Acid-stable nanofiltration membranes: Emerging materials for sustainable separation in harsh and extreme conditions

Acid-stable nanofiltration (ASNF) membranes have emerged as a transformative technology for enabling efficient and selective separations in chemically aggressive environments encountered across various industrial sectors. Applications such as acid mine drainage treatment, copper smelting and refining, steel pickling, hydrometallurgy, biomass processing, and resource recovery require membrane systems that can withstand extreme pH levels and elevated temperatures. This review provides critical insights into the current state of ASNF membranes, particularly those developed at the bench scale, and highlights the operational limitations of conventional membranes under such harsh conditions. It examines recent progress in ASNF membrane fabrication/material design strategies, and performance metrics in extreme environments alongside the chemical mechanisms that underpin their durability. Additionally, their applications in acidic wastewater separation and recovery are examined. Challenges encountered in their development and application, with prevailing research gaps including limited long-term stability data, scalability constraints, and the absence of standardized evaluation protocols are highlighted. Finally, perspectives for future studies in academia as well as industry are recommended, including molecular-level material engineering, selective nanomaterial integration, and data-driven design approaches. By bridging fundamental membrane science with industrial relevance, this review underscores the vital role of ASNF membranes in advancing sustainable separation technologies to achieve both industrial and ecological benefits.