Scientists discover new, more energy friendly method to de-salt sea water

“Figure 1. Schematic illustrations of a) the BPE desalination device and b) the region of interest near the BPE anode and ion depletion zone depicting the net velocity vectors of a cationic species under the combined forces of electromigration and convection. Gnd=ground.”

Electrochemically Mediated Seawater Desalination” is the title of the paper published by Angewandte Chemie, International edition earlier this month.

From the paper:

With global demand rising faster than availability, fresh water is quickly becoming a limited resource. In fact, the United Nations estimates one third of the world’s population is living in water-stressed regions, and by 2025 this number is expected to double.1 Seawater desalination is an attractive solution to this problem because seawater accounts for more than 97 % of the world’s water supply.2 Currently, the primary limitation preventing the widespread use of seawater desalination as a fresh water supply is the immense amount of energy required to drive the process.3 Here, we describe a new, electrochemically mediated desalination (EMD) method for membraneless seawater desalination.

Our approach for desalination is illustrated in Figure 1 a. A seawater feed is separated into brine and desalted water streams at the junction of a branched microchannel where a bipolar electrode (BPE)4 is present. The anodic pole of the BPE generates an ion depletion zone,5 and hence a local electric field gradient that redirects ions present in seawater to the brine channel. Importantly, this device operates with an energy efficiency of 25 mW h L−1 (25±5 % salt rejection, 50 % recovery), which is near the theoretical minimum amount of energy required for this process (ca. 17 mW h L−1).6 In addition to this energy efficiency, the approach provides three other important benefits relative to currently available desalination methods. First, EMD does not require a membrane, thereby eliminating a major drawback of reverse osmosis (RO), the most widespread method for desalination.7 Second, EMD requires only a simple 3.0 V power supply to operate and therefore, in the future, may be employed in resource-limited settings with a battery or low-power, renewable energy source. Third, the EMD platform may be prepared with little capital investment and could be implemented in a massively parallel format.8

Read the full article, click here.

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