Gutierrez-Bouzán, C.; Vilaseca, M.; Escalas-Cañellas, A.; Buscio, V.; García, M.G.; Gelabert, I.; Crespi, M. International Conference on Desalination Using Membrane Technology Presentation's date: 2015-07-28 Presentation of work at congresses
La presente Tesis Doctoral se basa en el estudio de la eliminación del color de efluentes textiles con colorantes reactivos. Los colorantes reactivos son ampliamente utilizados en la tintura de algodón y otras fibras celulósicas. Sin embargo presentan un grado de agotamiento bajo y son poco biodegradables, por lo que requieren de un tratamiento específico previo a su descarga a la depuradora biológica. Buena parte de los nuevos métodos de eliminación del color pueden ser clasificados en tres grandes grupos: los métodos de oxidación avanzada (MOA), la coagulación con productos naturales y la selección de microorganismos específicos. En esta Tesis Doctoral se ha seleccionado una técnica concreta de cada uno de estos tres grupos. Para ello se han realizado diferentes estudios mediante tratamiento de oxidación electroquímica, coagulación con un subproducto natural y tratamiento enzimático.La oxidación electroquímica se ha utilizado en efluentes sintéticos con colorantes reactivos y una vez tratados se ha estudiado su comportamiento antes y después de mezclarse con el resto de aguas residuales textiles, para comprobar si podían repercutir negativamente frente a un tratamiento posterior de depuración biológica con fangos activados. Se ha estudiado la biodegradabilidad de estos efluentes decolorados utilizando la técnica de respirometría electrolítica para determinar si existe algún problema de inhibición o toxicidad. Los resultados obtenidos demuestran que el tratamiento electroquímico no presenta problemas de inhibición frente a los microorganismos, si previamente los efluentes han sido aireados durante 24 horas. Este proceso asegura que el agua residual tratada seguidamente en una planta de depuración biológica no causará ningún problema sobre los fangos. Se ha comprobado la influencia de estos productos oxidantes generados durante el tratamiento electroquímico en dos plantas piloto de depuración por fangos activados. Se concluye que el agua residual con colorantes reactivos puede ser tratada mediante un proceso electroquímico para eliminar el color y el efluente resultante puede ser tratado directamente por fangos activados, sin previa eliminación del cloro residual que pueda haberse formado durante la electroquímica. Se ha estudiado un segundo método de decoloración, utilizando un coagulante natural extraído de las semillas del árbol Moringa oleifera, para decolorar aguas residuales textiles, en substitución de métodos de mayor coste económico que requieren el uso de reactivos químicos. Se compararon los resultados con los obtenidos usando un coagulante químico y polielectrolito, y se realizaron pruebas de tintura con el agua decolorada comparándola frente a referencias teñidas con agua limpia. Los buenos resultados obtenidos permiten pensar en la utilización de recursos naturales en países con menor poder económico para que puedan llevar a cabo tecnologías de depuración.Se han tratado dos colorantes con diferentes grupos reactivos (vinilsulfona y clorotriazina) con el enzima Laccase para estudiar su aplicabilidad en efluentes textiles para la decoloración, evaluando la influencia de parámetros, tales como la adición de mediador, la concentración de sales y la hidrólisis del colorante. De los resultados obtenidos puede concluirse que no es necesaria la adición de mediador o co-sustrato, que la presencia de sales en el efluente de tintura (NaCl) no inhibe la acción del enzima y que la hidrólisis de los colorantes estudiados no afecta la acción del enzima, obteniéndose decoloraciones del 70-90%, dependiendo del colorante.Finalmente se realiza un estudio comparativo de los resultados obtenidos de los tres métodos seleccionados para la eliminación del color, llegando a la conclusión de que el tratamiento electroquímico es el más eficiente, con eliminaciones de color del 95-100%, frente al 91-94% en el caso de utilizar coagulante natural extraído de Moringa Oleífera y 70-90% de decoloración con el tratamiento enzimático.
After the dyeing process, part of the dyes used to color textile materials are not fixed into the substrate and are discharged into wastewater as residual dyes. In this study, a heterogeneous photocatalytic process combined with microfiltration has been investigated for the removal of C.I. Disperse Red 73 from synthetic textile effluents. The titanium dioxide (TiO2) Aeroxide P25 was selected as photocatalyst. The photocatalytic treatment achieved between 60% and 90% of dye degradation and up to 98% chemical oxygen demand (COD) removal. The influence of different parameters on photocatalytic degradation was studied: pH, initial photocatalyst loading, and dye concentration. The best conditions for dye degradation were pH 4, an initial dye concentration of 50 mgL-1, and a TiO2 loading of 2 gL(-1). The photocatalytic membrane treatment provided a high quality permeate, which can be reused
This work is focused on the valorisation of an agricultural waste as natural coagulant to treat wastewater from the textile industry. In this paper, the waste of Moringaoleifera oil extraction is used as coagulant to remove five reactive dyes from synthetic textile effluents. Moringaoleifera shows better results for dye removal than conventional treatment of coagulation-flocculation with FeCl3 and polyelectrolyte. Treated water can be reused in new dyeing processes of cotton fabrics with high quality results
The reactive dye Cibacron Yellow S-3R was selected for the membrane filtration study, to evaluate the feasibility of nanofiltration membranes to treat textile wastewater. Synthetic effluents were treated by means of two nanofiltration membranes, Hydracore10 and Hydracore50, manufactured by Hydranautics. The membranes provided a high quality permeate, able to be reused in new dyeings. Up to 98% of dye removal was achieved. The influence of salt concentration and pH on membrane treatment was studied. The best conditions for dye removal were pH 3 and 60g·L-1 of NaCl. After the membrane filtration, the treated permeates were reused in new dyeing process. 100% of the obtained permeate was reused to perform different dyeings with four reactive dyes. Finally fabrics dyed with the reused water were evaluated respect to references carried out with softened tap water. The colour differences obtained were lower than 0.5, being 1 the maximum value generally accepted by the industry
The generation of high-coloured wastewater is one of the main environmental problems of the textile industry. Reactive dyes are widely used in the dyeing of cellulosic fibres. However, they have low exhaustion degree (70–90%). The degradation of residual dyes by aerobic biological treatment is very poor, being necessary the application of specific treatments. In this work, three different methods for the removal of reactive dyes were compared: electrochemical treatment, coagulation with Moringa oleifera waste and enzymatic treatment with laccase. Two azo bifunctional dyes with different reactive groups were selected: C.I. Reactive Black 5 (vinyl sulphone) and C.I. Reactive Red 231 (chlorotriazine). The influence of pH (5 and 9) and dye hydrolysis on the decolourisation yield was studied. The electrochemical treatment was the most efficient, with 95–100% colour removal yield. The coagulation with M. oleifera waste also achieved high colour removal efficiency (91–94%). Both methods showed an independent behaviour with respect to pH or dye hydrolysis. The enzymatic treatment should be performed at pH 5. This method was suitable to remove the chlorotriazine dye (92–93% efficiency), whereas the vinyl sulphone one showed a marked dependence on dye hydrolysis: moderately efficient for the hydrolysed dye and highly efficient without hydrolysis. The activity of laccase was not modified by the usual salinity of the reactive dyeing effluent (20 g/L NaCl). Nevertheless, the effluent salinity enhanced the electrochemical and M. oleifera treatment yield.
La industria textil por vía húmeda genera grandes cantidades de agua residual en sus procesos productivos, principalmente en las operaciones de ennoblecimiento (preparación, tintura y acabado). El sector textil precisa de tratamientos primarios, secundarios y tratamientos avanzados para eliminar la materia orgánica, sólidos no eliminados anteriormente y el color. En especial, la eliminación de los colorantes en este tipo de efluentes representa un reto tecnológico en los procesos de tratamiento de aguas residuales. Se estima que mundialmente se descargan 280.000 toneladas de colorantes en los efluentes textiles. La compleja mezcla de colorantes y compuestos que se emplean para el acabado, hace que las aguas residuales de la industria textil sean difíciles de tratar sólo por medio de sistemas biológicos o fisicoquímicos convencionales, por lo que se requieren estudios de tecnologías innovadoras para completar la depuración.
The wet textile industry generates large amounts of waste water in their production processes, especially in finishing operations (preparation, dyeing and finishing). Conventional technologies for colour removal are being implemented on an industrial scale, offering good levels of discoloration, but all have in common, their high cost. Recently, many research groups worldwide are working on a laboratory scale and pilot plant in what may be termed as “New technologies for colour removal”, although some of them are based on traditional methods
The textile industry is one of the largest consumers of water in the world and its wastewater is a serious problem when it is discharged without the proper treatment. In this work, wastewater generated by textile industry was treated coupling a homogenization–decantation treatment with polyvinylidene difluoride (PVDF) ultrafiltration membranes. Initially, the wastewater was aerated in a homogenization–decantation tank where 17% colour and 10% chemical oxygen demand (COD) were removed. The aerated effluent was treated with an ultrafiltration membrane in order to reuse the permeate in new dyeing processes. Firstly, the ultrafiltration treatment was performed in a laboratory plant. The permeate analysis showed 20% colour removal and 60% COD decrease. On the basis of these results, a semi-industrial system was built. With this plant, the permeate characterization showed similar results. The system was found to be scalable and suitable for the treatment of this kind of effluents. Finally, new dyeings were performed with both permeates. Monochromatic dyeings were carried out with 100% permeate whereas 50% permeate was reused for dyeings with a mixture of three dyes. The colour differences were found to be lower than 1.5, which was the acceptance value established
Indigo is one of the most consumed dyes in the textile sector, as it is widely used for the dyeing of denim clothes. About 15% of indigo used in the dyeing process is discharged to the wastewater treatment plants or sometimes into rivers, in countries where regulations are not strictly applied. In this work, real effluents that contained indigo dye were treated by means of 4 different ultrafiltration membranes. The feasibility to recover the concentrated dye with lab and semi-industrial pilots was also investigated. The studied membranes achieved up to 99% colour removal and 80% chemical oxygen demand (COD) decrease. Finally, the concentrates containing 20 g L_1 of indigo dye were reused in new dyeing processes. Colour differences (DECMC) and rubbing and washing fastnesses were evaluated. Fabrics dyed with the recovered indigo concentrates exhibited similar characteristics than the ones obtained with the commercial dye
In this work, the feasibility of polyvinylidene difluoride ultrafiltration membranes to treat textile wastewater was studied. The C.I. Disperse Orange 30 and C.I. Disperse Rubine 73 were selected as pollutant for the membrane filtration study. The results showed about 90 and 96% of COD decrease and dye removal, respectively. In addition, very low fouling was observed which demonstrated the feasibility of applying this type of membranes to treat textile wastewater. Finally, after the membrane treatment, 100% of the obtained permeate was reused. Fabrics dyed with the reused water were evaluated with respect to references carried out with softened tap water. No significant colour differences were observed between reference fabrics and the fabrics dyed with the permeate
Idel, R.; Valiente, M.; Gutierrez-Bouzán, C.; Vilaseca, M.; Yaacoubi, A.; Tanouti, B.; López-Mesas, M. Journal of Analytical Methods in Chemistry Vol. 2015, p. 7- DOI: 10.1155/2015/945489 Date of publication: 2015-01-01 Journal article
Fenton and Fenton-like processes, both in homogeneous and heterogeneous phases, have been applied to an aqueous solution containing the dye AR 14 in order to study the mineralization and toxicity of the solutions generated after color elimination. The mineralization of AR 14 occurred slower than the decolorization. The Microtox analysis of the treated solutions showed low toxicity intrinsic to the chemicals used in the process rather than the degradation products obtained after the treatment of the dye solution. The dye degradation for the Fenton oxidation process was initially faster than for the Fenton-like process but after a short time, the four processes showed similar degradation yields. All processes have shown good results being the heterogeneous process the most convenient since the pH adjustment is not necessary, the catalyst is recovered and reused and the generation of contaminated sludge is avoided
The indirect electro-oxidation of dyes results in a rapid break of the dye molecules. The influence of the dye chromophore in this process has already been demonstrated. In this work, an electrochemical treatment in a batch cell with Ti/Pt anode is applied to degrade two reactive dyes (Color Index Reactive Oranges 4 and 13) in the presence of chloride ions, usually used as dyeing electrolyte. For the two dyes, kinetic constants were modeled. A clear influence of the reactive group in the response surfaces was found despite the unique difference between both dyes being only one substituent (OH or NH2). Models are strongly dependent on pH and conductivity. Also, an important interaction of both factors was evidenced, which can be attributed to different mechanisms of oxidizing species generation.
In this work, the efficiency of a photo-electrochemical method to remove color in textile dyeing effluents is discussed. The decolorization of a synthetic effluent containing a bi-functional reactive dye was carried out by applying an electrochemical treatment at different intensities (2 A, 5 A and 10 A), followed by ultraviolet irradiation. The combination of both treatments was optimized. The final percentage of effluent decolorization, the reduction of halogenated organic volatile compound and the total organic carbon removal were the determinant factors in the selection of the best treatment conditions. The optimized method was applied to the treatment of nine simulated dyeing effluents prepared with different reactive dyes in order to compare the behavior of mono, bi, and tri-reactive dyes. Finally, the nine treated effluents were reused in new dyeing processes and the color differences (DECMC ((2: 1))) with respect to a reference were evaluated. The influence of the effluent organic matter removal on the color differences was also studied. The reuse of the treated effluents provides satisfactory dyeing results, and an important reduction in water consumption and salt discharge is achieved.