Yi Guo,Jinchao Chen,Chunmei Gao,Shifeng Ji,Yunqing Xing,Wenjing Tan
In this paper, ZIF-L was blended with citric acid (CA) and polyethersulfone (PES) to prepare a casting solution. A novel negatively charged ultrafiltration (UF) membrane (ZIF-L/CA/PES) was obtained using the reverse thermally induced phase separation (RTIPS) method. The hydrophilic carboxyl groups present in CA not only imparted high hydrophilicity and negative charge to the membrane surface, enhancing the membrane’s selectivity and contamination resistance, but also created an acidic environment to attack the Zn atoms in ZIF-L by the ionized H + from CA, resulting in the generation of micro-defective pores and an improvement in permeability. Additionally, the results showed that membranes generated through the RTIPS process exhibit uniform porous surfaces and spongy cross-sections, enhancing membrane performance. The optimized membranes demonstrated the capability to achieve a pure water flux of up to 2267 L/m 2 h with 93.1 % humic acid (HA) retention, and a remarkable membrane flux recovery rate of 75.8 %, suggesting the crucial roles played by CA and ZIF-L in the separation process. In conclusion, hydrophilic anti-fouling UF membranes with a high negative charge and excellent permeation selectivity were fabricated by establishing micro-defective channels through the incorporation of carboxylic acid and ZIF-L, combined with the RTIPS process.
In this work, the self-healing polyethersulfone ultrafiltration membrane constructed by host-guest chemistry between cucurbit [8]uril (CB [8] is a family of macrocyclic compounds comprising 8 glycoluril units) and two guest molecules based on reverse thermally induced phase separation (RTIPS) method was developed, which had excellent self-healing performance, better mechanical properties, and high permeation flux and BSA rejection rate. The membrane autonomously restored it BSA rejection rate up to about 89% from rejection rate levels as low as 21% after damage. The observed self-healing performance were attributed to the swelling of pore-filled CB [8] hydrogel into the damage position, the molecular interdiffusion of the hydrogel chains, the strong hydrogen bond of the hydrogel chains and the host-guest interaction between CB [8] and two guest molecules (HEC-Np and PVA-MV). SEM morphologies illustrated that the prepared pore-filled membrane via the RTIPS method had homogeneous and porous skin surface and sponge-like cross-section, which imparted the prepared membranes with improved permeability and better mechanical properties. Properties of MR-CB [8] membranes, which varied with increased content of CB [8], were evaluated by permeability, water contact angle, thermogravimetric analysis (TGA), mechanical properties, FRR, scanning electron microscope (SEM) and atomic force microscopy (AFM). The contact angle water showed that CB [8] hydrogel enhanced the surface hydrophilicity of the prepared membrane. TGA illustrated that the thermal stability improved with the increased content of CB [8]. The optimal pore-filled CB [8] hydrogel membrane (MR-CB [8] 2 ) exhibited that the pure water flux reached 2100.5 L/m 2 h, while the BSA rejection rate remained at 86.0%. The results of this work suggested pore-filled CB [8] hydrogel membrane was a more promising way to develop polyethersulfone ultrafiltration membranes with self-healing performance.
In this work, the NH 2 -MIL-125/F127/PES membranes with superior ultrafiltration , anti-fouling and self-cleaning were constructed via the RTIPS method. Characterizations showed the successful fabrication of NH 2 -MIL-125 with good photocatalysis activities, together with its stable anchoring in PES membrane. The loss of NH 2 -MIL-125 was suppressed by hydrogen bond between F127 and NH 2 -MIL-125, where hydrophilic F127 significantly boosted permeability and anti-fouling property. The permeability-selectivity trade-off effect was alleviated by NH 2 -MIL-125 with a regular size window. It was observed that the membranes prepared by the RTIPS method occurred a spongy-like cross-section and a porous surface, which imparted the membrane with improved ultrafiltration and mechanical properties over the finger-like cross-section and dense skin caused by the NIPS method. The optimal membranes exhibited decent permeability (1511 L/m 2 h), BSA rejection rate (85.3%) and high COD removal rate over the commercial membranes, whose flux recovery rate was up to 76.91% after two cycles under light irradiation by the synergistic effect of F127 and NH 2 -MIL-125. The membrane fouled with RhB exhibited excellent regeneration properties benefiting from the holes (h + ) and superoxide free radicals ( • O 2 − ), as well as reactive •OH. Overall, the membrane with F127 and NH 2 -MIL-125 presented a highly promising in improving ultrafiltration and self-cleaning via the RTIPS method.
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