From ultra to nanofiltration: A review on the fabrication of ZrO2 membranes

Zirconia (ZrO₂) membranes experienced rapid progress in applications demanding high-stability membranes own to their higher chemical resistance and hydrophilicity compared to silica and alumina. Moreover, ZrO₂ membranes have increased fouling resistance, high permeability, and a long lifetime making them broadly applied in drinking water production, wastewater treatment, petrochemical, food, and beverages industries. However, fabricating ZrO₂ membranes for Nanofiltration and Gas Separation is still challenging. This paper reviews the progress in fabricating ZrO₂ membranes, focusing on strategies for achieving smaller pores without losing their high permeability and selectivity. The current state of the art in commercial ZrO₂ membranes and the recent innovations in academia are critically reviewed. A comprehensive revision of sol-gel technique's critical synthesis and process parameters is presented along with the most recent molecular layer deposition method. This work aims to provide a guide for both starting and established researchers, thus filling a gap in the present literature.