Banca de DEFESA: LARISSA PINHEIRO DE SOUZA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : LARISSA PINHEIRO DE SOUZA
DATA : 18/01/2019
HORA: 08:00
LOCAL: AUDITÓRIO NUPEG
TÍTULO:

2,4,6-trichlorophenol degradation by means of a zero-valent-copper reductive process, coupled to UV / H2O2 oxidation. 

PALAVRAS-CHAVES:

2,4,6-trichlorophenol. Zero valent copper. Packed column. UV/H₂O₂. Toxicity

PÁGINAS: 127
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Química
RESUMO:

During the disinfection stage of water treatment, the combination of the remaining organic matter with free chlorine can lead to the generation of organochlorine compounds. Among these is 2,4,6-trichlorophenol (TCP), with high environmental persistence and carcinogenic character, which is included in the priority list of the United States Environmental Protection Agency – USEPA. Despite drinking water usually containing low concentrations of this compound (ng L^-1), its bioaccumulative effect may cause long-term health problems, which alerts to the need of TCP-contaminated water remediation. Advanced Oxidative Processes (AOPs) have been successfully applied in the removal of many persistent pollutants, although in the case of organochlorines, due to their deficient electron groups (halogens) and consequent oxidation resistance, AOPs effectiveness may drop. However, this can be surpassed by combining a pre-reductive step before oxidation, thus facilitating organochlorines degradation. Therefore, the present work proposes a system that couples a reductive process mediated by zero-valent-copper with an oxidation process mediated by hydroxyl radicals (^—OH). A preliminary study was undertaken to evaluate the influence of different reaction variables and system conformation: batch and recycling packed-column systems. In the latter, different reactive materials were tested, among them copper wires obtained from electronic waste, as well as different metal and contaminant concentrations, through statistical experimental design. From this study, the best reductive degradation conditions were obtained. Then, the degradation of TCP was performed by an advanced oxidation process (UV / H₂O₂), in order to compare with the first step. In this one, the influence of the oxidant concentration (H₂O₂) was evaluated, in order to adopt the most suitable for subsequent coupling with the reductive step. Finally, the combination of both processes was performed, by submitting the solutions that were previously reduced to the UV/H₂O₂ process. In both steps two aqueous matrices were tested (deionized and tap water). Toxicity assays with Vibrio fischeri luminescent bacteria were also carried out, in order to evaluate the processes effectiveness in the toxicity removal. With the aim of proposing degradation pathways for each process studied, the reaction intermediates were identified by mass spectrometry. The results showed that the best reductive degradation conformation was the packed-column system, achieving 80% of TCP degradation, with30.6 g of obsolete copper wires and [TCP] ₀ = 10 mg L^-1 (0.0506 mmolL^-1). However, this process only led to TCP dechlorination, not promoting any pollutant mineralization. On the other hand, a total TCP degradation and 40% mineralization was observed in 4 minutes of oxidation with the UV / H₂O₂process, using 0.056 mmol L^-1 of H₂O₂. By coupling the two processes, a 52% mineralization was achieved within the same reaction period, thus proving that the pre-reductive step improved the organochlorine oxidation. Solutions presenting high degradation values from the reductive step were generally more toxic than the parent-compound, while oxidized solutions presented a certain relation between mineralization and toxicity removal, although not linearly for all the cases.

MEMBROS DA BANCA:
Interno - 2929066 - ANDRE LUIS LOPES MORIYAMA
Externo à Instituição - CÁTIA ALEXANDRA LEÇA GRAÇA - USP
Presidente - 1149554 - OSVALDO CHIAVONE FILHO
Externo à Instituição - VITOR JORGE PAIS VILAR - UNIPORTO