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A Mission To Invent a Bottle That Takes the Salt Out of Saltwater

Scientists are exploring the potential of creating plastic containers that, with a little sun power, could desalinate seawater

University of California, Irvine chemist Shane Ardo is working to develop special plastic membranes and dyes that would enable a container to desalinate seawater. (Steve Zylius / UCI )
smithsonian.com

The planet has a water problem.

Despite all the videos you may have seen of raging rivers and double-digit downpours, the greater peril lies with too little, rather than too much water. It’s one of Earth’s great paradoxes—a place that has 70 percent of its surface covered with liquid facing the threat of a massive drought. By 2030, according to the United Nations, almost half the world’s population could be dealing with water scarcity.

The solution, it might seem, would be to dramatically ramp up desalination, the ages-old process of making seawater potable by removing salt from it. The methodology has come a long way since Greek sailors boiled water and collected the distilled drinkable droplets. Today, according to the International Desalination Association, there are close to 18,500 desalination plants around the world.  

The technology has had a profound impact in some places. In Israel, for instance, more than half of the country’s water supply now comes from desalination plants, including the $500 million, state-of-the-art Sorek facility south of Tel Aviv. And, last month the first farm in the world to run on solar power and desalinated water, went into operation in Australia.

But desalination plants require a lot of energy, which means that those powered by fossil fuels can be responsible for a high level of greenhouse gases. Their waste product—the brine removed from seawater—can harm marine life. And they can be very expensive. The largest desalination plant in the U.S. opened last year about 30 miles north of San Diego. It cost about $1 billion to build. 

A different approach

Shane Ardo concedes that it wasn’t all that long ago that he didn’t know a whole lot about the world of desalination. But Ardo and his small team of researchers at the University of California, Irvine may have found an alternative to big, pricey plants, which aren’t really an option in many places where the need for fresh water is greatest, such as Sub-Saharan Africa. 

They’re exploring whether it’s possible to produce containers from substances that could, using only sunlight, remove the salt from seawater.  “Imagine if you could dip a plastic bottle in the ocean and have that container take the salt out of the water in front of your eyes,” explains Ardo.

Such a magic bottle is still very much a hypothetical, but based on his research, Ardo believes that membranes can be created that will be able to absorb light and then use those solar photons to cause salt ions to move out of the water.

“Our entire society runs on moving electrons,” he says. “We move electrons in wires to run lots of things. We also know how to take solar energy and convert it to energized electrons and use them to run things. But to drive processes like desalination, you don’t really need electrons—you just need to move the ions and take them out of the water.

“There’s been a lot of excitement about what we’re doing,” Ardo adds. “No one’s taken a synthetic plastic material to drive this type of process, this ionic power generation. When I dreamed it up, on paper it looked reasonable.”

Looking for answers

Lab work over the past few years provided more support for his theory, and last week Ardo’s research received a big boost when he was named a “Moore Inventor Fellow” by the Gordon and Betty Moore Foundation and awarded an $825,000 grant to move the project forward.

Ardo knows that being able to develop a container that desalinates saltwater on its own is hardly a sure thing. But he says he’s determined to keep testing the concept.

"There have been people who have asked a lot of questions about this and I love that," he says. "I want them to push me hard. If I don't have the answer, well that's something I need to research. And if something is going to break our idea, I want to know. I don't want to spend time on something that has a fundamental reason why it's wrong. But I do think we’ve got something here.”

Ardo believes that by enabling desalination to occur in a relatively small container, perhaps even one a person can carry, you could dramatically reduce the cost and environmental impact of seawater conversion, and also create a viable way to provide freshwater where developable land and money are limited.

He admits that it’s hard to predict when a product like this could actually exist. One of the next steps is for him and his team to start making their own polymers from scratch “now that we have a good idea of what needs to be done.” He says they need to make dye molecules that can absorb more light.

“I don’t know exactly what the application looks like,” Ardo notes. “I have a general feel. But the trajectory is really exciting and promising.  What I like is that it allows us to look at this conversion in a new way. Maybe with my group, no matter how much we learn, we won’t figure it out. Maybe some neurobiologist will.

“But I think we can do a lot. I think this could be a big deal.”

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