Yi Wang,Yuqi Nie,Chunhong Chen,Hongjie Zhao,Ye Zhao,Yujin Jia,Jun Li,Zhanguo Li
MXene nano-sheets were introduced into a thin-film composite membrane (TFC) to reduce the mass transfer resistance (concentration polarization) and improve the membrane performance. The process entailed dissolving the MXene nano-sheets in a membrane casting solution using the blending method and introducing them into the porous support layer to prepare a modified thin-film composite forward osmosis (TFC-FO) membrane. The results showed that the water contact angle decreased by about 16%, indicating that the hydrophilicity was strengthened, and the O/N ratio of the active selective layer decreased by 13%, indicating an increased degree of crosslinking, thereby demonstrating that the introduction of MXene nano-sheets changed the properties of the membrane and played a positive role in its physicochemical properties. In contrast to the unmodified TFC-FO membrane, the modified membrane had a slightly higher reverse solute flux, while its water flux increased by about 80%. Its specific reverse osmosis flux was also significantly optimized (only 0.63 g/L). In conclusion, adding MXene nanosheets to TFC-FO membranes led to the modified membranes with better mass transfer, lessened internal concentration polarization (ICP), and better osmotic separation.Keywords:TFC-FO membrane;MXene nano-sheets;internal concentration polarization
Developing a forward osmosis (FO) membrane with superior ammonia selectivity and robust antifouling performance is important for treating domestic wastewater (DW) but challenging due to the similar polarities and hydraulic radii of NH 4 + and water molecules. Herein, we investigated the feasibility of using polyamidoamine (PAMAM) dendrimer to simultaneously enhance the ammonia rejection rate and antifouling capacity of the thin-film composite (TFC) FO membrane. PAMAM dendrimer with abundant, easily-protonated, terminal amine groups was grafted on TFC-FO membrane surface via covalent bonds , which inspired the TFC-FO membrane surface with appreciable Zeta potential (isoelectric point: pH = 5.5) and outstanding hydrophilicity (water contact angle: 39.83 ± 0.57°). Benefiting from the electrostatic repulsion between the protonated amine layer and NH 4 + -N as well as the concentration-induced diffusion resistance, the introduction of PAMAM dendrimer endowed the grafted membrane with a superior NH 4 + -N rejection rate of 98.23% and a significantly reduced the reverse solute flux when using NH 4 Cl solutions as feed solution. Meanwhile, the perfect balance between the electrostatic repulsion to positively-charged micromoleculer ions (metal ions and NH 4 + -N) and the electrostatic attraction to negatively-charged macromolecular organic foulants together with the hydrophilic nature of amine groups facilitated the enhancement of the grafted membranes in antifouling capacity and hence the NH 4 + -N selectivity (rejection rate of 91.81%) during the concentration of raw DW. The overall approach of this work opens up a frontier for preparation of ammonia-selective and antifouling TFC-FO membrane.
危险品化学品经营许可证（带存储）