Produção e caracterização de carvão ativado proveniente de cascas de grãos de café e de cascas de grãos de girassol

Abstract

The study of the use of biomass and lignocellulosic waste in the production of activated carbon has shown positive results for the development of new technologies that are used to collaborate with processes that involve the use of those adsorbents. Lignocellulosic residues from the cultivation of different biomasses are materials that are produced on a large scale and, if disposed of inappropriately in the environment, can cause environmental problems. Any carbonaceous material can be used to produce activated carbon, as long as it has a low content of inorganic components, low cost, high availability, does not suffer degradation during storage, is easy to activate and produces good adsorbents. The aim of this work is to produce and characterize activated carbon from coffee seed husks and sunflower seed husks, residual biomass found on a large scale in Brazil due to the production of coffee and sunflower oil. The method used consists of previously carbonizing the biomass at 700°C under an inert atmosphere of nitrogen (N2), followed by an activation process using potassium hydroxide (KOH) in a dry method. The activation parameters such as the activation temperature (600, 700 and 800°C) and the impregnation mass ratio (1:1, 1:2 and 1:4) were evaluated during the production of the adsorbents. The activated carbons produced were characterized using techniques such as: Fourier transform infrared spectroscopy (FT-IR), surface area analysis, average pore volume and pore distribution based on BET adsorption-desorption isotherms and scanning electron microscopy (SEM). The microscopy analyses indicated the development of a porous structure predominantly formed by mesopores and micropores, with a high carbon and oxygen content in the composition of the adsorbents. The activated carbon sample that showed the best results was the one produced from sunflower seed husks, activated at 700°C with an impregnation ratio of 1:4 (coal:KOH), showing a surface area of 1326,54 m2.g-1, an average pore volume of 0,7947 cm3.g-1 and an average pore diameter of 2.34 nm. Based on the results obtained, it is possible to state that both biomasses studied have favorable chemical and structural characteristics for the production of activated carbon, and also that the activation method used led to the development of a porous structure with a high surface area value when compared to other materials in the literature.