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Water desalination - efficient and environmentally friendly

Aachen-based research team develops highly efficient and continuous technology using novel, carbon particle-based electrodes

(PresseBox) (Aachen, ) As the oceans contain 95 percent of the world's water resources, it is not surprising that more and more countries worldwide focus on seawater desalination to obtain drinking water. A team of scientists from DWI - Leibniz Institute for Interactive Materials and 'Aachener Verfahrenstechnik' (RWTH Aachen University) now developed an environmentally friendly and highly efficient technology for water desalination. The applied electrochemical process uses novel, carbon particle-based electrodes and allows a continuous regeneration of the electrodes during the running desalination process (Electrochemistry Communications, 2014).

Nowadays, reverse osmosis is the most prevalent technology for seawater desalination. Under high pressure of 60 to 80 bar, seawater passes a fine membrane, which retains the salt. However, both the high energy demand and the low water recoveries of only 45 to 50 percent are a significant technical challenge.

Electrochemical processes are a promising alternative for desalination of water. The components of the salt, anions and cations, are adsorbed at the electrode's internal surfaces and are thereby removed from the water. So far, limitations concerned the capacity as well as the regeneration of these electrodes.

Matthias Wessling's Aachen-based research team now developed a fully continuous electrochemical desalination process. It is based on so-called flow electrodes consisting of suspensions of positively- and negatively-charged carbon particles. "The carbon particles are extremely capable of binding the dissolved salt. Within this novel process, we achieved salt adsorption rates equal to the apparent salt adsorption capacity of 260 milligram salt per gram of carbon particles. This is more than ten times as high as it was previously described for these type of processes," explains Matthias Wessling.

In the first module of the device, flow electrode particles bind salt ions from the water. A second module is used to continuously regenerate the electrode particles during the running desalination process. Being regenerated, the particles are transferred back into the first module to bind additional salt ions from the water. Using an initial salt concentration of one gram per liter, Wessling and colleagues were able to remove 99 percent of the salt from 90 percent of the water. The residual ten percent of water were used to regenerate the electrode particles and to concentrate the removed ions into a brine stream: This stream of water picks up the ions that are released during the regeneration process.

Being a kind of 'hybrid professor', Matthias Wessling on the one hand holds a chair at RWTH Aachen University and on the other hand is a member of the scientific board of DWI - Leibniz Institute for Interactive Materials. "My groups at RWTH and DWI research in a complementary manner. For this project, the RWTH-based group was responsible for the process development while the Leibniz scientists synthesized the required materials."

Publication:

Y. Gendel, A. K. E. Rommerskirchen, O. David, M. Wessling, Batch mode and continuous desalination of water using flowing carbon deionization (FCDI) technology, Electrochemistry Communications (2014), DOI: 10.1016/j.elecom.2014.06.004

http://authors.elsevier.com/a/1PP4n4xfgpiVTl