层层自组装法制备聚电解质/改性碳纳米管复合纳滤膜

Preparation of polyelectrolyte/carbon nanotubes nanofiltration membrane via layer-by-layer assembly

分别用浓硫酸和乙二胺对多壁碳纳米管(MWCNTs)进行改性,制得了磺化和氨化碳纳米管.研究了不同改性方式的碳纳米管在聚电解质中的分散特性及二者的相互作用,磺化碳纳米管在聚阳离子聚二烯丙基二甲基氯化铵(PDDA)中显示出最优的分散性能.以水解改性的聚丙烯腈(PAN)超滤膜为基膜,将磺化改性的碳纳米管添加到PDDA中,与聚阴离子聚苯乙烯磺酸钠(PSS)层层自组装制得了改性碳纳米管复合纳滤膜.接触角测试结果表明,复合膜表面亲水性随磺化碳纳米管加入量的增加而提高.加入磺化碳纳米管的复合膜表面zeta电位比未加入的膜略有升高.SEM结果表明,复合物和聚电解质成功组装在基膜表面.随着碳纳米管加入量的增加,复合膜对Na_2SO_4的截留率和水通量均出现先升高后降低的趋势,聚电解质PDDA中磺化碳纳米管浓度为0.04 g/L时,复合膜有最优的分离性能.

Multi-walled carbon nanotubes(MWCNTs) were modified with concentrated sulfuric acid and ethylenediamine, respectively. The dispersibility of the modified carbon nanotubes in the polyelectrolytes and their interaction were studied. Sulfonated carbon nanotubes showed the best dispersibility in poly(diallyl-dimethylammonium chloride)(PDDA)solution. The composite nanofiltration membrane was prepared by alternately depositing PDDA solution with addingsulfonated carbon nanotubesand poly(styrene sulfonate)(PSS) on the polyacrylonitrile(PAN) ultrafiltration membrane. Contact angle test revealedthat the hydrophilicity of the composite membrane was improved with the concentration of sulfonated carbon nanotubes. The addition of sulfonated carbon nanotubes also improved the zeta potential of the composite membrane in some degree. SEM results show that the complex and polyelectrolyte are successfully assembled on the PAN substrate membranes. With increasing concentration of carbon nanotubes, the rejection to Na_2SO_4 and water flux of the prepared membrane increased firstly and then decreased.The composite membrane showed the best separation performance when with a sulfonated carbon nanotubes concentration of 0.04 g/L in the PDDA solution.