Electrothermal hollow fiber membrane for convenient heat management in Joule vacuum membrane distillation

Membrane distillation (MD) for brackish groundwater desalination is a promising approach for alleviating water shortage in rural area. Conventional MD has very low single-pass water recovery leading to high energy consumption for hydraulic circulation. Heating the feed via electrothermal membrane at the interface diminishes the energy consumption for circulation, but the heat loss to the bulk feed and ambient environment critically needs to be managed to achieve higher Joule heat efficiency. An electrothermal hollow fiber membrane was prepared and employed in Joule vacuum membrane distillation (VMD). The narrow inner space of the luminal side of the membrane controlled the amount of feed and limited the heat loss to the bulk feed. The highest Joule heat efficiency of 78.0% was achieved when 0.27 W/cm2 of power was applied. In long-term operation for brackish groundwater desalination, the fluoride was effectively rejected and the single-pass water recovery of ~70% was achieved, which could critically decrease the energy consumption for circulation. The electrothermal hollow fiber membrane is convenient to conduct heat management in Joule VMD process.