Tuning micro-nano hierarchical structure and wettability of tubular SiC ceramic membrane pore channels for emulsification

Membrane emulsification has garnered increasing attention in various applications, attributed to its low energy consumption and precise droplet size control. However, current research on membrane emulsification rarely focuses on the microstructure of membrane pore channels, nor does it systematically clarify the correlation between such microstructural characteristics and emulsification performance. This study successfully prepared hydrophilic/hydrophobic (HL/HB) tubular SiC ceramic membranes with hierarchical micro-nano pore structures and different wettability via the combination of sol-gel, hydrothermal synthesis and silane polymerization grafting methods. After the in-situ uniform growth of ZnO nanoclusters onto SiC grains, the average pore size of the HL-SiC membrane decreased from 0.50 μm (the HL-SiC membrane) to 0.35 μm (the HL-ZnO@SiC membrane), and the surface roughness significantly increased to 556.0 nm. Silane grafting endowed the HB-ZnO@SiC membrane with superhydrophobicity, achieving a water contact angle of 160.88°. Systematic evaluation of key operational parameters revealed that, at a dispersed phase flow rate of 20 mL/min and a continuous phase flow rate of 1200 mL/min, the average droplet sizes for oil-in-water (prepared by the HL-ZnO@SiC membrane) and water-in-oil (prepared by the HB-ZnO@SiC membrane) emulsions were 0.98 and 0.90 μm, respectively, with Span values as low as 0.36 and 0.29. Notably, the membranes maintained stable emulsification performance even under high dispersed phase concentration (30 % v /v) and low emulsifier content (0.25 % w / v , Tween 80 and Span 80). This work offers a reliable strategy of micro-nano hierarchical pore engineering for enhancing membrane emulsification.