Membranes - Page 12

Researchers at the University of Manchester have demonstrated that graphene can simplify the production of heavy water and help clean nuclear waste by filtering different isotopes of hydrogen. The process could assist in producing heavy water for nuclear power plants with ten times less energy, making it simpler and cheaper.

Membranes made from graphene can act as a sieve, separating protons nuclei of hydrogen from heavier nuclei of hydrogen isotope deuterium. Deuterium is in wide use in analytical and chemical tracing technologies and, also, as heavy water required in thousands of tons for operation of nuclear power stations. The heaviest isotope, tritium, is radioactive and needs to be safely removed as a by-product of electricity generation at nuclear fission plants. Future nuclear technology is based on fusion of the two heavy isotopes.

Researchers from the University of Illinois at Urbana-Champaign have developed a new MoS2-based filter for water desalination that they claim might be cheaper and more effective than the filters used today. This filter reportedly performs better than graphene-based ones tested in the past.

This filter is made of single-layer sheet of molybdenum disulphide (MoS2) with nanopores in them. Graphene membranes are thinner than MoS2 filters, but MoS2 still seems to be more efficient - the slightly thicker filter gives MoS2 more physical strength to withstand pressure, and, unlike graphene filters, they are more easily manufactured. 

Researchers from the University of Illinois at Urbana-Champaign (UIUC) have developed a new nanopore sequencing method based on graphene nanoribbons that detects double and single stranded DNA in different configurations. This graphene-based detector shows great sensitivity and holds promise for developing a portable, high-throughput sequencer that can also detect DNA morphological transformations.

In a nanopore sequencing reaction, DNA passes through a nanopore drilled in a membrane to which an electrical voltage is applied. When DNA goes through the pore, it causes dips in the electrical current. Reading the magnitude and duration of the electrical changes allows to identify the bases that go through.

The Centre of Process Innovation (CPI) works to develop a graphene-based self-cleaning membrane filter with the potential to revolutionize liquid filtration across the globe, as part of a UK based collaboration that also includes G₂O Water International (G₂O), Haydale and Sellafield Ltd. CPI ‘s role in the project is to develop, characterize and scale-up the graphene based materials alongside applying the graphene coating onto the membrane.

The two year project aims to develop a low cost self-cleaning coating technology based on functionalized graphene, which should make the membranes highly resistant to fouling (the process in which a solution or particle is deposited on a membrane surface or in membrane pores such so that the membrane's performance is degraded). The coating will be formulated and validated by the consortium for deployment in a number of different applications, including desalination, oil and water separation and also nuclear waste water treatment.

Graphenea recently introduced large area monolayer graphene suspended over microcavities as a standard catalog product, that can be used for NEMS (Nanoelectromechanical systems) due to its reliance on small vibrating membranes, which are sensitive to tiny forces.

Image courtesy of Stefan Wagner / Max Lemme, University of Siegen

NEMS are entering mainstream technology through sensors and actuators in platforms as common as inkjet printers, accelerometers, displays, and optical switches. The membranes used in NEMS need to be lightweight and stiff, with a high Young's modulus. As such, graphene is a very promising candidate for applications that require ultrathin membranes with excellent mechanical properties.

Australia's Strategic Energy Resources entered into an exclusive worldwide licence to commercialize graphene-oxide membrane technology developed by Monash University.

SER's wholly-owned subsidiary Ionic Industries has full rights to exploit and commercialize the IP, including by direct sale or by sublicensing, within the field of energy storage and capacitor materials, and devices from indigenous natural graphite. Ionic will pay a royalty to Monash if the commercialization is successful.

Researchers at MIT, Oak Ridge National Laboratory, and King Fahd University of Petroleum and Minerals (KFUPM) have devised a process to repair leaks, cracks and holes that are formed in graphene in the process of creating membranes for water filtration and desalination.

The process relies on a combination of chemical deposition and polymerization techniques. The team also used a process it developed previously to create tiny, uniform pores in the material, small enough to allow only water to pass through. These two techniques combined yielded a relatively large defect-free graphene membrane, about the size of a penny.

A team of scientists led by the Department of Energy's Oak Ridge National Laboratory (ORNL) demonstrated an energy-efficient desalination technology that makes use of a porous membrane made of free-standing, porous graphene.

The scientists report that the flux through these graphene membranes was at least an order of magnitude higher than the water that pass through state-of-the-art reverse osmosis polymeric membranes. Many of the current methods for purifying water require a significant amount of energy. Making the membrane more porous and thinner (properteis graphene is well suited to supply), helps increase the flux through the membrane and reduce the pressure requirements to reduce the amount of energy that the process requires.

A collaboration of scientists from several institutions, including Northwestern, EFRC and more, discovered that graphene that is slightly imperfect can shuttle protons from one side of a graphene membrane to the other in seconds. The selectivity and speed of the imperfect version are compared to conventional membranes, opening the door to new and simpler model of fuel cell designs.

This, of course, goes against conventional efforts to create perfect graphene as it turns out that protons move better through imperfect graphene. The defects in the graphene trigger a chemical "conveyor belt" that shuttles protons from one side of the membrane to the other in a few seconds. In conventional membranes, which can be hundreds of nanometers thick, the desired proton selection takes minutes, compared to the quick transfer in a one-atom-thick layer of graphene.

Global security and aerospace company Lockheed Martin is testing nanofilters using its patented Perforene (graphene sheets with precisely sized holes as small as 1 nanometer meant for water desalination) for oil and gas industry wastewater management.

Simulated nanoporous graphene filtering salt ions

The company states that the ultimate goal is water desalination, but more feasible and immediate uses can be found in the oil and gas industry, where the requirements in terms of the quality of the graphene and hole sizes are less challenging.