Fabrication and characterization of a novel mullite-stainless steel composed hollow fibre membrane for oil/water separation

Low-cost mullite-kaolinite material has recently received more attention as an alternative to conventional ceramic materials such as alumina and silica to prepare ceramic hollow fibre membranes (CHFMs) due to its high alumina contents and silica and thermal/chemical stability. However, weak bending strength is still one of the key bottlenecks that delay their commercial applications. In this work, we successfully fabricate a novel mullite-SS HFM with enhanced bending strength using mullite-kaolinite power with different stainless steel alloy (SS) 316 L contents of 0.0, 2.5, 5.0, 7.5, 10 and 12 % (w/w) as a reinforcement material by phase inversion/sintering techniques. The SS alloy was a potential material to enhance the mechanical strength of mullite HFMs due to its excellent mechanical properties. The effects of the major fabrication parameters of SS contents, mullite contents, and fabrication parameters such as air gap distance and bore fluid flow rates were well studied and evaluated through the fabrication process. Fabricated mullite-SS HFMs were characterized by morphology, porosity, pore size/pore size distribution, and bending strength. Afterwards, they were evaluated in an oil/water separation system regarding water flux and oil rejection rate. Based on the findings, there was a gradual increase in the bending strength from 32.1 to 79.8 MPa with increased SS contents from 0 to 12 % (w/w). At 10 % (w/w) SS, the satisfactory morphology with the balance between the bending strength of 66.7 MPa and porosity of 29 % was obtained. This bending strength was significantly higher than reported for mullite-kaolinite HFMs in previous works. Moreover, At 10 % (w/w) SS, the oil–water rejection performance of 96.9% and the water permeation of 290 L/m2. h was satisfactory at the sintering temperature of 1300 °C. These findings suggest the advantage of this membrane for various water treatment applications, such as oil/water separation, due to its outstanding physical properties.