Abstract: The mixture of inorganic salt LiCl and soluble polymer polyethylene glycol (PEG) as non-solvent additive was introduced to fabricate hydrophobic polyvinylidene fluoride ( PVDF) hollow fiber membrane by phase inversion process. The membrane exhibited high rejection of inorganic salt solutes and a maximum permeate flux 40. 5kg/ (m²?h) was obtained. During direct contact membrane distillation (DCMD) process, the precipitation of CaCO₃ would be formed and clog the hollow fiber inlets with gradual concentration of the feed when natural brackish water was used directly as feed solution, which resulted in a rapid decline of membrane module efficiency. The negative influence of scale deposits could be eliminated by acidification of the feed. The DCMD desalination experiment of acidified brackish water showes that the PVDF membrane had stable permeate flux and the conductivity of the obtained distillate remained below 10 μS/ cm during the whole process.

Key words: polyvinylidene fluoride, permeate flux, membrane distillation, brackish water, membrane fouling

摘要： 采用相转化法以无机盐氯化锂(LiCl)和水溶性聚合物聚乙二醇(PEG)为添加剂, 制备了聚偏氟乙烯(PVDF)中空纤维疏水膜, 所制得的膜具有较高的盐截留率, 膜通量可达40. 5 kg/ ( m²?h) 。以自制的 PVDF 疏水膜进行了直接接触式膜蒸馏(DCMD) 苦咸水脱盐应用试验研究。实际苦咸水淡化过程 中, 随着浓缩倍率的提高在进料侧会产生 CaCO₃ 沉淀造成膜组件堵塞、疏水膜受到污染, 致使膜渗透通量下降、产水电导率升高。酸化预处理可以消除沉淀物对膜蒸馏过程的影响, 酸化后整个膜蒸馏过程中膜渗透通量保持稳定, 产水水质 良好, 其电导率不超过10μS/ cm。

关键词: 聚偏氟乙烯, 膜通量, 膜蒸馏, 苦咸水, 膜污染