Single and coupled electrochemical treatment of food azo dyes

• Autores: Abdoulaye Thiam
• Directores de la Tesis: Ignacio Sirés Sadornil (dir. tes.), Enrique Brillas Coso (dir. tes.)
• Lectura: En la Universitat de Barcelona ( España ) en 2015
• Idioma: inglés
• Tribunal Calificador de la Tesis: Mehmet Ali Oturan (presid.), Santiago Esplugas Vidal (secret.), Manuel Andrés Rodrigo Rodrigo (voc.)
• Materias:
  • Ciencias tecnológicas
    • Ingeniería y tecnología del medio ambiente
      • Tecnología de aguas residuales
    • Tecnología de los alimentos
      • Colorantes
      • Aditivos alimentarios
• Enlaces
  • Tesis en acceso abierto en:  TDX  Dipòsit Digital de la UB 
• Resumen

  • The present Doctoral Thesis constitutes a comprehensive study of the removal of food azo dyes in aqueous matrices by single and coupled electrochemical separation and destruction technologies. First, the work was focused on the selection of the most appropriate technology and the progressive optimization of operation conditions for the effective and efficient removal of each dye. The degradation of Ponceau 4R, Carmoisine, Allura Red AC and their mixtures was studied by different electrochemical advanced oxidation processes (EAOPs) such as electro-oxidation (EO), electro-Fenton (EF) and photoelectro-Fenton (PEF) using BDD or Pt anode and stainless steel (SS) or air-diffusion cathode (ADE). Different aspects including decolorization and mineralization of solutions were studied in details. The results revealed that PEF is the most efficient and promising process to degrade food azo dyes at lab-scale. Complete decolorization and almost total mineralization with 96-98% TOC abatement was attained, with electrolysis time depending on the initial dye content and applied current. The kinetic decay of dye always obeyed a pseudo-first-order reaction. In view of the promising results obtained by PEF, the study of the degradation of dyes was scaled-up to a 2.5 L pre-pilot plant, which allowed demonstrating the viability of the solar photoelectro-Fenton to mineralize the dyes within a short time. Analyses of dyes and their mixtures treated by EAOPs allowed the identification of some intermediates and end products, and plausible reaction sequences were proposed to explain the transformation of each compound. The mineralization of dyes led to the conversion of the heteroatoms (N and S) present in the molecules to inorganic ions such as ammonium, nitrate and sulfate. The degradation of Tartazine solution was studied by electrocoagulation (EC), which is a process of high industrial interest, several EAOPs and the sequential combination of EC/EAOPs. The findings demonstrated that the sequential EC (Fe/SS) / PEF (BDD/ADE) treatment favors both, the fast color removal and the destruction of the remaining persistent organic matter in the pre-treated solution by PEF. The complete decolorization and mineralization of solutions were thus achieved within relatively short time periods thanks to coagulation by Fe(OH)n and oxidation by electrogenerated hydroxyl radical and active chlorine species.