“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