Nanostructured nanofiltration hollow fiber membranes for metal recovery from industrial wastewater

Metal recovery from industrial wastewater is essential to mitigate environmental pollution and conserve natural resources. Membrane filtration technology, especially nanofiltration, has become a promising approach for metal recovery due to its high selectivity and efficiency. In recent years, nanostructured hollow fiber nanofiltration membranes (NHFNFMs) have gained increasing attention in water treatment and metal recovery due to their unique structure and properties. NHFNFMs exhibit a high surface area-to-volume ratio, which increases the adsorption capacity and reduces the fouling tendency. Additionally, the nanoscale pores of NHFNFMs selectively retain metal ions and exclude unwanted contaminants, leading to high separation efficiency. The fabrication of NHFNFMs with different morphologies and surface chemistries allows tailoring their performance to specific metal recovery applications. This review summarizes the recent advances in NHFNFMs for metal recovery, including their fabrication methods, structural characterization, and metal retention properties. Moreover, the applications of NHFNFMs for metal recovery from different sources such as electroplating and mining wastewater are discussed. Finally, the challenges and future directions of NHFNFMs for metal recovery are highlighted. There is a consensus in the literature that the incorporation of nanomaterials into the surface or the structure of hollow fibers NF (HFNF) could either lead to improve metals rejection but compromises pure water flux or improve the latter and maintain metal rejection at the same level. NHFNFMs have the potential to revolutionize the field of metal recovery and contribute to its sustainable development.