Preparation, characterization and solvent resistance of γ-Al2O3/α-Al2O3 inorganic hollow fiber nanofiltration membrane

•The γ-Al2O3/α-Al2O3 hollow fiber NF composite membranes were successfully prepared by sol–gel method.•NF membranes have positive charges, high pure water flux and high rejection rate of multivalent ions.•NF membranes are stable in organic solvents and strong acids.

γ-Al2O3/α-Al2O3 hollow fiber nanofiltration (NF) composite membranes with different molecular weight cut-offs (MWCOs) ranging from 1.4 kDa to 14.5 kDa were prepared by dip-coating γ-AlOOH sol on the ceramic membrane with a mean pore size of 229 nm. The effect of the preparation conditions including soaking time and coating times were investigated by scanning electron microscopy (SEM), dynamic contact angle and membrane performance. The optimal inorganic NF membrane demonstrated a high pure water permeance with high retentions of multivalent ions and low retentions of monovalent ions. The γ-Al2O3/α-Al2O3 inorganic hollow fiber NF membrane shows excellent solvent resistance and good stability.