1 day Ago By Amit Malewar
A nanofiltration process that could make aluminum production more efficient. While aluminum is the key material incorporated in products ranging from soda cans to circuit boards, it is nonetheless required for contemporary living. However, the rising global demand for this versatile metal is set to aggravate its environmental burden, as hazardous waste is produced during manufacturing.
This breakthrough may significantly reduce this dilemma: At MIT , engineers have devised a new ceramic nanofiltration membrane to mitigate waste generated during aluminum production and improve recycling efficiency. The new membrane technology can selectively capture aluminum ions from industrial waste streams. The new nanofiltration system, which could be deployed in existing aluminum plants, not only recycles valuable aluminum but also reduces the volume of harmful pollutants released into the environment.
“We’re not just preventing waste,” said Lienhard, the Abdul Latif Jameel Professor of Water in the Department of Mechanical Engineering at MIT. “This membrane technology also enables a circular economy for aluminum, which could reduce the need for new mining and help mitigate some of the industry’s environmental footprint.” The process of aluminum production Once the bauxite ore is mined, it is refined into aluminum oxide or alumina.
Then, alumina is subjected to high-temperature electrolysis in a molten mineral cryolite bath. Oxygen is separated from aluminum in this process, and the metal settles beneath the metal below after cooling. Still, cryolite accumulates certain impurities with time: sodium and potassium ions.
The efficiency of cryolite gets reduced because of this. To maintain the process, the electrolyte must eventually be replaced, resulting in the disposal of spent cryolite — a toxic mixture that contains leftover aluminum ions . “Up to 2,800 tons of aluminum can be wasted annually at a single production facility,” said Trent Lee, a mechanical engineering undergraduate at MIT and lead author of the study.
“We realized there was an untapped opportunity to recover aluminum from the cryolite waste stream and improve the efficiency of the aluminum production process.” New filter captures and recycles aluminum from manufacturing waste The new nanofiltration technology developed by Lienhard’s team filters out aluminum ions from waste while letting other ions, like sodium, pass through. If scaled up, it could recycle aluminum back into production, reducing waste and the need for new raw materials.
The membrane filters ions based on their charge. Traditional filtration membranes, commonly used in water treatment, repel ions with the same charge as the membrane’s surface. In this case, the MIT team worked with a specialized membrane developed by Nitto Denko, a Japanese membrane company, to develop a coating that attracts aluminum ions while repelling ions with weaker charges, such as sodium.
Applying a thin-layer, positively charged coating on the membrane would attract positively charged aluminum ions, allowing the weaker sodium ions to pass through. In laboratory tests, the membrane consistently captured over 99% of the aluminum ions from solutions simulating waste produced by aluminum plants. It also worked well in harsh, acidic conditions, common in cryolite waste.
“We were able to capture 99.5% of the aluminum ions, and even after sitting in highly acidic solutions for weeks, the membrane maintained its high performance,” said Zi Hao Foo, a postdoctoral researcher who collaborated on the project. “This is a huge advantage, as aluminum waste is typically acidic, which can degrade less durable materials.
” The researchers want to scale up this membrane, similar to those in desalination plants where long membranes are spiraled into cylinders for efficient filtration. This technique could find its application in recovering aluminum from waste loads for recycled production in the aluminum production industry; this would lead to lesser reliance on the consumption of the raw materials, reduced production costs, and lessened environmental impact. In addition to solving the problem of aluminum waste, this technology could contribute to the broader concept of a circular economy, where material is reused rather than retired after use.
Hence, it meets global sustainability goals to reduce industrial waste and carbon emissions , as aluminum production is a major contributor to both. With demand for aluminum soaring, innovations like this could make production more sustainable, efficient, and less harmful to the environment. The work of the MIT team on a nanofiltration membrane technology is a promising step toward reducing aluminum production’s environmental impacts.
That development could see a significant increase in aluminum recycling and waste management in the industry if scaling up is achieved in the next few years, possibly integrated with existing aluminum production facilities. Journal Reference: Trent R. Lee, Zi Hao Foo, Vinn Nguyen, and John H.
Lienhard. Enhancing Resource Circularity in Aluminum Production through Nanofiltration of Waste Cryolite. ACS Sustainable Chemistry and Engineering .
DOI: 10.1021/acssuschemeng.4c07268 Topics Metals.
