Forward osmosis using a nanoparticle slurry draw solution with DC-field-driven separation

Abstract

Forward osmosis (FO) is a membrane separation process in which water transport across a semipermeable membrane is driven by osmotic pressure differences and has attracted attention as a next-generation water treatment technology. This study proposes a novel FO process that uses nanoparticle slurry as a draw solution (DS) combined with a direct-current (DC) electric field and experimentally evaluates its feasibility. This process involves contacting the water and nanoparticle slurry across a membrane to induce osmotic-driven water permeation, followed by the application of a DC electric field to sediment nanoparticles and recover clarified water. The reusability of DS through repeated absorption–separation cycles was examined. The results indicate that the nanoparticle slurry functions as an effective DS, the nanoparticles are reproducibly separated by applying a DC electric field, and both water permeation and separation performance are maintained even after separation. Comparing energy consumption with existing technologies indicated that, although the present method faces efficiency challenges, it offers advantages because it does not require heating and can operate stably in cold or low-temperature environments. This study demonstrates the feasibility of an electric-field-driven, non-thermal FO process and highlights its potential as a promising next-generation water treatment technology.