Utilização de bagaço de cana-de-açúcar como adsorvente na clarificação de óleo de soja

Abstract

Soybean cultivation is widespread in Brazilian agribusiness and it is one of the main grains produced in the country, accounting for the biggest part of the economy generated by agriculture. Among its forms of commercialization, soybean oil is the most common product found in Brazil. In order for the soybean oil to be marketed, Crude soybean oil must be refined in order to remove its impurities and undesirable compounds, then soybean oil can be sold. Bleaching is a step of refining which aims to remove pigments and oxidation compounds, then clarifying earths and activated carbon are added. The sugar and ethanol mills have great importance for the economy, because they are an important source of jobs. Brazil is the biggest producer of sugarcane in the world. In the production of sugar and alcohol, a large amount of sugarcane bagasse is generated. Recent researches indicate the potential of this biomass as adsorbent in some processes, for example, in the purification of air, water and effluents. For this reason, this work aimed to produce adsorbents from the sugarcane bagasse and apply them in the bleaching process of the neutralized soybean oil. The adsorbents were characterized by physical, thermal (TGA), microscopic (SEM) and chemical (centesimal composition) assays. The neutralized oil and the bleached oils were characterized for peroxide value, acidity, TBA and color. The assays of adsorption were performed with the ground and dried bagasse and chemically activated bagasse with H3PO4 (60%), NaOH (49%), H2SO4 (41% and 70%) and NH4OH (9%). Evaluating the results, it was verified that there was no reduction of peroxides in the clarified oil, and the bagasse activated with H3PO4 (60%) was the best assay to remove pigments and secondary oxidation compounds. Thus, the activated carbon was produced using thermal activation of the bagasse impregnated with H3PO4 (60%) as well as of the dried and ground sugarcane bagasse. The thermal activation was made in a reactor adapted to a muffle furnace, under an inert atmosphere of nitrogen, until the temperature of 400°C. The two types of activated carbon produced were used in the clarification of the neutralized soybean oil. For comparative purposes, soybean oil clarification was also accomplished with commercial adsorbents used in industries (blending of clarifying earths and activated carbon). It was observed good results using chemical and thermally activated carbon to the oil clarification. This adsorbent removed peroxides in the same proportion as the commercial adsorbents and reduced the content of oxidation compounds by more than 80%. This reduction was four times higher than the results noted using clarifying earths. Regarding acidity, both adsorbents presented similar results, reducing this parameter by approximately 30%, and no significant difference was detected between treatments at a significance level of 95%. Regarding color of the clarified oil, the treatments with the activated carbon produced and the mixture of the commercial adsorbents exhibited similar results.