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Removal of color from dye-bearing water has been a bothering task from the health point of view and in the aesthetic sense as well. Finding out the effectiveness of Remazole Red RGB dye removal is the aim of the present work using banana stem, an agricultural waste, as an activated carbon. The preparation of the banana stem activated carbon was done in the laboratory by carbonization followed by activation. To assess the impact of varied exploratory variables such as pH of adsorbate, contact time, initial dye concentration and dosage of adsorbent on the removal of Remazole Red RGB dye from aqueous solution adopting batch studies were performed. The Freundlich and Langmuir isotherm models were used to predict the adsorption capacity of adsorbent at equilibrium conditions, the kinetic parameters were also determined. The concentration of dye remaining in the system was measured using a UV visible spectrometer. The batch test resulted in the removal of the maximum of 87% of dye when the dye concentration was 2 mg/L, at an adsorbent dose of 0.5 gm/L and dye pH 4 in 35 minutes. It is established from the studies that the equilibrium data suited excellently both Freundlich and Langmuir isotherms. The maximum adsorption capacity of 14.28 mg/L was established from the Langmuir isotherm model. To state the sorption kinetics, pseudo-first-order and pseudo-second-order kinetic models were evaluated. The intraparticle diffusion model was checked for the adsorption data and it was observed that intraparticle diffusion is not the only rate-limiting step. The regression analysis results indicated that the linear regression model gave the best results. The above detection exhibits that banana stems can be used productively for the removal of color from dye-containing wastewater.

The existing knowledge on the reactivity of green iron particles on textile dye and wastewater decolorization is very limited. In this study, the potential of green iron particles synthesized using grape leaves extract on reactive dye (reactive red 195, reactive yellow 145, reactive blue 4 and reactive black 5) decolorization were investigated. 95–98% of decolorization was achieved for all reactive dyes at 1.4–2.0 g/L of green iron. Maximum decolorization was attained at lower dye concentration and showed very little impact on decolorization when pH was increased from 3 to 11. The pseudo-first-order fit confirms the reaction between iron particles and dye molecules with rate constant 0.317–0.422 and it is followed by adsorption, data fit with pseudo-second-order model. Hence, not only adsorption but also the reduction process is involved in the reactive dye decolorization. Benzene, phenyl sodium, 2-chloro-1,3,5-triazine, naphthalene, sodium benzene sulfonate, benzene 1,2 di amine, anthracene-9,10 dione, aniline, phenol, benzene sulfonic acid were the major intermediates detected in dye decolorization and the respective reaction pathway is proposed. Green iron from grape leaves extract demonstrated better performance and it is recognized as the promising cost-effective material for textile wastewater treatment. HIGHLIGHTS Green iron particles synthesized from grape leaves extract.; Reactivity of bare and green iron particles on textile dye decolorization.; Dye decolorization pathway proposed.; Efficiency of green iron particles on textile wastewater decolorization.; Economic feasibility of synthesized green iron particles on textile wastewater treatment.

Recently, the utilization of wastes, recovery of high value-added products from waste, and their use as raw materials in other industries with the logic of industrial symbiosis has become an important issue. In this study, removal efficiency of Reactive Orange 16 (RO16) dye from aqueous solution was studied using TiO2 catalyst recycled from an industrial waste effluent. The recycling of TiO2 waste from a paints manufacturing industry was carried out by sintering the TiO2-containing waste. The catalyst usability of TiO2-containing powder was then investigated in the removal of RO16 dye by photocatalytic oxidation process. In photocatalytic oxidation studies, TiO2/UV and TiO2/UV/H2O2 processes were investigated, where the effect of annealing temperature, the effect of H2O2 concentration, and the adsorption and photocatalytic effects on RO16 dye removal were studied. The results showed that 100% RO16 removal was obtained for the 10 mg/L initial RO16 concentration using the TiO2 (1 g/L)/UV process. At high initial RO16 concentration (50 mg/L), 100% RO16 removal was achieved by adding 10 mM H2O2.

In this paper, ultrafiltration (UF) flat sheet membranes were manufactured by introducing two diverse halloysite nanotubes (HNT) size (5 mu m and 63 mu m) and five different (0, 0.63, 1.88, 3.13, 6.30 wt %) ratios by wet phase inversion. Some characterization methods which are contact angle, zeta potential, viscosity, scanning electron microscopy (SEM) and Young's modulus measurements were used for ultrafiltration membranes. Synthetic dye waters which were Setazol Red and Reactive Orange were used for filtration performance tests. These dye solutions were filtered in three different pH conditions and three different temperature conditions for pH and temperature resistance to understand how flux and removal efficiency change. The best water permeability results were obtained as 190.5 LMH and 192 LMH, for halloysite nanotubes (HNT) sizes of 5 mu m and 63 mu m respectively. The best water and dye performance of UF membrane contains 1.88% w/w ratio of HNT, which showed increased water flux and dye flux of membranes according to different HNT concentrations including ultrafiltration membranes. Scientific and Technological Research Council of Turkey (TUBI.TAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [113Y350, 113Y370, 113Y371, 113Y372] This work was supported by The Scientific and Technological Research Council of Turkey (TUBI.TAK) under project numbers of 113Y350, 113Y370, 113Y371 and 113Y372. B.K. (PhD student) did the experiments and wrote the article. M.A. (PhD student) did the experiments and revised the article. T.O.A. (Doctor) did the experiments and revised the article. T.T. (Doctor) did SEM characterization analysis. D.Y.I. (Associate Professor) revised the article. S.U. (Associate Professor) revised the article and is project manager. Y.Z.M. (Professor) revised the article. T.U.D. (MSc and R&D Manager) did HNT characterization analysis. I.K. (Professor) revised the article and is project manager.

The aim of the present study was to investigate the performance of a novel coagulant, i.e. ZrOCl2, for the removal of anthraquinone-based reactive dye from aqueous solution. An ideal experimental setup was designed based on central composite design using response surface methodology to determine the individual and interactive effects of different operational variables (i.e. pH, coagulant dose and dye concentration) on treatment performance in terms of dye and chemical oxygen demand (COD) removal efficiencies. Total 92.58% dye and 85.33% COD removal were experimentally attained at optimized conditions at low coagulant dose, i.e. 156.67 mg/L for the dye concentration of 105.67 mg/L at pH 2. To validate the working pH of the metal coagulant, the static charge of ZrOCl2 was measured using Eh value. The performance of the coagulant was validated with experimental and predicted values in the selected data set, and R2 values for both responses were found to be 0.99 and 0.95 respectively, which shows the reliability of the experimental design. Further, the toxicity of the coagulant was assessed and no such toxicity was found even up to the concentration of 500 mg/L, proclaiming the disposal of sludge may not exhibit any threat to humans. Experimental results suggested that the ZrOCl2 could be used as an eco-friendly coagulant for dye wastewater treatment.

High color concentrations in inflows at reclaimed water treatment plants are typically considered as emergency situations, which must be solved using an appropriate decolorizing process. Using the decoloration mechanism of a modified dicyandiamide-formaldehyde polymer (DFP), a urea-formaldehyde polymer and a melamine-formaldehyde polymer (MFP) were prepared with ammonium chloride and ammonium sulfate as the modifiers. An orthogonal experiment indicated that a modified urea-formaldehyde polymer had no effect on decolorization; however, the MFP modified by ammonium chloride in number 16 (MMFP-C16), the DFP modified by ammonium chloride in number 9 (MDFP-C9) and modified by ammonium sulfate in number 6 (MDFP-S6) were successful. The removal rates were above 50% in acidic and reactive dye reclaimed water. Fourier transform infrared spectroscopy was used to microscopically analyze the differences in decolorization effect among the polymers. The effect of pH on decolorization was analyzed. Compared to the MDFP-C9 and MDFP-S6, the MMFP-C16 was not sensitive to changes in conditions. The pilot plant test proved that the three optimal decolorizers also had a good decolorizing effect, and MMFP-C16 was better both at decolorizing and floc sedimentation. Thus, the latter can be considered as an efficient modified decolorizer for rapid treatment of high color reclaimed water.

The aim of this article was to clarify which type of dye chromophores could be decolorized efficiently with the use of laccase enzyme. For this purpose, enzymatic degradation of different type of dye classes (4 reactive, 2 acid and 1 basic dye) having various chromophore groups was investigated by using commercial laccase from Cerrena unicolor. It was observed that the chromophore structure of dye is very important on enzymatic color removal efficiency. According to the experimental results, it was found that color removal efficiencies (20 mg/L initial dye) were 98.7% for RB220 (0.1 g/L enzyme after 6 h), 95.1% for RB19 (0.1 g/L enzyme after 48 h), 90.8% for AR42 (0.1 g/L enzyme after 48 h) while they were 60.9% for AR114 (0.25 g/L enzyme), 58.6% for RB21 (0.5 g/L enzyme), 39.7% for RR239 (0.25 g/L enzyme) even after seven days. As a result, it can be said that the highest decolorization rate was achieved for the reactive dye having formazan copper complex (RB220) chromophore. On the other hand, the enzymatic degradation of basic dye (BB9) was found to be rather difficult compared to the acid and reactive dyes used in this study and the maximum color removal was 42.8% after seven days.

PubMedID: 27685968 In the present study, Eucalyptus camaldulensis bark/magnetite composite (EBMC) was used for a potential application as a low-cost adsorbent for the removal of Reactive Black 5 (RB5). The adsorption experiments were performed with aqueous solution (RB5 + distilled water) and synthetic dye bath wastewater (SDBW) in order to investigate the potential application of EBMC in the textile industry. The effects of the various parameters, the initial dye concentration, the temperature, the pH, and the EBMC dosage on the adsorption were investigated. It was found that the adsorption capacity of EBMC increases by increasing the RB5 concentration and temperature and by decreasing the dosage of EBMC. 0.8 g EBMC was found to be sufficient for the removal of 250 mg/L RB5 from 150 mL SDBW with ~85% removal efficiency. The Koble-Corrigan isotherm model described the adsorption process more effectively (R2 = 0.997) than the Langmuir, Freundlich, the Dubinin- Radushkevich and the Jovanovic isotherm models. The Langmuir isotherm predicted a 370.7 mg/g maximum adsorption capacity. The thermodynamic analysis showed that the adsorption of RB5 onto the EBMC was an endothermic process. The multiple linear regression analysis was used in order to determine the cumulative effects of independent variables on the adsorption capacity. © IWA Publishing 2016.

‘Batik’ is known as one of the most popular textile industries in Malaysia, and it produces wastewater in its processing. The wastewater contains reactive dye and is released into drains as well as rivers. It could cause harm to the environment and interrupt the food chain due to the chemicals contained in it. The aim of the present study is to determine the flux performance and modified fouling index using ultrafiltration (MFI-UF) by using different membrane materials, feed concentrations and feed chemistry. The sample was obtained from Romi Batik located at Chendering Terengganu. Two UF membranes were used, with the membrane materials made from cellulose acetate and polyvinylidene fluoride (PVDF). The permeate flux and fouling indices were investigated at the solution pH values of 3 and 7 for different concentrations. It was clearly observed that the highest percentage dye rejection and MFI-UF obtained at pH 7 using a PVDF membrane was a value of 85.3792% and 72,088 s/L2, respectively. Overall results revealed that an ultrafiltration process can be used to treat reactive dye from textiles before it is channelled into the sea or rivers, and has great potential to be commercialized as a new alternative in dye wastewater treatment.

A composite coagulant, polymeric aluminum ferric chloride-poly-epichlorohydrin-ethylenediamine (PAFC-EPI-ETA), was synthesized and then used for the treatment of synthetic reactive brilliant red (RBR) dyeing wastewater. Effects of (Fe + Al) to EPI-ETA mass ratio (P) on the color removal and zeta potential were investigated under different coagulant dosages and initial pHs. Experimental results indicate that the removal of reactive dye and the charge neutralization ability of composite coagulant were improved by increasing the content of organic EPI-ETA. PAFC-EPI-ETA with P = 1 achieved the best color removal percentage and strongest charge neutralization ability. Decolorization efficiency using PAFC-EPI-ETA was quite effecient with pH range of 6.0–7.5 for RBR dye removal. Characteristics of the formed floc were investigated with the dosage of PAFC-EPI-ETA under different P values. The low (Fe + Al) to EPI-ETA mass ratio contributed to the formation of flocs with high growth rate, large size and large size variation.

The adsorption of Everzol Black (EB) from synthetic aqueous solution onto active carbon (AC) and dried fungal biosorbent (Rhizopus arrhizus) was studied under the same experimental conditions. The effects of initial dye concentration, adsorbent dosage and contact time were examined at a batch-scale level. As an alternative to AC, fungus was investigated as a low-cost adsorbent for dye removal. The amount of EB adsorbed onto AC was lower compared with fungal biosorbent; dye adsorption capacity of AC and fungal biosorbent were 94.48 and 106.61 mg/g, respectively. The adsorbent dosage experiments showed that 4 g/L biosorbent removed 100% of EB (Co: 114.39 mg/L) after 2 hours. The results obtained from this study showed that biosorbent effectively removed reactive dye from dye-containing water in a short time period. Langmuir and Freundlich adsorption isotherm models were used for mathematical description of the biosorption equilibrium data; the Freundlich model was found to exhibit good fits to the experimental data. According to the Freundlich isotherm, the maximum dye adsorption capacities of AC and biosorbent were calculated as 344.82 and 357.14 mg/g, respectively. The Fourier transform infrared spectroscopy spectral analysis showed the involvement of functional groups for dye bindings.

PubMedID: 22678216 The objective of this study is to compare the performances of catalytic ozonation processes of two activated carbons prepared from olive stone (ACOS) and apricot stone (ACAS) with commercial ones (granular activated carbon-GAC and powder activated carbon-PAC) in degradation of reactive azo dye (Reactive Red 195). The optimum conditions (solution pH and amount of catalyst) were investigated by using absorbencies at 532, 220 and 280 nm wavelengths. Pore properties of the activated carbon (AC) such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by N 2 adsorption. The highest BET surface area carbon (1,275 m 2/g) was obtained from ACOS with a particle size of 2.29 nm. After 2 min of catalytic ozonation, decolorization performances of ACOS and ACAS (90.4 and 91.3%, respectively) were better than that of GAC and PAC (84.6 and 81.2%, respectively). Experimental results showed that production of porous ACs with high surface area from olive and apricot stones is feasible in Turkey. © IWA Publishing 2012.

The removal of Reactive Black 5 dye in an aqueous solution by electrocoagulation (EC) as well as addition of flocculant was investigated. The effect of operational parameters, i.e. current density, treatment time, solution conductivity and polymer dosage, was investigated. Two models, namely the artificial neural network (ANN) and the response surface method (RSM), were used to model the effect of independent variables on percentage of dye removal. The findings of this work showed that current density, treatment time and dosage of polymer had the most significant effect on percentage of dye removal (p0.8).

Toxicity tests using Sacharomycces cerevisiae were made with simulated textile effluents containing reactive dye (remazol red brilliant) treated by photoeletrolytic process, varying treatment time and applied current. The treatment incorporated an electrolytic reactor with rectangular titanium anode coated with 70% TiO2/30% RuO2 cathode and a rectangular stainless steel coupled with another photolytic reactor containing a high power UV lamp. The treatment system was used in batch recirculation, in other words, the simulated effluent was driven by the system through a helical pump. It was observed that the higher the value of current applied, the longer the treatment has greater color removal of textile effluent and higher mortality of S. cerevisiae, killing up to 100% of the cells at the end of the treatment. With a lower current applied and having the treatment time of 5 minutes, the effluent showed a color removal of 97% and a lower mortality of S. cerevisiae than the effluent simulated without any treatment.

Dyeing process of textile consumes large quantities of water, which results in huge amounts of colored wastewater. Most of the dye wastewater treating methods focused on the treatment of wastewater after the rinsing process of dyed textile. In this paper, tetraacetylethylenediamine/hydrogen peroxide (TAED/H2O2) active oxidation (AO) system was developed to rinse dyed textile and decolorize the rinsing wastewater simultaneously. The results indicated that the decolorization ratio of the rinse effluent obtained by AO method were in the range of 51.72%–84.15% according to different dyes and the COD value decreased more than 30% compared with that of traditional rinsing process. The decolorization kinetics investigation showed that the decolorization of dyes during AO rinsing process followed the law of pseudo-first order kinetics. The result of UV-Vis and UPLC-MS analysis demonstrated that the dye was degraded into colorless organic molecular fragments and partly mineralized during the AO rinsing process.

In the manufacture of liquid dyes, almost complete desalting, which helps to improve the stability of the product, enhances the solubility of the dye. Diafiltration is used to allow a high level of desalting to be achieved. The process of desalination of aqueous dye-salt solutions by polymeric nanofiltration membranes using commercially available modules was studied. The influence of dye and salt concentration on the salt rejection and pressure applied on the flux as well as comparison of individual NF membranes for desalting purposes is presented. The great interest is also devoted to the mathematical modelling of nanofiltration and description of discontinuous diafiltration by periodically adding solvent at constant pressure difference.

Reactive dye BES golden yellow simulated wastewater was treated with H(2)O(2)-assisted photolysis method. Influences of factors such as reaction time, initial pH and H(2)O(2) dosage were investigated, and the reaction kinetics of the process were explored. Results showed that, the degradation of 200 mg/L BES golden yellow solution happened only in the presence of both conditions: UV irradiation and H(2)O(2) addition. Initial pH and H(2)O(2) dosage had remarkable influence on the removal efficiency of the dye. Through several groups of univariate experiments, the optimum pH and H(2)O(2) dosage of the photolysis process were found to be 6-7 and 0.0375 mL 30% H(2)O(2) per milligram of BES golden yellow, respectively. The photolysis process was approximately in accordance with the second-order kinetic equation.

Textile wastewater is contaminated by reactive dye causing unattractive levels of wastewater color, high pH and high salt content when discharged into public water systems. Decolorization of textile wastewater by plant, phytoremediation, is an alternative, sustainable method which is suitable for long term operation. Narrow-leaved cattails are one species of wetland plant with efficiency for decolorizing and remediating textile wastewater. In addition, chemical oxygen demand (COD) can be lowered and dye residue can be removed. The plant also showed a good salt tolerance even after being exposed to a salt solution for 15 days. The narrow-leaved cattails were set up in a constructed wetland model with a vertical flow system operating from bottom to top for synthetic reactive dye wastewater (SRDW) removal. Narrow-leaved cattails could achieve the removal of SRDW at approximately 0.8 gSRDW m−2 day−1. Decolorization of SRDW by this plant was approximately 60%. The advantage of this method is that it is suitable for textile wastewater management and improvement of wetland. These plants could lower COD, remove dye, sodium and total dissolved solids (TDS) whereas other biological and chemical methods could not remove TDS and dye in the same time. These results suggested that the spongy cell structure of this plant has the ability to absorb large amounts of water and nutrients. Physico-chemical analysis revealed increasing amounts of sulfur, silicon, iron and calcium in the plant leafs and roots after exposure to wastewater. Proteins or amide groups in the plant might help in textile dye removal. Regarding decolorization, this plant accumulates dye in the intercellular space and still grows in this SRDW condition. Hence, it can be noted here that narrow-leaved cattails are efficient for textile dye wastewater treatment.

Textile wastewater normally has a visible color although it has low concentration. This may affect the aquatic ecosystem. Two dyestuffs, Reactive Red 141 (RR141) and Basic Red14 (BR14) were used as compound models. RR 141 is an anionic dye which has a big molecule whereas BR 14 is a cationic dye and has a small molecule. The target organisms for toxicity test were green algae (Chlorella sp.) and waterfleas (Moina macrocopa). The effect of humic acid on the toxicity of dyestuffs to test organisms was also investigated. From the observation of cell counts, Chlorophyll a and dry weight of algae in the dye solutions for 4 days, it was found that all parameters increased as times increased. This revealed that algae could utilize dyestuffs as a carbon source. However, BR14 gave higher absorbance than RR141 at the wavelength of 430 nm which competed to the Chlorophyll a for algal photosynthesis. This resulted in the 96-h EC50 of BR14 and RR141 to Chlorella sp. were 10.88 and 95.55 mg/L, respectively. As for dye toxicity to waterfleas, the 48-h LC50 of BR14 and RR141 to waterfleas were 4.91 and 18.26 mg/L, respectively. The high toxicity of BR14 to waterfleas related to the small molecule of dye could pass into the cell and was absorbed by organelles of waterfleas. Toxicity of BR14 in humic acid solution to Chlorella sp. showed less toxic than RR141 in humic acid solution. This dues to the negative charge of humic acid could bound with a positive charge of BR14, resulted in low amount of BR14 remaining in the bulk solution. The toxicity of BR14 and RR141 in humic acid solution to waterfleas was increased as humic acid increased. Hence, the proper treatment of textile wastewater to yield low concentration of dyes in the effluent before discharging to the natural water is needed.

The coagulation-flocculation method was used to treat aqueous solutions containing varying ratios of commercial disperse and reactive dyes. The effectiveness of this method was assessed using such coagulants as alum, polyaluminium chloride (PACl) and MgCl2, and an anionic coagulant aid. The jar test method was used to measure the effects of pH and coagulant type and dosage on colour removal and chemical oxygen demand (COD) reduction. The effect of coagulant aid on floc settling time was also measured. The results showed that the coagulant dosage needed to achieve optimum colour removal and COD reduction increased as the percentage of reactive dye in the mixture increased. Alum and PACl performed effectively in a lower pH range (pH 3.8 to 5.2), whereas MgCl2 performed effectively in a higher pH range (pH 10.4 to 10.9). PACl was more effective than MgCl2 and alum, achieving >99% colour removal and 96.3% COD reduction using a smaller quantity of the coagulant. The addition of coagulant aid improved floc settling time. These results show that PACl is more effective than MgCl2 and alum in removing both colour and COD in the treatment of the industrial textile wastewater samples.

This paper presents the results of the decolorization of azo dye K2G by the electrochemical process catalyzed by manganese mineral. It is proved that the MnOOH(s), main component of the manganese mineral, can catalyze the electrochemical process and enhance the decolorization efficiency. X-ray powder diffraction spectrum shows that the content of MnOOH(s) has not been changed at the end of the reaction. The effects of initial pH value, current density, concentration of electrolyte on the decolorization efficiency of the dye were investigated in detail. The initial pH effect on the decolorization efficiency of K2G dye is found not to be significant. The optimum current density is 0.26A/dm2. In addition, a proposed catalyzing mechanism of manganese mineral is discussed in this paper.

Granulated iron hydroxide (b-FeOOH) is used as a regenerable sorbent and catalyst for reactive dye removal in textile wastewater treatment. In oxidative regeneration the previously sorbed reactive dye is catalytically oxidized after activation of hydrogen peroxide to hydroxyl radicals on the FeOOH surfaces to regain adsorption capacity and reuse the sorbents. A high initial H2O2 concentration is needed for an efficient mass transfer water/solid but its consumption per oxidized dye results only in 7-25 mg mg−1. At room temperature a regeneration time of 3.5 h is necessary for decolorization and 6 h for further decomposition of the formed oxidation products to enable a reloading without any loss in adsorption capacity. Compared to Fenton's reagent, this oxidation process takes advantage of pH-independence between 4 and 8 and additionally no sludge is produced. Salts are commonly used in textile dying processes. While chloride improves the dye sorption, the presence of sulfate results in deteriorating sorption. Carbonate reacts as a scavenger of hydroxyl radicals resulting in a higher hydrogen peroxide consumption, but the efficiency of dye oxidation is only slightly affected. Nearly 20% of DOC of the sorbed dye can be attributed to short chain organic acids (formate, acetate, oxalate) indicating the far-reaching catalytic oxidation and enabling biological post-treatment.

The objective of this study was to assess the biological decolorization of two reactive anthraquinone dyes (Reactive Blue 4, RB 4; Reactive Blue 19, RB 19) under methanogenic conditions. Using a mixed, methanogenic culture, batch assays were performed to evaluate both the rate and extent of color removal as well as any potential inhibition. The effect of initial dye, biomass, and organic feed concentration, as well as the effect of repetitive dye addition on color removal kinetics and culture inhibition were assessed. Overall, a lower rate and extent of color removal was observed in RB 4-amended cultures as opposed to the RB 19-amended cultures. For an incubation time of ca. 15 days and an initial dye concentration of 2000 mg/L, the extent of color removal was 50 and 95% for RB 4 and RB 19, respectively. Inhibition of acidogenesis and to a larger degree of methanogenesis, resulting in accumulation of volatile fatty acids, was observed in both RB 4- and RB 19-amended cultures. Although the degree of inhibition varied among the two dyes tested (RB 19 was more inhibitory than RB 4), an increase of inhibition was observed with increasing initial dye concentration. At an initial dye concentration of 500 mg/L or higher, methane production was lower than 6% of that of the control culture for both RB 4 and RB 19. However, color removal occurred despite culture inhibition.

Degradation of a dye, C.I. Reactive Red 120, in dyeing wastewater by the process of UV/H2O2/US was studied with a bench-scale reactor under the continuous mode of operation. The effects of dyeing wastewater flow rate and the feeding rate of an oxidant, H2O2, on the color removal efficiency of the process were investigated. The significance of ultrasonic (US) combined with UV irradiation was also investigated and the performances of the process on color removal were evaluated. The results showed that the decoloration process followed a pseudo first-order kinetic model and the UV light is the most significant factor on dye removal. Besides, at higher flow rates, incomplete color removal was observed due to relatively insufficient irradiation time (low degradation rate). In order to achieve a higher degradation rate, the feeding rate of H2O2 should be increased.

The photocatalytic degradation of three reactive azo dyes (yellow-2, orange-16 and red-2) and one anthraquinone reactive dye (blue-19) was studied. The reactions were carried out in a reactor with recirculation using TiO2 immobilised on glass Raschig rings (system A) and compared with a batch system using the catalyst in aqueous suspension (system B). Both reaction systems were irradiated with a 125 W, l > 254 nm lamp. The suspended TiO2 system was also studied using a 125 W 360 nm lamp (system C). Kinetic studies indicated a rapid colour removal, following the order B > A > C. The same trend was observed in COD and TOC removal profiles. The energy consumption per order of magnitude of catalytic degradation of the dyes was lower in the batch reactor (system B) than in the reactor with recirculation and immobilised TiO2 (system A).

The decolourisation process of the Reactive Blue 81 was carried out in a laboratory bubble column reactor with inner diameter 110 mm and working height 550 mm, equipped with a porous glass ozone diffuser (diameter 50 mm). A model of ozone absorption with the chemical reaction in the liquid phase was employed. It was found that the decolourisation proceeds in the fast pseudo first-order regime. The average value of the enhancement factor was calculated from the experimental results and compared with those calculated according to the theory of mass transfer with a second-order chemical reaction. In order to determine the intrinsic kinetics of ozonation, a stopped-flow technique was employed. The rate constant of the dyestuff reaction with ozone was determined as equal to 4.5 × 107 mol/(dm3.s).

The photodegradation of textile azo dyes in aqueous solution containing acetone (ACE) photosensitizer was investigated at 253.7 nm. In this study, a typical azo reactive dye (C I Reactive Red 2 - RR2) is used as the probe compound. ACE is a powerful photosensitizer that possesses high triplet energy, and the presence of ACE significantly enhances the overall photodegradation reaction through simultaneous sensitization. In the UV/ACE system, at the optimum conditions, over 97% of RR2 can be successfully decomposed and decolored within 300 seconds of retention time. The photodegradation mechanisms of RR2 involve both photodechlorination and photoreduction, which follow pseudo first-order decay kinetics. The quantum yield of the photolysis system has been evaluated as a function of ACE concentration and the initial pH. RR2 contains the chlorotriazinyl group, which undergoes hydrolysis and results in the formation of hydrochloric acid, indicating that the photodechlorination process is the dominant reaction mechanism. The photo-product, H+, is likely to retard the quantum yield of dye decay, suggesting that the initial pH is a critical factor in changing the photodecolorization rates of dye. Generally, this system is more favorable at higher pH levels.

This paper examines a modified photo-Fenton (UV/Fe oxalate/H2O2 process. The degradation of oxalate in this system in the absence of Reactive Red 235 was studied using both experimentation and kinetic modelling. The degradation of Reactive Red 235 in this system was also studied. Light intensity and solution pH had large effects on the degradation of both oxalate and Reactive Red 235, with the effect of pH not due simply to speciation changes. The most important properties of the oxalate ligand in the UV/Fe oxalate/H2O2 process are that it forms Fe(III)-oxalato complexes that are easily photolysed and also is relatively unreactive with OH• radicals.

A thermophilic up-flow anaerobic sludge blanket (UASB) reactor was investigated for the decolouration of a synthetic textile wastewater. Textile wastewater is produced at high temperature and dyes are amenable to decolourisation under anaerobic conditions, however this is the first report of the use of such a thermophilic system to aid in the treatment of this wastewater. The decolouration efficiency and robustness of the thermophilic system were compared with a corresponding mesophilic anaerobic system to study the reduction of a selection of reactive dyes, the toxic effect of increasing influent dye concentration (up to 0.64 g.L-1), and the response during acclimation to high salinity conditions (up to 20 g.L-1 as sodium chloride) in three separate stages of experimentation. It was shown that compared with the mesophilic system, the thermophilic UASB treatment gave considerably higher dye decolouration with all the dyes tested, and under all operating conditions investigated. No loss in decolourisation potential was observed during an increase in influent dye concentration. However, toxicity effects were evident, noted by a decrease in COD removal and methane gas production. Acclimation to high salt concentrations also showed an adverse effect upon COD removal and gas production, however dye removal again remained virtually 100 % efficient.

This paper examines the use of three advanced oxidation processes in degrading the textile dye, Reactive Red 235. The dye was oxidised using ozonation, standard Fenton's reagent (Fe2+/H2O2) and a modified photo-Fenton's process (UV/Fe oxalate/H2O2) under a variety of conditions. The effects of initial dye concentration, initial pH and NaCl concentration were studied for each process. Each process was found to have different optimum conditions as determined by the underlying reaction mechanisms.

An Anaerobic/Aerobic SBR system was used to treat a synthetic wastewater with glucose and acetic acid (1000 mg/l COD) as carbon sources together with 20 and 100 mg/l of four different reactive dyes: disazo vinylsulphonyl, anthraquinone vinylsulphonyl, anthraquinone monochlorotriazinyle and oxazine. The decolorization efficiencies of the first three dyes at the 20 mg/l dye concentration were 63, 64 and 66%, respectively, and at the 100 mg/l dye concentration were 58, 32 and 41%, respectively. For the disazo dye, two color removal rates were evident, with the initial rate in the first two hours of the anaerobic stage higher than the latter. For the two anthraquinone dyes, only one rate of color removal was seen. For the oxazine dye, a high decolorization was observed in the reactor, but when disturbed, the color re-appeared for unexplainable reasons. The phosphorus removal efficiencies were 78, 52, 41 and 96% for the four dyes of 20 mg/l, respectively, while the corresponding numbers for the 100 mg/lcondition were 48, 48, 48 and 42%, respectively, and different types of dyes had different impacts on the phosphorus removal performance. COD and TKN removals were very high, i.e., 90–99 percent. The disazo reactive dye was decolorized by the reductive reaction, which resulted in the cleavage of the azo bond. Meanwhile, the decolorization of anthraquinone dyes is believed to be through the direct adsorption of dyes on to the floc materials.

Increasing reports of coloured effluent from waste water treatment plants receiving reactive dye waste from textile mills indicate the need to learn more about the fate of these dyes. The project concerns the development of analytical techniques for the analysis of reactive dyes in textile waste. An analytical procedure using High Performance Capillary Electrophoresis (HPCE) and High Performance Liquid Chromatography (HPLC) for the separation of a range of reactive dyes in textile waste water is described. The dyes belong to a range of bis-monochlorotriazinyl dyes used widely in the dyeing of cotton textiles.

This study examined the removal of reactive dye onto dead cells in activated sludge collected from the municipal sewage treatment plant in Suyoung, Pusan. The biosorption of reactive dye from aqueous solutions using the activated sludge was studied using a batch system with respect to the initial pH, temperature, amount of adsorbent and the pre-treatment of the adsorbent. Both the Freundlich and Langmuir isotherm models could describe the adsorption equilibrium of the reactive dye onto the activated sludge with the Langmuir isotherm showing the best agreement. First- and second-order kinetic models were used to investigate the adsorption mechanism. The adsorption capacity of Rhodamine-B(Rh-B) onto the activated sludge increased with decreasing initial pH and temperature.

Most studies on decolourization of reactive dye with Phanerochaete chrysosporium have been performed under sterile conditions. In this paper, Phanerochaete chrysosporium, suspended in liquid medium, immobilized on nylon nets, and immobilized on polyurethane foams were studied to decolorize a textile-reactive dye in agitated liquid incubation under non-sterile conditions. The results showed that the decolourization against reactive brilliant red K-2BP by mycelia pellets in suspended cultures, the fungi immobilized on nylon nets and immobilized on polyurethane foams were 0%, 52% and 95%, respectively. The suspended incubation system and the system with nylon nets were contaminated with yeasts, which deteriorated the decolourization effects. The three-dimensional reticular structure of polyurethane foam was benefit to Phanerochaete chrysosporium growth in spreading mycelia taking nutrients and oxygen effectively. The foam could quickly absorb liquid medium into its holes, leaving much less nutrients to support the growth of single cell micro-organisms such as yeast in liquid. The micro-environment existed in polyurethane foam was close to the wild growth conditions of white rot fungus in nature. In conclusion, immobilized culture with polyurethane foam carriers is advantaged to reduce the colonization of other micro-organisms, and makes Phanerochaete chrysosporium possess higher decolorizing ability under non-sterile conditions.

Color removal is an important task in textile wastewater treatment. Cucurbituril, a cyclic hexamer with internal hydrophobic cavity, has been studied as sorbent for removal of reactive dyes. Loadings as high as 1 g/g and more were obtained, making the method seem interesting for technical application. A minimum of 1 to 5 mmol/L calcium is needed for efficient sorption. However, salt concentrations of 100 mmol/L and above decrease sorption efficiency due to increased solubility of cucurbituril in salt solutions. The pH has little influence between 4 and 7.5, higher pH-values can result in decreased sorption. The salt influences are similar for most of the tested dyes whereas the pH-effect differs from dye to dye.

The objective of this research was to generate technical background for the development of a fixed-film anaerobic reactor to renovate reactive textile dyebaths and reuse the high salt-containing mixture in the dyeing process. Six commercial reactive azo dyes (Black-5; Red-2 and 120; Yellow-3, 15 and 17) were chosen for this study. Using an anaerobic, methanogenic culture enriched from municipal sewage sludge, batch assays were performed to evaluate potential toxicity of the selected dyes to the anaerobic microorganisms as well as to determine the anaerobic biodegradability of these dyes. Total gas and methane production were monitored. No significant toxic effects were observed at 300 mg/L concentration for all dyes tested. At the end of three consecutive feeding cycles all dyes exhibited overall color removals in the range of 77.8 and 97.1%. An assay intended to determine the toxic limit and kinetics of color removal of Red-2 revealed that up to 300 mg/L, this dye was not toxic and contributed to increased total gas and methane production over that of a control. However, higher concentrations of Red-2 (500, 1000 and 2000 mg/L) depressed gas production despite continued decolorization. These results suggest that color removal under the low redox conditions maintained by the methanogenic culture occurs irrespective of the culture activity level.