Membranas de celulose regenerada extraída da casca de amendoim para filtração de biodiesel: preparação, caracterização e aplicação

Abstract

The production of biodiesel via transesterification by basic catalysis is a process that results not only in the mixture of fatty acid methyl esters (FAME), but also in glycerol as byproduct of the reaction. Thus, at the end of production process it is necessary to purify the biodiesel, which is conventionally made by washing the biodiesel with treated water, generating a large volume of residual effluent. The purpose of this work was to develop and employ regenerated cellulose membranes from the peanut shell for the filtration of biodiesel, aiming at an efficient and environmentally friendly alternative to the conventional process. Cellulose was extracted from the peanut shell, which is usually discarded as residue, and regenerated as fine membranes. The membrane preparation process was optimized through experimental design, obtaining as optimal conditions the use of Na2SO4 as a porogenic agent, cuproethylenediamine:cellulose ratio of 25.0:1.00 (mL:g) and the mass of porogenic agent of 0.60 g. Membranes prepared under optimized conditions in addition to filtration efficiency ,% methyl esters > 96.5 %, were also shown to have good repeatability, RSD < 2 %. The thicknesses of the membranes were also defined as 51 μm, with thicker membranes presenting greater difficulty in filtration and thinner total passage of the transesterification products. The membranes were physicochemically characterized presenting themselves as dense and non-porous membranes, but with the contact of residual glycerol and methanol molecules from biodiesel the membrane undergoes expansion of its structure allowing the permeation of the methyl esters. In addition, the filtered biodiesel was characterized, and its characteristics compared to those of biodiesel obtained by the conventional purification process (washed biodiesel). All quality parameters evaluated, in special the free glycerol content, were within the limits specified by ANP Resolution 07/2008.