Removal of textile dyes from aqueous solution using PEG based aqueous biphasic system

Aqueous biphasic systems (ABSs) composed of polyethylene glycol (PEG) and salt have been examined for the removal of textile dyes from textile effluent. The partitioning of four dyes namely Cibacron Scarlet LS 2G, Rhodamine B, Brown ERN and Astacryl Red 3B was investigated. All the dyes studied were found to partition into the upper PEG rich layer. Sodium carbonate was found to be the most efficient salt for extraction of dyes. Sodium sulphate was found to be marginally less efficient. Sodium chloride did not cause partitioning at all. Partitioning occurred at all pH and was almost pH independent. The partitioning of these dyes in larger volume (100?mL) ABS was also demonstrated. Studies using dye bath effluent were also conducted. In all cases very high efficiencies consistently above 98% were obtained.     

Decolorization and degradation of acid dyes mediated by salt fractionated turnip ( Brassica rapa ) peroxidases

Peroxidases from turnip roots (524?U?g^?1 of vegetable) were highly effective in decolorizing acid dyes having wide spectrum chemical groups. Dye solutions, containing 40–170?mg?dye?L^?1, were treated by turnip peroxidases (TP) (specific activity of 122.0?U?mg^?1 proteins). These enzymes were able to decolorize most of the acid dyes in the presence of 2.0?mM 1-hydroxybenzotriazole (HOBT). Increasing concentration of enzyme and time in the absence of HOBT did not influence dye decolorization. The rate of decolorization was significantly enhanced when HOBT was added to the decolorizing solutions. The decolorization of all the used dyes was maximum at pH 5.0 and 40°C. Complex mixtures of dyes were significantly decolorized when treated with enzyme in the presence of HOBT (2.0?mM). Phytotoxicity test based on Allium cepa root growth inhibition has shown that majority of the TP-treated dye product were not more toxic than their parent dye. Kinetic parameters of the TP with various dyes showed that this enzyme has highest affinity for Acid Yellow 42. This study demonstrates that the peroxidase/mediator system was an effective biocatalyst for the treatment of industrial effluents from textile, dye manufacturing, dyeing and printing industries or complex mixtures of dyes.     

A comparative study of Cu (II) biosorption on Ca-alginate and immobilized live and inactivated Cladosporium sp

Spores of Cladosporium sp. were immobilized into Ca-alginate beads via entrapment. The alginate beads and both entrapped live and inactivated spores of Cladosporium sp. were used for comparison of biosorptive capacity from aqueous solutions. The factors affecting the adsorption ability on Cu (II), such as the contact time, initial pH, temperature were investigated. The results showed that the Ca-alginate beads containing live spores of Cladosporium sp. had the maximum biosorptive capacity. The biosorption equilibrium was established in about 3 h. The maximum biosorption of Cu (II) on Ca-alginate entrapping spores and no spores were obtained between pH 4.0 and 3.5. Temperature over the range of 15-45 degrees C had no significant effect on the biosorption capacity. The biosorptive capacity increased with initial concentrations in the concentration range of 30-800mg/l. The equilibrium was well described by Langmuir biosorption isotherms. The Ca-alginate beads could be regenerated using 0.1M HCl, The biosorbents were reused in three biosorption-desorption cycles with negligible decrease in biosorptive capacity.     

Treatment of textile dye wastewater using ozone combined with photocatalyst

Ozonolysis combined with photocatalysis was used as a new approach for the treatment of textile dye wastewater containing azo dyes. The color reduction was very fast when only ozone was used for the treatment, but a 90% Total Organic Carbon (TOC) reduction was obtained only during a combined treatment. Reactive Black 5 dye containing two different percentages of NaCl was used for the experiment. The color reduction was fast in the neutral and basic pH. However for a fast TOC reduction acidic pH was found to be more effective. On‐line UV‐Vis spectrophotometry was used to measure the color reduction.     

Solar photocatalytic decomposition of two azo dyes on multi-walled carbon nanotubes (MWCNTs)/TiO<Subscript>2</Subscript> composites

Multi-walled carbon nanotubes (MWCNTs)/TiO₂ 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 TiO₂, the combination of MWCNTs with titania could cause a significant absorption shift toward the visible region. The photocatalytic performances of the MWCNTs/TiO₂ 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 TiO₂ 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.     

Decolorization of anthraquinone dye by Aspergillus ficuum in various physiological states

Decolorization of reactive brilliant blue KN-R by Aspergillus ficuum was investigated on suspended spores, mycelial pellets, immobilized cells. It was found that Aspergillus ficuum could effectively decolorize reactive brilliant blue KN-R especially when grown as pelleted mycelia. Many factors affecting the decolorization process in nitrogen-limited media (NLM) were studied, including: initial pH, temperature, and mycelial age. Results showed that the media containing reactive brilliant blue KN-R at 50 mg/L could be decolorized by 96% of the initial color in 42 h, in most conditions tested, the dye degraded products assayed by UV-visible spectrophotometer and macroscopic observation showed that the decolorization of reactive brilliant blue KN-R by mycelial pellets includes two important processes: biodegradation and biosorption. Kinetic study revealed that reactive brilliant KN-R biodegradation by mycelial pellets and suspended spores conformed to first-order reaction model while reactive brilliant blue KN-R biodegradation by immobilized cell followed zero-order model. In addition, mycelial pellets was found to biodegrade KN-R more quickly than suspended spores and immobilized cell.     

Studies on the utility of plant cellulose waste for the bioadsorption of crystal violet dye

Several synthetic dyes employed in textile and food industries are discharged into aquatic environment. These visible pollutants in water damage environment, as they are carcinogenic and toxic to humans. The use of cost effective and ecofriendly plant cellulose based adsorbents have been studied in batch experiments as an alternative and effective substitution of activated carbon for the removal of toxic dyes from waste water. Adsorbents prepared from sugarcane baggase, were successfully used to remove certain textile dye such as crystal violet from an aqueous solution. The present investigation potentiate the use of sugarcane baggase, pretreated with formaldehyde (referred as Raw Baggase) and sulphuric acid (referred as Chemically Activated Baggase), for the removal of crystal violet dye from simulated waste water. Experiments were carried out at neutral pH with various parameters like dye concentration, temperature, contact time and adsorbent dosage. Efficiency of raw baggase was found better than chemically activated baggase for adsorption of crystal violet dye. The data obtained perfectly fits in the Freundlich adsorption isotherm.     

Mutagenicity assessment of textile dyes from Sanganer (Rajasthan)

Sanganer town, district Jaipur (Rajasthan, India) is famous worldwide for its hand block dyeing and textile printing industries. These industries use a variety of chemicals and dyes during processing and finishing of raw materials. Most of the textile dyes used by these industries have not been evaluated for their impact on health and the environment. The workers in these industries are exposed to such dyes with no control over the length and frequency of exposure. Further, untreated and sometimes even treated effluents from these industries are released into surface waters of Amani Shah drainage or through the drainage systems, seep into the ground water and adjoining water bodies. Since many textile dyes are known carcinogens and mutagens, a complete evaluation of the safety of these dyes in the human environment must include an evaluation of their genotoxicity or mutagenicity. A total of 12 textile dyes from Sanganer were tested for their mutagenicity, by Ames Salmonella reversion assay using strain TA 100 of Salmonella typhimurium. Only 1 dye, Red 12 B showed absence of mutagenic activity. The remaining 11 dyes were all positively mutagenic.     

Aspects of the biology of resting spores of Thalassiosira nordenskioeldii and Detonula confervacea

Large numbers of resting spores of Thalassiosira nordenskioeldii Cleve and Detonula confervacea (Cleve) Gran were produced when these species were grown at low levels of ammonia and nitrate. The production of resting spores by T. nordenskioeldii was inversely related to temperature. At 0° and 5°C between 68 and 96% of the total cells were resting spores, while at 15°C resting spores were not produced. Resting spores of both species would not survive 7 days in the dark at 20°C. At 0°, 5°, 10° and 15°C, the length of time that the resting spores of both T. nordenskioeldii and D. confervacea remained viable was inversely related to temperature. At 0°C, T. nordenskioeldii remained viable for 576 days. The data suggest that the production of resting spores by these two species does not aid them in the survival of unfavorably high temperatures such as are found in temperate estuaries during the summer. Rather, they appear to be an adaptation for the survival of long periods of darkness in polar regions.     

High adsorption of dyes by water hyacinth fixed on alginate

Pollution from synthetic dyes has emerged to be a significant environmental issue over the past few decades. This has mainly been triggered by the increasing global dye production, possible toxic effects, undesirable colour and high persistence in the environment. Biosorption, which involves dye removal from aqueous solution by passive linkage in live and dead biomass, has shown great potential in removing dyes from aquatic environments. Among aquatic macrophytes, water hyacinth, Eichhornia crassipes, has shown great potential as a biosorbent. In this work, we investigated the removal of two basic dyes, methylene blue and crystal violet, using E. crassipes immobilized on alginate. Results showed that the Langmuir model better described the equilibrium sorption data when compared to the Freundlich model. Optimum amounts of methylene blue and crystal violet dyes were adsorbed in the alkaline pH range (8–10), 8 % biomass dose, and the amount of dye removed increased with increasing initial dye concentration. The equilibrium monocomponent adsorption capacities for the dyes were 111.1 and 43.5 mg/g, while the binary adsorption capacities were 26.1 and 11.6 mg/g for methylene blue and crystal violet, respectively. To conclude, we show for the first time that E. crassipes fixed on alginate beads can uptake and adsorb methylene blue and crystal violet dyes very effectively in batch systems and show great potential for dye removal from aquatic environments.     

Polyurethane for removal of organic dyes from textile wastewater

Synthetic organic dyes are extensively used in consumer products from textile to pharmaceuticals. A large amount of organic dyes is ultimately discharged as effluent into water bodies, thus posing a serious threat to environment and life. Therefore, removal of dyes from water bodies is needed. To address this problem, various synthetic and natural materials have been used to adsorb dyes. Here, we review the application of polyurethane for removal of organic dyes. First, we review the application of simple and modified polyurethane as efficient and economic adsorbents for dyes. Secondly, we review the polyurethane-based membranes for separation and adsorption of various dyes. Thirdly, we describe polyurethane composites with improved efficiency of dyes removal. Finally, we review the bioremediation of dyes where polyurethane has been proven as an excellent inert support.     

Natural dyes and antimicrobials for green treatment of textiles

Increasing studies on extraction, purification and modification processes of natural dyes and antimicrobials, and their subsequent application on textiles demonstrate the revival of natural dyeing and finishing. Natural dyes have been widely used in textile coloration since ancient times. But, with advent of man-made synthetic dyes in the mid-nineteenth century, the dye market has been captured due to a variety of competitive properties of synthetic dyes against natural ones such as lower cost, higher fastness, color variety, ability to dye synthetic fibers and availability in large industrial scale. However, most of the synthetic dyes raise some serious problems in human health and cause environmental risks. Due to these drawbacks along with the growing awareness about cleaner surroundings and healthy lifestyle, there has been recently a worldwide interest in the production and application of dyes from two natural sources, plants and microorganisms. Most of these natural dyes have also inherently antimicrobial properties and could consequently possess high medicinal activity. They are extracted from different types of microorganisms as well as various parts of the plants that contain coloring materials such as tannin, flavonoids and quinonoids. Here we review the latest scientific researches on extraction and application of natural dyes/antimicrobials on textiles as effective coloring and antibacterial agents. First, different methods of extraction of natural dyes/antimicrobials will be discussed, and then, current methods of textile treatments and examples of early applications of these dyes on textile processing, properties achieved and the results obtained will be presented.     

Depollution of indigo dye by anodic oxidation and electro-Fenton using B-doped diamond anode

Hazardous wastes are generated in the synthesis of dyes and pigments applied in industries. Efficient methods are thus needed to clean wastewaters. Here, we use anodic oxidation and electro-Fenton with B-doped diamond anode to degrade the synthetic dye indigo in aqueous sodium dithionite. Results show the near-complete mineralization of the dye within 80 min at 500 mA. Mineralization was faster by electro-Fenton than anodic oxidation. The second-order rate constant (k) for the reaction of indigo with ^·OH was measured as 4.03 × 10⁹ M^?1 s^?1 at pH 3.0 and was compared with the rate constants of reactions between dyes and ^·OH. The results clearly demonstrate that both electro-Fenton and anodic oxidation can be used to depollute dyes in textile effluent with high efficiency and low cost. The main oxidant, ^·OH, being a non-selective reagent, the method could be applied to degrade other organic pollutants.     

Ionic dye adsorption by zinc oxide nanoparticles

The adsorption behaviour of Basic Red 12, Acid Orange 7 and Acid Blue 1 on zinc oxide nanoparticles (ZNP) has been investigated to understand the physicochemical process involved and to explore the possible use of nanoparticles in the treatment and management of textile waste matter. The dye removal capacity of ZNP towards Basic Red 12, Acid Orange 7 and Acid Blue 1 was found to be 15.64, 6.78 and 6.38 mg g^?1, respectively. The adsorption process was pH dependent and optimum pH values of 9.0, 2.0 and 4.0 were obtained for Basic Red 12, Acid Orange 7 and Acid Blue 1, respectively. Equilibrium was established after 1.0 h for all dyes. Langmuir, Freundlich and Temkin isotherm models were applied to the system. The adsorbent ZNP was characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and Fourier transform infrared (FTIR) techniques. SEM analysis revealed the noticeable nanoporous morphology of the material. The results of FTIR spectroscopy showed that the process is driven by an electrostatic complexation mechanism. XRD studies revealed the nanocrystalline structure of ZNP. BET surface area measurement suggested a high pore volume and large surface area for the adsorbent. The kinetic measurements suggested pseudo-second-order kinetic processes with high regression coefficients and smaller standard error of estimate values and lower residual sum of squares. The thermodynamic measurements suggested that all processes were exothermic and accompanied by negative values for Δ G⁰, Δ S⁰ and Δ H⁰.     

固定化球形红假单胞菌处理电镀废水中Cd和Cr的研究

比较了4种固定化球形红假单胞菌(Rhodopseudomonas sphaeroides)处理含Cd、Cr重金属废水的效果,对固定化菌吸附Cd和Cr的工艺条件进行了优化,并通过生物反应器连续处理实际电镀废水,分析了处理后的效果。通过比较,确定了20g.kg-1沸石和20g.L-1海藻酸钠组合作为共固定材料,固定化菌对Cd和Cr的去除效果明显优于游离菌。采用正交试验优化废水处理工艺条件,结果表明,废水pH值、菌体投加量对固定化菌体的处理效果影响较大,当处理废水的pH值为6.0、菌体投加量为10.00g.L-1时,对40.00mg.L-1含Cd废水的去除率可达96.68%。4轮吸附-解吸循环试验结果显示,固定化菌体可重复利用3次,固定化菌体在使用第3次时,Cd去除率仍可达51.20%。在生物反应器中,用固定化菌体处理质量浓度为92.61mg.L-1的含Cd电镀废水,3h时对Cd的去除率达到98.80%,对含Cu、Au、Ni废水中重金属的去除率也高于90.00%。     

Biological treatment of the dye Reactive Blue 19 by cattails and anaerobic bacterial consortia

This study demonstrates the bioremediation potential of anaerobic sludge and cattail (Typha angustifolia) for the treatment of the dye Reactive Blue 19 (RB19). The anaerobic sludge and cattails used in this study were not previously exposed to dyes or other xenobiotics. Different anaerobic sludge concentrations (30%, 50%, and 70%) were used along fixed dye concentrations at pH 8.0 and 25 °C. Subsequently, 50% sludge was selected to treat RB19 at various concentrations. The discoloration of non-hydrolyzed dye was between 70% and 85% using 50% biomass. For the hydrolyzed form of RB19, the range of decoloration was 70%–90%. Dye treatment efficiencies between 50% and 75% were observed for the two forms of the dye when treated with T. angustifolia. Overall, the anaerobic biomass at pH 8.0 showed better potential than cattails to treat RB19. The observation that non-enriched anaerobic sludge can decolorize RB19 is important because it opens up the prospects of developing anaerobic treatment systems, which can easily decolorize dyes in industrial wastewaters and also possesses potential advantages over systems using defined bacterial cultures.     

Removal of textile dyes from water by the electro-Fenton process

An environmentally friendly electrochemical treatment, electro-Fenton process, was applied to the depollution of a synthetic dismissal composed of three dyes, yellow drimaren, congo red and methylene blue, frequently used in textile and dyehouses. Here, we show that those dyes and their mixture are quickly degraded under current controlled electrolysis conditions, leading to an almost complete mineralization. The results show the efficiency of electro-Fenton process to quickly degrade aqueous effluents polluted by synthetic organic dyes.     

PAN-DCD用于染料废水的脱色研究

本文以聚丙烯腈为高分子链,用双腈双胺与聚丙烯腈大分子上的腈基改性,制得含有多种活性基团的聚合物PAN-DCD.研究了PAN-DCD对活性染料、分散染料及酸性染料废水的脱色效果,并初步探讨了其脱色机理.实验结果表明,PAN-DCD的脱色效果与染料的种类、废水的酸度以及脱色剂的用量有关.PAN-DCD对染料颜色的去除率在pH=3.0和pH=13.0时达到极大值,显示了它的两性特征.脱色机理的研究结果表明,聚合物分子中的胍胺结构与染料分子发生了化学作用,通过静电键和分子间氢键的形成以及聚集作用,将分布于水中的有色物质絮凝、沉降.     

Analysis of carcinogenic and mutagenic aromatic amines: An overview

The aromatic amines represent a category of considerable importance in terms of their broad industrial utilization per se as well as intermediates in the manufacture, of a wide variety of dyes which have been broadly used in textile, leather, plastic and paper products as well as in permanent and semi‐permanent coloring products. The exposure to these agents, a number of which are carcinogenic and/or mutagenic, can occur primarily via skin contact and inhalation and covers the spectrum of occupational, consumer and the general public. This overview will principally highlight a number of the recently applied methodologies (including GLC, HPLC, and SPF) for the analyses of benzidines, naphthylamines, aminobiphenyls, methylene bis(2‐chloro‐aniline); 2,4‐diaminotoluene and 2,4‐diaminoanisole with a focus on their determination in environmental and occupational samples.     

二氧化氯对有机染料脱色效果的研究

本文对二氧化氯二两种直接染料和两种活性染料脱色效果的影响因素－ClO2的投加量、染料的初始浓度、pH值、温度以及反应时间等进行了研究。结果表明，在适当的条件下，二氧化氯对这几种有机染料均具有很好的脱色效果。