Daniella Carla Napoleão

Heterogeneous photocatalytic degradation of phenol and derivatives by (BiPO4/H2O2/UV and TiO2/H2O2/UV) and the evaluation of plant seed toxicity tests

We examined the photocatalytic degradation of phenol from laboratory samples under UV radiation by using BiPO4/H2O2 and TiO2/H2O2 advanced oxidation systems. Both catalysts prepared were characterized by scanning electron microscopy, Fourier transform infrared and X-ray diffraction. Surface area tests showed about 3.46 and 31.33m2·g−1, respectively, for BiPO4 and TiO2. A central composite design was developed with the following variables--catalyst concentration, time and concentration of hydrogen peroxide--to optimize the degradation process. Removal rates of 99.99% for phenol degradation using BiPO4 and TiO2 were obtained, respectively. For mineralization of organic carbon were obtained 95,56% when using BiPO4 and 63,40% for TiO2, respectively. The lumped kinetic model represented satisfactorily the degradation of phenol process, using BiPO4/H2O2/UV (R2=0.9977) and TiO2/H2O2/UV (R2=0.9701) treatments. The toxicity tests using different seed species showed the benefits of the proposed advanced oxidation process when applied to waste waters containing these pollutants.

DEGRADATION AND KINETIC STUDY OF REACTIVE BLUE BF-5G AND REMAZOL RED RB 133% DYES USING FENTON AND PHOTO-FENTON PROCESS

The textile industry is responsible for the generation of highly colored effluents, which need adequate treatment. Thus, the advanced oxidative processes (AOP) have been used to degrade the dye and convert organic matter. In the present study, the degradation of the reactive blue dyes BF-5G and red remazol RB 133% were evaluated through Fenton and photo-Fenton processes (solar and sunlight). To determine the best working condition, the pH, peroxide concentration, iron concentration and time variables were evaluated by performing a kinetic study in this condition. From a preliminary study, it was verified that the Fenton and photo-Fenton processes, using different radiations, presented similar results, reaching a degradation of more than 98% for each dye. The factorial design indicated better results for a concentration of H 2 O 2 of 10 mg · L -1 , iron concentration of 5 mg · L -1 and time of 15 min, obtaining degradation above 88% for the studied dyes. A good kinetic adjustment was verified for a pseudo first order kinetic model (R 2 = 0.9921 and 0.9867 for blue and red dyes, respectively). Ultimately, the study of chemical oxygen demand indicated a conversion of 75.98% for the Fenton process, 86.63% photo-Fenton solar and 87.02% photo-Fenton sunlight.

EVALUATION OF EFFICIENCY OF ADVANCED OXIDATIVE PROCESS IN DEGRADATION OF 2-4 DICHLOROPHENOL EMPLOYING UV-C RADIATION REATOR

The study accomplished to analyze, identify and quantify 2,4-dichlorophenol employing high efficiency chromatography with a previously validated analytical methodology. The validation was made by using some analytical parameters: linearity, precision, accuracy, quantification limit (LOQ) and detection limit (LOD). The analytical curve was linear for the studied range of concentration (10 up to 100 mg.L -1 ) presenting a linear regression coefficient (R 2 ) above 0,99. Regarding the methodology accuracy, a repeatability analysis was performed by observing a coefficient of variance (CV) below 20% for each of the concentrations used. The LOD and LOQ were adequate for the analyzed compound, showing the values of 1.42 mg.L -1 and 4.30 mg.L -1 , respectively. The tests to verify the accuracy, by the recovery method provided values above 79%, thus resulting in specific, sensitive, precise, linear and accurate methodology in the studied concentration range. In the advanced oxidative process UV/H 2 O 2 , the compound was degraded to 88.04% under the following experimental conditions: [H 2 O 2 ] = 1016.0 mg∙L -1 in 120 minutes. Therefore, it can be affirmed that the treatment employed can be used as an alternative for industrial effluent treatment with phenolic compounds.

Application of the advanced oxidative process on the degradation of the green leaf and purple açaí food dyes with kinetic monitoring and artificial neural network modelling

The study evaluated the advanced oxidative processes concerning the degradation of green leaf and purple açaí dyes, as well as the prediction of data through artificial neural networks (ANNs). It was verified that percentage of degradation on the wavelengths (λ) of 215, 248, 523 and 627 nm was 5.95, 49.99, 98.17 and 95.99%, respectively, when UV/H2O2 action and UV-C radiation was applied. A non-linear kinetic model proposed by Chan and Chu presented a good fit to the experimental data, reaching an R2 value between 0.978 and 0.999, for the studied λ. Within the ANN simulations through Statistica 6.0, the multilayer perceptron (MLP) (3-9-4) presented a better fit to the experimental data. However, higher values of R² were obtained when utilizing the sklearn package with Python language and an MLP (4-5-4) model. Assays with Staphylococcus aureus and Staphylococcus pyogenes bacteria isolates were performed and it was verified that after employing the UV/H2O2 process, there was a decrease in the toxicity of the solution of dyes. In evaluating S. aureus toxicity, normal growth was observed. However, for S. pyogenes bacteria, it was found that when using the UV/H2O2 process, toxicity was evidenced at post-treatment solution concentrations of 100, 70 and 50%.

Degradation of textile dyes Remazol Yellow Gold and reactive Turquoise: optimization, toxicity and modeling by artificial neural netwoks

In this work, the degradation of Remazol Yellow Gold RNL-150% and Reactive Turquoise Q-G125 were investigated using AOP: photolysis, UV/H2O2, Fenton and photo-Fenton. It was found that the photo-Fenton process employing sunlight radiation was the most efficient, obtaining percentages of degradation above 87%. The ideal conditions for the degradation of the dyes were determined from a factorial design 23 and study of the [H2O2] ([H2O2] equal to 100 mg·L-1); [Fe] equal to 1 mg·L-1 and pH between 3 and 4. In the kinetic study, a degradation of more than 97% was obtained after 150 min for the chromophoric groups and 91% for the aromatic compounds. The experimental data obtained presented a good fit to the nonlinear kinetic model. The model of artificial neural networks multilayer perceptron (MLP) (4-11-5) using the software Statistica 8.0 enabled the modeling of the degradation process and showed a better prediction of the data. The toxicity to the seeds of Lactuca sativa and the bacteria Escherichia coli and Salmonella enteritidis allowed to evaluate the effectiveness of the process. The results of this study suggest that the use of photo-Fenton process with sunlight radiation is an effective way to degrade the dyes under study.

Degradação do contaminante emergente paracetamol empregando processos oxidativos avançados

Uma classe de poluentes tem sido investigada por pesquisadores de todo o mundo, estes sao os contaminantes emergentes, que sao considerados persistente e refratario. Estes compostos estao presentes em diferentes matrizes ambientais em baixas concentracoes que requerem tratamentos alternativos de polimento capazes de promover a degradacao destes poluentes, uma vez que os tratamentos convencionais nao sao capazes de remove-los. Este estudo avaliou a degradacao do paracetamol utilizando processos oxidativos avancados (acao UV/H 2 O 2 e foto-Fenton). Os resultados mostraram que o processo acao UV / H 2 O 2 foi mais eficiente conseguindo promover a degradacao de 99% do paracetamol, o que e corroborado pela estatistica que mostraram que as experiencias isentas da adicao de ferro (UV / H 2 O 2 ) foram os mais eficientes na degradacao do paracetamol em solucao aquosa solucao. A metodologia para a identificacao atraves de cromatografia foi validado de acordo exigencia das agencias existentes (INMETRO e ANVISA), assegurando a confiabilidade dos resultados.