A new method for removing radioactive material from solutions is the result of collaboration between Rice University and Lomonosov Moscow State University. The vial at left holds microscopic particles of Graphene oxide in a solution. At right, Graphene oxide is added to simulated nuclear waste, which quickly clumps for easy removal.
"Another tiny miracle: Graphene oxide soaks up radioactive waste"
January 10th, 2013
NUCLEAR POWER DAILY
Graphene oxide has a remarkable ability to quickly remove radioactive material from contaminated water, researchers at Rice University and Lomonosov Moscow State University have found. A collaborative effort by the Rice lab of chemist James Tour and the Moscow lab of chemist Stepan Kalmykov determined that microscopic, atom-thick flakes of Graphene oxide bind quickly to natural and human-made radionuclides and condense them into solids. The flakes are soluble in liquids and easily produced in bulk.
The experimental results were reported in the Royal Society of Chemistry journal Physical Chemistry Chemical Physics. The discovery, Tour said, could be a boon in the cleanup of contaminated sites like the Fukushima nuclear plants damaged by the 2011 earthquake and tsunami. It could also cut the cost of hydraulic fracturing ("fracking") for oil and gas recovery and help reboot American mining of rare earth metals, he said.
Graphene oxide's large surface area defines its capacity to adsorb toxins, Kalmykov said. "So the high retention properties are not surprising to us," he said. "What is astonishing is the very fast kinetics of sorption, which is key."
"In the probabilistic world of chemical reactions where scarce stuff (low concentrations) infrequently bumps into something with which it can react, there is a greater likelihood that the 'magic' will happen with Graphene oxide than with a big old hunk of bentonite," said Steven Winston, a former vice president of Lockheed Martin and Parsons Engineering and an expert in nuclear power and remediation who is working with the researchers. "In short, fast is good."
Determining how fast was the object of experiments by the Kalmykov group. The lab tested Graphene oxide synthesized at Rice with simulated nuclear wastes containing uranium, plutonium and substances like sodium and calcium that could negatively affect their adsorption. Even so, Graphene oxide proved far better than the bentonite clays and granulated activated carbon commonly used in nuclear cleanup.
Graphene oxide introduced to simulated wastes coagulated within minutes, quickly clumping the worst toxins, Kalmykov said. The process worked across a range of pH values.
"To see Stepan's amazement at how well this worked was a good confirmation," Tour said. He noted that the collaboration took root when Alexander Slesarev, a graduate student in his group, and Anna Yu. Romanchuk, a graduate student in Kalmykov's group, met at a conference several years ago.
The researchers focused on removing radioactive isotopes of the actinides and lanthanides - the 30 rare earth elements in the periodic table - from liquids, rather than solids or gases. "Though they don't really like water all that much, they can and do hide out there," Winston said. "From a human health and environment point of view, that's where they're least welcome."
Naturally occurring radionuclides are also unwelcome in fracking fluids that bring them to the surface in drilling operations, Tour said. "When groundwater comes out of a well and it's radioactive above a certain level, they can't put it back into the ground," he said. "It's too hot. Companies have to ship contaminated water to repository sites around the country at very large expense." The ability to quickly filter out contaminants on-site would save a great deal of money, he said.
He sees even greater potential benefits for the mining industry. Environmental requirements have "essentially shut down U.S. mining of rare earth metals, which are needed for cell phones," Tour said. "China owns the market because they're not subject to the same environmental standards. So if this technology offers the chance to revive mining here, it could be huge."
Tour said that capturing radionuclides does not make them less radioactive, just easier to handle. "Where you have huge pools of radioactive material, like at Fukushima, you add Graphene oxide and get back a solid material from what were just ions in a solution," he said. "Then you can skim it off and burn it. Graphene oxide burns very rapidly and leaves a cake of radioactive material you can then reuse."
The low cost and biodegradable qualities of Graphene oxide should make it appropriate for use in permeable reactive barriers, a fairly new technology for in situ groundwater remediation, he said.
Romanchuk, Slesarev, Kalmykov and Tour are co-authors of the paper with Dmitry Kosynkin, a former postdoctoral researcher at Rice, now with Saudi Aramco. Kalmykov is radiochemistry division head and a professor at Lomonosov Moscow State University. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science at Rice.
The Office of Naval Research Multidisciplinary University Research Initiative, M-I SWACO and the Air Force Office of Scientific Research funded work at Rice. The Ministry of Education and Science of the Russian Federation, a Russian Federation President stipend to Romanchuk and the Russian Basic Research Foundation funded research at Moscow State.
"Graphene oxide acts as sponge for radioactive material"
January 13th, 2013
Scientists have recently discovered adding graphene oxide to water contaminated by radioactive material will make environmental clean up easier. They discovered the compound quickly causes radionuclides to clump into particles that can more efficiently be removed from the water.
In a post-Fukushima world, that comes as welcome news.
Houston's Rice University and Lomonosov Moscow State University conducted the joint experiments with atom-thick flakes of the graphene oxide. They found the water-soluble flakes quickly attracted both natural and man-made radionuclides, creating solid clumps that make for easier disposal.
The large surface area of the graphene oxide is what makes it able to absorb large amounts of toxins, creating the clumps. The real surprise to scientists was the speed of the reaction.
In a Rice University press release, Stepan Kalmykov from Lomonosov Moscow State University noted:
"…the high retention properties are not surprising to us," he said. "What is astonishing is the very fast kinetics of sorption, which is key."
Researchers put the compound through its paces regarding speed. They used water containing highly toxic uranium and plutonioum along with other substances such as calcium and sodium. The latter two compounds have been found to slow down absorption in normal circumstances, but the graphene oxide was not affected by the PH of the water and still clumped the radioactive toxins in minutes.
The team also tested whether graphene oxide would work on natural radioactive isotopes that may come to the surface as a result of fracking and mining of rare earth metals. Often the groundwater that comes to the top during the process is too radioactive to put back in the ground and must be treated.
The current process uses bentonite clays and activated carbon, and while it gets the job done, the experiments with graphene oxide proved the larger solid clumps formed quicker and were more easily harvested and disposed of.
Rice University chemist James Tour said in the press statement:
"Where you have huge pools of radioactive material, like at Fukushima, you add graphene oxide and get back a solid material from what were just ions in a solution. "Then you can skim it off and burn it. Graphene oxide burns very rapidly and leaves a cake of radioactive material you can then reuse."
Fukushima taught us that radioactive disasters can occur on a large scale, and water can easily be contaminated. Non-disaster scenarios like fracking and mining also play their part.
The discovery of a quicker, easily reproduced compound such as graphene oxide means these kinds of contaminations can be more efficiently dealt with, hopefully mitigating human health dangers by enabling quicker clean up.
The results of the joint Rice University and Lomonosov Moscow State University study were reported in the Royal Society of Chemistry journal Physical Chemistry Chemical Physics.