Narrowing the pore size distribution of a piperazine-based ultrathin polyamide film with the addition of 1,3-diamino-2-propanol (DAP)

Sharpening the pore size distribution is challenging but highly efficacious to boost the performance of polyamide (PA) membranes in nanofiltration (NF). Herein, a facile and applicable strategy for narrowing the pore size distribution of a piperazine (PIP)-based NF membrane is proposed by introducing 1,3-diamino-2-propanol (DAP) into the aqueous phase. The results show that the selective layer can be effectively remodeled via the incorporation of DAP. A thicker, rougher and more hydrophilic selective layer with a narrowed pore size distribution can be attained by adding 0.03 w/v% DAP to the 0.1 w/v% PIP solution, which exhibited a pure water permeance (PWP) of 20.7 L m −2  h −1 ·bar −1 and a MgSO 4 rejection up to 97.4 %. This transformation can be attributed to the stronger polarity and higher reactivity of DAP compared to PIP. During the IP process modified by DAP, the strong polarity of DAP could result in a slower and more homogeneous diffusion of PIP into the organic phase through hydrogen interaction to facilitate a uniform interfacial polymerization reaction. Meanwhile, the higher reactivity of DAP could remedy the probably produced defects. This work provides a straightforward route for the regulation of NF membrane structure and performance.