Manufacture of ceramic membranes for application in demulsification process for cross-flow microfiltration

This paper describes the manufacture of tubular ceramic membranes and the study of their performance in the demulsification of soybean oil/water emulsions. The membranes were made by iso-static pressing method and micro and macro structurally characterized by SEM, porosimetry by mercury intrusion and determination of apparent density and porosity. The microfiltration tests were realized on an experimental workbench, and fluid dynamic parameters, such as transmembrane flux and pressure were used to evaluate the process relative to the oil phase concentration (analysed by TOC measurements) in the permeate. The results showed that the membrane with pores’ average diameter of 1.36 µm achieved higher transmembrane flux than the membrane with pores’ average diameter of 0.8 µm. The volume of open pores (responsible for the permeation) was predominant in the total porosity, which was higher than 50% for all tested membranes. Concerning demulsification, the monolayer membranes were efficacious, as the rejection coefficient was higher than 99%.

Fig. 4. Measurements of TOC (mg/L) relative to the permeate samples collected during the process in three transmembrane pressures. process. On the other hand, the lowest TOC was reached under lower pressure (1 bar), as the hydraulic pressure (of the concentrate) is not higher than the capillary pressure (into the pores), which hinders the forced access of the oil droplets through the pores. This may explain the fact that the membrane with pores of 0.8 µm size presents higher TOC, but in this case the capillary pressure was lower than the hydraulic pressure. How did the membrane with a larger pores average size achieve lower TOC? There are two possible explanations. The retention may have occurred by adhesion, i.e., the oil droplets with smaller size than the pores’ diameter were retained in the pores’ wall, instead of crossing them over. Another possibility is that the oil droplets may have been adsorbed in the close pores of this membrane (due to its large volume of close pores). As for the emulsion characterization, the analysis indicated the presence of oil droplets of 1.2 µm size. This result confirms the arguments presented above, in relation to the membrane of 1.36 µm. Both tested membranes were efficacious. Although the membrane of 0.8 µm presented higher TOC, the rejection coefficient was on The process of manufacture of tubular porous ceramic membranes has shown to be efficacious as the membranes produced have yielded good results according to the application they were destined to. Moreover, the rejection coefficient and transmembrane flux are in accordance with what is recommended [6], that is, coefficient of rejection higher than 99.0% and transmembrane flux between 15 and 90 L/h m2.