In-situ modification of nanofiltration and reverse osmosis membranes for organic micropollutants and salts removal: A review

The thin film composite (TFC) polyamide (PA) nanofiltration (NF) and reverse osmosis (RO) membranes are the two of the most robust technologies for the removal of organic micropollutants (OMPs) for (waste) water treatment, and improving sodium chloride (NaCl) rejection for sea water desalination to tackle water scarcity. However, the neutral, smaller and polar OMPs are often ineffectively removed by commercial NF/RO membranes. In-situ NF and RO membrane surface modification is a promising and viable option for improving the rejection of OMPs in existing membrane-based treatment plants without changing the production process. However, there is a research gap in the retention of different groups of OMPs by in-situ modified NF and RO membranes. To fill the research gap in recent years, this current review comprehensively analyzed the impact of reported in-situ NF and RO membranes modification strategies on water permeability, the retention of OMPs grouped by size, hydrophobicity, and charge, and NaCl rejection, where the tradeoff between water/OMPs permeability and water/NaCl permeability received special emphasis. Furthermore, optimal modification strategies to improve OMPs rejection in different groups by NF and RO have been suggested.