Banca de DEFESA: ALEXSANDRO JHONES DOS SANTOS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ALEXSANDRO JHONES DOS SANTOS
DATA : 25/01/2018
HORA: 15:00
LOCAL: Auditório do NUPPRAR
TÍTULO:

Treatment of water contaminated with azo dyes by the application of advanced oxidative processes: photochemical, electrochemical and photoelectrochemical using UVA and solar radiation

PALAVRAS-CHAVES:

azo dye, solar photocatalysis , anodic oxidation, electro-Fenton, solar fotoelectro-Fenton

PÁGINAS: 160
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Físico-Química
ESPECIALIDADE: Eletroquímica
RESUMO:

Advanced oxidation processes (POAs) are promising technologies for environmental remediation. These technologies are based on the high oxidation power of hydroxyl radicals (^●OH), which have a high reactivity to oxidize organic compounds present in liquid effluents.

In this thesis, the application of different POAs to treat synthetic and real solutions containing azo dyes has been studied. These compounds present a serious socio-environmental risk since they have high toxicity and are resistant to conventional treatment methods. The obtained results were divided into four distinct chapters. In chapter 1, two valuable natural resources of Brazil were used, namely, the sun in the Northeast region and the niobium. By combining these two goods, it has been found that solar photocatalysis whith niobium oxide (Nb₂O₅) is an effective and economical method for discoloring dyes at low concentrations. The photocatalytic efficiency of Nb₂O₅ was evaluated by varying the concentrations of dye, H₂O₂, Nb₂O₅ and pH. The best operating conditions were 1 g L^-1 of Nb₂O₅, 5 mg L^-1 of dye and 0.20 M of H₂O₂ and pH 5. At the end of five treatment cycles, Nb₂O₅ photocatalyst efficiency remained constant. In the case of chapters 2, 3 and 4, electrochemical and photoelectrochemical treatments using UVA and solar radiation were used. In chapter 2, a solution containing the dye diazo Pounceau SS was treated using a pre-pilot flow plant equipped with boron doped diamond (BDD) or platinum (Pt) anode and air diffusion cathode, connected to a photoreactor containing a 160 W UVA lamp. Anodic oxidation with H₂O₂ electrogenerated (AO-H₂O₂) was more efficient with BDD, due to the greater oxidation capacity of heterogeneous ^●OH radicals formed on its surface. In electro-Fenton (EF) and photo electro-Fenton (PEF), the ^●OH radicals produced by Fenton’s reaction were more reactive. The PEF had a better performance due to the additional photolysis of intermediates and photodecarboxylation of Fe (III) complexes with UVA light. The influence of light minimized the effect of the anode in the process, which was relevant in AO-H₂O₂ and EF processes. Chapter 3 had the objective of evaluating the influence of water hardness on the treatment of the color of eriochrome black T  by means of the EF process. The dye molecule forms complexes with calcium and magnesium. These complexes being stable make electrophilic attack of ^●OH radicals difficult. Thus, water hardness should be an highlihted parameter in the EF process. In chapter 4, it was taken into account that daily activities as the washing of clothes generate dyes that need to be treated. A viable alternative is to consider the wastewater treatment at a domestic scale. Therefore, an actual laundry washing machine effluent was treated by advanced electrochemical oxidation processes, demonstrating high efficiency and could be applied as decentralized small scale treatment devices. The solar PEF has shown to be a suitable process for complete removal of color and organic matter after 240 min of treatment applying a current density of 66.6 mA cm^-2. The POAs studied in this work proved to be satisfactory and sustainable technologies for the treatment of liquid effluents.

MEMBROS DA BANCA:
Interno - 1753094 - ALCIDES DE OLIVEIRA WANDERLEY NETO
Presidente - 348475 - DJALMA RIBEIRO DA SILVA
Externo ao Programa - 2524058 - DOUGLAS DO NASCIMENTO SILVA
Externo à Instituição - ELIANE BEZERRA CAVALCANTI - UNIT
Externo à Instituição - SUELY SOUZA LEAL DE CASTRO - UERN