Researchers find new way to pull hydrogen from wastewater

A research team at Princeton University has harnessed sunlight to isolate hydrogen from industrial wastewater. In a paper published in the journal Energy & Environmental Science, the researchers reported that their process doubled the currently accepted rate for scalable technologies that produce hydrogen by splitting water.

The technique uses a specially designed chamber with a ‘Swiss-cheese’ black silicon interface to split water and isolate hydrogen gas. The process is aided by bacteria that generate electrical current when consuming organic matter in the wastewater; the current, in turn, aids the water-splitting process.

The team, led by Zhiyong Jason Ren, professor of civil and environmental engineering and the Andlinger Center for Energy and the Environment, chose wastewater from breweries for the test. They ran the wastewater through the chamber, used a lamp to simulate sunlight and watched the organic compounds break down and the hydrogen bubble up.

The process “allows us to treat wastewater and simultaneously generate fuels”, said Jing Gu, a co-researcher and assistant professor of chemistry and biochemistry at San Diego State University.

The researchers said the technology could appeal to refineries and chemical plants, which typically produce their own hydrogen from fossil fuels and face high costs for cleaning wastewater.

Hydrogen is a critical component in the manufacture of thousands of common products from plastic to fertilisers, but producing pure hydrogen is expensive and energy intensive. Historically, hydrogen production has relied on oil, gas or coal, and an energy-intensive method that involves processing the hydrocarbon stock with steam. Chemical manufacturers then combine the hydrogen gas with carbon or nitrogen to create high-value chemicals, such as methanol and ammonia.

Although hydrogen can be used as a vehicle fuel, the chemical industry is currently the largest producer and consumer of hydrogen. Producing chemicals in highly industrialised countries requires more energy than producing iron, steel, metals and food, according to a 2016 report from the U.S. Energy Information Administration. The report estimates that producing basic chemicals will continue to be the top industrial consumer of energy over the next two decades.

“It’s a win-win situation for chemical and other industries,” said Lu Lu, the first author on the study and an associate research scholar at the Andlinger Center. “They can save on wastewater treatment and save on their energy use through this hydrogen-creation process.”

Image: Researchers run the wastewater through a specially designed chamber, use a lamp to simulate sunlight and watch the organic compounds in the waste break down and the hydrogen bubble up.