Avaliação do uso da fibra do coco como adsorvente para purificação do biodiesel e da glicerina

Abstract

The search for energy sources with less environmental impact has led to biodiesel studies, a biofuel, from curiosity to necessity. In this sense, synthesis routes with less polluting and biodegradable materials encourage research on the use of vegetable feedstock to make the process more and more ecologically sustainable. To study the application of an adsorbent to decrease the level of impurities in biodiesel and its by-product, glycerin, the use of unripe coconut fiber, a product of high availability in Brazil, is proposed. The use of a solid adsorbent in one of the biodiesel purification stages complements the objective of its use, which is to reduce emission or generation of pollutants resulting from the use of water washing. The fiber efficiency test as an adsorbent was carried out with the sample of biodiesel and glycerin. However, the biodiesel first went through the washing process with water and vacuum drying. The coconut fiber sample was sun-dried, followed by oven drying. Three samples of adsorbents were generated: 1- coconut fiber carbonized at 250 °C in a muffle furnace (FCC), 2- milled coconut fiber without carbonization (FCT) and, 3- coconut fiber ground and carbonized at 250 °C (FCTC). The biodiesel and glycerin were prepared by transesterification process in a homogeneous medium and subsequently subjected to the adsorption process with the prepared coconut fiber samples. Then its acidity is determined to evaluate the efficiency of the adsorbent. The “blonde” glycerin was also subjected to the adsorption process. All samples, biodiesel and glycerin, were analyzed by UV-Vis spectroscopy. The results presented show that the FCT sample releases tannin for biodiesel and more significantly for glycerin, affecting its color and determining the acidity index. However, the FCC and FCTC samples decreased the acidity of biodiesel, which, despite being not very expressive, results point to the possibility of improving the performance after carrying out new stages of adsorbent activation.