Low-cost solar-powered water filter removes lead, other contaminants
2021-12-15
A new invention that uses sunlight to drive water purification could help solve the problem of providing clean water off the grid.The device resembles a large sponge that soaks up water but leaves contaminants-like lead, oil and pathogens-behind. To collect the purified water from the sponge, one simply places it in sunlight. The researchers described the device in a paper published this week in the journal Advanced Materials. The inspiration for the device came from the pufferfish, a species that takes in water to swell its body when threatened, and then releases water when danger passes, said the device's co-inventor Rodney Priestley, the Pomeroy and Betty Perry Smith Professor of Chemical and Biological Engineering, and Princeton's vice dean for innovation. 
"To me, the most exciting thing about this work is it can operate completely off-grid, at both large and small scales," Priestley said. "It could also work in the developed world at sites where low-cost, non-powered water purification is needed." Xiaohui Xu, a Princeton Presidential Postdoctoral Research Fellow in the Department of Chemical and Biological Engineering and co-inventor, helped develop the gel material at the heart of the device. "Sunlight is free," Xu said, "and the materials to make this device are low-cost and non-toxic, so this is a cost-effective and environmentally friendly way to generate pure water." The authors noted that the technology delivers the highest passive solar water- purification rate of any competing technology. One way to use the gel would be to place it in a water source in the evening and the next day place it in the sunlight to generate the day's drinking water, Xu said. The gel can purify water contaminated with petroleum and other oils, heavy metals such as lead, small molecules, and pathogens such as yeast. The team showed that the gel maintains its ability to filter water for at least ten cycles of soaking and discharge with no detectable reduction in performance. The results suggest that the gel can be used repeatedly.
