Freeze-casting of alumina ultra-filtration membranes with good performance for anionic dye separation

Abstract

Nowadays, ceramic membranes occupy small share in filter membranes due to their high preparation costs and complex manufacturing processes. In this account, a super-fast and one step molding method was developed for preparing alumina ultra-filtration membranes. The procedure is based on camphene freeze-casting process with airflow treatment on the surface, where a thin separation layer and its macroporous support could naturally form. The results confirmed formation of an upper separation layer due to the rapid camphene evaporation controlled by airflow treatment on its surface. The membrane optimized by calcination at 1150 °C yielded most frequent pore size of 33.0 nm, pure water flux of 458.0 L m−2 h−1 bar−1, and bending strength of 36.5 MPa. Also, the membrane possessed high rejection rate of 99.6% towards Direct Red 80 solutions with permeate flux of 230.3 L m−2 h−1 at applied pressure of 2 bar. This method may render preparation processes simple and efficient, making it very promising for large-scale applications.