电纺及疏水改性制备CA/SiNPs-FAS超疏水复合膜及膜蒸馏脱盐研究

以1-甲基-2-吡咯烷酮/丙酮为混合溶剂，无纺布为支撑层，采用静电纺丝技术与溶胶-凝胶方法，制备了醋酸纤维素/二氧化硅复合纳米纤维膜，并将其浸渍于全氟烷基硅烷/正己烷分散液中进行疏水化改性。利用场发射扫描电子显微镜、红外光谱仪、孔径分析仪、接触角测量仪器等表征了改性前后复合膜表面形貌、官能团变化、孔径分布及润湿性等膜性能参数并将其应用于连续性直接接触式膜蒸馏盐浓缩过程。结果表明，静电纺丝复合膜呈三维空间网状结构，且利用正硅酸乙酯生成的纳米二氧化硅颗粒内陷于醋酸纤维素纤维内部形成微米-纳米梯级分布。经全氟烷基硅烷修饰后，红外特征峰明显，复合膜水接触角最高可达156°，且对质量分数为5%的十二烷基硫酸钠液滴也同时展示出优良的抗润湿性能（接触角125°）。以60℃、35 g·L^-1的NaCl溶液为进料液进行持续性直接接触式膜蒸馏脱盐实验，当渗透温度为20℃时，各复合膜盐截留率均能达到99.99%以上，其中，CA/SiNPs-FAS膜通量可稳定在11.2 kg·（m²·h）^-1。

Preparation of superhydrophobic CA/SiNPs-FAS electrospun nanofibrous membranes for direct contact membrane distillation

In this study, cellulose acetate/silica nanoparticles (CA/SiNPs) composite membranes were prepared by electrospinning and PET nonwoven were used as a support layer. Then the fiber mats were modified by immerged into fluoroalkyl silane (FAS) solution. In polymer dope, the mixture of 1-methyl-2-pyrrolidone (NMP) and acetone80/20,%(mass)] was selected as a mixture solvent and the content of CA was 10%(mass). The morphology, pore size distribution and wettability of the composite membranes properties were investigated. The CA and CA/silica fibers were found to be randomly oriented as nonwoven mats with fiber diameters around 0.8 μm. With the addition of SiNPs in the polymer dope, the SEM surface morphology images of flat-sheet composite membranes exhibited a microscale (SiO₂ aggregation node) to nanoscale (SiO₂ nanoparticles) hierarchical stratum structure. After the FAS modification, the surface wettability of the CA/silica mats was converted from hydrophilic to superhydrophobic. Compared with commercial PVDF membrane, the fluorinated mats with the metastable structure showed the highest water contact angle (WCA) of 156° and exhibited an excellent property of anti-surfactant wettability4.0 μl 5%(mass), SDS solution, the contact angle is 125°]. The composite membrane salt rejection rate could reach more than 99.99%; the CA/SiNPs-FAS membrane flux could be stabilized at 11.2 kg·(m²·h)^-1 with the feed solution at 60℃ and the cold distillate water at 20℃ during the desalination process of 35 g·L^-1 sodium chloride solution through direct contact membrane distillation.