Moreover, commonly used nanofiltration membranes have abundant hydrophobic sites (i.e., benzene rings) in their polyamide chains. These sites are prone to adsorb hydrophobic foulants.
The researchers attempted to enhance the antifouling performance of a polyamide nanofiltration membrane by narrowing its pore size distribution via a one-step multiple IP process.
In this strategy, an aqueous solution of piperazine anhydrous (PIP) and γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) undergoes IP with an organic solution of trimesoyl chloride and tetraethyl orthosilicate (TEOS) on the porous support.
The reactive additive KH560 accelerates the diffusion rate of PIP so it becomes enriched at the reaction boundary. Moreover, the hydrolysis/condensation of KH560 and TEOS at the aqueous/organic interface forms an interpenetrating network with the polyamide network, thus regulating the separation layer structure.
The characterization results indicate that the polyamide-silica membrane has a denser, thicker and more uniform separation layer. The mean pore sizes of the polyamide-silica membrane and a traditional polyamide membrane are 0.62 nm and 0.74 nm, respectively, and these correspond to geometric standard deviations (namely, pore size distribution) of 1.39 and 1.97, respectively. Thus, the polyamide-silica membrane with a narrower pore size distribution shows stronger antifouling performance. In this case, the flux decay ratio decreases from 18.4 percent to 3.8 percent.
