Abstract:

To overcome the "trade-off" between the solvent permeability and solute separation selectivity of traditional thin film polyamide composite (TFC-PA) nano filtration (NF) membrane, the interface polymerization (IP) was regulated by dodecyl sulfate (SDS) and strong base (NaOH) in the aqueous phase. Presence of SDS could reduce interface tension, enrich PIP monomer through electrostatic interaction, protect poly(acyl chloride) monomer from hydrolysis and accelerate the uniform diffusion of PIP molecules across interfaces, leading to improved reaction speed and uniformity in the interface polymerization, while NaOH further accelerated the interface polymerization by absorbing the produced acid to keep the activity of SDS as surfactant and also de-protonating PIP monomer for faster reaction. This synergistic enhancement effect enabled the PA layer of generated composite membrane MPA-SDS-NaOH with aqueous phase containing 0.35%SDS and 0.3%NaOH to have narrowed pore size, increased crosslinking degree from 44.8% to 88.4%, decreased thickness from 125nm to 42nm, leading to increased water permeance from 6.04L/(m²·h·bar) to 19.20L/(m²·h·bar), and increased separation selectivity of NaCl and Na₂SO₄ from 29.4 to 152.6. This cooperative compensatory regulation strategy of SDS and NaOH may provide new avenues for preparing highly permeable and selective TFC-PA NF membranes.

Key words: synergistic effect, interface polymerization regulation, selectivity, nanofiltration membrane, polyamide composite membrane

摘要：

针对传统聚酰胺复合（TFC-PA）纳滤（NF）膜溶剂渗透性和溶质分离选择性相互制约、无法同时提升的问题，本文从界面聚合调控出发，由适当比例表面活性剂十二烷基硫酸钠（SDS）和强碱（NaOH）组成二元调节剂。其中，SDS单分子层通过静电作用富集哌嗪（PIP），包裹有机酰氯避免其被NaOH水解，同时降低界面张力，加快PIP分子跨界面均匀扩散，提高界面聚合的速度和均匀性；适量的NaOH吸酸保持SDS的表面活性，同时去质子化活化PIP，加快界面聚合速度，形成均匀聚酰胺分离层。这种协同增强效应使在水相溶液含有0.35%（质量体积浓度）SDS和0.3%（质量体积浓度）NaOH条件下，生成的聚酰胺复合膜MPA-SDS-NaOH与TFC-PA NF膜相比，聚酰胺层交联度从44.8%提高到88.4%，孔径分布变窄的同时，厚度从125nm降到42nm，渗透通量从的6.04L/(m²·h·bar)提高到19.20L/(m²·h·bar)（1bar=0.1MPa），NaCl和Na₂SO₄的单盐分离选择性也从29.4上升到152.6，实现了膜渗透通量和分离选择性的同时提升。SDS和NaOH协同补偿调控策略为制备高渗透选择性脱盐聚酰胺纳滤膜提供了新的思路。

关键词: 协同效应, 界面聚合调控, 选择性, 纳滤膜, 聚酰胺复合膜