Micromechanism Underlying Wetting Behavior of the Vacuum Membrane Distillation during Desalination

Membrane wetting is a crucial issue in the desalination process by vacuum membrane distillation (VMD). However, the micromechanism of the wetting behavior is far from clear. Here, electrospun nanofiber membranes (ENMs) had been utilized to clarify the pore variations inside the membrane for desalination from NaCl aqueous solution, where the distinct open pore structure of ENMs could address the characterizing limitations for the change occurring in the membrane pores. A wetting formation model had been depicted on the basis of characterized results, illustrating that the basic reason for wetting was the initial NaCl crystallization caused by supersaturation, which was different from the membrane pores blocking or the structure damage caused by scaling. Moreover, membrane regeneration experiments also showed that the wetting caused by the crystallization of NaCl was reversible. By a reasonable regeneration strategy, VMD used for desalination was expected to achieve continuous operation with rejection over 99.9%.