Structures and performance of alcohol activated thin film composite polyamide (TFC-PA) nanofiltration (NF) membranes prepared with and without Co(II) modulation

Structures and NF performance of TFC-Co and TFC membranes activated with 50 % alcohol solutions were studied. Methanol and glycol solution activation increased water flux 2–4 times without trading off salt rejection while glycerin solution activation increased water flux 3–4 times with reduced salt rejection and increased dye/salt retention selectivity. The Stokes radius of TFC-Co membrane changed from 0.77 nm to 0.66, 0.78 and 0.92 nm while the TFC membrane changed from 0.54 nm to 0.55, 0.65 and 0.70 nm after activation with methanol, glycol and glycerin solutions, respectively. Capillary pore filling models were developed from pure alcohol absorption experiments including the stages of initial pore filling, pore expansion, pore relaxation and pore adjustment, while most Stokes radius after 50 % solutions activation were found to be close to the relaxed pore radius values (rrx) or half of the expanded pore radius values (rex) from pure alcohol absorption experiments.