Título da Dissertação: Aplicação de Diferentes Biossorventes na Remoção do Corante Amarelo Tartrazina de Soluções Aquosas.

Orientadora: Profa. Dr.ª Angélica Marquetotti Salcedo Vieira

Data da Defesa: 22/02/2017



The presence of synthetic dyes in industrial effluents that are discharged into water bodies without treatment, is a threat to the health of humans and animals by causing imbalance in aquatic ecosystems and trigger various environmental problems. Thus, the adsorption process has emerged as an alternative to conventional processes involving chemical coagulants and an efficient and low cost operation process.
This study aims to remove the yellow dye tartrazine aqueous solutions through the adsorption process in batch and fixed bed, using seeds of Moringa oleifera Lam. as biosorbent, activated babassu coconut carbon (ACBC) and activated bone carbon (ABC) like conventional adsorbents.
The dye used to adsorption studies was tartrazine yellow, donated by the company Duas Rodas Industrial, in Jaraguá do Sul - SC, which was used to obtain dye solutions of 15 mg L-1. Moringa seeds used in the trials were from Aracaju-SE and the carbons were provided by the company Tobasa - Tocantins Babaçu S/A, Cinelandia - RJ. After obtaining the adsorbents was possible to perform the characterization of them from the scanning electron microscope analysis (SEM), X-ray diffractometry (XRD), BET method and point of zero charge (PZC). Batch tests were conducted using the seeds of moringa seeds, activated carbon of babassu coconut and activated bone carbon. During the tests, variables were modified, like pH, temperature and concentration of adsorbate and constructed kinetic curves Lagergreen pseudo first-order and Ho and McKay pseudo second-order and applied Langmuir adsorption isotherms, and Freundlich. Finally, the regeneration of adsorbents in batch process were conducted. For fixed bed tests, moringa seeds were used as biosorbent. During the process were analyzed the effect of bed height, feed rate, pH and adsorbate concentration at the bed inlet. The breakthrough curves were constructed, calculated the values of adsorption capacity and percentage of removal and applied the Adams-Bohart models, Thomas and Dose-Answer. The regeneration of the biosorbent in a fixed bed was also performed.
The results related to the characterization of the adsorbents showed that PCZ was 7 for the moringa seeds and the ABCC and 9 for the ABC and XRD images of adsorbents show unresolved peaks, indicating predominance of amorphous material. By SEM analysis, it was possible to observe heterogeneous and porous morphology on the carbons and moringa seeds, available spaces present facilitate the adsorption process. The dye adsorption capacity increases with decreasing pH for the three types of adsorbent, and the optimum pH for adsorption of tatrazina the pH is 3 to ABCC and moringa seeds and pH 2 for ABC. The kinetics showed that adsorption reached equilibrium in 12 hours to ABCC, 10 hours for ABC and 4 hours for the seeds of Moringa oleifera. Moringa seed and the ABC fixed the model of Lagergren pseudo first order and the pseudo second-order model suggests that the adsorption of tartrazine with ABCC is a process in multi-steps. Through the isotherms and thermodynamic calculations, it was found that the adsorption process with seeds of Moringa oleifera is an exothermic adsorption and with both carbons are endothermic processes. The values of ΔG°<0 suggests that the adsorption process is spontaneous and thermodynamically favorable for these adsorbents. Furthermore, the decrease in the value of ΔG° for the ABCC of -3,701 kJ/mol to -7,927 kJ/mol, and ABC -0,592 kJ/mol to -2,818 kJ/mol, with increasing temperature, it indicates that the process is more favorable at high temperatures. The opposite happens to the seeds of Moringa oleifera. It was possible to carry out the regeneration of adsorbents, with loss of moringa seed capacity over the cycles. The investigation of the fixed bed adsorption process shows that biosorption is enhanced when operated at low feed flow rate (1mL/min), 14 cm bed height, pH 5 and concentration of 15 mg L-1. After the construction of rupture models, it is concluded that the Adams-Bohart model is the one that best represents the initial portion of the forward curve, while Dose-Response Model is that best reproduces the entire curve. The biosorbent regeneration experiments showed a dye removal decline from 44.9 to 33.82% in the cycles.
With the development of this study, it was possible to determine the effectiveness of Moringa oleifera Lam. seeds in biosorption of tartrazine yellow dye in aqueous solutions when compared with adsorption process using conventional adsorbents. The batch process has reached a removal of 95 % while the continuous process with fixed bed reached 44.9 %. Because of the adsorbate present as an anionic molecule, the adsorption was favored at low pH values for all adsorbents and the two adsorption methods. From the results, it can be concluded that moringa seeds are an alternative adsorbents which have a high capacity for removal of tartrazine yellow dye.
KEYWORDS: moringa seeds, activated carbon, adsorption, tartrazine

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