静电喷雾结合热压处理制备荷负电PVA-SA/PAN纳米纤维基复合滤膜及其纳滤性能研究

以静电纺丝聚丙烯腈(PAN)纳米纤维作为多孔支撑层,以亲水材料聚乙烯醇(PVA)和海藻酸钠(SA)为亲水表层材料,通过静电喷雾技术将亲水表层材料沉积在纳米纤维多孔基膜表面,然后将表层PVA-SA纳米串珠层通过水蒸气加湿辅助热压成膜处理在PAN基膜上软化压延形成完整的致密薄膜,最后经过戊二醛交联制备PVA-SA/PAN纳米纤维基复合滤膜.通过对加湿时间、热压温度、热压时间以及PVA-SA静电喷雾时间等成膜工艺条件和交联条件进行优化制备出结构完整的PVA-SA/PAN纳米纤维基复合滤膜.所制备的复合滤膜荷负电,它对阴离子染料具有较好的过滤效果:在0.6 MPa的操作压力下对100 mg/kg的固绿染料的渗透通量为57.1 L/(m~2h),截留率为96.8%.

PVA-SA/PAN Thin-film Nanofibrous Composite Membrane Prepared by Combining Electrospray Technique and Hot-pressing Treatment

Inspired by conventional powder coating technology,a novel negative-charged membrane made of thin-film nanofibrous composite (TFNC) with polyacrylonitrile (PAN) nanofibers as the substrate and polyvinyl alcohol (PVA)-sodium alginate (SA) as the hydrophilic barrier layer was successfully developed.The PVA-SA nanobeads were firstly electrosprayed onto the electrospun PAN substrate and then hot-pressed under steam humidification.Water molecules were absorbed from the ambient moisture acted as the "plasticizer" in PVA-SA nanobeads,which could facilitate softening or melting of PVA-SA during the film-formation process.The moistened PVA-SA nanobeads layer would then be pressed imperceptibly into an integrated barrier film on the PAN supporting layer under the gravity pressure of hot plate at a certain temperature.Deposition time (the timespan for PVA-SA electrospraying),moist-curing time,heating temperature (the preset temperature for thermal treatment) and curing time (the timespan for thermal treatment) were carefully adjusted to explore the optimal film-formation condition.And it was found that with the deposition time of 18 min,moist-curing time of 120 s,heating temperature of 60 ℃ and curing time of 6 min,an integrated and nonporous PVA-SA barrier layer was achieved for TFNC membrane.Finally,the resulting barrier layer was chemically crosslinked by glutaraldehyde (GA) and its compactness could be easily controlled via different crosslinking degree and the composition of crosslinking bath for nanofiltration (NF) applications.The optimized PVA-SA/PAN TFNC membrane (crosslinked by GA with concentration of 0.4 wt％) was negatively charged owing to the carboxyl groups of SA,and it possessed high NF performance in anionic dye filtration.Tests at low feeding pressure of 0.6 MPa showed a permeate flux of 57.1 L/(m2 h) and rejection ratio above 96.8％ for the membrane product toward Acid Blue 90 solutions.Besides,the resultant PVA-SA/PAN TFNC membrane exhibited excellent pressure resistance and antifouling properties during the long-term experiment,and the negatively charged SA played a key role in the NF process.