Zou Lusi, Gusnawan Pri, Jiang Ying-Bing, Zhang Guoyin, Yu Jianjia
Petroleum Recovery Research Center, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, United States.
Materials Engineering Department, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, United States.
ACS Appl Mater Interfaces. 2020 Jun 24;12(25):28655-28668. doi: 10.1021/acsami.0c06902. Epub 2020 Jun 11.
A polyvinylidene fluoride (PVDF) hollow fiber membrane was fabricated through water-induced dope crystallization by allowing a facile spinning process delay (SPD) in the nonsolvent-induced phase separation (NIPS) process for direct contact membrane distillation (DCMD). The SPD was achieved by the addition of a small amount of water to the PVDF dope solution that was held in a closed container for a particular time. The crystalline property of the PVDF dope solution was investigated by differential scanning calorimetry. The obtained PVDF hollow fiber membranes were characterized with different techniques, including field emission scanning electron microscopy, X-ray diffraction, and the mechanical strength. Both the formation mechanism and properties were studied for the membranes with different SPD times. The results showed that macrovoid-inhibited PVDF membranes were obtained from 12 days of the SPD via the crystallization-dominated membrane formation process. The obtained membrane 4D-12 exhibited desirable membrane structure and properties for DCMD, which includes an improved liquid entry pressure of 2.25 bar, a surface water contact angle of 129°, a maximum pore size of 0.40 μm, and a mean pore size of 0.34 μm. The membrane 4D-12 possessed a twofold increase in both energy efficiency and permeate water flux in DCMD and stable permeate water flux and salt rejection through 224 h of continuous desalination operation. Compared to the commonly used approach by adding chemicals to the external coagulant, the SPD method provided a low-cost and environmentally friendly alternative to pursuing the macrovoid-free PVDF membranes for DCMD.
通过在非溶剂诱导相分离（NIPS）过程中进行简便的纺丝过程延迟（SPD），利用水诱导铸膜液结晶法制备了用于直接接触膜蒸馏（DCMD）的聚偏氟乙烯（PVDF）中空纤维膜。通过向封闭容器中保存特定时间的PVDF铸膜液中添加少量水来实现SPD。采用差示扫描量热法研究了PVDF铸膜液的结晶性能。用包括场发射扫描电子显微镜、X射线衍射和机械强度在内的不同技术对所得PVDF中空纤维膜进行了表征。研究了不同SPD时间的膜的形成机理和性能。结果表明，通过12天的SPD，经由以结晶为主导的膜形成过程，获得了抑制大孔的PVDF膜。所得的4D-12膜展现出适用于DCMD的理想膜结构和性能，包括2.25 bar的改进液体进入压力、129°的表面水接触角、0.40μm的最大孔径和0.34μm的平均孔径。4D-12膜在DCMD中的能量效率和渗透水通量均提高了两倍，并且在224小时的连续脱盐操作中具有稳定的渗透水通量和脱盐率。与向外部凝固剂中添加化学物质的常用方法相比，SPD方法为制备用于DCMD的无大孔PVDF膜提供了一种低成本且环境友好的替代方案。
