Decolorization Of Reactive Dyes Research Articles

Application of ozone on the decolorization of reactive dyes — Orange-13 and Blue-19

This study investigated the feasibility of applying ozone (O 3) to reduce the color content of wastewater caused by two commercial reactive dyes (Blue-19 and Orange-13). In the bench-scale experiment, experimental parameters including pH, ozone dosage, and reaction time were evaluated in a 14-L reactor to obtain the optimal operating conditions. Results show that ozone dosage and pH dominated the effectiveness of the decolorization process. The color content could be reduced from 2000 to 200 ADMI (American Dye Manufacture Institute) values within a reaction time of 30 min with the ozone input rate of 2.66 g/h. The pH values of 3 and 10 favored decolorization of Blue-19 and Orange-13, respectively. This was due to the effects that reactive and oxidizing species of molecular ozone and hydroxyl radicals were predominant at low and high pH, respectively. Moreover, molecular ozone was more selective to certain dye structures during the oxidation process. Kinetic analyses show that decolorization of Orange-13 and Blue-19 followed first-order kinetics. The degree of decolorization was primarily proportional to the ozone dosage. Results from this study provide insights into the characteristics and mechanisms of decolorization by the O 3 technique. Results will also aid in designing a system for practical application.

Preparation and characterization of epoxy-functionalized magnetic chitosan beads: laccase immobilized for degradation of reactive dyes

Cross-linked magnetic chitosan beads were prepared by phase-inversion technique in the presence of epichlorohydrin under alkaline condition, and used for covalent immobilization of laccase. The activity of the immobilized laccase on the magnetic chitosan was about 260 U (g/dry beads) with an enzyme loading of about 16.33 +/- 0.39 mg [(g/dry beads) mg/g]. Kinetic parameters, V (max) and K (m) values were determined as 21.7 U/mg protein and 9.4 microM for free enzyme, and 15.6 U/mg protein and 19.7 microM for the immobilized laccase, respectively. The operational and thermal stabilities of the immobilized laccase were improved compared to free counterpart. The immobilized laccase was operated in a batch reactor for the decolorization of reactive dyes from aqueous solution. The laccase immobilized on magnetic chitosan beads was very effective for removal of textile dyes from aqueous solution which creates an important environmental problem in the discharged textile dying solutions.

Applications of Celite-adsorbed white radish ( Raphanus sativus) peroxidase in batch process and continuous reactor for the degradation of reactive dyes

White radish peroxidase immobilized on Celite has been employed for the treatment of reactive dyes: Reactive Red 120 and Reactive Blue 171. A comparative study of decolorization of these dyes by soluble and immobilized white radish peroxidase was made. Effect of different redox mediators: 1-hydroxybenzotriazole, syringaldehyde, verataryl alcohol and violuric acid on the decolorization of reactive dyes by white radish peroxidase was tested. The investigated dyes were decolorized to different extents in the presence of these mediators. However, 1-hydroxybenzotriazole was found to be the most effective mediator for decolorization of Reactive Red 120 and Reactive Blue 171 by white radish peroxidase. Maximum decolorization of the dyes was observed at pH 5.0 and 40 °C in 1 h. Comparative operational stability performance of soluble and immobilized white radish peroxidase for the treatment of dyes was checked in the presence of various denaturing and inhibiting agents such as sodium azide, organic solvents and mercuric chloride. Among the studied dyes, white radish peroxidase exhibited significantly higher affinity for Reactive Red 120. Toxicity of the dyes was tested by Allium cepa test. Immobilized peroxidase decolorized dyes more effectively in batch process. Absorption spectra of treated and untreated dye solutions were found to show a marked difference. Efficiency of immobilized peroxidase was checked in a continuous reactor where the immobilized enzyme exhibited 73% decolorization of Reactive Red 120 even after 1 month of operation of the reactor.

Effect of metal ions on reactive dye decolorization by laccase from Ganoderma lucidum

In this work, the influence of different metal ions on laccase activity and laccase-catalyzed dye decolorization was investigated under in vitro conditions using crude laccase obtained from a white rot fungus Ganoderma lucidum. Laccase activity was enhanced by metal ions such as Ca 2+, Co 2+, Cu 2+ and Zn 2+ at low concentrations (1 mM). Increasing the concentration of metal ions except that of Cu 2+ and Zn 2+ up to 5 mM and above decreased the enzyme activity. Among several heavy metals, Fe 2+ highly inhibited the enzyme activity. Effect of metal ions was tested on decolorization of two reactive dyes, namely Remazol black-B (RB-5) and Remazol brilliant blue R (RBBR) at a concentration of 50 mg l −1. The presence of heavy metals generally did not exert much influence on the decolorization except Fe 2+. Cu 2+ and Cr 6+ enhanced the decolorization of both dyes. In the presence of 1 mM Cu 2+, 94% of RB-5 and 35.5% of RBBR were decolorized during 1 h incubation. G. lucidum laccase was able to tolerate mixture of several metal ions. Treatment of simulated reactive dye effluent by laccase showed that the redox mediator system is necessary for effluent decolorization. Syringaldehyde, a natural redox mediator, was very effective than the synthetic mediator 1-hydroxybenzotriazole (HBT). The initial rate of effluent decolorization in presence of syringaldehyde (0.0831 h −1) was 5.6 times higher than HBT (0.0152 h −1). Although the rate of decolorization was markedly decreased in the effluent containing mixed metal ions, presence of syringaldehyde showed effective decolorization. This study indicates that G. lucidum laccase and natural redox mediator system could be a potential candidate for color removal from reactive dye effluent.

Decolorization of reactive dyes under batch anaerobic condition by mixed microbial culture

Decolorization of reactive dyes, which are used in textile industry, under batch anaerobic conditions by mixed microbial culture was investigated in this study. Decolorization of C.I. Reactive Black 5 (RB 5), C.I. Reactive Red 24 (RR 24) and C.I. Reactive Blue 49 (RB 49) with initial concentrations ranging from 150 to 2400 mg/L was investigated. Decolorization efficiencies obtained were 93.4% for RB 5 and 98.9% for RR 24 both with initial concentration of 2400 mg/L after 24 h incubation period. However, decolorization was lower for the dye of RB 49 than other two dyes in all concentrations despite 72 h incubation period by mixed anaerobic culture. All of the three dyes correlated with 1st order reaction kinetic with respect to decolorization kinetics. The results of the study demonstrated that high decolorization was obtained under anaerobic condition depending on chemical structure of the dye.

Decolorization of reactive dyes by Clostridium bifermentans SL186 isolated from contaminated soil

Decolorization of textile reactive azo dyes by a strain of bacteria (SL186) isolated from a contaminated site was investigated. SL186 was identified as Clostridium bifermentans by phenotypic characterization and 16S rDNA sequence comparison. Under anaerobic conditions, SL186 had decolorized the dyes Reactive Red 3B-A, Reactive Black 5, and Reactive Yellow 3G-P by over 90% after 36 h post-inoculation. The bacterium retained decolorizing activity over a wide range of pH values (6–12), with peak activity at pH 10. Additionally, SL186 decolorized a relatively high concentration of Reactive Red 3B-A dye (1,000 ppm) by over 80% and raw industrial effluent effectively. The addition of glucose increased the decolorization rate a little. Spectrophotometric analyses of the reactive dyes showed no distinct peak indicating aromatic amines. However, a new peak was detected between 300 and 450 nm from the decolorized raw industrial effluent. These results suggest that C. bifermentans SL186 is a suitable bacterium for the biological processing of dye-containing wastewater.

Decolorization of reactive dyes by laccase immobilized in alginate/gelatin blent with PEG

To achieve effective decolorization of reactive dyes, laccase immobilization was investigated. Laccase 0.2% (m/V) (Denilite IIS) was trapped in beads of alginate/gelatin blent with polyethylene glycol (PEG), and then the supporters were activated by cross-linking with glutaraldehyde. The results of repeated batch decolorization showed that gelatin and appropriate concentration of glutaraldehyde accelerated the decolorization of Reactive Red B-3BF (RRB); PEG had a positive effect on enzyme stability and led to an increase of color removal. While the beads contained 0.2%, 2.0%, 2.0%, and 0.5% (m/V) of laccase, alginate, gelatin, and PEG, respectively. The dye of 50 mg/L initial concentration of RRB was decolorized down to 50% during the tenth repeated batch. As far as the decolorization mechanism was concerned, the thermal and pH stabilities of the immobilized laccase were also investigated and were both appreciably improved. The study indicates that the immobilized laccase can be potential candidate for utilization in biodecolorization processes.

Comparative study on using carbon or nitrogen limited medium to culture white rot fungi for reactive brilliant red dye K-2BP decolotization under non-sterile conditions

In order to explore ways for the application of white rot fungus in dye effluent treatment under non-sterile conditions, experiment on decolorization of reactive brilliant red was carried out, employing nitrogen-limited and carbon-limited medium with C/N ratio of 56/2.2 and 28/44 (in mmol/L), respectively. The results showed that the decolorization rate reached 92% while culturing white rot fungus with nitrogen-limited medium; however, the decolorization process ended in carbon-limited medium (n(C)/n(N) = 28/44) because of bacterial contamination. In addition, pH rose up to 9.31 after 4 d of decolorization, which was caused by bacterial contamination in the carbon-limited system. Therefore, it is concluded that nitrogen-limited medium can inhibit bacterial growth to some extent while carbon-limited medium is more easily contaminated by bacteria. Nitrogen-limited medium is more suitable in culture of white rot fungus for decolorization of reactive dye. Medium with the ability of inhibiting yeast growth should be developed by adjusting other components of nitrogen-limited medium.

An optimization study using response surface methods on the decolorization of Reactive Blue 19 from aqueous solution by ultrasound

The decolorization of reactive dye C.I. Reactive Blue 19 from aqueous solution was studied by using ultrasound, activated carbon and combined ultrasound/activated carbon. The combined effects of independent variables, such as ultrasound power, temperature, time, activated carbon concentration, dye concentration and initial pH were investigated on the decolorization by using the central composite design. The decolorization of RB 19 was modelled statistically and optimized by means of the Matlab computer software. The decolorization were accomplished at optimum conditions by using ultrasound, activated carbon and combined ultrasound/activated carbon as 36%, 91% and 99.9%, respectively. The application of ultrasonic irradiation was found to be beneficial for decolorization of RB 19 from aqueous solution by adsorption.

Decolorization of reactive dyes by a thermostable laccase produced by Ganoderma lucidum in solid state culture

Dye decolorizing potential of the white rot fungus Ganoderma lucidum KMK2 was demonstrated for recalcitrant textile dyes. G. lucidum produced laccase as the dominant lignolytic enzyme during solid state fermentation (SSF) of wheat bran (WB), a natural lignocellulosic substrate. Crude enzyme shows excellent decolorization activity to anthraquinone dye Remazol Brilliant Blue R (RBBR) without redox mediator whereas diazo dye Remazol Black-5 (RB-5) requires a redox mediator. Polyacrylamide gel electrophoresis (PAGE) of crude enzyme confirms that the laccase enzyme was the major enzyme involved in decolorization of either dyes. Native and SDS-PAGE indicates that the presence of single laccase with molecular weight of 43 kDa. N-Hydroxybenzotriazole (HBT) at a concentration of 1 mM was found as the best redox mediator. RB-5 (50 mg l −l) was decolorized by 62% and 77.4% within 1 and 2 h, respectively by the crude laccase (25 U ml −1). RBBR (50 mg l −l) was decolorized by 90% within 20 h, however, it was more efficient in presence of HBT showing 92% decolorization within 2 h. Crude laccase showed high thermostability and maximum decolorization activity at 60 °C and pH 4.0. The decolorization was completely inhibited by the laccase inhibitor sodium azide (0.5 mM). Enzyme inactivation method is a good method which averts the undesirable color formation in the reaction mixture after decolorization. High thermostability and efficient decolorization suggest that this crude enzyme could be effectively used to decolorize the synthetic dyes from effluents.

Submerged microfiltration membrane coupled with alum coagulation/powdered activated carbon adsorption for complete decolorization of reactive dyes

Even the presence of very low concentrations of dyes (1 mg L −1) in the effluent is highly visible and is considered aesthetically undesirable. It must be removed from wastewater completely. This study systematically evaluates the performance of adsorption (three kinds of powdered activated carbons), coagulation (AlCl 3·6H 2O) and membrane (submerged hollow fiber microfiltration) processes individually in treating two kinds of reactive dyes (Orange 16 and Black 5) and then using a hybrid process with combined coagulation–adsorption–membrane treatment system. Adsorption capacity and kinetics of Orange 16 were much higher and faster than those of Black 5. The dye removal efficiency by coagulation was highly dependent on dye concentration and solution pH. The hybrid process performance was far more superior that individual process in removing both kinds of dyes. It was evident that the combined coagulation–adsorption–membrane process has a great potential application for complete reactive dye removal, production of high-quality treated water and allows the reduction in the use of coagulant and adsorbent.

Decolorization of reactive dyes using inorganic coagulants and synthetic polymer

A coagulation/flocculation process was employed for the treatment of high concentration reactive dye wastewater. A polymer flocculant synthesized from cyanoguanidine and formaldehyde under acidic conditions was applied with inorganic coagulant (alum or ferric salt) for the dyeing wastewater. The flocculant was tested for synthetic wastewater containing four model reactive dyes (Black 5, Blue 2, Red 2 and Yellow 2) and real wastewater containing reactive dyes from a local dyeing industry. For the synthetic wastewater, the use of inorganic coagulant (1 g/L) alone achieved only 20% of color removal or less. However, with the aid of polymer flocculant, almost 100% of color removal was obtained. The dye removal efficiency increased as polymer dose increased and the efficiency was affected by solution pH and types of the used inorganic coagulant. The use of inorganic coagulant alone appeared little effective in the removal of reactive dyes from the real wastewater. However, alum/polymer and ferric salt/polymer combinations improved color removal up to 60% and 40%, respectively.

Decolorization of reactive dyes by mixed cultures isolated from textile effluent under anaerobic conditions

In the present study mixed cultures that could grew in the molasses media were isolated from textile dye effluent and its decolorization activity was studied in a batch system under anaerobic conditions, in order to determine the optimal conditions required for the highest decolorization activity. The optimum pH value for decolorization was determined as 8 for all the dyes tested. In the experiment with pH 8 dye decolorizations by mixed cultures were investigated at about 96.2–1031.3 mg l −1 initial dye concentrations. The highest dye removal rates of mixed cultures were 94.9% for Reactive Red RB, 91.0% for Reactive Black B and 63.6% for Remazol Blue at 953.2, 864.9 and 1031.3 mg l −1 initial dye concentrations respectively within 24 h incubation period. When the Reactive Red RB was used, approximately 82–98% total color removal was obtained at between 96.2 and 953.2 mg l −1 initial dye concentrations after 12 h of incubation at 35 °C. These results show that our enriched mixed cultures have the potential to serve as an excellent biomass for the use in reactive dye removal from wastewaters under anaerobic conditions.

Application of photoactivated periodate to the decolorization of reactive dye: reaction parameters and mechanism

The decolorization of the reactive dye, reactive black 5 (RB5), by the photoactivated periodate (UV/IO 4 −) was investigated under ultraviolet (UV) irradiation at 254 nm, and its possible mechanism based on periodate photochemistry was discussed, in order to elucidate the main oxidants involved in the decolorization of RB5 as the reaction parameters, such as the light intensity, periodate concentration, dissolved oxygen, and solution pH, were varied, with the intermittent employment of an OH scavenger. The decolorization rate of RB5 increased linearly with increasing light intensity. The decolorization rate was found to increase at low periodate concentrations (0–5 mM), but slightly decrease at higher concentrations (>5 mM). Dissolved oxygen did not have any measurable effect on the decolorization rate of the reactive dye. No pH dependence of the decolorization rate was observed over the pH range of 1.5–10, regardless of the periodate speciation. Based on these results, the main oxidants responsible for the RB5 decolorization with UV 254 were found to be OH and IO 3 (I VI ), after considering the six intermediate species which are reported to be produced as a result of periodate photolysis, namely the radical species ( OH, IO 3 , and IO 4 ) and the non-radical species (O 3, IO 4 −, and IO 3 −).

Reactive dye decolorization using combined ultrasound/H 2O 2

The decolorization of six vinylsulphone reactive dyes (C.I. Reactive Yellow 15, C.I. Reactive Red 22, C.I. Reactive Blue 28, Remazol Dark Black N 150%, C.I. Reactive Blue 220 and C.I. Reactive Black 5) in aqueous solution was investigated using ultrasound and ultrasound/ hydrogen peroxide degradation. Two different concentration levels of hydrogen peroxide were used. The efficiency of the decolorization was evaluated by measuring the absorbance of the dye solutions. The results show that ultrasound treatment was significantly enhanced in the presence of H 2O 2.

Decolorization of reactive dyes by immobilized laccase

Immobilization of laccase by Trametes versicolor on silica chemically modified with imidazol groups, amberlite IRA-400, glass–ceramic chemically modified with carbodiimide/glutaraldehyde and by aminoprolyltriethoxysilane/glutaraldehyde and montmorillonite modified by aminoprolyltriethoxysilane/glutaraldehyde were afforded. These supports were used in the decolorization of textile reactive dyes (Remazol Brilliant Blue R, Remazol Black B, Reactive Orange 122 and Reactive Red 251). One of the most efficient supports was studied in a more detailed way, silica modified by imidazole SiIm led us to obtain almost total immobilization of laccase at contact times lower than 45min. The immobilized laccase showed high decolorization efficiency toward aqueous solutions of the dyes. In the first stages of the process, the decolorization is mainly due to adsorption of the dyes onto the support surface. However, when working in a successive dye addition system, the adsorption capacity of the supports decrease (saturation) and the enzymatic decolorization process is clearly evidenced. The use of a brief photochemical pre-treatment permitted a significantly increase on the efficiency of the enzymatic decolorization process.

Understanding decolorization characteristics of reactive azo dyes by Pseudomonas luteola: toxicity and kinetics

This study provides a first attempt from a toxicological perspective to put forward, in significant terms and explanations, decolorization of reactive dyes. The toxicity series of three dyes used is Reactive acid yellow (RAY)>Reactive black B (BB)>Reactive red 22 (RR22). The less toxic dye (e.g. RR 22) is more readily biodecolorized. The oxygen-repression characteristics of decolorization of RR 22 are due to the obligatory requirement of oxygen-sensitive azoreductase expression to proceed decolorization. Therefore, microbial decolorization of RR 22 is termed non-growth-associated. Biotoxicity of BB is greater than RR 22, as ≈50% of initial cell concentration was lost after 1-day static decolorization. Relatively high toxicity to P. luteola was due to two azo-bonds present on BB for decolorization. In addition, intermediary products of BB may be more toxic or chemically stable than the parent compound BB. A longer persistence of intermediary metabolites may also augment toxicity to bacterial populations. Biosorption accounts for pseudo-decolorization of more toxic dyes (e.g. RAY). A threshold dose of RAY (≈50 mg l −1) is that immediately above which death responses begin to manifest themselves. Decolorization is not growth-associated, but is still metabolism related. Maintenance of cellular viability is thus of importance, since a basic metabolism to express azoreductase activity must be sustained for decolorization. A failure to preserve cellular viability due to chronic toxicity to cells leads to the occurrence of biosorption rather than decolorization.

Decolorization of reactive dyes by the white rot fungus Trametes versicolor in sequencing batch reactors.

The white rot fungus Trametes versicolor was shown to be capable of decolorizing three reactive dyes in a sequencing batch process, using glucose as the carbon and energy source over an extended period without supplementation of new mycelium. Decolorization activity was related to the expression of extracellular peroxidases and could be continuously reactivated by sheering the suspended pellets. Pure culture experiments were carried out simultaneously in agitated Erlenmeyer flasks and in completely stirred tank reactors with two azo dyes, C.I. Reactive Black 5 and C.I. Reactive Red 198 as well as the anthraquinone dye C.I. Reactive Blue 19 (Brilliant Blue R). Results show high and stable degrees of decolorization of 91%-99% in both systems, which could be repeated without decrease in activity over time. Under nonsterile conditions only five cycles of decolorization could be achieved. An increasing bacterial population suppressed fungal growth and the formation of peroxidases.

Decolorization of reactive dyes with different molecular structures under different environmental conditions

Reactive dyes have been identified as problematic compounds in textile wastewaters as they are water soluble and cannot be easily removed by conventional aerobic biological wastewater treatment systems. Anaerobic systems could reduce the color intensity more satisfactorily than the aerobic processes. However, the intermediate products are carcinogenic aromatic amines which need to be further decomposed by an aerobic treatment. An anaerobic/aerobic SBR system was used to treat a synthetic dye wastewater with glucose and acetic acid (1000 mg/l COD) as carbon sources, together with 20 mg/l of four different reactive dyes; i.e., bisazo vinylsulphonyl, anthraquinone vinylsulphonyl, anthraquinone monochlorotriazinyl and oxazine. The color reduction of the first three dyes was 63, 64 and 66%, respectively. The decolorization efficiency of the last or oxazine dye was not determined because of a strange phenomenon or re-appearance of the color when samples were disturbed. More color removal was achieved in the anaerobic phase than in the aerobic step. The initial decolorization rate was 11.9, 0.37 and 0.48 SU/h for the first three dyes, respectively. Though the system comprised anaerobic and aerobic tanks, the color reduction did not rely on phosphorus accumulating organisms (PAOs). High temperature and photo-oxidation through exposure to sunlight could increase the decolorization rate, and the decolorization was not possible if viable organisms were not present in the system. Nitrate, when present, could interfere with the color reduction while sulfate did not. The bisazo reactive dye was decolorized by the reductive reaction, which resulted in the cleavage of the azo bond. Meanwhile, the decolorization of anthraquinone dyes was through the adsorption of dyes on floc materials.

Decolorization of Reactive Dyes and Dyeing Wastewater by Microorganisms under Anaerobic Conditions

The decolorizations of four reactive dyes with azo or anthraquinone group, printing wastewater and winch wastewater were investigated using microorganisms under anaerobic conditions. Reactive dyes with azo group were effectively decolorized. The mechanism of decolorization was suggested to be a reductive cleavage of azo bond. Decolorization rate increased in the presence of organic nutrients such as desizing wastewater. Decolorizations of printing and winch wastewaters were easily achieved as good as for azo dyes. For an artificial wastewater made from 70% of the solution of four reactive dyes and 30% of desizing wastewater, 85% decolorization and 65% COD removal were attained using anaerobic-aerobic continuous treatment.