Hydrophilic Hollow Nanocube-Functionalized Thin Film Nanocomposite Membrane with Enhanced Nanofiltration Performance

The performance of thin film nanocomposite (TFN) membrane is significantly determined by the inherent structure and composition of the incorporated nanofillers. In this work, hydrophilic hollow nanocubes (HHNs) derived from zeolitic imidazolate framework 8 (ZIF-8) were incorporated into the polyamide layer via an interfacial polymerization approach. The HHNs with abundant hydroxyl groups on the surface were obtained by etching solid ZIF-8 using tannic acid. Benefiting from the hydrophilicity, hollow structure, and negative charge of HHNs, the outstanding nanofiltration performance of the composite membrane was achieved. With the assistance of HHNs, the permeance and Na₂SO₄ rejection of the TFN membrane increased up to 19.4 ± 0.6 L/(m²·h·bar) and 95.2 ± 1.4%, corresponding to an improvement of 190% of the permeance and 2.0% of the rejection compared to the pristine thin film composite membrane. Comparatively, the performance of TFN membranes prepared with solid ZIF-8 only shows 116% improvements of the permeance with slightly increased salt rejection. More importantly, the antifouling property of the TFN-4H membrane was also elevated. The flux recovery ratios of the TFN-4H membrane are 93.2 and 84.7% corresponding to humic acid and bovine serum albumin solutions, respectively. The results indicate that the nanofiltration performance of the composite membrane was significantly enhanced with the incorporation of HHNs.