From crab shells to potable water: Solar-powered desalination system earns Northeastern professor a Fulbright
Northeastern University professor Yi Zheng sees two major sustainability issues facing humanity: limited energy and water.
His solar-powered desalination system addresses both. Oh, and it’s made from crab shells and cuttlefish ink.
“There are over 8 billion people in the world right now, and energy and fresh water scarcity are two major issues humans are facing,” says Zheng, an associate professor of mechanical and industrial engineering at Northeastern. “If I can contribute a little bit to save more energy or to generate low-cost, affordable fresh water, that will be great.”
Zheng studies nanoscale functional materials for freshwater generation, especially those utilizing solar energy, and has an interest in sustainability.
He explains that the commonly used desalination systems use reverse osmosis technology, where added pressure forces seawater through a semi-permeable membrane to make it salt-free.
The process is efficient; however, it also requires land, facilities, equipment and electricity.
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“It may not be available in some remote regions or off-grid regions,” Zheng says. “So that pushed me to study an affordable and eco-friendly approach: solar-driven water desalination.”
The result?
A porous hydrogel made of crab shells and cuttlefish ink that floats on the surface of the ocean, absorbing seawater on its bottom and sunlight on its top. The hydrogel filters the seawater, it evaporates in the sun onto a transparent cover that is connected to a removable water collection tank.
During a trial run at Revere Beach just north of Boston, the system reduced the sodium concentration of ocean water from over 10,000 milligrams of sodium per liter to 5.5 milligrams per liter.
There is no federal standard for sodium in drinking water; however, the World Health Organization says most water has 20 mg of sodium per liter and the organization has set a guideline of 200 mg of sodium per liter based on taste.
But Zheng is looking beyond the North Shore.
This coming spring, Zheng will travel to Australia as a Fulbright US Scholar to work with researchers at the Center for Technology in Water and Wastewater at the University of Technology Sydney to test and further develop his innovative water-treatment technology.
“There will be different ambient conditions throughout the four seasons, different humidity and even different water quality in Sydney,” Zheng says. “I also need to spend more time with the Australian research team to study the durability and longevity of the hydrogel materials under extreme conditions, including high temperature, high salinity levels and also even wastewater.”
But even if the hydrogel breaks down eventually, it’s not going to deposit anything inorganic in the ocean.
“My goal is to make a totally sustainable system for ocean water desalination,” Zheng says. “The system itself comes from the ocean, and it will also be desalinating the ocean water.”
