Graziele Elisandra do Nascimento

Adsorption of azo dyes using peanut hull and orange peel: a comparative study

This work proposes the use of agro-industrial wastes, specifically peanut hull (HP) and orange peel (OP), as adsorbents for dyes, such as Remazol Golden Yellow RNL-150% (RYG), Gray Reactive BF-2R (RG) and Reactive Turquoise Q-G125 (RT). Characterization by Brunauer-Emmett-Teller indicates that the adsorbents are mesoporous, with pHzpc values of 5.0 for HP and 4.0 for OP. Fourier transform-infrared spectroscopy identified carbonyl and sulphonic groups. The initial pH of the best-adsorbing solution of the three colours was 2.0. Increasing the concentration of the adsorbent promoted an increase in the percentage of removal until saturation of the adsorbent. In a factorial design, the largest value of q was obtained with 0.25 g of the adsorbent, with a particle size of<0.4 mm and a stirring speed of 300 rpm. Such conditions were used in kinetic studies and studies of adsorption equilibrium. The evolution kinetics were rapid in the first few minutes, and after 180 min the system reached equilibrium. The kinetic model that best fit the experimental data to a 95% confidence level for the F test was the pseudo-second-order model for RYG/HP, RG/OP and RT/OP. There was no significant difference between the kinetic models as evaluated by the F test for RYG/OP, RG/HP and RT/HP. The experimental results indicated favourable dye adsorption characteristics for the adsorbents studied. The results of the F test showed that for RYG and RG, there was no significant difference between the two evaluated models. This study suggests that HP and OP are viable alternatives for the treatment of effluents containing RYG, RG and RT dyes.

Adsorption of the reactive gray BF-2R dye on orange peel: kinetics and equilibrium studies

AbstractAdsorption of the reactive gray BF-2R dye from an aqueous solution using orange peel as the adsorbent was investigated by the batch method. Experiments characterizing the chemical and physical properties of the adsorbent found that orange peel is a microporous material with a pHzpc 3.9 and containing carboxylic and sulfonic groups. The greatest adsorption capacity was obtained using a 23 factorial design for 0.25 g of adsorbent, particle size <0.419 mm and at 300 rpm. The pseudo-second-order model provided the best fit of the experimental data. The Weber–Morris model indicated that two or more mechanisms control the process. Statistical analysis of the equilibrium studies indicated that there was not a significant difference between the Langmuir and the Fritz–Schlunder models according to an F-test. The results showed that orange peel can remove the reactive gray BF-2R dye.

Adsorption of anionic dyes from an aqueous solution by banana peel and green coconut mesocarp

AbstractBanana peel (BP) and green coconut mesocarp (GCM) were evaluated as adsorbents for the removal of the dyes reactive gray BF-2R (RG), reactive turquoise Q-G125 and remazol golden yellow RNL-150% (RGY). Adsorbents were classified as mesoporous materials, with the pHzpc of 5 for BP and 7 for GCM. The initial pH of the best-adsorbing solution of the dyes was 2.0. There was no significant difference between the kinetic models evaluated by the F test at a 95% level of confidence, except for the RGY/GCM system. The adsorption process is not merely a function of an intraparticle diffusion step. The Freundlich model was the best fit for RGY/GCM, and no significant difference was evident between the two models evaluated for the other systems by the F test. For RG/BP, the models did not fit the experimental data. The adsorbents evaluated may be useful for the treatment of effluents that contain dyes.

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.

Kinetic and Equilibrium Adsorption Studies for Removal of Naphthenic Acids Present in Model Mixture of Aviation Kerosene

In this work, the adsorbent Sr-MCM-41 was evaluated for its ability to remove naphthenic acids present in model mixture of aviation kerosene (jet fuel) by conducting kinetic and adsorption equilibrium studies in finite bath systems. The adsorption isotherm model of Brunauer, Emmett, and Teller (BET) was used for the equilibrium modeling. Additionally, the linear driving force model was used for the kinetic modeling. The analysis of variance was incorporated to judge the compatibility of the models. The kinetic study found that the system reached equilibrium after 480 min. The equilibrium study showed a maximum adsorption capacity of 2.0 g g−1. The models represented the experimental data satisfactorily, and this was confirmed by the variance analysis. Under the conditions studied, the presented results show the technical potential of using the adsorbent for the removal of naphthenic acids from jet fuel.

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.

Use of TiO2 photocatalyst supported on residues of polystyrene packaging and its applicability on the removal of food dyes

ABSTRACT This work proposes the use of plastic residues, more specifically polystyrene packaging, to support TiO2, used as a photocatalyst in the degradation of erythrosine and Brilliant Blue food dyes. The scanning electron microscopy and Fourier transform infrared spectroscopy analyses exhibited the surface coating and the presence of TiO2 in the material, respectively. The UV/H2O2/TiO2 ((SP)supported) process was used in the preliminary study, given the high percentage of degradation, operational advantages and greater reductions in peaks related to the aromatic rings when compared to the other processes studied. For the factorial design, the highest efficiency was reached for 150 mg of TiO2, a H2O2 concentration of 11.2 mmol L−1 and pH of 5.0. These conditions were used in the degradation kinetics, which was rapid during the first 30 min, with the concentration of dyes in the solution reaching values close to zero after 180 min. Based on the mechanism proposed, the pseudo-first order kinetic model presented the best adjustment to the experimental data. After treatment, the solution presented greater biodegradability and lower toxicity, verified by the lettuce seed germination test (Lactuca sativa). Thus, the UV/H2O2/TiO2((SP)supported) process showed great potential in the treatment of industrial effluents contaminated by these food dyes, as well as in reusing discarded polystyrene packaging to support the photocatalyst.