Sangeetha Vivekanandan, Kaleekkal Noel Jacob, Vigneswaran Saravanamuthu
Membrane Separation Group, Department of Chemical Engineering, National Institute of Technology Calicut, Kozhikode 673601, Kerala, India.
Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia.
Polymers (Basel). 2022 Dec 7;14(24):5350. doi: 10.3390/polym14245350.
Membrane distillation (MD) is an emerging technology for water recovery from hypersaline wastewater. Membrane scaling and wetting are the drawbacks that prevent the widespread implementation of the MD process. In this study, coaxially electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) nanofibrous membranes were fabricated with re-entrant architecture and enhanced hydrophobicity/omniphobicity. The multiscale roughness was constructed by incorporating Al2O3 nanoparticles and 1H, 1H, 2H, 2H Perfluorodecyltriethoxysilane in the sheath solution. High resolution transmission electron microscopy (HR-TEM) could confirm the formation of the core-sheath nanofibrous membranes, which exhibited a water contact angle of ~142.5° and enhanced surface roughness. The membrane displayed a stable vapor flux of 12 L.m−2.h−1 (LMH) for a 7.0 wt.% NaCl feed solution and no loss in permeate quality or quantity. Long-term water recovery from 10.5 wt.% NaCl feed solution was determined to be 8−10 LMH with >99.9% NaCl rejection for up to 5 cycles of operation (60 h). The membranes exhibited excellent resistance to wetting even above the critical micelle concentration (CMC) for surfactants in the order sodium dodecyl sulphate (SDS) (16 mM) > cetyltrimethylammonium bromide (CTAB) (1.5 mM) > Tween 80 (0.10 mM). The presence of salts further deteriorated membrane performance for SDS (12 mM) and Tween-80 (0.05 mM). These coaxial electrospun nanofibrous membranes are robust and can be explored for long-term applications.
膜蒸馏（MD）是一种用于从高盐废水中回收水的新兴技术。膜结垢和润湿是阻碍MD工艺广泛应用的缺点。在本研究中，制备了具有凹腔结构和增强疏水性/超疏油性的同轴电纺聚偏氟乙烯-共-六氟丙烯（PVDF-co-HFP）纳米纤维膜。通过在鞘层溶液中加入Al2O3纳米颗粒和1H，1H，2H，2H全氟癸基三乙氧基硅烷构建了多尺度粗糙度。高分辨率透射电子显微镜（HR-TEM）可以证实核壳纳米纤维膜的形成，其水接触角约为142.5°，表面粗糙度增强。对于7.0 wt.%的NaCl进料溶液，该膜显示出12 L·m−2·h−1（LMH）的稳定蒸汽通量，渗透质量和数量均无损失。从10.5 wt.%的NaCl进料溶液中进行长期水回收，在长达5个操作周期（60小时）内，测定回收率为8−10 LMH，NaCl截留率>99.9%。即使在高于表面活性剂临界胶束浓度（CMC）的情况下（十二烷基硫酸钠（SDS）（16 mM）>十六烷基三甲基溴化铵（CTAB）（1.5 mM）>吐温80（0.10 mM）），这些膜也表现出优异的抗润湿性。盐的存在进一步降低了SDS（12 mM）和吐温80（0.05 mM）的膜性能。这些同轴电纺纳米纤维膜性能稳定，可用于长期应用。
