3D electrospray printing TFC nanofiltration membrane with narrow distributed pore size for the precise separation of mono-/divalent ions

초록

Nanofiltration membranes inherently possess the ability to selectively separate ions due to their differing rejection characteristics for mono-/divalent ions. However, in the applications of complex ionic systems such as brine and wastewater reuse, nanofiltration membranes fabricated by conventional interfacial polymerization (IP) often face challenges to achieve precise separation of mono-/divalent cations, as well as anions, due to nonuniform pore structure (ultrafast reaction kinetics) and strong electronegativity (hydrolysis of acyl chloride groups). In this study, we fabricated a dense thin-film composite (TFC) nanofiltration membrane through multiple scans of three-dimensional (3D) electrospray printing, using piperazine (PIP) and trimesoyl chloride (TMC) as monomers and (+/-)-camphor-10-sulfonic acid-triethylamine (CSA-TEA) as the aqueous phase additive. The results show that the nanofiltration membrane prepared by 25 scans of 3D electrospray printing exhibited a dense pore structure of 2.91 & Aring; with a narrow distribution. Meanwhile, the surface of the nanofiltration membrane demonstrated weak electronegativity of -13.24 mV at pH 7. The prepared membrane achieved precise selective separation of mono-/divalent anions and cations, based on the difference in hydration energy. The membrane demonstrated a separation factor of 120.52 for Cl-/SO42-and 22.47 for Li+/Mg2+, along with a high pure water permeability. This work provides a novel paradigm for expanding the application of 3D electrospray printing in the preparation of TFC nanofiltration membranes.

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