Engineers developed a process of 3D printing graphene aerogels that overcomes two key hurdles for water treatment: scalability and creating a version of the material that’s stable enough for repeated use.
The goal is to safely remove contaminants from water without releasing any problematic chemical residue. The aerogels hold their structure when put in water treatment systems and they can be applied in diverse water treatment applications.
An aerogel is a light, highly porous solid formed by replacement of liquid in a gel with a gas, so that the resulting solid is the same size as the original. They are similar in structural configuration to Styrofoam: porous and lightweight, yet strong and resilient. Graphene is a nano-material formed by elemental carbon and is composed of a single flat sheet of carbon atoms arranged in a repeating hexagonal lattice.
To create the right consistency of the graphene-based ink, the researchers added to the graphene two bioinspired polymers — polydopamine (a synthetic material often referred to as PDA, which is similar to the adhesive secretions of mussels) and bovine serum albumin (a protein derived from cows).
In tests, the reconfigured aerogel removed certain heavy metals, such as lead and chromium, that plague drinking water systems. It also removed organic dyes, such as cationic methylene blue and anionic Evans blue, as well as organic solvents like hexane, heptane, and toluene. To demonstrate the aerogel’s reuse potential, the researchers ran organic solvents through it 10 times. Each time, it removed 100 percent of the solvents. The researchers also reported the aerogel’s ability to capture methylene blue decreased by 2 to 20 percent after the third cycle.
The aerogels can also be scaled up in size because unlike nanosheets, aerogels can be printed in larger sizes. This eliminates a previous problem inherent in large-scale production and makes the process available for use in large facilities, such as in wastewater treatment plants. The aerogels can be removed from water and reused in other locations and they don’t leave any kind of residue in the water.
The aerogels can be used not only to contain graphene particles, but also nano-metal particles that can act as catalysts. The future goal is to have nanometal particles embedded in the walls and the surface of the aerogels to degrade or destroy biological as well as chemical contaminants.