US team develops desalination process for hypersaline brines

The process has been developed specifically to treat the so-called hypersaline brines, produced through a range of industrial process such as oil and gas production.

These brines, which contain far higher concentrations of dissolved salts than ocean water, are challenging to treat, and present a growing environmental concern around the world.

Currently, hypersaline brines are desalinated either by membrane (reverse osmosis) or water evaporation (distillation). However, reverse osmosis methods are ineffective for high-saline brines because the pressures applied in reverse osmosis scale with the amount of salt: hypersaline brines require prohibitively high pressurisations.

Distillation techniques, which evaporate the brine, are very energy-intensive.

The process developed by the Columbia team, an approach described as temperature swing solvent extraction (TSSE) is claimed to be able to desalinate brines with up to seven times the concentration of seawater far more efficiency than existing methods.

Based on a separation method widely employed for chemical engineering processes, TSSE utilises a low-polarity solvent with temperature-dependent water solubility for the selective extraction of water over salt from saline feeds. Because it is membrane-less and not based on evaporation of water, it can sidestep the technical constraints that limit the more traditional methods. Importantly, TSSE is powered by low-grade heat (< 70 deg C) that is inexpensive and sometimes even free.