Environment

Orange peels used to extract valuable metals from spent batteries

Orange peels used to extract v...
Lead scientists Asst. Prof. Dalton Tay (left) and Prof. Madhavi Srinivasan
Lead scientists Asst. Prof. Dalton Tay (left) and Prof. Madhavi Srinivasan
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Lead scientists Asst. Prof. Dalton Tay (left) and Prof. Madhavi Srinivasan
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Lead scientists Asst. Prof. Dalton Tay (left) and Prof. Madhavi Srinivasan

Just because a lithium-ion battery no longer holds a charge doesn't mean it no longer holds any value. It still contains useful metals, which can now be reclaimed via a more eco-friendly technique – the key ingredient is orange peel waste.

Ordinarily, in a smelting process, spent lithium batteries are heated to over 500 ºC (932 ºF). This causes the contained metals to melt and run out of them. Those metals are then collected and reused. However, not only does the process require a lot of energy, but it also produces toxic gases.

One possible alternative involves shredding and crushing used batteries, then precipitating the metals from them by adding acids and hydrogen peroxide while heating the mixture. This still-experimental technique, known as hydrometallurgy, is more environmentally friendly than smelting. However, on an industrial scale, it could still produce a significant amount of pollutants.

With that limitation in mind, scientists at Singapore's Nanyang Technological University tried using orange peels instead of the usual acids and hydrogen peroxide. More specifically, they utilized oven-dried orange peels that had been ground into a powder, combined with citric acid obtained from citrus fruit.

Doing so, the researchers were able to extract about 90 percent of the lithium, cobalt, nickel and manganese from spent lithium-ion batteries. This level of efficiency is roughly what had been achieved previously. Importantly, though, when using the orange peels, the residue was found to be non-toxic.

"The key lies in the cellulose found in orange peel, which is converted into sugars under heat during the extraction process," says Asst. Prof. Dalton Tay, one of the leaders of the study. "These sugars enhance the recovery of metals from battery waste. Naturally occurring antioxidants found in orange peel, such as flavonoids and phenolic acids, could have contributed to this enhancement as well."

The researchers used the reclaimed metals in new lithium-ion batteries, that have a charge capacity similar to that of commercially available models. Further testing is now being conducted, to see if the new batteries last for a comparable number of charge/discharge cycles.

A paper on the research, which is being co-led by Prof. Madhavi Srinivasan, was recently published in the journal Environmental Science & Technology.

Source: Nanyang Technological University

4 comments
sidmehta
Very impressive. Hope this catches on.
moreover
Reminded me of another orange peel 'miracle' from Costa Rica where a thousand truckloads of orange peel were dumped on barren land which then turned back into lush forest. https://www.princeton.edu/news/2017/08/22/orange-new-green-how-orange-peels-revived-costa-rican-forest
Citrus is also widely use for degreasing and removing goo.
KenMills
way more effective to disassemble the batteries. an 18650 for instance can be opened and unrolled providing access to a sheet of copper, a casing of likley nickel, a roll of plastic, and a roll of aluminum. rinsing these with a solvent to remove the lithium "ink" for metal recovery and done. unemployed folks need work. "hire" them to do this at low cost while they are collecting unemployment checks and between interviews for better work. Alternatively, build a machine that will do the same. No need to slice, crush, burn and dissolve metals using tremendous amounts of precious energy and that creates air and water pollution that are so easilly physically sorted by otherwise idle hands. spend hundreds to ruin the environment and waste energy to recycle a dime
ljaques
Quick, inexpensive methods to salvage of the lithium will be instantly grabbed. And ecologically sound methods will be the first to be taken up. Kudos, Professors!