Less than 1 percent of Earth’s water is drinkable. Removing salt and other minerals from our biggest available source of water—seawater—may help satisfy a growing global population thirsty for fresh water for drinking, farming, transportation, heating, cooling and industry. But desalination is an energy-intensive process, which concerns those wanting to expand its application.
Now, a team of experimentalists led by the Department of Energy’s Oak Ridge National Laboratory has demonstrated an energy-efficient desalination technology that uses a porous membrane made of strong, slim graphene—a carbon honeycomb one atom thick. The results are published in the March 23 advance online issue of Nature Nanotechnology.
“Our work is a proof of principle that demonstrates how you can desalinate saltwater using free-standing, porous graphene,” said Shannon Mark Mahurin of ORNL’s Chemical Sciences Division, who co-led the study with Ivan Vlassiouk in ORNL’s Energy and Transportation Science Division.
“It’s a huge advance,” said Vlassiouk, pointing out a wealth of water travels through the porous graphene membrane. “The flux through the current graphene membranes was at least an order of magnitude higher than [that through] state-of-the-art reverse osmosis polymeric membranes.”
Current methods for purifying water include distillation and reverse osmosis. Distillation, or heating a mixture to extract volatile components that condense, requires a significant amount of energy. Reverse osmosis, a more energy-efficient process that nonetheless requires a fair amount of energy, is the basis for the ORNL technology.
Making pores in the graphene is key. Without these holes, water cannot travel from one side of the membrane to the other. The water molecules are simply too big to fit through graphene’s fine mesh. But poke holes in the mesh that are just the right size, and water molecules can penetrate. Salt ions, in contrast, are larger than water molecules and cannot cross the membrane. The porous membrane allows osmosis, or passage of a fluid through a semipermeable membrane into a solution in which the solvent is more concentrated.
“If you have saltwater on one side of a porous membrane and freshwater on the other, an osmotic pressure tends to bring the water back to the saltwater side. But if you overcome that, and you reverse that, and you push the water from the saltwater side to the freshwater side—that’s the reverse osmosis process,” Mahurin explained.
Today reverse-osmosis filters are typically polymers. A filter is thin and resides on a support. It takes significant pressure to push water from the saltwater side to the freshwater side. “If you can make the membrane more porous and thinner, you can increase the flux through the membrane and reduce the pressure requirements, within limits,” Mahurin said. “That all serves to reduce the amount of energy that it takes to drive the process.”
Graphene to the rescue
Graphene is only one-atom thick, yet flexible and strong. Its mechanical and chemical stabilities make it promising in membranes for separations. A porous graphene membrane could be more permeable than a polymer membrane, so separated water would drive faster through the membrane under the same conditions, the scientists reasoned. “If we can use this single layer of graphene, we could then increase the flux and reduce the membrane area to accomplish that same purification process,” Mahurin said.
The Latest on: Desalination
via Google News
The Latest on: Desalination
- Seawater desalination isn’t feasibleon October 27, 2019 at 7:15 pm
Its hydraulic capacity will later be increased to 150MGD, he added. His company has many other water-related plans, including a desalination plant of 5MGD for DHA Karachi. In the future, Hubco may ...
- Positive Operating Performance Boosts Carlsbad Desalination Plant's Bond Ratingon October 25, 2019 at 2:56 pm
Facility ownership transfer approved by Water Authority Board; Poseidon to continue plant management Bonds from the Carlsbad Desalination Plant and pipeline were upgraded to BBB and given a stable ...
- World’s largest reverse osmosis desalination project to open in Abu Dhabi in 2022on October 24, 2019 at 2:28 am
ABU DHABI - Emirates Water and Electricity Company, EWEC - a subsidiary of Abu Dhabi Power Corporation - and ACWA Power - the Saudi-based developer, investor and operator of power generation and ...
- West Basin water district releases final EIR for El Segundo desalination planton October 23, 2019 at 11:44 pm
West Basin Municipal Water District released on Wednesday, Oct. 23, the final environmental impact report for an El Segundo desalination plant that would convert 20 million gallons per day of seawater ...
- Video: Can sea water desalination save the world?on October 22, 2019 at 11:56 pm
And that’s the result of many things, but one of them is that 96.5% of that water is found in our oceans. It’s saturated with salt, and undrinkable. Most of the freshwater is locked away in glaciers ...
- Poseidon, Doheny desalination plants advance in EPA funding queston October 22, 2019 at 11:11 pm
Desalination plants proposed for Huntington Beach and Dana Point got a boost Tuesday when the federal EPA selected them to apply for huge low-interest loans that would increase the viability of the ...
- U.S. EPA to Provide $585 Million for Climate-Resilient Huntington Beach Seawater Desalination Planton October 22, 2019 at 5:40 pm
Finance Program Will Reduce Ratepayer Water Costs; Support 3,000 Jobs During Construction Poseidon Water released the following statement in response to today’s announcement that the U.S.
- Acciona puts spotlight on desalination industry issueson October 21, 2019 at 6:38 am
Spanish infrastructure major Acciona is at the ongoing IDA World Congress in Dubai to discuss the major challenges being faced by the desalination and water reuse industry. IDA World Congress, which ...
- How desalination plants make ocean water drinkableon October 20, 2019 at 6:31 am
Today, one out of three people don't have access to safe drinking water. One reason is that 96.5% of that water is found in our oceans. It's saturated with salt, and undrinkable. Desalination plants ...
- EWEC and ACWA secure $869 mln for Abu Dhabi desalination planton October 19, 2019 at 5:35 am
ABU DHABI, Oct 19 (Reuters) - Emirates Water and Electricity Company (EWEC) and Saudi Arabia’s ACWA Power said on Saturday they had secured financing of 3.19 billion dirhams ($869 million) for Abu ...
via Bing News