John Tolley, October 30, 2017

Water, water, everywhere,
Nor any drop to drink.

So is the predicament of the doleful sailor in Samuel Taylor Coleridge?s The Rime of the Ancyent Marinere, beset by thirst, yet adrift on an ocean too saline to drink.

Today, as ocean levels rise due to climate change, that salty water threatens to spill over into the aquifers of coastal communities, creating brackish, unusable water tables.

Desalination systems currently operating around the world can sufficiently filter salt from highly saline water, but require massive amounts of energy and are costly to operate.

A recent paper, published by University of Illinois at Urbana-Champaign researchers in the journal Electrochimica Acta, outlines a revolutionary desalinization model, based on modern battery technology, which could slash the energy consumption and related costs of treating low-salinity brackish water. And, the system removes more than just salt from the water

?In our new study, we constructed and experimented with a batterylike device that uses electrodes made from a different material. That material can remove from brackish water not only sodium ions but also potassium, calcium, magnesium and others,? said Illinois mechanical science and engineering professor Kyle Smith, speaking with the UIUC news service. ?This is important because salt and brackish waters do not contain just sodium chloride. It is often in a mix with other salts like potassium, calcium and magnesium chloride.?

Whereas reverse osmosis across a thin, porous membrane is the ubiquitous method of desalination, the electrodes in this new system sequester salt and other elements away from the fresh water in a separate chamber using a process known as capacitive deionization.

The material used in the process, Nickel Hexacyanoferrate, is widely available and cheap, both of which, Smith notes, are key factors to driving adoption of the technology.

So far, the process has been shown to work only with brackish water, the kind likely to be found in aquifers near large salt water bodies and in some industrial run off. Further testing will verify the process? efficacy in treating water with a greater salt content, such as ocean water.