Crude fatty acid ethyl ester microfiltration using aluminosilicate composite microfiltration membrane

Abstract

The purification of crude biodiesel demands large amounts of water. This paper presents a technological alternative for eliminating one of its critical by-products (glycerol 0.105 wt%) from a sample of crude ethyl esters obtained by transesterification of soybean oil with ethanol. Low water content emulsions were prepared by adding up to 1% water and Span 80. The use of a microfiltration composite ceramic membrane allowed a reduction of 38.1–69.3% of this by-product. The structural characteristics of the membrane show that it has a hydraulic pore radius of 0.09 μm, an intrinsic porosity of 40%, and a selective layer thickness of 30 μm, while the emulsions obtained have an average droplet size of up to 8–15 μm which were reduced by viscous effects to 4–6 μm during permeation experiments. Hydraulic permeability values of 1510 L/m2 h bar and permeate flows of between 60 and 303 L/m2 h were achieved in a permeation optimization process using a cross-flow filtration system. The separation process was studied by infrared spectroscopy, optical microscopy, contact angle, and water content. The results allow to conclude that a demulsification process occurs after 1 h of filtration. The addition of Span 80 did not improve the separation efficiency.