Hierarchical meso-macroporous γ, α-alumina membrane: Ultrahigh permeability in tight ultrafiltration for water treatment

Research into tight ultrafiltration (TUF) membranes has been primarily directed towards achieving a delicate equilirium between selectivity and permeability. The enhancement of TUF membranes with concurrent improvements remains a challenging endeavor. In this study, a hierarchical meso-macroporous γ, α-alumina membrane is synthesized through the impregnation of gel-casted α-alumina disks with mesoporous alumina sol. The objective of this investigation is to develop ultra-permeable TUF membranes possessing a suitable molecular weight cut-off (MWCO). Mesoporous γ-alumina forms in situ within the macropores of α-alumina. These mesopores serve as a filtration mechanism through molecular sieving, while secondary macropores significantly enhance permeability to an exceptionally high degree and facilitate rapid access to the mesopores. The primary and secondary pore sizes measure 5.81 and 280 nm, respectively. The hierarchical meso-macroporous TUF membrane exhibits exceptionally high pure water permeability (18.50 L.m−2.h−1.bar−1) and low membrane resistance (1.95 × 1012 m−1). Retention curves for dextran and polyethylene glycol (PEG) indicate a molecular weight cut-off of 7626 Da for the membrane. The prepared TUF membrane can remove over 90 % of pollutants larger than 2.26 nm. The hierarchical meso-macroporous membrane offers adequate compressive strength, enhances TUF membrane permeability, and diminishes transport resistance while maintaining membrane separation efficiency. The findings indicate that the developed membrane possesses attributes that are conducive to sustainable water and wastewater treatment as a TUF membrane. [Display omitted] •Hierarchical meso-macroporous γ, α-alumina membranes for tight ultrafiltration•Innovative design with γ-alumina mesopores inside α-alumina macropores•Fabrication method for multiporous structure and reliable mechanical strength•Balancing permeability and molecular weight cut-off for efficient filtration