Pore Structure Optimization of a Silica Porous Ceramic Ultrafiltration Membrane for Highly Efficient O/W Emulsion Separation

The ceramic membrane with chemical, thermal, and mechanical stability is expected to realize oil-in-water (O/W) emulsion separation with high efficiency. A simple and cost-effective approach was adopted to fabricate a three-dimensional (3D) silica porous ceramic ultrafiltration membrane, leveraging diatomite as an abundant and economical mineral resource. A porous structure with high porosity and good mechanical properties was prepared by a sacrificial template method. Recognizing the distinct composition of ceramic powders, appropriate additives were carefully selected. By systematically adjusting parameters such as plasticizer and flux content, molding pressure, and holding time, the formation and distribution of the porous ceramic structure were effectively optimized. It was demonstrated that this method not only enabled the tunable pore size of the porous ceramic but also achieved a balance between its porosity and mechanical properties. The porous ceramic exhibited an average pore size of 6.48 nm, a porosity of 62.24%, water absorption of 70.6%, and a compressive strength of 10 MPa. These properties were achieved under fabrication conditions of 5 MPa molding pressure and 20 s dwell time, with the addition of 15% plasticizer (the mixture of poly(vinyl acetate) and ethylene glycol) and 10% flux (sodium silicate). The silica porous ceramic ultrafiltration membrane showed excellent performance in oil–water separation due to its hierarchically interconnected mesopores and strong water absorption, suitable for an O/W emulsion of 26,378 ppm high-concentration toluene and silicone oil. The separation efficiency reached up to 99.6%, with a flux as high as ∼1530 L m–2 h–1 bar–1. Furthermore, the ceramic membrane demonstrated excellent durability, maintaining a stable performance over 50 consecutive filtration cycles. This work provides new insights into the construction of an advanced porous ceramic ultrafiltration membrane for the efficient removal of water from oil products.