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Single-calcination fabrication of γ-Al2O3 nanofiltration membranes via a polyvinyl alcohol sacrificial interlayer for enhanced water permeance

Rongxue Li,Hongdan Wu,Yuqing Sun,Zhihui Zhou,Shiyi Wang

To overcome the limited permeance of conventional γ-Al 2 O 3 nanofiltration (NF) membranes caused by sol penetration into porous supports and poor interfacial defect control, a single-calcination fabrication strategy incorporating a PVA sacrificial interlayer was developed in this study. This approach enabled simultaneous structural optimization and performance enhancement, while also simplifying the overall fabrication process. At a PVA concentration of 3 wt% and a pre-filling time of 2 min, the average pore size of the γ-Al 2 O 3 separation layer increased from 2.04 to 2.39 nm, and the pure-water permeance improved from 8.22 to 17.68 L m −2  h −1 ·bar −1 . This enhancement is attributed to the PVA pre-filling, which effectively suppressed the infiltration of AlOOH sol into the large pores of the support and generated open micro-pores upon calcination, thereby forming a more uniform and better-connected pore structure and consequently reducing mass-transfer resistance, which contributed to a synergistic “shielding-pore-forming” effect. Owing to the optimized pore architecture and stabilized interfacial charge, the γ-Al 2 O 3 membrane exhibited high rejection of MgCl 2 (91.62 %) and CaCl 2 (86.86 %), while maintaining relatively high permeace toward NaCl and Na 2 SO 4 . This separation behavior is governed by the combined effects of size sieving and the Donnan exclusion. Long-term operation and NaClO-cleaning tests further verified that the membrane retained its structural integrity and stable separation performance. This green and facile fabrication strategy offers a practical route for the low-cost production of high-performance ceramic NF membranes and shows considerable promise for engineering-scale applications.