Carbon-Based Membrane Bioreactors for the Anaerobic Decolorization of Dyes
- Autores: Mohammad Shaiful Alam Amin
- Directores de la Tesis: Josep Font Capafons (dir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2022
- Idioma: inglés
- Tribunal Calificador de la Tesis: Azael Fabregat Llangostera (presid.), Albert Guisasola Canudas (secret.), Natalia Soledad Inchaurrondo (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencia, Materiales e Ingeniería Química por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
- español
La industria textil es el segundo sector más contaminante del agua, ya que produce una quinta parte de las aguas residuales del mundo. Estos efluentes pueden ser perjudicial tanto para la vida acuática como para el ecosistema acuático en su conjunto. Las membranas de carbono acopladas con biodegradación anaerobia han demostrado ser una técnica única de tratamiento de aguas residuales para los efluentes con colorantes. Este biorreactor compacto actua simultáneamente como soporte de la biopelícula, mediador redox y nanofiltro, aumentando así la eficiencia en la decoloración del tinte. En esta tesis, se sintetizaron varias membranas planas y tubulares basadas en carbono mediante soluciones de poliimida Matrimid 5218 y óxido de grafeno sobre un elemento cerámico plano de UF. Posteriormente, se exploró la prestación de los biorreactores de membrana de carbono plana y tubular y de los biorreactores de membrana de óxido de grafeno para decolorar soluciones azoicas y otros colorantes estructuralmente diferentes. Independientemente de la configuración del biorreactor de membrana (plano y tubular), la concentración inicial de alimentación y el flujo de permeado, los resultados revelaron que la superficie conductora de la membrana de óxido de grafeno dio lugar a una mejor eliminación de color que la membrana de polímero carbonizado. Además, se analizó la biopelícula formada sobre la membrana durante la decoloración anaerobia de los colorantes azoicos y se identificaron los microorganismos predominantes. Estos resultados ponen de manifiesto que los fenómenos combinados en los biorreactores de carbono dan lugar a un método de decoloración de colorantes eficiente, rentable y ecológico.
- català
La indústria tèxtil és la segona més contaminant d'aigua, produint una cinquena part de les aigües residuals a tot el món. Aquests efluents poden ser perjudicials tant per a la vida aquàtica com per a l'ecosistema aquàtic en conjunt. Les membranes amb base de carboni acoblades amb biodegradació anaeròia s'han demostrat com una tècnica única de tractament d'aigües residuals per a efluents amb colorants. Aquest bioreactor compacte actua com a suport del biofilm, mediador redox i nanofiltre simultàniament, augmentant així l'eficiència de la decoloració. En aquesta tesi, es van sintetitzar diverses membranes planes i tubulars amb base de carboni a partir de solucions de poliimida i òxid de grafè sobre un element ceràmic pla d’UF. Després, explora les prestacions dels bioreactors de membrana de carboni i d'òxid de grafè per eliminar diversos colorants azoics i no azoics. Independentment de la configuració del bioreactor de membrana (plana i tubular), la concentració d'alimentació inicial i el flux de permeat, els resultats revelen que la superfície conductora de la membrana d'òxid de grafè dona lloc a una millor eliminació de color que la membrana carbonitzada. A més, es va analitzar el biofilm que format sobre la membrana i es van identificar els microorganismes predominants. Aquests resultats fan evident que els fenòmens combinats als bioreactors basats en carboni donen lloc a un mètode de decoloració de colorants eficient, rendible i ecològic.
- English
The textile dyeing sector is the world's second most polluting industry, responsible for 20% of global water pollution. This polluted water not only ruins the environment but also harms people because it enters the food chain in a variety of ways, including drinking water. Many industrially developed or developing countries face many problems in treating textile industrial effluent waste materials that mainly contain azo dye waste, which is typically xenobiotic and recalcitrant in nature. Dye-containing wastewater mixed with freshwater reduces the amount of dissolved oxygen in the water and causes catastrophic damage to aquatic animals and the environment. The presence of these compounds in the effluents must reduce to use or reuse water. For this reason, environmentally friendly wastewater treatment is now a top concern of nations around the world.
The presence of a modest quantity of such recalcitrants in massive volumes of wastewater failed to treat and remove them efficiently by conventional treatment processes, including physical, chemical, physicochemical, and biological methods. Researchers worldwide have been working on different techniques such as incineration, chemical precipitation, ionic exchange, catalytic and no catalytic oxidation, peroxidation, anaerobic treatments, membrane filtration, anaerobic biological activated carbon for the treatment of textile wastewater.
The significant factors for dye removal from textile wastewater are operating cost, installation cost, retention time, secondary sludge, or toxic byproduct. Toxic byproducts or sludges are highly environmental pollutants that need further treatment. Considering all of these, membrane separation processes and biological treatment are the most cost-effective eco-friendly methods. Our previous research demonstrated the biological activated carbon and carbon-based membrane's beneficial effect on anaerobic dye degradation. UF ceramic composite support with the pore sizes equivalent to 50 kg‧mol-1 molecular weight cut-off (MWCO), comprised of ZrO2 and TiO2, was chosen because of the superb physical, chemical, and thermal stability that provides longevity and reusability of the membrane. Thus, an anaerobic compact membrane bioreactor greatly enhanced the mineralization of this compound. However, this new system had some imperfections, such as decolorization efficiency with higher flux and dye concentration and weak electron shuttle mechanism between membrane and microbes.
Therefore, this thesis exploits a novel system that integrates the electron carrier and separation element into a single unit. The idea is to combine the membrane separation and bio-reduction processes by inoculating or growing anaerobic biofilms on top of ceramic-supported carbon membranes. The carbon-based membranes were prepared from several carbonaceous materials, for example, Matrimid 5218 polyimide and exfoliated graphene oxide solution. The flat and tubular ceramic-supported carbon-based membranes were fabricated using both membrane precursors. Spin coating and up-flow method were employed to deposit the polyimide layer over and inside the ceramic support, respectively, to synthesize flat and tubular membranes. The coated membranes were then carbonized at high temperatures in an inert atmosphere to achieve their final shape. On the contrary, both the ceramic-supported flat and tubular graphene oxide membrane utilized the vacuum-assisted filtration of exfoliated graphene oxide solution to achieve the carbon-based graphene oxide membrane.
Due to the feasibility of using carbonaceous material with anaerobic microorganisms, an optimization study was conducted on decolorizing dye molecules with structurally different dye molecules. The influence of amounts and membrane precursors (Matrimid 5218 and Graphene Oxide) over the carbon-based membrane was investigated based on two independent factors: feed concentration and permeate flux. As a result of this study, both ceramic-supported nano-sized carbon-based membranes were able to decolorize mono azo Acid Orange 7 (AO7), diazo Reactive Black 5 (RB5), and triazo Direct Blue 71 (BD71). The ceramic-supported graphene oxide membrane (CSGOM) facilitates a better electron transport mechanism than the ceramic-supported matrimid membrane (CSCM) that enhances the color removal rate in this dead-end anaerobic membrane bioreactors. That’s why at a higher feed concentration (100 mg‧mL-1) and permeate flux (0.10 L‧m-2‧h-1), CSGOM shows three times higher decolorization rate than CSCM.
Since the single compact carbon-based membrane bioreactor was demonstrated to be an effective technology for accelerated decolorization of azo dyes, similar reactors worked well with other dyes instead of the individual azo dyes. In this experiment, the color removal properties of an azo dye mixture (ADM) (equimolar ratio of AO7, RB5, and DB71), phenothiazine Methylene Blue (MB), and sticky fluorescent Rhodamine B (RhB) dye solution were studied. CSGOM performs optimally in each scenario, regardless of the operating conditions or parameters. This concept is later applied to the tubular membrane as this module has high crossflow and pressure drop as well as a low tendency to fouling and easy cleaning. As in prior trials, the tubular ceramic-supported graphene oxide membrane (TCSGOM) decolorized azo dye more efficiently than the ceramic-supported carbon-based membrane (TCSC M).
Finally, the thesis studies the kinetic model of the biodecolorization process of the CSGOM bioreactor in order to determine the ideal operating parameters for maximum dye removal. More precisely, the model was used to study the effect of critical operating factors on the dye removal mechanism, including dye structures, initial dye concentration, and permeate flux. This study also scrutinized the hydrolysis behavior of complex dye molecules and the effect of biofilm support materials. The results suggest that the external carbon sources and hydraulic retention time be optimized for the maximum biodecolorization rate.
- español
