Desalination by electret technology

A purification process of making use of electret technology for efficient but cost effective deionization was discussed in this paper. Douglas MacGregor claimed that PTFE electret works as a means of ions separation for desalination due to the polarization of an electrolyte and ions migration under a permanent electrostatic field generated by a pair of electrets with opposite polarities. The electrostatic field attracts counter-ions to the charged solid surface, and thus generates a purified effluent in the mainstream. Theoretical and experimental analyses were made to investigate the practicality of desalination by electret technology. It is found that MacGregor's design is meaningful only for a dilute electrolyte or a system with very high surface charge density because the number of the counter-ions attracted to the surface is limited and cannot exceed that of the surface charges at the electret.