While graphene has been recognized for its ability to filter out contaminants in water, it has remained limited by feasibility issues - until now.

An engineering team from the University at Buffalo has devised a new 3D printing technique for graphene aerogels that supposedly works around the material's limitations such as scalability and making the material stable enough for repeated use in water filters and treatment applications.

The University at Buffalo team presented their findings in the report "Emerging investigator series: 3D printed graphene-biopolymer aerogels for water contaminant removal: a proof of concept" appearing in the journal Environmental Science: Nano.

An Aerogel Cube at NASA
(Photo: NASA/JPL-Caltech via Wikimedia Commons)
Aerogel cube & Peter Tsou, JPL Scientist, Stardust Deputy Principal Investigator.

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Making Reusable and Scalable Graphene Aerogels

"The goal is to safely remove contaminants from water without releasing any problematic chemical residue," says Nirupam Aich, Ph.D., and an assistant professor from the School of Engineering and Applied Sciences at UB, in a statement from the university. He adds that the aerogels that they fabricated can maintain their structures even when placed in water treatment systems, making them potentially applicable for a variety of water filters and treatment applications.

Generally, the term aerogel refers to light and highly porous solid created by replacing the liquid in a gel material with gases, resulting in a solid that is roughly the same size as the liquid-filled original. The material has been compared with styrofoam, porous and lightweight yet strong and resilient.

On the other hand, graphene is a modern nanomaterial fabricated from naturally occurring carbon made up of carbon atoms arranged in an ultrathin sheet of hexagonal lattice arrangements.

To create the graphene aerogel, researchers focused on a graphene ink of the right consistency. In order to achieve this, researchers found inspiration in nature: adding the carbon-based material to a pair of bio-based polymers: polydopamine, which is a synthetic material also known as PDA and is similar to the sticky secretions of mussels, and the bovine serum albumin, which is a protein derived from cows.

In their experiments, researchers found that their reconfigured graphene aerogel was able to filter out heavy metals like lead and chromium, which contaminate drinking systems all over the world. Additionally, it was also able to remove organic dyes in water - such as cationic methylene blue, or anionic Evans blue - and organic solvents hexane, toluene, and heptane.

A Working Proof of Concept

As a proof of concept for the new graphene aerogel, researchers also ran organic solvents through the material ten times in total, testing its reusability. For each of the ten trials, the 3D printed material removed 100% of the solvent contaminants. However, they also discovered that the graphene aerogel's ability to filter out methylene blue fell by 2 to 20 percent after the third cycle.

Meanwhile, the material's scalability is not a problem according to the researchers. Unlike nanosheets, which are limited to ultrathin fabrications, graphene aerogels could be 3D printed in larger sizes. With this possibility, graphene-based filters could be used in larger water treatment applications, such as those in wastewater treatment facilities.

"We can use these aerogels not only to contain graphene particles but also nanometal particles which can act as catalysts," Aich adds.

 

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