Rationally designed in-situ fabrication of thin film nanocomposite membranes with enhanced desalination and anti-biofouling performance

Silver nanoparticle (AgNP)-incorporated thin film nanocomposite (Ag-TFN) membranes with enhanced reverse osmosis (RO) separation and anti-biofouling performance were fabricated via a rationally designed in-situ hybridization technique based on the dual action of reactant materials: (1) m-phenylenediamine (MPD) monomer, conventionally employed to form a polyamide (PA) selective layer, can also reduce Ag precursors (AgNO3) to form AgNPs; (2) sodium dodecyl sulfate (SDS) surfactant, widely used to facilitate PA formation, can also stabilize AgNPs and transfer them to the interface where the PA layer is formed. The simple addition of AgNO3 to an MPD solution containing SDS during interfacial polymerization enabled the simultaneous formation of the PA layer and AgNPs, which led to the uniform incorporation of AgNPs into the PA matrix, creating the PA-AgNP interfacial free volume (nanovoids) without impairing PA crosslinking. Hence, the Ag-TFN membrane exhibited remarkably higher water permeance with similar NaCl rejection in comparison with the pristine thin film composite (TFC) and commercial membranes, mainly owing to its enhanced interfacial free volume and increased hydrophilicity. The Ag-TFN membrane also exhibited better anti-biofouling performance than control TFC owing to the antibacterial ability of AgNPs and reinforced anti-adhesion enabled by its reduced surface roughness and enhanced surface hydrophilicity.