Liu Jie, Li Jiding, Chen Quan, Li Xiaoduan
National Institute of Clean-and-Low-Carbon Energy, Beijing 102211, China and State Key Laboratory of Water Resource Protection and Utilization in Coal Mining of Shenhua Group, Beijing 100011, China E-mail:
State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
Water Sci Technol. 2018 Apr;77(7-8):1861-1869. doi: 10.2166/wst.2018.067.
Polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) composite membranes were fabricated and subsequently applied in ethanol recovery from an ethanol-water mixture by pervaporation (PV) using fractional condensation. The effects of feed temperature and feed flow velocity on the pervaporative properties of PDMS/PVDF composite membranes were investigated. Scanning electron microscopy (SEM) results showed that PDMS was coated uniformly on the surface of porous PVDF substrate, and the PDMS separation layer was dense with a thickness of 1.7 µm. Additionally, it was found that with increasing feed temperature, the total flux of the composite membrane increased, whereas the separation factor decreased. As the feed flow velocity increased, the total flux and separation factor increased. Besides, the permeate vapor was condensed by a two-stage fractional condenser maintained at different temperatures. The effects of the condensation conditions on fractions of ethanol-water vapor were studied to concentrate ethanol in product. The fractional condensers proved to be an effective way to enhance the separation efficiency. Under the optimum fractional condensation conditions, the second condenser showed a flux of 1,329 g/m h and the separation factor was increased to 17.2. Furthermore, the long-term operation stability was verified, indicating that the PV system incorporating fractional condensation was a promising approach to separate ethanol from the ethanol-water mixture.
制备了聚二甲基硅氧烷（PDMS）/聚偏氟乙烯（PVDF）复合膜，并随后将其应用于通过分凝渗透汽化（PV）从乙醇 - 水混合物中回收乙醇。研究了进料温度和进料流速对PDMS/PVDF复合膜渗透汽化性能的影响。扫描电子显微镜（SEM）结果表明，PDMS均匀地涂覆在多孔PVDF基材表面，PDMS分离层致密，厚度为1.7μm。此外，发现随着进料温度升高，复合膜的总通量增加，而分离因子降低。随着进料流速增加，总通量和分离因子增加。此外，渗透蒸汽由保持在不同温度的两级分凝器冷凝。研究了冷凝条件对乙醇 - 水蒸气馏分的影响，以浓缩产物中的乙醇。分凝器被证明是提高分离效率的有效方法。在最佳分凝条件下，第二冷凝器的通量为1329 g/m²·h，分离因子提高到17.2。此外，验证了长期运行稳定性，表明结合分凝的PV系统是从乙醇 - 水混合物中分离乙醇的一种有前景的方法。
