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| Author(s): |
Guilherme Garcia Bessegato
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Araraquara. 2017-03-06. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara |
| Defense date: | 2017-02-17 |
| Advisor: | Maria Valnice Boldrin Zanoni |
| Abstract | |
Intense effort has been devoted to the treatment of effluents and surface water contaminated by dyes, and one of the alternatives of interest is the photoelectrocatalysis (PEC), based on the use of processes capable of generating •OH radicals, with great oxidizing potential. The present work investigates the preparation, characterization and application of TiO2 nanotubes (TiO2NTs), doped with boron and modified with Sb2S3, as anodes in the photoelectrocatalytic treatment of hair dyes of the temporary type. Such modifications could circumvent limitations of conventional TiO2 oxide films. The TiO2 nanotubes electrodes were prepared by electrochemical anodization of metallic titanium plates in fluoride-containing electrolytes. The deposition of nanoparticles of Sb2S3 was carried out by chemical bath deposition technique and the doping with boron was done by the addition of a boron precursor in the anodizing electrolyte. These electrodes were characterized and applied in the photoelectrocatalytic degradation of Basic Red 51 (BV51), Basic Blue 99 (BA99) and Acid Yellow 1 (AA1) dyes, chosen as models of hair dyes for treatment. Both electrodes promoted degradation efficiency significantly higher than that obtained for unmodified electrodes, in addition to the photoactivation in the visible region. To circumvent PEC limitation, which is the low efficiency in highly colored solutions, the combination of PEC technique with ozonation was investigated in order to improve the treatment efficiency of the AA1 dye in higher concentration and in the treatment of effluents resulting from hair dyeing. The combined method was the most efficient among those tested and the simple application of a voltage (O3 + FEC) greatly increases the decolorization rate (2×), decreases the time required for mineralization and the consumption of 'electric energy per order' compared to an ozonation + photocatalysis system. Finally, it was investigated the properties of a hair dye effluent and applied the combined method for its treatment. These effluents presented high organic carbon and chemical oxygen demand contents, intense color and high turbidity, in addition to the presence of the precursors p-phenylenediamine and resorcinol, used in permanent dyes, as well as the occurrence of Bandrowski base, an undesirable mutagenic byproduct. Different combinations of AOPs were applied in the treatment of this effluent: ozonation (O3), ozone/UV-C (O3/UV-C), ozone/photoelectrocatalysis (O3/PEC), O3/UV-C/H2O2 and O3/PEC/H2O2. The O3/PEC/H2O2 system presented the lowest energy consumption and the highest mineralization rate, which could completely degrade p-phenylenediamine, resorcinol and Bandrowski’s base in less than 5 min of treatment. Considering the great use of hair dyes, a large amount of contaminants can reach surface waters or sewage stations, therefore our results are an important step in the evaluation of an efficient and simple method for treatment of complex wastewater. (AU) | |