Flashover-Inspired Electro-Assisted Crystallization for Controllable Freeze Desalination

Abstract

Freeze desalination (FD) offers a promising solution for desalining industrial saline wastewater in cold regions. However, salt entrapment in the close-dendritic ice pore network is uncontrollable, which makes ice-salt separation a challenge. To address this issue, this study reported the electro-assisted crystallization (EAC) to realize the controllable FD, inspired by the ice purification during insulator flashover frequently observed in power transmission systems. The experiment performed at −20 °C demonstrated that EAC allowed ice crystallization with an open ice pore network, whose open-area percentage was increased from 25 to 41% as current density was raised from 10 to 30 mA cm^–2. The EAC could achieve 89.3% desalination efficiency from 35 g L^–1 saltwater at 30 mA cm^–2, the value being four times that obtained for direct FD. Based on the principle of physical field synergy, the spontaneous salt release and controllable FD were likely the results of electro-heat synergy between Joule heating and dipole polarization effects. This study not only provides a novel pathway for controllable ice-salt separation inspired by flashover phenomenon but also suggests a potential technology for desalination treatment of water or wastewater in cold regions.