Lu Xiaohui,Yu Shouwu,Gao Tian,Chen Yifu,Zhao Xiang,Xiao Shujuan
The wettability of the membrane surface is very important for the separation of oil-in-water emulsion. In this paper, the hydrophilic NH 2 -CAU-1 was added to the membrane surface by interfacial polymerization, which greatly improved the separation efficiency of oil-in-water emulsion. The effect of the amount of NH 2 -CAU-1 on the separation efficiency of TFN membrane was studied, and it was determined that TFN-1 membrane had ultra-high separation efficiency of oil-in-water emulsion (> 97.60%). TFN-1 membrane has a high underwater oil contact angle (higher than 139.53°), resulting in excellent oil adhesion resistance on the membrane surface. The universality and cycling performance of TFN-1 membrane were tested, and UWOCA had good stability under strong acid, strong base and different NaCl concentrations, and the separation efficiency did not change significantly after 8 cycles. The results show that TFN-1 membrane has excellent performance in separating oil-in-water emulsions and has broad application prospects in separating oil-in-water emulsions stabilized by surfactants. Graphical abstract
Over the last decade, thin-film nanocomposite (TFN) membranes have been extensively utilized in desalination and wastewater treatment. The most reported nanochannels in the TFN membranes lack sufficient observational evidence. We conducted a systematic study on the TFN membrane that incorporated two-dimensional (2D) MXene nanosheets and provided evidence that nanovoids existed in the polyamide layer surrounding the nanosheets. The nanovoids functioned as nanochannels for water, which led to a significant increase in membrane permeance by 2.8 times compared to the blank membrane. The Na2SO4 rejection of the MXene polyamide membrane is as high as 96.4% and has obvious advantages in seawater desalination. The size of the nanochannels was correlated with the quantity, size, and spreadability of MXene nanosheets. Larger water nanochannels could be formed if there is a considerable amount and size of nanosheets, and they were evenly distributed. After being subjected to a sustained pressure environment, the nanochannels remained intact and the membrane maintained its excellent permeance across varying pressures. Our work could offer a perspective on the generation of internal nanochannels in the TFN membrane and optimize nanochannels to provide better desalination performance.
Thin film nanocomposite membranes have become a feasible technology for heavy metal wastewater treatment . However, how to enhance the dispersibility and compatibility of nanomaterials in the selective layer is an important issue to improve the membrane performance of heavy metal removal . In this study, silica-poly(ionic liquid) nanoparticles were incorporated in the selective layer of TFN membranes. 1-Allyl-3-methyl imidazolium hexafluorophosphate ([AMIm]PF 6 ) was selected to modify silica (SiO 2 ) particles. The formed poly([AMIm]+) brushes provided charge properties to enhance dispersibility and organic part to improve compatibility in the polyamide layer of NF membranes. The resultant TFN membranes incorporated with SiO 2 -[AMIm]PF 6 particles exhibited an increment of 34% water permeation and 41.6% MgCl 2 rejection. Moreover, with an average rejection improvement of around 15% for heavy metal ions at pH = 5–6, the SiO 2 -[AMIm]PF 6 /PA membrane showed its superiority beyond the PA membrane. The electropositivity and microporous structure of the SiO 2 -[AMIm]PF 6 particles enhanced their dispersibility and compatibility in the polyamide layer. Meanwhile, the proper pore size and structure of the SiO 2 -[AMIm]PF 6 particles contributed to the channels for water transport and the sieving effect for most heavy metal ions. This work may facilitate the applications of TFN membranes in heavy metal wastewater treatment to alleviate the “trade-off” phenomenon.
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