Fluorosilanes Modified Ceramic Membrane Used In Vacuum Membrane Distillation For Seawater Desalination

Membrane distillation (MD) is a new solution for seawater desalination. MD also has several limitations, such as the limitation of membrane types, the high cost of the membrane, the high resistance of the mass transfer process, the low flux, which has resulted in unsuccessfully use in industrial scale. This paper focuses on making a membrane suitable for MD process. In this study, the hydrophobic active layer was created by grafting fluorosilanes 1H,1H,2H,2H-perfluorooctyltrichlorosilane(PFAS) or 1H,1H,2H,2H-perfluor-odecyltriethoxysilane (PFDS) on the commercial ceramic membrane. Then the grafted ceramic membranes were prepared and characterized:the membrane surface formed many needle-like structures, which may be an organic polymer of low surface energy. The highest contact angle of grafted ceramic membranes is 159°, which shows the hydrophobicity of the membrane. In addition, the pretreat solvent, the solvent, the photoinitiator, the modifiers are also investigated.The grafted ceramic membrane was used in vacuum membrane distillation of simulated seawater. Main operating conditions of the process and the performance of the grafted membrane were evaluated. The results show that: in ideal conditions, the permeation flux reached 27.28kg m-2 h-1, and the rejection remained 99.99%. This shows that the grafted ceramic membrane can be used in membrane distillation process and has good effect.The commercial polypropylene membranes were used in vacuum membrane distillation for concentration and purification of the four major categories of eight kinds of hydrophilic ionic liquid aqueous solution. The process operation conditions are analyzed, The results show that:the permeate flux increases with the increasing of feed temperature, flow rate and vacuum degree of the cold side; the permeation flux decreases with the increasing of the feed solution concentration; all the experimental recovery rate has been maintained at above 99.5%, indicating that the operation condition has little effect on the recovery rate, effect of recovery rate is mainly affected by the membrane performance; test results show that recovery of ionic liquid by vacuum membrane distillation is feasible and very effective.