Preparation of high permeance thin-film composite nanofiltration membrane on macroporous ceramic support

Thin-film composite (TFC) nanofiltration (NF) membranes have been widely used in water purification processes. In harsh conditions, however, the application of TFC membrane was limited by selectivity loss because of swelling or dissolution. In this study, a defect-free polyamide (PA) layer was directly prepared on a tubular alumina ceramic membrane with a pore size of 100 nm to compensate these shortcomings. The ceramic support, owing to its superior hydrophilicity, showed excellent affinity with aqueous diamine monomers, preventing defects caused by large pore sizes. Besides, the narrow aperture distribution of support is conductive to control the water-oil interface at an appropriate position that the active layer can form near the support by simple airdrying. Different morphologies and performances were easily obtained by changing the monomer concentration and reaction time. The resulting organic-inorganic composite membrane exhibited pure water permeance of 21.7 LMH/bar and desirable rejection to Na2SO4 of 99.0%. Moreover, the prepared NF membrane showed satisfactory compaction resistance at pressure from 2 to 12 bar owing to the excellent mechanical strength of the support. The inorganic support also endowed the TFC membrane with good performance stability even at 75 degrees C and after soaking in different organic solvents for one week.

Automated summary

In this study, a defect-free polyamide (PA) layer was directly prepared on a tubular alumina ceramic membrane to overcome the selectivity loss issue of thin-film composite (TFC) nanofiltration (NF) membranes in harsh conditions. The resulting organic-inorganic composite membrane exhibited high water permeance and good rejection to Na2SO4, as well as excellent compaction resistance and performance stability.