Use of graphene foam to filter uranium and other heavy metals from drinking water


Reusable 3D functionalized reduced graphene oxide foam (3D-FrGOF) is used as an in situ electroplating electrode to extract uranium from contaminated water.Credit: Image provided by the researcher

MITLeading fashion research team Graphene Whisk in a device that can extract uranium and other heavy metals from tap water.

Some types of water pollution, such as algae outbreaks and plastics that pollute rivers, lakes and the marine environment, are clearly visible. However, other pollutants are not so readily apparent, so their effects are potentially more dangerous. Among these invisible substances is uranium. It can be seen that this element, which is draining water resources from mining operations, nuclear waste sites or natural underground sediments, is currently pouring out of taps around the world.

In the United States alone, “many areas are affected by uranium pollution, including the high plains, which provide drinking water to 6 million people, and the central valley aquifer,” said Ahmed. Samiheral, postdoctoral researcher at the Faculty of Nuclear Sciences and Engineering. Said. This pollution represents a danger close to current. “Even small concentrations have a negative effect on human health,” said Ju Li, professor of nuclear science engineering and professor of materials science engineering at the Battelle Energy Alliance.

Today, a team led by Li has developed a very efficient method of extracting uranium from drinking water. When loaded into graphene oxide foam, researchers can capture uranium in solution, which precipitates as condensed solid crystals. The foam can be reused up to 7 times without losing its electrochemical properties. “Within hours, our process can purify large amounts of drinking water below the EPA uranium limit,” says Li.

The treatise explaining this work was last week Advanced hardware. The first two co-authors are MIT postdocs Heral and Chao Wang, who are currently studying and enrolled in the Faculty of Materials Science and Engineering at Tongji University in Shanghai. Researchers from the Argonne National Laboratory, Taiwan’s National Yangmei Jiao Tong University, and the University of Tokyo also participated in the research. The Defense Threat Reduction Agency funded later stages of this work.

Target pollutants

The project, which began three years ago, began as an effort to find a better approach for the environmental clean-up of heavy metals from mine sites. To date, repair methods for metals such as chromium, cadmium, arsenic, lead, mercury, radium, and uranium have proven to be limited and expensive. “These technologies are very sensitive to organic matter in the water and the separation of heavy metal pollutants is insufficient,” Heral explains. “Consequently, they involve long operating times, a high investment cost and produce more toxic sludge at the end of the extraction. “

Uranium seemed to be a particularly attractive target for the team. Field tests by the US Geological Survey and the Environmental Protection Agency (EPA) show that natural rock sources in the northeastern United States and the ponds and pits that store old nuclear weapons and fuel, as in Hanford, is unsanitary. Levels of uranium have been found to migrate to reservoirs and aquifers. Mining activities in Washington and many western states. This type of pollution is widespread in many other countries. A surprising number of these sites have uranium concentrations near or above the EPA recommended limit of 30 ppb. This is the level associated with kidney damage, cancer risk, and changes in human neural behavior.

The main challenge was to find a practical repair process that was sensitive only to uranium and could extract the uranium from solution without producing toxic tailings. Previous studies have shown that charged carbon fiber can filter uranium from water, but the results were partial and inaccurate.

Wang succeeded in solving these problems based on a study of the behavior of graphene foam used in lithium-sulfur batteries. “The physical performance of this moss was unique due to its ability to attract certain species to its surface,” she says. “I thought graphene foam ligands would work well with uranium.”

Simple, efficient and clean

The team began work on converting graphene foam to the equivalent of a uranium magnet. They learned that by sending an electric charge through the foam, breaking down the water and releasing hydrogen, it could raise the local pH and cause a chemical change that extracts the uranium ions from the solution. Researchers have found that uranium attaches to the surface of the foam, where it forms unprecedented crystalline uranium hydroxide. When the charge was reversed, the fish scale-like minerals easily slipped out of the foam.

Hundreds of trials were required for proper chemical composition and electrolysis. “We kept modifying the functional groups to make them work properly,” Heral explains. “And the foam was very brittle at first and had a tendency to break, so we had to make it stronger and more durable,” says Wang.

According to Li, this uranium filtration process is simple, efficient and clean. “Each time we use it, our foam can capture four times its own weight of uranium and achieve an extraction capacity of 4000 mg per gram, which is a significant improvement over other methods,” a- he declared. Said. “The foam can undergo 7 cycles without loss of extraction efficiency, which has made great strides in reuse.” Graphene foam also works in seawater, reducing the uranium concentration from 3 ppm to 19.9 ppb. This indicates that other ions in the brine do not interfere with filtration.

The team believe their inexpensive and efficient device could be a new type of home water purifier that fits into faucets like brand name faucets. “Some of these filters already use activated carbon, so maybe we could change them and add low voltage electricity to filter the uranium,” Li explains.

“The uranium mining performed by this device is very impressive compared to existing methods,” said Ho Jin Ryu, associate professor of nuclear and quantum engineering at the Korea Institute of Advanced Science and Technology. Ryu, who was not involved in the study, said demonstrating the reusability of graphene foam was a “significant advance” and that “a local pH control technique that promotes uranium deposition because the scientific principles can be applied more generally. Is considered influential. For the extraction of heavy metals from contaminated water. “

Researchers have already started to explore the wider applications of their methods. “Due to the science of this, we can change the filter to select other heavy metals such as lead, mercury and cadmium,” says Li. He states that radium is another serious danger for the States. United and other areas where resources for a reliable drinking water infrastructure are scarce.

“In the future, instead of passive water purifiers, we could use smart filters powered by clean electricity that activate electrolysis. This will extract several toxic metals and filter the filters. You will know when to regenerate and quality assurance will be provided. The water you drink. “

Reference: “Uranium in-situ electrolysis with reusable functional graphene foam electrodes” by Chao Wang, Ahmed S. Helal, Ziqiang Wang, Jian Zhou, Xiahui Yao, Zhe Shi, Yang Ren, Jinhyuk Lee, Jeng- Kuei Chang, Bunshi Sedimentation “Fugetsu in Juri, August 4, 2021 Advanced hardware..
DOI: 10.1002 / adma.202102633

Using Graphene Foam To Filter Uranium And Other Heavy Metals From Drinking Water Source Link Using Graphene Foam To Filter Uranium And Other Heavy Metals From Drinking Water

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