Micro-extrusion 3D printing and sewage filtration performance of multi-layer cross-hole alumina ceramics

The ceramic slurry is prepared using alumina and calcium carbonate powder as matrix materials，polyvinyl alcohol solution as a binder，and acetic acid as a dispersant. Different porous alumina-based ceramics are printed by micro-extrusion 3D printing technology. The effects of hole structure and thickness on the sewage filtration performance and its affecting mechanism of porous alumina-based ceramics are investigated. The results show that the multi-layer cross-hole alumina-based ceramic samples with the hole diameter less than 0.1 mm are successfully fabricated by the micro-extrusion 3D printing method with a stepwise 30° filling angle and varying filling rates. The cross hole distribution can divert sewage flow and increase the effective filtration area，while the thicker multi-layer cross-hole porous alumina-based ceramic provides a longer path for sewage filtration，facilitating the removal of small molecular particles in the sewage. When the filling rate is 90% and the ceramic thickness exceeds 8 mm，the sewage turbidity removal rate exceeds 90%，and the filtered sewage turbidity is below 10 NUT，satisfying the industrial and agricultural requirements for water. Based on adsorption，screening-filter cake-deep bed filtration mechanism，a filtration mechanism model of the multi-layer cross-hole and through-hole structures is established. The multi-layer cross-hole alumina-based ceramics with submicron and micron-sized holes perform better in terms of permeability and filtration ability，compared to through-hole alumina filtration ceramics，possessing higher potential for sewage treatment applications. This research provides valuable reference for the application of micro-extrusion 3D printing technology in the field of porous ceramic filtration.