GO-Shrimp! US Army ERDC creates unique graphene composite

This article was originally published in the Nixene Journal, Vol. 4, Issue 9, September, 2020

In summer, 2020, Nixene Publishing had the opportunity to speak with Dr. Chris Griggs, principal investigator for Sustainable Water Infrastructure and Materials Research (SWIMR) at the United States Army Research & Development Center in Vicksburg, Mississippi. Debbie Nelson discovered his trio of roles - as Research Physical Scientist; as Adjunct Professor of Chemical Engineering at the University of Arkansas; and as Polymer Science and Engineering at University of Southern Mississippi - keeps him busy directing his team and leading students in developing advanced materials and biomaterials to address environmental challenges.

“In the past three years, our group was granted two patents, one for water filtration membranes which had a challenge of energy requirements...

Since that time, we have improved separation efficiency at low operational pressures of <50 psi (344KPa) “, said Griggs. “The way we accomplished the task is quite unique and takes us back to a series of natural and manmade disasters that impacted coastal economies. This included economic damage from hurricanes and the Deepwater Horizon oil spill in 2010,” he explained. “The spills inspired research into how coastal companies could use the by-products of their shrimp and crustacean catch, to create alternative marketable products.”

At that time, Griggs was working on his PhD dissertation. Shrimp shells came into play, as crustacean shells are composed of a biological polymer chitin which is the second most abundant polymer after cellulose. Initial research was focused on novel ways to extract the chitin polymer from the shell waste. They also focused on using a renewable waste product - containing biological polymers like chitin and its derivative chitosan - to produce innovative materials for advanced applications.

The Department of Energy funded those early efforts to examine how chitosan fibres could be used to selectively remove metals (such as uranium) from seawater. In 2015, Dr. Griggs and his engineers needed a polymer that could help produce scalable water treatment membranes from graphene oxide (GO).

Griggs said, “At that point, we recalled my PhD dissertation research work with shrimp shells and realized that chitosan was the ideal polymer to stabilize GO in water. ERDC rapidly produced scalable chitosan- GO composites (CSGO) that were not only linearly scalable, but 100% recyclable.”

The composite is inherently sustainable using bulk chitosan, which is positively charged with dilute acetic acid and mixed with small amounts of graphene oxide. The blend is wet cast, evaporated, then made into sheets that are amenable to roll-to-roll (R2R) manufacturing. Sheets of the composite behave as membranes for water filtration and may be produced in any size.

The membrane is not pore-based. It is a dense membrane that has interspaced layers which create a tortuous path for water to navigate through, purifying the water. This new membrane design is advantageous over pore-based systems due to their inherent trade-off between permeability and selectivity.

The ERDC team is working to optimize the layered system, to make it tuneable for a variety of water purification applications, including low energy desalination. Dr. Griggs’ team uses a discovery driven approach.

He said, “It was like ‘shake and bake’ - watch, adjust and assemble. Test a little, build a little...

Put a charge on it for lower water flow. The flux, measured in litres per square metre per hour (lmh), increased from 2 lmh to 30 lmh with 50psi efficiency, which is comparable to commercial nanofiltration membranes.”

The wet process is laid out on a surface for evaporation, resulting in a membrane that peels right off the surface, not sticking to anything. In an interesting exception, the membrane composite mixture adheres relentlessly to metal. The surprising discovery was made after excess mixture was poured into a metal sink for disposal and remains to this day.

The team’s discovery driven approach opened the door for using the composite as a coating. The coating is currently being tested. On surfaces, Griggs said the composite “unequivocally works as anti-bacterial, destroying the cell wall and causing oxidative stress to bacterial cells such as e. coli. Current events have placed an emphasis on viruses which are trickier business due to smaller size and differing mechanisms of inactivation, but this material looks promising.”

He went on to explain that by shuttling electrons on the edges, they found radicals - superoxide, independent of light - coming from the edge functional groups. The process produces oxygen radicals which have broad spectrum disinfection performance. Simply using a UV light to disinfect coated surfaces, they found the light to be modifying the graphene oxide.

Griggs observed, “This made surface medication possible, to enhance the oxidative effects by preferentially generating the chemical groups producing the radicals.”

To accomplish its objectives, ERDC works on soft funding cycles and must compete for research dollars based on milestones and expectations.

“Having Mississippi State Senator Roger Wicker active in the American Graphene Summit on Capitol Hill was serendipitous in gaining salience of graphene research occurring in the state,” said Griggs.

The next step for the ERDC team is proposed collaborations with Rice University’s Dr. James Tour and strategic private partners such as Universal Matter, which produces flash graphene developed by the Tour Research Group. Together they hope to examine what Griggs calls “polymers that play well with graphene, and help realize graphene’s immense potential.”

On their own, ERDC currently works with 20-30 different types of graphene. For instance, flash graphene is also being evaluated in polyurethane foams for use in lightweighting structural materials. This includes expanding graphene into infrastructure materials such as asphalt and concrete. An interesting application emerged, as the technology left the lab in small batches and entered field testing on a large scale at Camp Shelby.

The Joint Forces Training Center is the largest state-owned training site in the United States. Its location is halfway between the ERDC location in Jackson and the Mississippi Gulf Coast.

Trailer-based systems for deployment in water filtration emergencies were created out of 20-foot shipping containers.

The collaboration between “chemical engineers who like to make big things” and laboratory chemists is unique and not often seen in the typically military silo-approach. “Their focus is not about quantity, it is about quality “, said Griggs.

He also indicated the importance of this water filtration technology in regards to Space applications. Griggs emphasized, “ALL water in space will need to be recycled. The water needs to be treated to a safe degree.”

To date, Dr. Griggs’ team has impressively been awarded three patents, just in the past 7 months.

1. An easy process to recycle the graphene oxide-chitosan composite, completely restoring exact properties
2. GO-Chitosan Composite patented divisional 4 coatings
3. In collaboration with the University of Arkansas graphene group, spiral round roll-to-roll manufacturing, “as big as we want”, containing 20% graphene oxide

To conclude the lively and engaging interview, Griggs humorously stated, “We’re with the government; we’re here to help!”

Indeed, they are.