Estudo da remoção do corante reativo azul 5G utilizando bagaço de cana-de-açúcar como adsorvente

• Autor(a) principal: Scheufele, Fabiano Bisinella
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/3637
• topic: Adsorção; Biossorção; Corante têxtil; Corantes reativos; Parâmetros termodinâmicos; Secagem; Bagaço de cana-de-açúcar; Brasil.; Adsorption; Reactive dyes; Sugarcane bagasse; Thermodynamic parameters; Biosorption; Brazil.; Engenharias; Engenharia Química

Sugarcane bagasse is a significant agroindustrial residue due to its abundance and availability. In this sense, the aim of this work was to evaluate the removal of the reactive Blue 5G dye using sugarcane bagasse as sorbent material. The bagasse coming from the sugarcane sector was initially submitted to a drying process, where it was evaluated the kinetics, moisture sorption equilibrium and the temperature conditions to prepare as a adsorbent material. The bagasse was later characterized regarding to granulometry, scanning electron microscopy (SEM), surface area analysis by nitrogen adsorption, centesimal analysis, elemental characterization (SR-TXRF), charge point zero and infrared spectroscopy (FT-IR). The preliminary adsorptions tests was performed at closed and batch system to evaluate operational parameters: granulometry and drying temperature of the adsorbent, initial pH and stirring speed. Kinetic and equilibrium data were obtained at the best preliminary attained conditions, and described by mathematical models. Finally, fixed bed adsorption process was studied by the breakthrough curves at different feed concentration. Regarding to the drying process, high temperatures led to shorter drying times and equilibrium moisture contents. The sugarcane showed falling rate drying period, in which the solid diffusion limit the global process. Moisture sorption isotherms and isosteric heat of sorption indicated an elevated water affinity, characterizing the bagasse as a hygroscopic material. The results states the drying necessity for the adsorbent application. By centesimal analysis at adsorbent characterization it was noticed the preponderance of fibers, related to the lignocellulosic structure from the bagasse. It was found by SEM and surface area analysis that bagasse presents low porosity due to the values of specific surface area (7.1 m2 g-1) e volume de pores (0.0098 cm3 g-1), the average diameter of pores was typical of mesoporous. At infrared spectroscopy of the bagasse before and after the adsorption process a change at carboxyl and hydroxyl group bands was observed, inferring that the sorption process occurred at these groups. At preliminary tests the best conditions observed was: granulometric mixture, initial pH 2, stirring speed 150 rpm and drying temperature 30 °C. The bagasse was employed with no chemical treatments because of acid, alkali and Fenton treatments did not enhance the sorption capacity of the adsorbent. Kinetic adsorption experiments exhibited 48 h equilibrium times, wherein the Elovich model presented the best fit to experimental data. Intraparticle diffusion model interpretation has demonstrated that the sorption process occurs by external and intraparticle diffusion steps and monolayer adsorption, additionally, multilayer sorption at high values of dye concentration in solution. At equilibrium adsorption evaluation it was verified isotherms type II related to multilayer sorption. The temperature influenced the dye removal leading to an multilayer process more evidenced. BET and Langmuir-BET modification isotherms showed the best fit at equilibrium data at studied temperature. However, the drying temperature at the range of 30 to 80 °C did not influence adsorption equilibrium. The process thermodynamic parameters indicated distinct steps at dye adsorption. Initially, and exothermic and chemical nature monolayer formation, followed by the multilayer formation, which is endothermic and physical. Both steps were spontaneous and favorable. The more efficient desorption eluent was the NaOH (0.1 mol L-1), nevertheless the desorption was not complete due to the chemical adsorbed dye portion. At fixed bed process a similar behavior to batch system was observed with multiple layers formation. The breakthrough curves showed elevated inclination, favorable mass transfer zones and higher adsorption capacities than in batch system. Moreover, at fixed bed were attained higher desorption yields showing the possibility of the bagasse reuse at cyclic adsorption-desorption process. The results indicate the viability of this adsorbent material, the possibility of continuous operation and scale up of the process. Based on the results at batch and fixed bed system, the bagasse without treatment has shown high levels of reactive Blue 5G removal. In this way, considering that the sugarcane bagasse is an underused abundant residue originating from a renewable source. It characterizes as an alternative potential material for the treatment of textile effluents containing the reactive Blue 5G dye.