Application of asymmetric Si3N4 hollow fiber membrane for cross-flow microfiltration of oily waste water

Abstract The asymmetric morphology of silicon nitride (Si3N4) ceramic hollow fiber membrane with a selective spongiform outer layer was optimized by the air gap distance and the internal rate of coagulate for oil/water emulsion microfiltration. The effect of trans-membrane pressure (TMP), feed flow rate (FFR), and pH of the feeding emulsion on the separation performance were determined experimentally. Membrane fouling has increased by dissociation of oil droplets during filtration at high TMP and FFR values. Fouling phenomena were studied based on standard pore blocking model. The pH by affecting the surface charge of the Si3N4 hollow fibers and zeta potential of the feed emulsion has also been introduced as a prominent influential factor on separation efficiency. The highest values of permeate flux (390 Lm−2h-1) and oil rejection (95%) were recorded in alkaline pH. The fabricated Si3N4 ceramic membranes were completely recovered (≤99%) by simple thermal treatment at 400 °C.