Uncovering nature's deeply held secrets
Out of the findings described above under Water Science, and published in a recent book, fresh opportunities have arisen for addressing pressing societal needs for scarce drinking water and renewable energy. Here are three examples:
|Exclusion-zone separates solutes from water, in the absence
of any physical filter.
• Filterless filter. The discovery of large solute-exclusion zones next to hyrdrophilic surfaces implies that solute-free and solute-containing water can be separated naturally, without need for physical filters. The required energy comes from incident light. The solute-exclusion zones are macroscopic; hence, collection is feasible through simple processes.
Proof-of-principle has been demonstrated: model contaminants could be separated to a ratio up to 200:1 in a single pass (Klyuzhin et al., 2008). With successful demonstration, it should be possible to scale up the process and collect solute-free, particle-free, and pathogen-free water in a simple, economically feasible way.
• Desalination. Obtaining drinking water from seawater has been fraught with the problem of excessive energy requirements. This limits practicality. The separation principle outlined above is a promising alternative because it is powered by radiant energy, which is typically abundant in areas in which drinking water is most seriously needed. Hence, the idea of exploiting this principle for desalination is attractive. At present we are exploring the underlying scientific issues that could make this approach practical.
|Separation of charge allows for the drawing of electrical
energy from the water-based battery.
• Energy from Water and Light. We found that the solute-exclusion zone is charged, while the zone beyond is oppositely charged. This separation constitutes a battery, from which current can be drawn. The battery is re-charged by incident radiant energy. Hence, the process resembles photosynthesis in that incident light yields charge-separation and useful energy. It is effectively a photoelectric effect, except that the medium is ordered water.
Experiments are underway to explore the phenomenon of charge separation in water. The scientific underpinning of this separation is extremely interesting, and is revealing as much about the structure, chemistry, and physics of water as about the prospects of obtaining clean electrical energy from water.