Use of compost to recover rare earth metals

Use of compost to recover rare earth metals

News Summary:

  • “Waste materials such as corn cobs, pulp, cotton and tomato skins often end up in landfills and compost,” said co-author Amir Sheikhi, an assistant professor of chemical engineering. says. “We wanted to transform these wastes into micro- or nanoscale particles that could extract rare earth elements from e-waste.” Rare earth metals are used to make powerful magnets used in motors such as electric and hybrid vehicles, speakers, headphones, computers, wind turbines and television screens.

  • Both can be used to recover valuable rare earth elements such as neodymium from electronic waste. Researchers at Penn State University used micro- and nanoparticles made from organic materials to capture rare earth elements from aqueous solutions. Their results are now available online and will appear in his November issue of Chemical Engineering Journal.

However, Sheikhi said mining these metals is proving to be difficult and environmentally friendly as it takes vast areas of land to mine even small amounts of the metals. Instead, the focus is on recycling metals from e-waste such as old computers and circuit boards. The challenge, Sheikh said, is to efficiently separate the metals from the waste. “We used organic materials as a platform to create highly functional micro- and nanoparticles that can adhere to metals such as neodymium and separate them from surrounding liquids,” said Sheikh. “Through electrostatic interactions, negatively charged materials in the micro- and nano-range bind positively charged neodymium ions and separate them.”

In this latest paper, Sheik improved the separation process demonstrated in his previous work, extracting a larger sample amount of neodymium from a less concentrated solution. Sheikh plans to extend the disconnect mechanism to real-world scenarios and work with interested industries to further test the process. “We hope to test the process on realistic industrial samples in the near future,” said Sheikhi. “We also want to tune the selectivity of the material towards other rare earth elements and precious metals such as gold and silver so that we can separate them from the waste.”

To set up the experiment, Shake’s team chopped up tomato skins and corn cobs, cut pulp and cotton paper into small, thin pieces, and soaked them in water. These materials were then chemically reacted in a controlled manner and broken down into three different functional materials: microproducts, nanoparticles and solubilized biopolymers. Addition of microproducts or nanoparticles to the neodymium solution initiated the separation process and captured the neodymium sample.

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