Seawater desalination processes require electric or thermal energy to separate saline seawater into two streams, a fresh water stream containing a low concentration of dissolved salts and a concentrated brine stream. A variety of desalination technologies have been developed over the years. Reverse osmosis requires a large electrical energy input, which accounts for 44% of its cost, and it is based on selective membranes, which are prone to fouling and require frequent replacement. Recent research on high-flux membranes based on carbon nanotubes could potentially reduce the energy consumption, while alternative electrical-based desalination technology such as ion concentration polarization in nanodevices can potentially avoid the fouling.
Thermal energy based multistage flash distillation requires energy intensive heating to temperatures above 90 °C, accounts for 50% of its cost. Multiple effect distillation is gaining popularity due to its higher efficiency and lower top brine temperatures (about 70 °C) than multistage flash technology. Forward osmosis is a promising new process that utilizes lower temperatures (60 °C) but still requires the use of membranes. Solvent extraction using directional solvents like decanoic acid at mild temperatures (30−50 °C) has been demonstrated recently by Bajpayee and co-workers.