Estudo da síntese de carvões ativados a partir do bagaço de cana-de-açúcar e análises estatísticas e termodinâmicas no processo de adsorção de corantes

Abstract

Several methodologies are found in the current literature for the synthesis of activated carbons, starting with the available varieties of precursors, the types of processes, which can be physical and/or chemical, in addition to a multitude of activating agents, which can have different chemical functions that range from chlorides, acids and hydroxides. In this context, this work's first objective is to study the influence of the process and chemical agents used in the production of activated carbon (AC), with sugarcane bagasse as a precursor, as well as to evaluate the impacts of each process on the final characteristics of this product. To this end, two activated carbon synthesis processes were used, the first using fresh sugarcane bagasse as a precursor and the second in carbonized form, also varying the chemical activation agents, one with an acidic function and the other with a basic function (H3PO4 and KOH), in the end, 4 activated carbons were obtained, which were characterized by the techniques of XRD, FRX, SEM and N2 Volumetrics, Zeta Potential and capacity to remove the methylene blue dye (AM). The best results were obtained for activated carbon CA1A (produced through process 1 using the acidic chemical agent) reaching specific surface area values of around 1200 m2.g-1. Following the work, with the second objective of optimizing the adsorption process with CA1A, a study was carried out with an anionic dye, Erionyl Yellow A-R (EY). The adsorption tests for EY were carried out by varying the pH and temperature of the medium. Through the data obtained statistically, it was verified that the studied variables had significant effects and that the test at 30°C and pH 2 obtained the highest amount of adsorbed dye (q), reaching a value of 61.1 mg/g. In the search for a process with predictive characteristics, another adsorption process was studied, this time with the cationic dye, Methylene Blue (AM). For this adsorption study, it was found that the variables studied presented significant and predictive effects, within the range of experimental levels studied for the 95% confidence interval. It was also found that the largest amount of dye adsorbed by activated carbon (q) was 288.4 mg/g, with the test using 10mg of CA, at 27°C and pH 2. Still for Methylene Blue, the equilibrium, kinetics and thermodynamic factors were studied, under the conditions optimized by the experimental design.