Degradação térmica de podas de árvores (Syzygium Cumini) visando a produção de carvão ativado para uso industrial

Abstract

This work aims to produce activated carbon using as precursor material the pruning of urban trees in the city of Palmas - TO of the species Suzygium cumini, in a pyrolysis process. The research had the following phases: (a) characterization of the biomass, (b) kinetics of mass loss, (c) planning of selection of variables of the heat treatment process, (d) characterization of activated carbon and (e) adsorption. The biomass was characterized through immediate analysis, elemental analysis, thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR). The study of the loss kinetics was carried out at a temperature of 50 °C. In the biomass pyrolysis tests, the following process variables were studied: pyrolysis temperature (350, 500 and 650 °C), inert gas flow in the pyrolysis reactor (4, 6 and 8 mL/min), heating rate of the pyrolysis reactor (25, 35 and 45 °C/min), biomass particle diameter (6.3, 8 and 12.5 mm), biomass heating temperature in wet steam (110, 120 and 130 °C) and biomass contact time with wet steam (20, 30 and 40 min). Activated carbon was characterized by immediate and elemental analyses, pH, point of zero charge (pHPCZ), iodine number, thermogravimetry, Fourier transform infrared spectroscopy. The planning for the methylene blue adsorption test was designed with 7 factors, including: temperature (20, 25 and 30 °C), methylene blue concentration (5, 10 and 15 mg/L), adsorption time (20, 40 and 60 min), activated carbon mass (0.5, 0.75 and 1 g), stirring speed (71, 119 and 167 rpm), pH of the methylene blue solution (6.5, 7 .5 and 8.5) and adsorbent granulometry (0.45, 1.2 and 2 mm). The biomass showed the following characteristics: (a) moisture = 5.97%, (b) volatile material = 81.90%, (c) ash = 0.66%, (d) carbon = 45.09%, (and ) nitrogen = 0.19% and (f) hydrogen = 5.57%. In the pyrolysis tests, the maximum carbon yield was 78% obtained under the following conditions: reactor temperature = 350 ºC, heating rate = 25 ºC / min and inert gas flow = 4 mL/min. At the temperature of the pyrolysis reactor of 650 °C, the average yield of coal was 15.87%. The coal presented a pH between 8.02 and 9.02, with a C/H ratio equal to 31.09. The pHPCZ of the carbonaceous material at 650°C was pHPCZ 7.042. The determination of the iodine number obtained results above 1162.07 mgI2/g, a value well above the minimum limit established by the standard for the acceptance of activated carbon. In the adsorption tests, the factors that showed significance were the concentration of methylene blue and the mass of carbon. The maximum adsorption capacity was 1.48 mg/g of carbon in the tests. The data related to the characteristics of the coal obtained in the pyrolysis process from the residual biomass Suzygium cumini point to its use as adsorbing material for micropollutants.