Researchers Develop Element Extracting Coating
Researchers at Penn State University have reportedly developed a new mussel-inspired nanocellulose coating (MINC) that can recover rare earth elements from secondary sources such as industrial wastewater.
According to the university's release, rare earth elements can play a key role in clean energy and are vital to the production of lightweight, efficient batteries, as well as essential components in wind turbines.
Conventional extraction methods for these elements have reportedly raised environmental concerns, ranging from habitat destruction to water and air pollution due to the high amount of energy needed to extract and process them.
The release states that mussels have a remarkable ability to adhere to surfaces underwater because of the adhesive properties of catechol-based molecules that are found in mussel proteins. The MINC reportedly mirrors this adhesion by consisting of ultra-tiny, hairy cellulose nanocrystals with “uniquely sticky” properties.
Mussels inspire an eco-friendly way to extract critical rare earth elements https://t.co/yvU7EWAyIF#nanotechnology #materialsscience #advancedmaterials #engineering #innovation #technology #scienceandtechnology #energy pic.twitter.com/b3iOoidioI— Nanotechnology World Association (@NanotechnoWorld) August 11, 2023
For the research, the MINC was reportedly applied to a substrate by a technique known as dopamine-mediated ad-layer formation. A chemical reaction then reportedly enables the MINC to form a thin layer of molecules on a surface, making it able to stick to a broad range of substrates.
“The MINC approach offers a sustainable and eco-friendly alternative to conventional extraction methods, minimizing the environmental footprint and contributing to the long-term availability of critical elements,” said lead author Amir Sheikhi, assistant professor of chemical engineering and of biomedical engineering.
Researchers reportedly focused on applying MINC to extract a particular rare earth element, neodymium. The U.S. Department of Energy listed the element as a critical material due to supply shortages and its high impact on emerging sustainable technologies like electric car batteries and magnets for powering wind turbines.
The team says that neodymium is especially rare, as the lack of ready-to-extract supply of the element forces the extraction of it from secondary sources like industrial wastewater recycling. According to Sheikhi, this can be both inefficient and energy intensive.
“The limited global supply of neodymium and the environmental impact of current extraction methods necessitate the development of eco-friendly and sustainable approaches for REE recovery,” Sheikhi said, explaining that conventional extraction techniques use significant amounts of toxic chemicals, such as kerosene, to purify the target element.
“Prior rare earth extraction methods have utilized adsorbents such as alginate gels, phosphorus sol-gel materials, nanotubes and porous carbon, but these techniques demonstrate limited efficiency.”
The release states that the “MINC coating is to neodymium what a magnet is to iron,” pulling the rare earth elements out of the water even when the element is only present in amounts as limited as parts per million.
“The challenge in extracting neodymium lies in achieving efficient and selective removal of it at low concentrations,” Sheikhi said. “The MINC presented in this study offers improved selectivity and capacity for neodymium removal, overcoming limitations of previous methods.”
According to the release, this selectivity allows MINC to avoid recovering undesired elements like sodium and calcium, which Sheikhi said would waste time and energy if they had to be filtered to further refine the neodymium.
“The public and society will benefit from this work through the potential for increased availability of neodymium, a crucial element for not just developing clean energy technologies, but also for creating new medical and electronic devices,” Sheikhi said, adding that he plans to investigate how the MINC method may work to extract other REEs.
“By providing a sustainable and efficient method for neodymium recovery, this research contributes to the advancement of these technologies and helps address supply shortage concerns, and in turn will increase the possibility of translating this technology to other REE recovery efforts in the future.”
Along with Sheikhi, other authors of the paper from Sheikhi’s team include Shang-Lin Yeh, doctoral candidate in chemical engineering; Dawson Alexander, undergraduate student in chemical engineering; Naveen Narasimhalu, undergraduate student in chemical engineering; and Roya Koshani, post-doctoral researcher in chemical engineering.
This research was supported by the Energy and Environmental Sustainability Laboratories Green Student Seed Grant program and the Penn State College of Engineering Diefenderfer Graduate Fellowship in Entrepreneurship.
Earlier this month, engineers at the University of Bath in England developed a new kind of polymer-coated membrane that can separate chemicals for water filtration. The thin-film composite nanoporous membrane (TFC NPM) reportedly has the capability to separate salts and other chemical components from wastewater.
According to the release, the development presented a new opportunity for industries to improve sustainability, while extracting valuable by-products and chemicals from water that can then be reused.
The development was published in the journal Nature Water, detailing the membrane’s performance and explaining how its properties are reportedly inspired by mussels. The release said that this could pave the way for a more sustainable management of water within industries such as pharmaceuticals, oil and gas, textiles and food processing.
The paper was authored by academics from the University of Bath alongside colleagues based in China, South Korea, Singapore, Australia and Belgium.
The coating is reportedly made up of the polymer polyethyleneimine (PEI) and polydopamine (PDA), a compound which mussels excrete and use to stick to rocks or wood in wet conditions. The coating’s stickiness, according to the release, makes the membrane highly selective, allowing water to pass through but blocking other compounds and organic materials.
The multi-stage process reportedly results in improved filtration of the water and a highly efficient, low-energy way to fractionate, or separate, chemicals individually.
The researchers stated that the membrane could replace current equivalents used in electrodialysis, a process for treating water by transporting ions through membranes from one solution to another under an electrical current.
According to the release, electrodialysis has shown its adaptability to several applications, specifically management of highly saline waste streams. In the electrodialysis process, electrical potential is reportedly used to drive the positive and negative ions of dissolved salts through a semipermeable synthetic membrane.
Existing membranes are reportedly expensive and can achieve separation efficiencies of 90-95%. The researchers state that the new TFC NPM can improve this significantly, with efficiencies of over 99%, while using less energy at a lower cost.
During tests, the researchers reportedly used four antibiotics—ceftriaxone sodium, cefotaxime sodium, carbenicillin disodium and ampicillin sodium—to prove the PDA/PEI-coated membrane’s electro-driven filtration performance.
According to the release, the membrane showed “unprecedentedly” high recovery efficiency in removing antibiotics from saltwater solutions, with over 99.3% desalination efficiency, as well as more than 99.1% recovery of the antibiotics.
The report states that if incorporated in industrial wastewater treatment, the membrane could carry out “highly effective” electrodialytic fractionation of various organic/NaCl mixed solutions, more effectively than standard exiting processes.