Decolourization of textile wastewater by manganese-aluminium metallic particles
- Autores: Mitra Abolighasemabadi
- Directores de la Tesis: Eloi Pineda Soler (dir. tes.), Joan Josep Suñol Martínez (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Mohamed Khitoun (presid.), Pere Bruna Escuer (secret.), Núria Llorca i Isern (voc.)
- Programa de doctorado: Programa de Doctorado en Física Computacional y Aplicada por la Universidad Politécnica de Catalunya
- Materias:
- Texto completo no disponible (Saber más ...)
- Resumen
Waste treatment is an important aspect of an industry. Organic dyes are used in many fields, such as textile, paper or food. Residual dye compounds from these industries are one of the most critical sources of environmental pollution due to their visibility and harmful effects on ecosystems as well as potential carcinogenic properties. Azo compounds are the most common dyes used in textile and leather treatments. An important step during the treatment of water polluted by these compounds is the decomposition of the -N=N- bonds, producing the decolorization of the water. Modern dyes are often intended to resist the long-term exposure to sunlight, water, and other conditions, thus making them more resistant to decomposition. Different physical, chemical, and biological approaches are employed for the removal of azo dyes from aqueous solutions. Among these approaches, the reduction with zero-valent metals (ZVM), like iron, magnesium or aluminum has been studied as a promising route because of its merits of low cost and rapid degradation efficiency. Recently, it has been discovered that the use of metallic particles in a metastable state (amorphous or nanocrystalline) multiplies significantly the efficiency of the decolorization water treatment step. Indeed, it is known that the metastable structures generated during rapid solidification or mechanical alloying tend to increase the chemical activity of the alloys.
In this thesis, we study the use of Mn-Al metallic particles to provide a rapid degradation of these dye compounds. We firstly studied the use of a ball-milling process, under an argon gas atmosphere, to produce the Mn-Al powder. Different types of powders were obtained using different milling protocols and compositions, and they were characterized by X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray microanalysis system. Secondly, the decolorization process of aqueous solutions colored with various types of dyes was monitored by ultraviolet-visible spectrophotometry. Various parameters such as pH, initial dye concentration, dosage, and temperature were studied in terms of their effect on the reaction progress. The changes in the solvent water produced by the metallic particles reaction were also analyzed with high-performance liquid chromatography, Mass Spectrometry and Atomic Absorption flame spectrometry.
The efficacy of the Mn-Al metallic particles in the degradation of Orange II dye, using four different alloys with different proportions of Mn and Al, determined that Mn70Al30 was the composition that showed the highest efficacy and reproducibility. The analysis of the treated water identified several intermediary components and two amines, as well as the liberation of Mn ions. We also analyzed the kinetics of degradation of other colorants such as Acid Black 58 and Orange G dyes. The results showed the efficacy of the intervention on Acid Black 58 dye, but only partial decolorization was observed in the solution with Orange G. The chance to reuse the particles in successive cycles of decolorization was also studied, as it has a big interest from both environmental and economic point of views. The results quantified the loss of efficiency after each cycle of decolorization, the best results obtained when no additional chemical reagent was added during the washing method. This result is important for designing real application methodologies using this type of particles. Lastly, this work analyses the efficiency of Mn-Al metallic powders for degrading azo dyes and compares the results with the ones obtained in a pilot scale trickling filter. The bacterial microorganisms selected in the trickling filter presented the ability to remove dye under aerobic conditions at pH values between 6 and 7.5 but with low efficiency. Lower rates of dye removal were observed with the bacterial approach as compared to the Mn-Al metallic powder approach.
