Scientists use fruit peel to turn old batteries into new

Date:
August 26, 2020
Source:
Nanyang Technological University
Summary:
Scientists have developed a novel method of using fruit peel
waste to extract and reuse precious metals from spent lithium-ion
batteries in order to create new batteries. The scientists say
that their waste-to- resource approach tackles both food waste
and electronics waste, supporting the development of a circular
economy with zero waste.



FULL STORY ========================================================================== Scientists led by Nanyang Technological University, Singapore (NTU
Singapore) have developed a novel method of using fruit peel waste to
extract and reuse precious metals from spent lithium-ion batteries in
order to create new batteries.


==========================================================================
The team demonstrated their concept using orange peel, which recovered
precious metals from battery waste efficiently. They then made functional batteries from these recovered metals, creating minimal waste in the
process.

The scientists say that their waste-to-resource approach tackles both food waste and electronics waste, supporting the development of a circular
economy with zero waste, in which resources are kept in use for as long
as possible. An estimated 1.3 billion tonnes of food waste and 50 million tonnes of e-waste are generated globally each year.

Spent batteries are conventionally treated with extreme heat (over
500DEGC) to smelt valuable metals, which emits hazardous toxic
gases. Alternative approaches that use strong acid solutions or weaker
acid solutions with hydrogen peroxide to extract the metals are being
explored, but they still produce secondary pollutants that pose health
and safety risks, or rely on hydrogen peroxide which is hazardous and
unstable.

Professor Madhavi Srinivasan, co-director of the NTU Singapore-CEA
Alliance for Research in Circular Economy (NTU SCARCE) lab, said:
"Current industrial recycling processes of e-waste are energy-intensive
and emit harmful pollutants and liquid waste, pointing to an urgent need
for eco-friendly methods as the amount of e-waste grows. Our team has demonstrated that it is possible to do so with biodegradable substances.

"These findings build on our existing body of work at SCARCE under
NTU's Energy Research Institute (ERI@N). The SCARCE lab was was set up
to develop greener ways of recycling e-waste. It is also part of the NTU
Smart Campus initiative, which aims to develop technologically advanced solutions for a sustainable future." Assistant Professor Dalton Tay
of the NTU School of Materials Science and Engineering and School of
Biological Sciences said: "In Singapore, a resource- scarce country,
this process of urban mining to extract valuable metals from all kinds of discarded electronics becomes very important. With this method, we not
only tackle the problem of resource depletion by keeping these precious
metals in use as much as possible, but also the problem of e-waste and
food waste accumulation -- both a growing global crisis."


==========================================================================
The findings were published in the scientific journal Environmental
Science & Technology in July.

A low-cost, sustainable approach With industrial approaches to recycling battery waste generating harmful pollutants, hydrometallurgy -- using
water as a solvent for extraction -- is increasingly being explored as a possible alternative. This process involves first shredding and crushing
used batteries to form a crushed material called black mass. Researchers
then extract valuable metals from black mass by dissolving it in a mix
of strong acids or weak acids plus other chemicals like hydrogen peroxide
under heat, before letting the metals precipitate.

While relatively more eco-friendly than conventional methods, the use of
such strong chemicals on an industrial scale could generate a substantial amount of secondary pollutants, posing significant safety and health
risks, said Asst Prof Tay.

The NTU team found that the combination of orange peel that has been
oven-dried and ground into powder, and citric acid, a weak organic acid
found in citrus fruits, can achieve the same goal.



==========================================================================
In lab experiments, the team found that their approach successfully
extracted around 90 per cent of cobalt, lithium, nickel, and manganese
from spent lithium-ion batteries -- a comparable efficacy to the approach
using hydrogen peroxide.

Asst Prof Tay explained: "The key lies in the cellulose found in orange
peel, which is converted into sugars under heat during the extraction
process. 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." Importantly, solid residues generated from this process were
found to be non- toxic, suggesting that this method is environmentally
sound, he added.

From the recovered materials, they then assembled new lithium-ion
batteries, which showed a similar charge capacity to commercial
ones. Further research is underway to optimise the charge-discharge
cycling performance of these new batteries made from recovered materials.

This suggests that this new technology is "practically feasible for
recycling spent lithium ion batteries in the industrial sense," said
the researchers.

The team is now looking to further improve the performance of their
batteries generated from treated battery waste. They are also optimising
the conditions to scale up production and exploring the possibility of
removing the use of acids in the process.

Prof Madhavi, who is also from NTU's School of Materials Science and Engineering and ERI@N, said: "This waste-to-resource approach could
also potentially be extended to other types of cellulose-rich fruit and vegetable waste, as well as lithium-ion battery types such as lithium
iron phosphate and lithium nickel manganese cobalt oxide. This would help
to make great strides towards the new circular economy of e-waste, and
power our lives in a greener and more sustainable manner." The research,
which comes under NTU SCARCE, is supported by the National Research
Foundation, the Ministry of National Development, and the National
Environment Agency under the Closing the Waste Loop R&D Initiative as
part of the Urban Solutions & Sustainability Integration Fund.


========================================================================== Story Source: Materials provided by
Nanyang_Technological_University. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Zhuoran Wu, Tanto Soh, Jun Jie Chan, Shize Meng, Daniel Meyer,
Madhavi
Srinivasan, Chor Yong Tay. Repurposing of Fruit Peel Waste
as a Green Reductant for Recycling of Spent Lithium-Ion
Batteries. Environmental Science & Technology, 2020; 54 (15):
9681 DOI: 10.1021/acs.est.0c02873 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200826101623.htm

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