RYF3R and 2.466 min and 1.640 min for Joyfix Red RB supported biodegradation by this organism. The chemical identities of the metabolites revealed after Gas Chromatography-Mass Spectrometry (GC-MS) analysis was used in the prediction of each dye’s metabolic pathway of degradation based on their molecular weight and mass-to-charge ratio. They were found to be (2Z)-but-2-ene, 1,3,5-triazine, (3E)-penta-1,3-diene for RYF3R and (methylsulfonyl)benzene, phenol, buta-1,3-diene, 1,3,5-triazine-2,4(1H,3H)-dione, nitrobenzene for JRRB. Overall, the use of adapted and non-adapted microbes is highly promising as an efficient, cost-effective, time-saving and universal green strategy for biodegradation of textile effluent containing azo dyes.

Fabrication of myoglobin hybrid nanoflowers for decolorization process of evans blue and congo red

• Synthesis and characterization of Myoglobin hybrid nanoflowers (MbNFs@Cu) in the first time. • Enhanced peroxidase-like activities of MbNFs@Cu. • The MbNFs@Cu exhibited excellent dye decolorization efficiency for Evans blue and Congo red dyes. Here, myoglobin hybrid nanoflowers (MbNFs@Cu) were synthesized in various pH values and protein concentrations considering the organic–inorganic hybrid nanoflower method for the first time. Synthesized material was characterized by using EDX, XRD, and FTIR analyses. After determining the optimum morphology, the MbNFs@Cu exhibited great stability and peroxidase-mimic activity towards various pH values and temperature, and provided excellent dye decolorization efficiency for evans blue (EB) and congo red (CR) dyes with more than 90 % within 20 min. These results prove that this material has a potential in the removal of some organic dyes and in catalytic applications.

Enhanced photosensitivity of heterostructure SiO2/Bi2WO6/GO composite nanoparticles

The Bi2WO6, Bi2WO6@GO, SiO2/Bi2WO6, and SiO2/Bi2WO6@GO nanocomposites were synthesized using a simple process. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), EDX mapping investigations confirmed the successful synthesis, related chemical bonding, and elements in the structure. According to the TEM and FESEM images, composite nanoparticles consisting of cubic-like Bi2WO6 and regular spherical-like particles of SiO2 between the GO sheets. The strong emission color of green under ultraviolet excitation was obtained. The radiation sensitivity of the SiO2/Bi2WO6@GO nanocomposite under the 241Am alpha source was the best compared with other samples. It was observed that the incorporation of SiO2 and reduced graphene oxide in composite structures can lead to further sensitivity of ionizing radiation and luminescence intensity at room temperature. Furthermore, prepared SiO2/Bi2WO6 NPs showed a high decolorization efficiency of MB dye (98.2%) under UVA irradiation for 100 min. These results present a promising potential for applications in photonic devices.

Isolation, Screening and Production of Fungal Laccases

Abstract: Laccase (E.C. 1.10.3.2) are enzyme belonging to the group of blue multi-copper oxidases. Laccases catalyze the oxidation of variety of phenolic compounds, diamines and aromatic amines. Fungal isolate producing laccase was screened on Potato Dextrose Agar medium enriched with 0.02% guaiacol from soil as well as decaying wood samples collected from farm/forest site. Confirmation of laccase production was done by Bavendam test which is a plate assay technique using 3mM guaiacol. The isolate was identified and found to belong genera Aspergillus and was tested for producing laccase enzyme. An attempt was made to isolate, screening and production of laccase enzyme produced from Aspergillus niger. Isolate giving best result was processed further for production of laccase using Submerged fermentation. Guaiacol and sodium citrate buffer were used to assay laccase production. Characterization of fungal isolate was done by morphological analysis. This study showed that enzyme production can be increased by media manipulation in the fungal cultures. Optimization of the media condition can maximize the desired enzyme production. Application or Dye decolorization assay was been performed using 0.1ml crystal violet solution, where dye decolorization efficiency showed the ability of laccase to decolorize dyes. It is present in Ascomycetes, Deuteromycetes and Basidiomycetes and abundant in lignin degrading white / brown rot fungi. In the recent years, these enzymes have gained application in the field of textile, pulp and paper and food industries. Recently, it is also used in the design of biosensors, biofuel cells as a medical diagnostics tool and bioremediation agent to clean up herbicides, pesticides and certain explosive in soil. Laccases have received attention of researchers in the last few decades due to their ability to oxidize both phenolic and non phenolic lignin related compound as well as highly recalcitrant environmental pollutants.

Eucalyptus (camaldulensis) bark-based composites for efficient Basic Blue 41 dye biosorption from aqueous stream: Kinetics, isothermal, and thermodynamic studies

For the recycling of polluted water bodies to protect and maintain the eco-friendly future environment herein for the first time Eucalyptus Bark (EB) and its composites were designed to eliminate the dye Basic Blue 41 (BB41) from an aqueous medium. Physicochemical properties of as-fabricated native EB and their composites were analytically determined. From the batch adsorption experiments, the optimum recorded adsorption factors by as-designed adsorbents were pH: 8 for EB, 7 for MG/EB, and 10 for Ppy/EB, adsorbent dosage: 0.05 g/L, agitation speed: 120 rpm, contact time: 90 min, particle size of adsorbent: ≤ 300 μm, initial concentration: 200 mg/L, and temperature: 300 K. Under optimized conditions, as-prepared adsorbents exhibited high BB41 dye adsorption capacity and decolorization efficiency (186.7 mg/g and 93.0%) due to existence of negatively charged functional groups on the adsorbent surface because of its cellulosic nature. Isothermal and kinetic studies revealed that BB41 adsorption experimental data were best fitted by Freundlich and pseudo 2nd order models. From thermodynamic examination, the adsorption process is spontaneous, chemisorption, and exothermic in nature. Furthermore, the influence of salts and surfactants on dye adsorption capabilities by adsorbents has also been determined. From desorption experiments, it was concluded that low concentration of eluting agents is responsible for high amounts of dye desorption. This study revealed that the magnetic and polypyrrole composites with EB biomass have promising adsorption potential and this class of adsorbent could be used for the eco-friendly remediation of wastewater containing BB41 dye.

Decolorization of the benzidine-based azo dye Congo red by the new strain Shewanella xiamenensis G5-03.

Shewanella xiamenensis G5-03 was observed to decolorize the azo dye Congo red in synthetic wastewater. The influence of some factors on the dye decolorization efficiency was evaluated. The optimal decolorization conditions were temperature 30-35 °C, pH 10.0, incubation time 10 h, and static condition. The kinetic of Congo red decolorization fitted to the Michaelis-Menten model (Vmax = 111.11 mg L-1 h-1 and Km = 448.3 mg L-1). The bacterium was also able to degrade benzidine, a product of azo bond breakage of the Congo red, which contributed to reduce the phytotoxicity. The ability of S. xiamenensis G5-03 for simultaneous decolorization and degradation of Congo red shows its potential application for the biological treatment of wastewaters containing azo dyes.

Preparation of CuO/γAl2O3 catalyst for degradation of azo dyes (reactive brilliant red X–3B): An optimization study

Wastewater from the printing and dyeing industries has become one of the critical concerns for remediation by water treatment due to its refractory and toxic characteristics. In this paper, CuO/γ-Al2O3 catalyst with excellent reuse properties was synthesized, which could be used for catalytic wet peroxide oxidation method (CWPO) to degrade reactive brilliant red X–3B. The preparation and reaction conditions of the catalyst were optimized with the decolorization efficiency and stability of the catalyst as measuring indexes. The results showed that the optimal conditions for CuO/γ-Al2O3 synthesis were: roasting temperature of 450 °C, roasting time of 4 h, and Cu loading of 5 wt%. Single-factor experiments and orthogonal experiments indicated that 0.39 mol/L H2O2, 5.50 g/L catalyst, initial pH of 8, and 2.50 h of reaction time were the best reaction conditions to degrade 0.30 g/L reactive brilliant red X–3B with CuO/γ-Al2O3. Under the optimal reaction conditions, the CuO/γ-Al2O3 showed effective reusability. After degradation of the dye wastewater repeatedly 11 times, the dye decolorization efficiency was 90.72%, and the amount of Cu2+ leached was below 0.90 mg/L. This study is an important reference, significant for the treatment of dye wastewater, and could be informative for the sustainable development of future catalysts.

Studies on production and evaluation of biopigment and synthetic dye decolorization capacity of laccase produced by A. oryzae cultivated on agro-waste.

The present study investigated the screening of mono and co-culture fungal cultivations for laccase production using extracted lignin as the substrate obtained from cauliflower wastes by two different pretreatment methods. Amongst mono and mixed culture fungal cultivations, monoculture of Aspergillus oryzae exhibited the highest enzymatic activity of 29.7 ± 0.6 U mL-1 under submerged conditions and using alkali extracted lignin as substrate. Under the optimal conditions (pH 4.5, 30°C, 12days, 1% (w/v) lignin and 0.5mM Cu2+ concentration) the maximum laccase activity was estimated to be 41.3 ± 2.8 U mL-1 and production yield of 153.3 ± 2.4mg L-1. Maximum decolorization of pigment extracted from Aspergillus heteromorphus CBS 117.55 cultivated culture media was achieved by administration of 40 U g-1 of crude enzyme concentration. Thermal and pH stability of crude laccase was observed over wide ranges. The dye decolorization efficiency of crude A. oryzae laccase was studied and Congo Red exhibited maximum decolorization percentage (64 ± 1.3%) at 15µM, 50°C and pH 4.5. The kinetic study of different dye (Congo Red) concentrations obtained Vmax and Km values of 0.123 × 10-3M and 0.724mol L-1min-1, respectively.