Polysulfone (PSf) membranes typically have a negligible rejection of salts due to the intrinsic larger pore size and wide pore size distribution. In this work, a facile and scalable heat treatment was proposed to increase the salt rejection. The influence of heat treatment on the structure and performance of PSf membranes was systematically investigated. The average pore size decreased from 9.94 ± 5.5 nm for pristine membranes to 1.18 ± 0.19 nm with the increase in temperature to 50 °C, while the corresponding porosity decreased from 2.07% to 0.13%. Meanwhile, the thickness of the sponge structure decreased from 20.20 to 11.5 μm as the heat treatment temperature increased to 50 °C. The MWCO of PSf decreased from 290,000 Da to 120 Da, whereas the membrane pore size decreased from 5.5 to 0.19 nm. Correspondingly, the water flux decreased from 1545 to 27.24 L·m−2·h−1, while the rejection ratio increased from 3.1% to 74.0% for Na2SO4, from 1.3% to 48.2% for MgSO4, and from 0.6% to 23.8% for NaCl. Meanwhile, mechanism analysis indicated that the water evaporation in the membranes resulted in the shrinkage of the membrane pores and decrease in the average pore size, thus improving the separation performance. In addition, the desalting performance of the heat-treated membranes for real actual industrial wastewater was improved. This provides a facile and scalable route for PSf membrane applications for enhanced desalination.Keywords:PSf membrane;heat treatment;rejection performance
Based on previous studies, we prepared ultrafiltration membranes by cross-linking PEEKWC/PEI using a non-solvent induced phase separation method, this membrane has excellent hydrophilicity. We also incorporated silica (SiO 2 ) into the cross-linked membrane system through distribution blending in this study. The membranes underwent characterization using various methods including SEM, ATR-FTIR, and water contact angle tests. To assess the impact of silica addition on membrane performance, tests were conducted on pure water flux, dye flux, dye retention, salt solution flux, salt-dye mixed solution flux, and retention. The results indicated a noticeable improvement in the hydrophilicity of the membrane following the addition of silica, as evidenced by a reduction in the hydrophilic angle from 22.175° to 6.271°, pure water flux up to 850 LMH at 0.3 MPa. Moreover, the retention performance of the membrane was enhanced, with the Congo red solution reaching a retention rate of 99.9% at 0.3 MPa pressure. Subsequently, a fixed silica ratio was chosen (2wt%), and different ratios of silane coupling agent were added using the distribution blending method to explore their effects on membrane performance. The tests revealed an improvement in the retention performance, the group with the largest change in the Congo Red cut-off rate, with an increase in the Congo Red cut-off from 88.7% to 97.9%.
In order to improve the permeability and desalination performance of the thin-film nanocomposite (TFN) membranes supported by polyphenylene sulfide ( PPS ), the polydopamine (PDA) modified HKUST-1 (mHKUST-1) nanocomposite materials were added into polyamide ( PA ) functional layer. The mHKUST-1 nanoparticles with good dispersity and chemical compatibility were successfully embedded in PA layer to develop a new negative charged nanofiltration membrane . The optimized PPS/ [email protected] membrane showed an excellent permeability of up to 27.35 L∙m −2 h −1 ∙bar −1 , twice as much as the [email protected] membranes. Meanwhile, the considerable rejection performance of 91.67% to MgSO 4 and 90.06% to Na 2 SO 4 at 4 bar was mainly up to the repulsive effect of negative charge on membrane surface. Moreover, the PPS/ [email protected] membranes also has stable filtration performance under long time operation. The results suggested that the membrane modification method in this work have great potential for applications in desalination.
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