Scientists Discover How to Produce Clean Drinking Water From an Unexpected Source


The news: Water, water, everywhere but not a drop to drink? Try mixing sunlight and graphite.

That's the new, mind-blowing solution coming out of MIT to solve a big problem: How to cheaply desalinate salt water and make it safe for human consumption.

Usually, it takes a lot of energy to make the water evaporate into salt and condensation. The trick, then, is to find a way to reduce this energy loss. "Why do we need to heat the bulk of the liquid to get steam?" MIT engineer Hadi Ghasemi told NPR. "Why not concentrate the solar energy at 'hot spots?'"


How it works: According to the MIT study, published in July in Nature Communications, it ultimately came down to the material inside the filter: the graphite in pencils.

"We took graphite and put it into the microwave for seven seconds," Ghasemi told the journal, adding that the outer layer expanded and popped "exactly like a popcorn."

Through capillary action, water fills tiny holes in the graphite. The holes concentrate solar energy, quickly evaporating any water in them. 

"It creates steam at a low concentration of solar energy," Ghasemi continued. "So you don't need such expensive optical systems to concentrate the solar energy."

Why this is important: At a time when 780 million people lack access to clean water and there are massive droughts and water shortages around the world, news like this is welcome indeed. Not only does the evaporation process desalinate the water, it sterilizes it as well — and with the graphite material, that process can take place much quicker and more efficiently.

World Water Development Report 4

There are still ways to improve this model and make it even cheaper and more powerful. But for now, the study represents an ambitious step in the right direction. "The raw materials are very cheap compared to those used in other solar power generation now," study lead Gang Chen told NPR. "The idea is just so simple. I don't know why we didn't think about it earlier."