A desalination process that pumps ions instead of water

By Paul Grad |

Researchers from Indonesia’s Bogor Agricultural University (Bogor, Indonesia; www.ipb.ac.id), the University of Bath (U.K.; www.bath.ac.uk), and the University of Johannesburg (Johannesburg, South Africa; www.uj.ac.za), led by Budi Riza Putra, have developed a low-cost, low-energy and low-maintenance, solar-powered desalination system that can be operated in mobile units. The system could service a small number of households, or homesteads in remote locations where freshwater is scarce. The prototype desalination unit is a 3D-printed system with two internal chambers designed to extract or accumulate salt (diagram). When power is applied, salt cations (positively charged ions) and salt anions (negatively charged ions) flow between chambers through arrays of micro-holes in a thin, negatively charged, membrane. The system combines the membrane with an anionic resistor that only allows the flow of negative ions when power is applied. As a result of this one-way flow, salt is pumped out of seawater. This contrasts with the classical desalination process, where water rather than salt is pumped though a membrane. The proof-of-concept prototype is currently able to remove 50% of the salt from saltwater, but to make seawater drinkable,…
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