Analytical methods in photoelectrochemical treatment of phenol

Abstract

O presente estudo visou o tratamento de efluente simulado, contendo fenol por processos fotocatalítico e fotolítico com análise toxicológica das soluções fenólicas. Dois sistemas de tratamento foram propostos com radiação UV, eletrodos maciços e potencial elétrico. No primeiro sistema (S1), a concentração de fenol foi determinada por espectrofotometria direta em 269 nm e o segundo (S2) por meio do método fotométrico direto (4-aminoantipirina). Testes de toxicidade foram realizados com dois microrganismos: Escherichia coli e Saccharomyces cerevisiae. Os resultados de S1 demonstraram que conclusões errôneas podem ser retiradas em relação ao aumento de absorbância no pico do fenol de acordo com o tempo de tratamento. Contudo, o método fotométrico direto foi capaz de identificar a redução do fenol em S2 e observou-se que os tratamentos propostos degradaram as moléculas de fenol em solução. Também, no tratamento com fonte ultravioleta de alta energia (UVC), a degradação fenólica deve-se principalmente à fotólise.The aim of the study was to propose a treatment of simulated wastewater containing phenol by photocatalytic and photolytic processes and analyze the toxicity of these phenolic solutions. Two treatment systems were performed with UV radiation, solid electrodes and electric potential. In the first system (S1) phenol concentration was determined by UV direct spectrophotometry (269 nm) and in the second (S2) by direct photometric method (4-aminoantipyrine). Toxicological tests were carried out using two microorganisms: Escherichia coli and Saccharomyces cerevisiae. S1 results showed that erroneous conclusions can be drawn by absorbance values increase at phenol peak. Nevertheless, direct photometric method was able to identify phenol reduction in S2 and the proposed treatments degraded phenol in solution. Also, in treatment using high energy ultraviolet radiation (UVC), the phenol degradation was mainly due to the photolytic process.

A high-performance doped photocatalysts for inactivation of total coliforms in superficial waters using different sources of radiation

“…Furthermore, Estruga et al (2010) discovered that silicon-doped electrodes increased catalyst surface area. However, the TiO 2 has a large surface area (around 50 m 2 .g À1 ) and its complex crystalline microstructure promotes better charge separation which inhibits recombination (Lopes et al, 2011), resulting in a better performance in degrading processes.…”

“…AOPs are oxidation processes in which hydroxyl radicals (OH ) are generated in sufficient quantities to serve as the main oxidizing agents (Lopes et al, 2012;Wang et al, 2014). Among the AOPs, heterogeneous photocatalysis has been widely studied and its principle involves the activation of a semiconductor by sunlight or artificial light (Lopes et al, 2011;Gulyas, 2014).…”

“…Titanium dioxide (TiO 2 ) materials of different types and forms have shown great potential as an ideal and a powerful semiconductor photocatalyst for various significant reactions due to their chemical stability, low cost, nontoxicity, and high reactivity (Lopes et al, 2011;Gulyas, 2014;Schneider et al, 2014;Wu et al, 2014;Wang et al, 2014). Other semiconductors have also been studied in photocatalysis, namely zinc oxide (ZnO), tungsten trioxide (WO 3 ), ferric oxide (Fe 2 O 3 ), zinc sulfide (ZnS), etc.…”

Fabrication of magnetic Fe3O4/C/TiO2 composites with nanotube structure and enhanced photocatalytic activity

“…The source of visible light was achieved by the Xenon lamp with a 420 nm cutoff filter to ensure the desired irradiation. The method used to determine the phenol concentration in this present research is direct photometric method, 49 which was performed according to the 5530-D procedure of the ‘Standard methods for the examination of water and wastewater’. 50 This procedure is based on the reaction at pH 7.9 ± 0.1 of phenolic compounds with 4-aminoantipyrine forming an orange compound.…”

Solar Photodegradation of Phenol Using a Composite Catalyst of Silica and TiO2

“…From the results, it can be seen that there was some instability in the first 2 hours of photodegradation. This can be attributed to the brown colouration of the solution during the first two hours when phenol was degraded to coloured intermediates [18]. The coloured intermediates interfered with UV-vis measurements thus resulting in inaccurate readings.…”