Eucalyptus pulp as an adsorbent for biodiesel purification

This work proposes the use of eucalyptus pulp as an adsorbent for biodiesel purification. Methyl sunflower biodiesel was produced by alkaline transesterification and passed through a column containing the adsorbent. The evaluated impurities were free glycerol, methanol, water content and alkali metals (Na⁺, K⁺, Ca²⁺ and Mg²⁺). The cellulose fibers were fractionated by sieving in three fractions (sieve pore sizes of 500, 600 and 1,180 μm). The pulp was characterized by infrared, x-ray diffraction, viscosimetric molecular weight, water content, morphological analysis and fiber content of α-cellulose and hemicelluloses. The size of fibers, mass of adsorbent (0.2 and 1.0 g), column diameter (1.0 and 1.3 cm) and the aid of pressure for filtration (atmospheric or 18 psi) on the impurities removal were also evaluated. The physicochemical characterization of biodiesel was performed following tests in accordance with the limits set by the European Standard for oxidative stability at 110 °C, density at 20 °C, water content, acid value, free glycerol, kinematic viscosity at 40 °C, and residual methanol. The optimal condition was observed using 1.0 g of cellulose in a column of 1.3 cm in diameter under pressure of 18 psi was applied. In this condition the free glycerol, methanol and water content in the permeate presented values of 0.0081 ± 0.0001, 0.268 ± 0.009 % w/w and 636 mg kg⁻¹, respectively. The results indicate that this cellulosic adsorbent is a promising material for biodiesel purification instead of using water washing, avoiding the generation of high wastewater volumes.