Donnan Dialysis Desalination with a Thermally Recoverable Solute

This study presents a novel desalination technology that couples Donnan dialysis (DD) with thermally-recoverable solutes and utilizes low-grade heat as energy input. In the proposed process, saline feed streams receiver solutions of concentrated NH4HCO3(aq) flow stepwise across cation- anion-exchange membranes. The large transmembrane concentration differences NH4+ HCO3– set up electrochemical potential gradients to drive uphill transport Na+ Cl– ions, respectively, from into stream. Warming two outlet using low-temperature thermal sources volatilizes NH3 CO2, thus removing NH4HCO3 yield desalinated product water brine. separated NH3(g) CO2(g) are then recycled reconstitute solution. concept was first experimentally validated by desalinating brackish simulated 100 mM NaCl freshwater salinities (<17 mM). DD demonstrated for larger ranges concentrations 100–1000 mM, experimental salt removals showed good agreement theoretical equilibria (within 5%). results revealed unavoidable permeation solute co-ions due imperfect membrane permselectivities is main factor prevents thermodynamic being reached. Nonetheless, current commercial ion-exchange membranes sufficient suppress undesired co-ion leakage, yielding adequate practical desalination. Module-scale analysis quantitatively countercurrent operation can obtain higher performance compared co-current flows, achieving recovery yields high 95.5 87.5%, respectively. utilization sources, such waste geothermal reservoirs, primary input innovative approach opens opportunities lower carbon intensity