Biobased materials used to recover rare earth elements

What do corn cobs and tomato peels have to do with electronics? They can both be used to recover valuable rare earth elements, like neodymium, from electronic waste. Penn State researchers used microparticles and nanoparticles created from organic materials to capture rare earth elements from aqueous solutions.

Their findings, available online now, will also be published in the November issue of Journal of Chemical Engineering.

“Waste like corn cobs, wood pulp, cotton and tomato peels often end up in landfills or in compost,” said corresponding author Amir Sheikhi, an assistant professor of chemical engineering. “We wanted to transform this waste into micro or nanoscale particles capable of extracting rare earths from electronic waste.”

Rare-earth metals are used to make powerful magnets used in electric and hybrid car motors, speakers, headphones, computers, wind turbines, TV screens, and more. However, extracting these metals proves to be difficult and costly for the environment, according to Sheikhi, as vast land is required to extract even small amounts of metals. Instead, efforts have turned to recycling metals from e-waste like old computers or circuit boards.

The challenge is to effectively separate the metals from the waste, Sheikhi said.

“Using the organic materials as a platform, we have created highly functional microparticles and nanoparticles that can attach to metals like neodymium and separate them from the fluid around them,” Sheikhi said. “Via electrostatic interactions, negatively charged micro- and nanoscale materials bind to positively charged neodymium ions, pulling them apart.”

To prepare for the experiment, Sheikhi’s team ground up tomato peels and corn cobs and cut wood pulp and cotton paper into small, thin pieces and soaked them in water. Then, they chemically reacted these materials in a controlled way to disintegrate them into three distinct fractions of functional materials: microproducts, nanoparticles and solubilized biopolymers. The addition of microproducts or nanoparticles to neodymium solutions triggered the separation process, resulting in the capture of neodymium samples.

In this most recent paper, Sheikhi improved on the separation process demonstrated in previous work and extracted larger sample sizes of neodymium from less concentrated solutions.

Sheikhi plans to extend his separation mechanism to real-world scenarios and partner with interested industries to further test the process.

“In the near future, we want to test our process on realistic industrial samples,” Sheikhi said.

“We also hope to adjust the selectivity of the materials towards other rare earth elements and precious metals, such as gold and silver, to be able to separate them from the waste as well.”

In addition to Sheikhi, Mica Pitcher, a Penn State chemistry PhD student and first author of the paper; Breanna Huntington, Penn State undergraduate student in agricultural and biological engineering; and Juliana Dominick, a Penn State undergraduate student in biomedical engineering, contributed to the article.

Penn State supported this work.

Source of the story:

Materials provided by Penn State. Original written by Mariah Chuprinski. Note: Content may be edited for style and length.

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