Thanks to the power of the sun and nanoparticles, the process of purifying saltwater can be improved.
Desalination is a term that Cape Town residents have most likely become familiar with. The process of purifying saltwater serves as an ideal solution to drought and a shortage of drinking water. It is not without limits though, as scientists are always looking to improve it in terms of how much filtered water can be produced and how much energy that production needs. One group of scientists may have found the answer.
Researchers from Rice University’s Laboratory for Nanophotonics in Texas demonstrated a solar-powered desalination system that could increase the output of purified water by 50%. This increase is thanks to an inexpensive addition to the process: nanoparticles.
According to applied physics graduate and one of the project’s leaders, Pratiksha Dongare, desalination can be improved by redistributing the light that is captured during the solar power conversion process.
In traditional desalination, heated saltwater is flowed across one side of a membrane, while cold purified water flows across the other side. The difference in temperature causes two different levels of water vapour pressure, which then forces the vapour to travel through the membrane which in turns filters out chemicals. This technology can be difficult to scale up to industrial sizes, as the bigger the membrane is, the bigger difference in water temperature and the less water that can be filtered.
The solution, Dongare and her colleagues found, is simple and cost-effective. By putting light-absorbing nanoparticles into the membrane itself, it becomes a solar-powered heating element. The saltwater is heated up by the membrane, which then saves on energy costs and helps with purified water amounts when the technology is built on a bigger scale.
With this discovery, rural areas that have little or no access electricity, can produce their own drinking water in times of crisis. The technology could also be applied to desalination plants in South Africa, such as the one located at Cape Town’s Waterfront.