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Singaporean Researchers Use Orange Peels to Extract 90% of Rare Metals from Discarded Lithium-Ion Batteries
2020-09-15   |  Editor:et_editor  |  85 Numbers

Lithium-ion batteries are an indispensable form of power source that provides convenience in people’s daily lives and drives development in many technological fields. However, the immediate benefits that they offer come with some trade-offs related to the impacts of battery waste and the mining of the rare metals such as cobalt. With a focus on solutions that support the circular economy, industry experts and researchers around the world have been working on battery recycling processes that can extract as much of the rare metals as possible for reuse in the manufacturing of new batteries. A major concern in the recovery of the rare and highly valuable metals from discarded lithium-ion batteries is that breaking down these devices into their constituent parts or materials could create more pollution. Hence, there are efforts being made to not only reduce the cost of the battery recycling process but also minimize the amount of toxic byproducts that it might create.

Recently, researchers at Singapore’s Nanyang Technological University (NTU) have devised a low-cost and environment-friendly approach to extract metals from discarded lithium-ion batteries. What is interesting about their solution is that discarded orange peels get to play a very vital role. According to the paper on their work, this new method that uses fruit peels offers an efficiency of around 90% in the recovery of the rare metals from batteries. It is also highly effective in reducing secondary pollution.

The official press release concerning this research states that approximately 1.3 billion metric tons of food waste and 50 million metric tons of e-waste are produced globally every year. Researchers who participated in the development of the new and environment-friendly battery recycling process claim that their solution, which can be described as “turning trash into gold”, simultaneously addresses the challenges of dealing with both types of wastes. If successfully implemented, their recycling method could contribute significantly to the realization of the circular economy.

The conventional approaches to recover metals from discarded lithium-ion batteries include smelting and chemical treatment. In the first method, batteries are heated to a temperature of more than 500°C so that the rare metals are melted for collection. The NTU team points out that this process is very energy-intensive and produces toxic gases. The second method involves crushing batteries into tiny pieces and place them in a heated chemical solution containing acid or hydrogen peroxide. The rare metals eventually leach out from the pieces of broken batteries through chemical precipitation. Although the second method is more commercially viable, it also has the shortcoming of creating a large amount of pollutants in liquid form.

The NTU team has hit upon the idea that industrial chemicals are not necessary to achieve the chemical reactions that allow for the extraction of the rare metals from crushed batteries. Peels from citrus fruits such as orange can substitute for commonly used acids and hydrogen peroxide. According to the study published by the team in the journal Environmental Science & Technology, orange peels are first oven-dried and grounded into a powder that is then combined with citric acid. This mixture is a key ingredient in the chemical solution for the precipitation of metals. The study states that the hydrometallurgy process that uses acid derived from fruit peels is able to recover around 90% of cobalt, lithium, nickel, and manganese from discarded lithium-ion batteries. The efficacy of using acid made from fruit peels is comparable to that of using hydrogen peroxide. Furthermore, the new approach developed by the NTU team leaves no toxic residue.

Dalton Tay, assistant professor and co-lead author of the paper, says in the press release that the cellulose in the orange peels plays a key role. When heated, the cellulose turns into sugars that work with the natural antioxidants that are also in the peels to ramp up the extraction of metals from battery waste.

Madhavi Srinivasan, co-lead author of the paper and co-director of the laboratory for the NTU Singapore-CEA Alliance for Research in Circular Economy (NTU SCARCE), says in the press release that high energy consumption and toxic pollutants are the two major obstacles in the development of industrial recycling processes for e-waste. Srinivasan further points out that sustainable and environment-friendly solutions for recycling e-waste are urgently needed as more and more electronic devices are adopted in people’s daily lives. Tay adds that the battery recycling process that his team is working on addresses the issue of Singapore having limited natural resources. All in all, the new approach to battery metal recovery coming out of NTU has an enormous potential of relieving the pressure of resource depletion and reducing the accumulation of organic waste from homes and farms at the same time.

 (News source: TechNews. Photo credit: Pixabay.)