University at Buffalo (UB) researchers have developed a novel 3D printed water-purifying graphene aerogel that could be scaled for use at large wastewater treatment plants.
Composed of a styrofoam-like aerogel, latticed graphene and two bio-inspired polymers, the novel material is capable of removing dyes, metals and organic solvents from drinking water with 100% efficiency. Unlike similar nanosheets, the scientists’ design is reusable, doesn’t leave residue and can be 3D printed into larger sizes, thus they now aim to commercialize it for industrial-scale deployment.
“The goal is to safely remove contaminants from water without releasing any problematic chemical residue,” explained study co-author and assistant professor of environmental engineering at UB, Nirupam Aich. “The aerogels we’ve created hold their structure when put into water treatment systems, and they can be applied in diverse water treatment applications.”
Graphene’s purification potential
With a high specific surface area and ability to exert electrostatic and hydrophobic interactions simultaneously, graphene nanomaterials have recently emerged as a promising means of absorbing water contaminants. In particular, the material’s graphene oxide (GO) derivative has been tested extensively for water purification purposes, but recovering GO devices from industrial processes has proven difficult.
Recently, scientists have experimented with assembling nanosheets into macroscopic aerogels, lending them a higher absorption capacity and making them more retrievable. However, such graphene aerogels are rarely deployed within treatment facilities due to processing restrictions, that prevent them from being incorporated into industrial purifying reactors, columns and filters.
By contrast, Direct Ink Writing (DIW) offers users precise control over the size, shape and architecture of parts produced, while the process’ repeatability makes it highly scalable. Already, 3D printing has been deployed to create thermal, energy and biomedical graphene devices, hence the Buffalo scientists surmised that it could be used to develop a mass-manufactured water purifying system as well.
A scalable water-cleansing aerogel
In order to produce aerogels quickly and consistently, the researchers first needed to create a graphene-based ink, with the properties to allow water absorption while preventing particle agglomeration. To achieve this, the Buffalo team added the bio-inspired polydopamine (PDA) and bovine serum albumin (BSA) to a GO powder, yielding a novel viscoelasticity-optimized 3D printing material.
Leveraging a retrofitted Ultimaker 2 GO 3D printer, the researchers then fabricated a 12 mm (D) x 4 mm (H) cylindrical test sample, before freezing and freeze-drying it, leaving a G-PDA-BSA aerogel. During subsequent testing, the team repeatedly exposed their material to organic solvent loaded-water, as a means of assessing its contaminant removal capacity.
On each occasion, the graphene aerogel was able to remove 100% of the solvents, while reducing colored dye contamination by up to 20%. In later design iterations, the scientists even managed to reconfigure their aerogel, so that it could root-out heavy metals like lead and chromium, alloys that remain difficult to remove at current water decontamination facilities.
With further development, the scientists believe that their scalable approach could also be applied to create other functional reusable nanomaterials, with potential end-use applications at water filtration plants in the form of devices such as adsorbents, reactors or filters.
“We can use these aerogels not only to contain graphene particles but also nanometal particles which act as catalysts,” concluded Aich. “The future goal is to have nanometal particles embedded in the walls and the surface of these aerogels, and they would be able to degrade or destroy not only biological contaminants, but also chemical contaminants.”
3D printed purification devices
Given the low cost and design flexibility permitted by 3D printing, it’s increasingly being used to create novel devices that make drinking water more readily available to those in need. Just last year, the University of Cambridge spin-out Blue Tap received Innovate UK funding for its 3D printed chlorine doser, which can be fitted to water systems in developing countries in order to make it safe to drink.
Similarly, researchers at the University of Bath have developed a 3D printed water purifying ‘slab,’ that uses the sun’s heat and UV light to kill the harmful microbes living in liquids. The technology is designed to help provide clean drinking water to less well-off Asian, African, and Latin American communities.
On a more militaristic note, GE Research was recently awarded $14.3 million by the Defense Advanced Research Projects Agency (DARPA) to 3D print a device that creates water out of thin air. The portable system is being built to provide water for up to 150 troops at a time, and could later be deployed to address water scarcity around the world.
The researchers’ findings are detailed in their paper titled “Emerging investigator series: 3D printed graphene-biopolymer aerogels for water contaminant removal: a proof of concept.” The research was co-authored by Arvid Masud, Chi Zhoub and Nirupam Aich.
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Featured image shows the scientists’ freeze-dried ultra-light G-PDA-BSA aerogel on top of a Kim wipe. Photo via University at Buffalo.