A new solar-powered reactor developed by researchers at the University of Cambridge could revolutionize plastic waste recycling by using acid from old car batteries to convert waste materials into clean hydrogen, a process that uses acid from old car batteries to transform waste materials into clean hydrogen.
Two waste streams can be used to produce clean hydrogen and industrial chemicals, helping to solve the problem of the millions of tons of plastic produced each year around the world.
Researchers at the University of Cambridge have developed a solar-powered photo-modification method for acids that uses battery fluid from old car batteries to break down previously difficult-to-recycle plastic waste, such as nylon fibers, polyurethane foam, and polyethylene terephthalate (PET) plastic bottles.
As reported in Joule, the team first applied car battery acid to plastic waste to break down long polymer chains. This produces ethylene glycol, which when exposed to sunlight is converted by a photocatalyst into acetic acid and hydrogen.
Acid-stable photocatalysts were the key
“This discovery was almost serendipitous,” said study leader Erwin Reisner, professor at the Yusuf Hameed Department of Chemistry at the University of Cambridge. “We thought acids were completely off-limits in these solar systems because they would simply dissolve everything. But our catalyst developers weren’t, and suddenly a whole new world of reactions opened up.”
“Although acids have long been used to break down plastics, there have been no inexpensive, scalable photocatalysts that can withstand acids,” said lead author Dr. Kay Kwarten. Candidate from the Reissner research group that developed photocatalysts. “Once we solved that problem, the benefits of this type of system became clear.”
The reactor operated continuously for 260 hours without any loss in performance and was effective against multiple forms of plastic waste where current methods are limited.
The process was tested using laboratory-grade acid and recovered car battery acid. This presents a useful route for recycling car batteries, where the lead content is extracted and reused, while the neutralized acid becomes excess waste.
The acid used in this study’s photovoltaic acid photomodification can also be reused rather than being consumed or wasted.
“This is an untapped resource,” Kwarteng said. “If we can recover the acid before it is neutralized, it can be used multiple times to break down the plastic. It is truly a win-win, as it can be used to produce clean hydrogen while avoiding the environmental costs of neutralizing the acid.”
Approximately 91% of plastic produced worldwide is not recycled
Global plastic production is estimated at 400 million to 460 million tonnes and is expected to triple by 2060.
Only 9% of this plastic is recycled, and the rest is incinerated, left in landfills, or mismanaged. All of these options have a negative impact on the environment, with 140 million tonnes of plastic waste ending up in rivers and oceans.
Establish a more cost-effective circular economy
The process could open up new avenues for plastics previously thought to be difficult or too expensive to recycle, with high clean hydrogen yields and reusable battery fluid making the effort more cost-effective.
“These acids are already being safely handled in industry,” Kwarteng continued. “The problem now is engineering: how do you build a nuclear reactor that can operate continuously and process real-world waste?”
“We’re not promising to solve the global plastic problem,” Reisner said. “But this shows how waste can become a resource. The fact that we can create value from plastic waste using sunlight and waste battery fluid makes this a very promising process.”
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