Nanofiltration membranes for sustainable removal of heavy metal ions from polluted water: A review and future perspective

The increase demand on clean water accompanied with water shortage is now threatening the ecosystem and human life, which is aggravated with the rising of heavy-metal-ion polluted water. Thus, water purification from metal-ion contained wastewater is of significance. The metal ions removal could achieve two aims simultaneously: harvesting clean water and recovering the valuable metal resource. Nanofiltration (NF) membranes, featured with the nanopore size and energy-efficiency, demonstrate great promise for separation of metal ions from wastewater, which has not been fully exploited with the rapid growth of advanced materials. Thus, a summarization on the recent progress in this field is essential. In this review, we will start with the introduction of separation mechanism. Then, the possible materials used for NF membrane construction will be given. Subsequently, the commonly used NF fabrication techniques will be detailed with some examples. Next, the NF applications in treatment of various heavy metal ions polluted water will be thoroughly discussed. Finally, the perspectives future directions will be provided. This review is expected to shine a light on the fabrication of NF membranes for high-performance removal of heavy metal ions from the wastewater, realizing the water purification and metal recovery.