NEW TECHNOLOGY MAXIMIZES COLLECTION OF ALUMINUM DURING RECYCLING
COLUMBUS, Ohio -- Researchers at Ohio State University have developed a patented process to maximize the amount of aluminum collected from recycled cans.
The new process involves running an electric charge through the salt bath used in the melting of cans, said Yogesh Sahai, a professor of materials science and engineering who conducted the research.
This method allows companies to collect most of the 20 percent of aluminum that is normally trapped in the salt cake and discarded.
"There is a great need to improve the recycling process," Sahai said. "If companies lost less aluminum during the process, they would see a bigger profit from recycling."
After cans are collected, they are shredded and heated to 500 degrees Celsius to burn the lacquer and remove the paint coating. The shredded cans are then placed in a furnace containing molten salt -- composed of sodium and potassium chlorides and fluoride -- and heated to 750 degrees. The aluminum settles to the bottom of the furnace and is removed.
About 20 percent of the aluminum becomes trapped in the salt mixture, which collects impurities from the aluminum during the melting process. Until now, companies have been able to retrieve about 10 percent of that aluminum by squeezing the thick salt cake.
Sahai found that by passing electricity through the salt mixture during the melting process, the aluminum droplets suspended there become negatively charged and migrate toward positive electrodes in the molten aluminum pool.
The process would not only enable companies to collect more metal during the recycling process, it would also increase the number of times the salt mixture can be used.
Before it can be disposed of, the salt mixture must be purified, which is a costly procedure, Sahai said. By removing the aluminum droplets that are currently suspended in the mixture during the melting process, the salt becomes thinner and can be used longer.
"This technology could also be useful in the recycling and melting process of other metals," Sahai said.
The process should be available to metal companies in about a year, Sahai said.
A patent for the technology has been granted. Ohio State's Office of Technology Transfer department has signed a non-exclusive license with the Reynolds Metals Company in Virginia, who provided funding for the patent and partial financing for Sahai's research.
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Contact: Yogesh Sahai, (614) 292-1968
Written by Kelli Whitlock, (614) 292-9475