Functional Tuning of Polyacrylonitrile Support Chemistry via Diamine Crosslinking and Hydrolysis for Enhanced Organic Solvent Nanofiltration Performance of Thin‐Film Composite Membranes

ABSTRACT This study focuses on tuning active‐layer features by altering the chemistry of the underlying polyacrylonitrile (PAN) to assess its impact on the membranes' organic‐solvent nanofiltration (OSN). The PAN supports are tailored via diamine crosslinking (1,3‐diaminopropane (DAP), ethylene diamine [EDA], and hydrazine [Hz]) and hydrolysis, and the resulting supports were used for interfacial polymerization (IP) to develop a poly(piperazine amide) active layer. Use of hydrolyzed and EDA crosslinked supports leads to hydrophilic surface wettability, with water contact angles (WCAs) of 35.4° and 33.93°, respectively. The separation efficiencies of the membranes have also been tested using various dyes in different solvent media. In terms of separation performance, the EDA cross‐linked thin‐film composite (TFC) membrane shows a balanced behavior in terms of selectivity‐permeability trade‐off, whereas the Hz cross‐linked TFC membrane (PAN support crosslinked using hydrazine) has an organophilic feature, and the hydrolyzed TFC membrane is the most hydrophilic with a water permeance of 18.3 L m −2 h −1 bar −1 . In the case of rejection of solutes with varying molecular sizes and charges, the EDA cross‐linked TFC membrane shows improved performance in methanol and ethanol, whereas Hz and hydrolyzed supported TFC membranes show reduced selectivity for the model cationic Methylene Blue (MB) dye.