The team demonstrated the concept using orange peel. With that he recovered the precious metals from the battery waste efficiently. He then made functional batteries from these recovered metals, creating minimal waste in the process.
Scientists say this waste-to-resource approach addresses both food waste and electronics waste, recycling batteries and supporting the development of a zero-waste circular economy.
An economy in which resources are kept in use for as long as possible.
It is estimated that 1,3 billion tons of food waste and 50 million tons of electronic waste are generated globally every year.
Recycle Batteries, the conventional treatment
Spent batteries are usually treated with extreme heat (over 500 ° C) to melt precious metals, which emit dangerous toxic gases. Alternative approaches are being studied that use strong acid solutions or weaker acid solutions with hydrogen peroxide to extract the metals. However, these battery recycling solutions still produce secondary pollutants that pose health and safety risks.
Professor Madhavi Srinivasan he is co-director of the NTU Singapore-CEA Alliance for Research in Circular Economy (NTU SCARCE) laboratory.
He said: “Current industrial e-waste recycling processes are energy-intensive and emit harmful pollutants and liquid waste. This indicates an urgent need for eco-friendly methods as the amount of electronic waste increases. Our team has shown that it is possible to do this with biodegradable substances. These results are based on our work at the SCARCE laboratory within the NTU Energy Research Institute (ERI @N).
The SCARCE laboratory was created to develop greener ways to recycle batteries and other electronic waste ”.
Professor Dalton Tay of the NTU School of Materials Science and Engineering and School of Biological Sciences said: “In Singapore, a country with scarce resources, this urban mining process to extract precious metals from all types of waste electronics becomes very important. With this method, we not only address the problem of resource depletion by keeping these precious metals in use as much as possible, but also the problem of electronic waste and the accumulation of food waste, both of which are a growing global crisis. "
A sustainable low-cost approach
With the recycling of battery waste generating harmful pollutants, hydrometallurgy, which uses water as a solvent for extraction, is increasingly being explored as a possible alternative.
This process involves first shredding and crushing the battery used to form a shattered material called a black mass. The researchers then extract precious metals from the black mass by dissolving them in a mixture of strong acids or weak acids plus other chemicals such as hydrogen peroxide, before precipitating the metals.
While more environmentally 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.
The NTU team found that combining oven-dried orange peel ground into a powder and citric acid, a weak organic acid found in citrus fruits, can achieve the same goal.
In laboratory experiments, the team found that their approach successfully extracted about 90% cobalt, lithium, nickel and manganese from spent lithium ion batteries, an effectiveness comparable to the approach using hydrogen peroxide.
Recycling battery with fruit peel: how does it work?
The key lies in the cellulose found in the orange peel, which is converted into sugars during the extraction process. These sugars improve the recovery of metals from battery waste. The natural antioxidants present in orange peel, such as flavonoids and phenolic acids, further contribute to efficiency ”.
There's more. The solid residues generated by this process were found to be non-toxic. This method is environmentally friendly.
From old to new
From the recovered materials, the researchers then assembled new lithium-ion batteries. Batteries that have shown similar charging capacity to commercial ones.
Further research is ongoing. The aim is to optimize the performance of the charge-discharge cycle of these batteries made with recovered materials.
This suggests that this new technology is “practically feasible for recycling lithium-ion batteries on an industrial scale”.
The team is now looking to further improve the performance of batteries generated by treated battery waste.
This waste-to-resource approach can also be extended to other types of cellulose-rich fruit and vegetable waste. This approach can go a long way towards the new circular economy of e-waste.