纳米Al2O3溶胶的稳定性及PVDF/Al2O3杂化膜的性能研究

以异丙醇铝(AIP)为原料,采用溶胶-凝胶法,制备了纳米氧化铝(Al2O3)溶胶。研究了酸解剂、酸铝比[n(H+)/n(Al3+)]、陈化时间等因素对溶胶粒径和稳定性的影响,得到了制备稳定、透明纳米Al2O3溶胶的最佳工艺条件,即酸解剂HNO3;n(H+)/n(Al3+)=0.18~0.25;陈化时间20 h。为了改善聚偏氟乙烯(PVDF)膜的性能,通过PVDF与AIP的原位聚合,制备了不同PVDF含量的PVDF/Al2O3杂化膜。采用扫描电镜(SEM)、原子力显微镜(AFM)、红外光谱(FI-IR)、差示扫描量热法(DSC)、热失重分析(TGA)等手段对膜的结构和性能进行了表征。结果表明:杂化膜的纯水通量随着PVDF浓度的增大呈下降趋势,截留率则随着PVDF浓度的增大逐渐升高;AIP的加入使得杂化膜两相之间存在键合,可以增强Al2O3和PVDF之间的化学连接,从而提高杂化膜的亲水性和机械强度;添加AIP后,杂化膜的热分解温度向低温移动,即杂化膜的热稳定性下降;而AIP对PVDF膜的熔点影响不明显。

Stability of Nano-Al2O3 Sol and Properties of PVDF/Al2O3 Hybrid Membrane

The nano-Al2O3 sol was prepared in a sol-gel process, using AIP as raw material. The effects of peptization agent, n(H+)/n(Al3+) and aging time on the particle size and stability of the sol were studied. The optimal conditions of preparing stable and transparent nano-Al2O3 sol were obtained. HNO3 was chosen as the best peptization agent. The optimal n(H+)/n(Al3+) ratio and aging time were 0.18~0.25 and 20 h, respectively. Then, in order to improve the ultrafiltration performance of PVDF membrane, PVDF/Al2O3 hybrid membranes with different PVDF contents were prepared via the in-situ polymerization of AIP and PVDF in a sol-gel process. The structure and properties of the hybrid membranes were characterized by means of SEM, AFM, FI-IR, DSC and TGA. The results indicated that the pure water flux of hybrid membranes declined with the increase of PVDF concentration, while the rejection rate increased gradually. The introduction of AIP can enhance the chemical bond between PVDF and Al2O3 of the hybrid membrane and hence greatly improved the mechanical properties and hydrophilicity of these membranes. The thermal decomposition temperature of hybrid membrane decreased to a lower temperature with the introduction of AIP, which meant tht the thermostability of hybrid membrane declined, while AIP had no obvious effect on the melting point of hybrid membrane.