This present project has focused on the fabrication of novel membranes for the separation of secondary dispersions of water-in-diesel. The quest of improving the efficiency and reduce the pressure drop of such filtrations has, due to the introduction of biodiesel, increased caused by the content of surfactants in biodiesel. The surfactants decrease the drop size distribution and increase the concentration of total water, which decreases the combustion efficiency and lifetime of engines.
The separation of secondary dispersions of water-in-diesel has previously been demonstrated to be dependent on the hydrophobicity of the membrane surface. The hydrophobicity of a surface is both dependent on the surface energy and surface morphology. In the search of a novel mem- brane material an inverse-quantitative structure-activity relationship was developed on the basis of polymers’ critical surface tensions.
The model predicted new potential polymers with low critical surface tensions, i.e. hydro- phobic materials. The solutions were then subjective evaluated, which resulted in the purchase of poly(styrene-co-a-methylstyrene), PSMS.
The surface of PSMS was experimentally characterized by measuring the water contact angle, which resulted a contact angle of 94.10±3.73o, thus PSMS could be characterized as being hydrophobic.
To further increase the hydrophobicity, PSMS was electrospun. This is a process that utilize electrostatic forces to form polymeric fibers with induced pores and hollows, thus increasing the hydrophobicity of the surface. The electrospinning of PSMS resulted in surfaces with a water contact angle of 165.85±0.51o hereby producing superhydrophobic surfaces.
Membranes were, on the basis of the previous results, fabricated by electrospinning PSMS on a support material. Membranes, that were electrospun using a 60 w/w % PSMS/DMF solution and a deposited mass of 30 g PSMS/m2, achieved the highest separations efficiencies of 93.85±2.65 % with a pressure drop of 0.64±0.17 kPa.