Bioremediation of Textile Azo Dyes Amido Black 10B, Reactive Black 5, Reactive Blue 160 by Lentinus squarrosulus AF5 and Assessment of Toxicity of the Degraded Metabolites

Bioremediation is an eco-compatible and economical approach to counter textile dye menace. The isolated Lentinus squarrosulus AF5 was assessed for decolourization of textile azo dyes, and had shown ~93%, 88% and 70% decolorization of Reactive blue 160 (RB160), Reactive black 5 (RB5) and Amido black 10B (AB10B) respectively. Further analysis using UV-vis, HPLC, and FTIR, 1H NMR had shown the degradation of the dyes. Toxicity analysis of the metabolites was performed using seed germination and plant growth on two agriculturally important plants Guar (Cyamopsis tetragonoloba) and wheat (Triticum aestivum) as well as cytotoxicity analysis using the human keratinocyte cell line (HaCaT). The dye mix appeared inhibitory for seed germination (20% - 40%), whereas metabolites were non-inhibitory for germination. Treatment of HaCaT cells with of dye mix and metabolites led into 45% and ~100% of cell viability of HaCaT cells respectively. Therefore, metabolites following degradation of the dye mix were observed to be non-toxic.

Comparison of decolorization of reactive azo dyes by microorganisms isolated from various sources

Azo dyes are among the oldest man made chemicals and they are still widely used in the textile, printing and the food industries. About 10%-15% of the total dyes used in the industry is released into the environment during the manufacturing and usage. Some dyes and some of their N substituted aromatic bio transformation products are toxic and/or carcinogenic and therefore these dyes are considered to be environmental pollutants and health hazards. These azo dyes are degraded by physico chemical and biological methods. Of these, biological methods are considered to be the most economical and efficient. In this work, attempts were made to degrade these dyes aerobically. The organisms which were efficient in degrading the following azo dyes Red RB, Remazol Red, Remazol Blue, Remazol Violet, Remazol Yellow, Golden Yellow, Remazol Orange, Remazol Black were isolated from three different sources viz., wastewater treatment plant, paper mill effluent treatment plant and tannery wastewater treatment plant. The efficiency of azo dye degradation by mixed cultures from each source was analyzed. It was found that mixed cultures from tannery treatment plant worked efficiently in decolorizing Remazol Red, Remazol Orange, Remazol Blue and Remazol Violet, while mixed cultures from the paper mill effluent worked efficiently in decolorizing Red RB, Golden Yellow and Remazol Yellow. The mixed cultures from wastewater treatment plant efficiently decolorized Remazol Black.

Biodegradation of azo dyes by genetically engineered azoreductase

A azoreductase gene with 537 bp was obtained by PCR amplification from Rhodobacter sphaeroides AS1 1737 The enzyme, with a molecular weight of 18 7 kD, was efficiently expressed in Escherichia coli and its biodegradation characteristics for azo dyes were investigated. Furthermore, the reaction kinetics and mechanism of azo dyes catalyzed by the genetically engineered azoreductase were studied in detail. The presence of a hydrazo-intermediate was identified, which provided a convincing evidence for the assumption that azo dyes were degraded via an incomplete reduction stage.

Quinone-mediated decolorization of sulfonated azo dyes by cells and cell extracts from Sphingomonas xenophaga

The effects of various quinone compounds on the decolorization rates of sulfonated azo dyes by Sphingomonas xenophaga QYY were investigated. The results showed that anthraquinone-2-sulfonate （AQS） was the most effective redox mediator and AQS reduction was the rate-limited step of AQS-mediated decolorization of sulfonated azo dyes. Based on AQS biological toxicity tests, it was assumed that AQS might enter the cells and kill them. In the cytoplasmic extracts from strain QYY, AQS more effectively increased decolorization rates of sulfonated azo dyes than other quinone compounds. In addition, we found a NADH/FMN-dependent AQS reductase using nondenaturing polyacrylamide gel electrophoresis （Native-PAGE）.

Decolorization and bio degradation metabolism of azo dyes by Pseudomonas S-42

A bacterial strain was isolated from activated sludge and has been identified as Pseudomonas sp. S-42 capable of decolorizing azo dyes such as Diamira Brilliant Orange RR (DBO-RR), Direct Brown M (DBM), Eriochrome Brown R (EBR) and so on. The growing cells, intact cells, cell-free extract and purified enzyme of strain S-42 could decolorize azo dyes under similar conditions at the optimum pH 7.0 and temperature of 37℃. The efficiencies of decolorization for DBO-RR, DBM, EBR with intact cells stood more than 90%. When the cell concentration was 15mg (wet)/ml and the reaction time was 5 hours, the decolorizing activities of intact cells for above three azo dyes were 1.75, 2.4, 0.95 μg dye/mg cell, respectively. Cell-free extract and purified enzyme belonged to azoreductase with molecular weight about 34000±2000 and Vmax and Km values for DBO-RR of 13μmol/mg protein/nun and 54μmol, respectively. The results from the detection of the biodegradation products of DBO-RR by spectrophotometric and NaNO2 reaction methods showed that the biodegradation of azo dyes was initiated by the reducing cleavage of azo bonds. The biodegradation metabolism path for DBO-RR by Psued. S-42 was hypothesized.

Degradation of Azo Dyes by Photocatalysis of Fe(Ⅲ)-oxalate Complexes/H_2O_2 in Aqueous Non-ionic Surfactant Triton X-100 Solution

Two azo dyes,C.I.Reactive Red 195(RR195)and C.I.Acid Black 234(AB234)were degraded by photocatalysis of Fe(Ⅲ)-oxalate complexes/H2O2 in aqueous non-ionic surfactant,Triton X-100(TX-100)solution.Some factors affecting the dye degradation such as TX-100 concentration,irradiation intensity,and sodium chloride were investigated.The interaction and competition between dye and TX-100 during the degradation were also examined using spectrophotometry and maximum bubble pressure method,respectively.The results indicated that TX-100 showed a significant reduction effect on degradation of two azo dyes,but which was largely confined to TX-100 concentration below the Critical Micellar Concentration(CMC).And the reduction was considerably decreased above the CMC,especially in the case of AB234.Moreover,the reducing effect of TX-100 on dye degradation almost did not vary with irradiation intensity.And the impact of sodium chloride on dye degradation was limited by the addition of TX-100.

Effect of Quinoid Mediators on the Decolorization of Azo Dyes by the Strain CD-2

In the present study, the effects of various quinone compounds on the decolorization rates of azo dyes by the E. coli strain CD-2 were investigated. The results showed that Lawsone was the most effective redox mediator. The optimum concentration for Lawsone is 0.1 mmol/L. The effects of physic-chemical parameters on the Methyl Orange degradation by the strain were determined. The results indicated that, in the quinone mediated decolorization system, strain CD-2 exhibited a good degradation ability in the range of pH from 4 to 9, temperature from 20°C to 50°C and salinity from 1% to 6%. With Lawsone as a redox mediator, a broad spectrum of azo dyes with different structures could be decolorized by the strain. All the results showed that the addition of a redox mediator can be valuable for treating dye-colored wastewaters.

STUDY ON ENRICHMENT AND SEPARATION OF TRACE ELEMENTS WITH SILICA GELS MODIFIED BY HETEROCYCLIC AZO DYES

Two types of modified silica gels were prepared by adsorption method and bonding method respectively. Enrichment and separation of trace metal ions have been done by using the column packed with modified silica gels.

Biocoagulation of Direct Red-31 and Direct Yellow-12 Azo Dyes from Synthetic Wastew ater with Moringa Oleifera Seed Presscake

Batches experiments were carried out to study the removal potentials of Moringa oleifera seed presscake( MOSP),the residual solids of Moringa oleifera seed after oil extraction used as a natural coagulant for the removal of two direct azo dyes including Direct Red-31( DR-31) and Direct Yellow-12( DY-12). The results indicated that the MOSP contained active proteins which were active agents and efficient for the removal of the two dyes. Higher temperature and lower p H were favorable for dye removal. The removal rates of the two dyes increased with the increasing MOSP dosage. Inorganic salts improved the dye removal efficiencies by the salt-in effect that prompted the release of proteins from the MOSP particles. Suspended solid simulated by kaolin decreased the dye removal efficiencies because of the competition for active sites of the MOSP between the kaolin particles and the dye molecules. The most likely mechanism for the removal of the two dyes by using MOSP as coagulant was a combined effect of adsorption and neutralisation of charges and the nucleation of the MOSP particles. The results provide new insight into the MOSP utilization and development of new coagulant for dye removal.

An efficient CuZr-based metallic glasses electrode material for electrocatalytic degradation of azo dyes

Metallic glasses have received a lot of attention on wastewater treatment due to their unique atomic structure,and the use of metallic glasses as electrodes has produced unexpected electrocatalytic degradation effects for many pollutants through combining with electrochemical technology.However,it still is a formidable challenge to find a metallic glass electrode material with both efficient and clean for the catalytic degradation of pollutants.In this work,the Cu_(55)Zr_(45)metallic glassy ribbons are used as an electrode to degrade azo dyes and show the excellent degradation effect,which can reach 95.6%within 40 min.In the degradation process,almost no additives are produced and Cu_(55)Zr_(45)metallic glassy ribbons have excellent effects under different pH conditions.Meanwhile,it exhibits good stability for degradation efficiency during the 8 cycle degradation tests of the amorphous alloy electrode.When the copper nanoparticles are exposed on the surface of the ribbons,the oxidized copper obtained synergistically produce activated radicals is the primary degradation mechanism,where the auxiliary degradation mechanisms include electron transfer and the promotion of active chlorine.This research develops a new type of electrode material for wastewater treatment,and the economy and high efficiency of Cu55Zr45metallic glass endow it the expandable functional applications.

Progress and prospects of Mg-based amorphous alloys in azo dye wastewater treatment

Mg-based amorphous alloys exhibit efficient catalytic performance and excellent biocompatibility with a promising application probability,specifically in the field of azo dye wastewater degradation.However,the problems like difficulty in preparation and poor cycling stability need to be solved.At present,Mg-based amorphous alloys applied in wastewater degradation are available in powder and ribbon.The amorphous alloy powder fabricated by ball milling has a high specific surface area,and its reactivity is thousands of times better than that of gas atomized alloy powder.But the development is limited due to the high energy consumption,difficult and costly process of powder recycling.The single roller melt-spinning method is a new manufacturing process of amorphous alloy ribbon.Compared to amorphous powder,the specific surface area of amorphous ribbon is relatively lower,therefore,it is necessary to carry out surface modification to enhance it.Dealloying is a way that can form a pore structure on the surface of the amorphous alloys,increasing the specific surface area and providing more reactive sites,which all contribute to the catalytic performance.Exploring the optimal conditions for Mg-based amorphous alloys in wastewater degradation by adjusting amorphous alloy composition,choosing suitable method to preparation and surface modification,reducing cost,expanding the pH range will advance the steps to put Mg-based amorphous alloys in industrial environments into practice.

Synthesis of 6-chloro and 6-fluoro-4-hydroxyl-2-quinolone and their azo disperse dyes

In this study,6-chloro-4-hydroxy-2-quinolone and 6-flouro-4-hydroxy-2-quinolone were synthesized from corresponding dianilides.These compounds were coupled with some diazotized aromatic amines to give the corresponding azo disperse dyes.The structures of the quinolone derivatives and new azo dyes were confirmed by UV-vis,FT-IR,;H NMR and elemental analysis.

Bio-synthesized palladium nanoparticles using alginate for catalytic degradation of azo-dyes

Palladium nanoparticles(PdNPs)were synthesized in a green way using sodium alginate functioning as both reductant and stabilizer.The formation of as-synthesized Pd NPs was supervised by Ultraviolet–visible(UV–Vis)spectroscopy and confirmed by the surface plasmon resonance(SPR)band.The effect of several synthesis factors such as precursor ratio,solution p H,reaction time,and temperature were investigated by the factorial design of experiments in order to optimize the experimental conditions.The optimal synthesis parameters were achieved by heating 1.0 ml of 1.0%sodium alginate(SA),3.0 ml of 10-2 mol·L-1 H2PdCl4 at 80°C for a period of 30 min in a neutral reaction medium(pH=6).High-resolution transmission electron microscope(HRTEM),energy dispersive X-ray(EDX)spectroscopy,selected area electron diffraction(SAED)pattern,X-ray powder diffraction(XRD),and dynamic light scattering(DLS)were used to confirm the uniform spherical shapes and high crystallinity of Pd NPs with average particle size of(2.12±1.42)nm.The SEM images show the distribution of Pd NPs presented among the SA.FTIR spectra indicate that SA is a good capping agent to stabilize Pd NPs for a long time.The catalytic degradation of model azo-dyes such as mono-azo(Cibacron Yellow FN–2R)and di-azo(Cibacron Deep Red S–B)were confirmed the catalytic activity of Pd NPs.The Pd NPs can accelerate the degradation rate by more than 80 and 10 times respectively as confirmed by kinetics constant(k)values.

Novel azo dyes derived from 8-methyl-4-hydroxyl-2-quinolone:Synthesis,UV-vis studies and biological activity

In this study,N,N＇-di-（2-methylphenyl）malonamide was synthesized and reacted with polyphosphoric acid to afford 8-methyl-4-hydroxyl-2-quinolone.Eight novel azo disperse dyes were then synthesized by linking diazotized p-substituted aniline derivatives with 8-methyl-4-hydroxyl-2-quinolone.The solvatochromism of these azo dyes in various solvents was evaluated.All the compounds were then evaluated for their antibacterial activity against four bacteria,namely.Bacillus subtilis.Micrococcus luteus, Salmonella enterica,and Pseudomonas aeruginosa.The results showed that some of these compounds have high levels of antibacterial activity.

Visible and near-infrared light activated azo dyes

The photoisomerization properties of azo derivatives have been widely used in the fields of materials and biology.One serious restriction to the development of functional azo-based materials is the necessity to trigger switching by UV light,which damage the corresponding surfaces and penetrate only partially through the matter.Therefore,developing the visible and near-infrared light activated azo switches can solve this problem.This review provides a summary of molecular design strategies for driving the isomerization of azo derivatives with visible light and near-infrared light:(1) smart design directly excited by visible light,(2) the addition of upconversion nanoparticles,(3) the employment of twophoton absorption,(4) indirect excitation in combination with metal sensitizer.

Ant colony optimization as a descriptor selection in QSPR modeling for prediction of λ_(max) of azo dyes

A quantitative structure-property relationship （QSPR） study was suggested for the prediction of λ-max of azo dyes. After optimization of 3D geometry of structures, different descriptors were calculated by the HyperChem and Dragon softwares. A major problem of QSPR is the high dimensionality of the descriptor space; therefore, descriptor selection is the most important step for these studies. In this paper, an ant colony optimization （ACO） algorithm was proposed to select the best descriptors.

Evaluating the effectiveness of marine actinobacterial extract and its mediated titanium dioxide nanoparticles in the degradation of azo dyes

Aim of the present study was to synthesize titanium dioxide nanoparticles （YiO2 NPs） from marine actinobacteria and to develop an eco-friendly azo-dye degradation method. A total of five actinobacterial isolates were isolated from Chennai marine sediments, Tamilnadu, India and analyzed for the synthesis of TiO2 NPs using titanium hydroxide. Among these, the isolate PSV 3 showed positive results for the synthesis of TiO2 NPs, which was confirmed by UV analysis. Further characterization of the synthesized TiO2 NPs was done using XRD, AFM and FI＇-IR analysis. Actinobacterial crude extract and synthesized TiO2 NPs was found efficient in degrading azo dye such as Acid Red 79 （AR-79） and Acid Red 80 （AR-80）. Degradation percentage was found to be 81% for AR-79, 83% for AR-80 using actinobacterial crude extract and 84% for AR-79, 85% for AR-80 using TiO2 NPs. Immobilized actinobacterial ceils showed 88% for AR-79 and 81% for AR- 80, dye degrading capacity. Degraded components were characterized by FT-IR and GC-MS analysis. The phytotoxicity test with 500 μg/mL of untreated dye showed remarkable phenotypic as well as cellular damage to Tagetes erecta plant. Comparatively no such damage was observed on plants by degraded dye components. In biotoxicity assay, treated dyes showed less toxic effect as compared to the untreated dyes.

Solar photocatalytic decomposition of two azo dyes on multiwalled carbon nanotubes(MWCNTs)/TiO_(2)composites

Multi-walled carbon nanotubes(MWCNTs)/TiO_(2)composite photocatalysts with high photoactivity were prepared by sol-gel process and further characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared(FT-IR),and UV-vis absorption spectra.Compared to pure TiO_(2),the combination of MWCNTs with titania could cause a significant absorption shift toward the visible region.The photocatalytic performances of the MWCNTs/TiO_(2)composite catalysts were evaluated for the decomposition of Reactive light yellow K-6G(K-6G)and Mordant black 7(MB 7)azo dyes solution under solar light irradiation.The results showed that the addition of MWCNTs enhanced the adsorption and photocatalytic activity of TiO_(2)for the degradation of azo dyes K-6G and MB 7.The effect of MWCNTs content,catalyst dosage,pH,and initial dye concentration were examined as operational parameters.The kinetics of photocatalytic degradation of two dyes was found to follow a pseudo-first-order rate law.The photocatalyst was used for seven cycles with photocatalytic degradation efficiency still higher than 98%.A plausible mechanism is also proposed and discussed on the basis of experimental results.

Biodegradation of carcinogenic textile azo dyes using bacterial isolates of mangrove sediment

Objective:To evaluate the biodegrading property against carcinogenic azo dyes using bacterial isolates of mangrove sediment.Methods:The bacterial isolates were subjected to submerged fermentation and their growth kinetics were studied.The potential strain was characterized using 16S rDNA sequencing.Results:In the present study,dye degrading bacterial colonies were isolated from the mangrove sediment samples of Parangipettai estuarine area,Tamil Nadu.Of the 30 morphologically different strains isolated,5 showed antagonistic property.The growth kinetics of the two strains,P1 and G1,which showed potent activity were calculated.One particular isolate(P1)showing promising dye degrading potential in the submerged fermentation was further characterized.The strain was identified as Paenibacillus sp.by 16S rDNA sequencing.Conclusions:This study reveals the less explored microflora of mangrove sediments.The novel strain may further be analyzed and used in the treatment of effluent from dye industry so as to reduce the impact of carcinogenic contaminants.

Continuous treatment of azo acid dyes by photo-dependent denitrifying sludge

Simultaneous removals of dye and nitrate by photo dependent denitrifying sludge(PDDS) have been demonstrated in a continuous flow bench scale reactor. The best C/N for the degradation of azo dyes by PDDS was 1.5. The specific removal rate of azo dye AB92 decreased with a decrease in hydraulic retention time and increased with a decrease in solids retention time. The degradation rate of TOC decreased with a decrease in hydraulic retention time. AB92, which has nitro and hydroxyl substitutions in non para positions, was uniquely degraded. During continuous flow treatment experiments using PDDS, complete degradation of azo dyes AB92 and AO20 at influent concentrations of 40 mg/L and 30 mg/L, respectively, was achieved with an HRT of 16.