Reactive dyestuffs are used more than other suitable dyes in dyeing and printing of cotton fabrics with relatively good washing fastness. Time, temperature and alkali concentration constitute the most important parameters affecting the fixation process, in other words, the colour yield. Reactive dyes are fixed on cotton through a covalent link formed between the reactive group of the dyestuff and hydroxyl groups of cellulose. It is the aim of this research to present a model for colour yield as a function of these three parameters. For this purpose, two phase wet fixation dyeing trials were carried out for 9 reactive dyestuffs belonging to vinyl sulphone, monocholorotriazine, dicholorotriazine and tricholoropyrimidine groups. The samples were padded with dyestuff solution, dried and fixed in fixation baths with conditions according to a matrix of time, temperature and alkali concentration values. After measuring the reflectance values of these samples, their K/S and FK values were calculated. These values with their related parameters were used to obtain models through regression analysis. From the first set of obtained models for the nine dyestuffs, only one met the necessary conditions. Modification was carried out for the other eight and at the end five other models could be accepted as a representation of the colour yield of the dyes as a function of time, temperature and alkali concentration.

Electrocoagulation (EC) is one of the most effective electrochemical wastewater treatment techniques for removing color and organic pollutants from wastewater and reducing sludge formation. In this study, the removal of Remazol Ultra Red RGB (reactive red 239) dye, which is used for commercial purposes, by the EC process was investigated. For this purpose, an electrochemical reactor was designed using monopolar parallel connected aluminum and iron electrodes. The effect of operational parameters such as the initial pH of the solution, current density, and electrolysis time were investigated to achieve higher color, Chemical Oxygen Demand (COD), and turbidity removal efficiency. The optimum conditions of the EC process were determined by evaluating the data obtained as a result of the experimental studies. It was observed that the removal efficiency increased with the increase of the electrolysis time and stabilized after 20 min. The optimum experiment conditions for the aluminum electrode were pH:3, current density of 50 A/m2, and conductivity of 250 µS/cm, for the iron electrode was pH: 5, current density of 75 A/m2, and conductivity of 500 µS/cm was found as. In all studies, the mixing speed was chosen as 250 rpm. As a result of this study, 95.49-99.94% color, 89.34-66.83% COD, and 92.18%-83.15% turbidity removal efficiencies were obtained with aluminum and iron electrodes under optimal conditions. Under optimum conditions, electrical energy consumption was calculated as 11.48 for Al, 6.60 kWh/m3 for Fe, and the energy consumption 0.56, 0.46 kg/m3. As a result of the experimental studies, high removal efficiencies were obtained in color, COD, and turbidity removal with the EC process. As a result, it was concluded that EC treatment is an effective method for the purification of synthetic textile dyestuffs.

In recent years, the textile industry has produced more than 50 % of the colored wastewater in the world. Clean water is essential in the lives of humans, aquatic organisms, and agricultural products. Due to their toxicity, dyestuff in water causes adverse quality, endangers their health, and causes environmental changes. There are different methods for wastewater treatment, which, based on the research, shows that today's surface absorption method is mainly used for wastewater treatment due to its cheapness, simplicity, and cost-effectiveness. In this article, the removal of dyestuff from wastewater was investigated using different nanocomposites, and the effect of adsorption with nanocomposites was investigated based on factors affecting adsorption, including contact time, initial concentration, the effect of temperature, and pH of the solution. Adsorbents significantly impact removing dyestuff and can perform wastewater treatment with good quality. This research used activated carbon nanocomposites, carbon nanotubes, silver nanoparticles, zinc ferrite, ZnO, TiO2, Fe3O4 and zero-valent iron nanoparticles for wastewater decolorization. In this article, the results show that different nanocomposite adsorbents are promising. They are a promising future for the treatment of colored wastewater.

Background & Objective: Reactive dyestuff causes difficulties including toxicity, carcinogenesis, and mutagenesis in the environment. Traditional physical and chemical treatment methods such as coagulation, flocculation, and adsorption can’t destroy these compounds and cause secondary environmental pollution. Advanced oxidation processes like Fenton oxidation are one of the most efficient processes for dyestuff pollutants removal from aqueous solution. In this study, the ability of Remazol Black- B (RB-B) removal from aqueous medium by Fenton oxidation process was investigated.Methods: This experimental-intervention study was carried out in laboratory scale. In order to determine the effect of Fenton oxidation on decolorization of RB-B, optimum levels of variables such as pH, FeSO4 and H2O2 and reaction time was measured in a 1 L batch reactor.Results: The results of the experiments showed that for 100 mg/L of dyestuff the respective optimum concentrations of FeSO4 and H2O2 were10 and50 mg/L. For 200 and 500 mg/L of dyestuff they were50 and 300 mg/L, respectively. Under the optimal condition, pH=3 and 15 min of reaction time, up to 95% decolorization efficiency was achieved for all three concentrations of dyestuff.Conclusion: Based on the results of this study, the Fenton process is an effective method for the treatment of different concentrations of RB-B dyestuff in wastewater. The selection of proper concentration of Fenton is important to reduce treatment costs, environmental problems, and sludge produced.

Backgrounds and Objectives: Reactive dyestuff has potential of toxicity, carcinogenesis and mutagenesis for mammals and aquatic organisms. The current physical and chemical methods such as adsorption, coagulation, precipitation, filtration and … can been used for removing of dyestuff.Biological treatment which is effective and economic for decontamination of dyestuff wastewaters was preferred because of limitation and difficulty of physicochemical methods. In order to investigate the trend of pollution reduction of color compounds, ability of Remazol Black-B dyestuff removal from aqueous medium by bacterial consortium under anoxic conditions was studied.Materials and Methods: The mix culture of bacteria from textile industries activated sludge was enriched in luria broth medium containing RB-B dyestuff as a carbon source. Then biodegradation was assessed in 4 batch reactors. Microbial population of bacterial and decolorization quantities of samples were detected by MPN and UV-Vis spectrophotometer.Results: Decolorization efficiency by the bacterial consortium was obtained more than 99% for 50 and 250 mg/L concentrations in 72 and 144 h (3 and 6 days) respectively, while for the initial concentration of 500 mg/L was 98.1 in 240 h (10 days) of biodegradation period. Dyestuff reduction rate after completed removal was about 0.69, 1.74, 2 mg/L/h for initial concentration of 50, 250, 500 mg/L respectively.Conclusion: Results showed that Alcaligenes denitrificans and Alcaligenes xylosoxidans bacteria which were isolated from activated sludge have good potential of RB-B dyestuff removal and this removal is depending on primary concentration of dye. Removal efficiency increased as primary concentration went up.