Researchers have developed a new separation membrane with 2D layered transition metal dichalcogenides (tungsten disulfide) for size-selective separation of small molecules of about 3 nm. The as-prepared WS2 membranes exhibit 5 times higher water permeance than graphene oxide membranes with similar rejection. To further improve the water permeance, they team employed ultrathin metal hydroxide nanostrands to create more fluidic channels while keeping the rejection rate of specific molecules unchanged.
One of the problems with activated carbon is the disposal of adsorbed contaminants along with the adsorbent. Another concern is that its pores are often blocked during adsorption. By contrast, carbon nanotubes' (CNTs) open structure offers easy, undisrupted access to reactive sites located on nanotubes' outer surface. That's why researchers see CNTs as an attractive potential substitute for activated carbon. Researchers now have demonstrated that individual CNTs can be integrated into micrometer-sized colloidal particles without using a heavy or bulky particulate support.
The development of sustainable, robust, energy-efficient and cost-effective water purification technologies is a challenging task. Conventional practices adopted for water purification suffer from certain limitations such as high cost, low adsorption capacity, generation of toxic sludge, etc. A possible solution to tackle this problem has been demonstrated by scientists in India. They developed nanotechnology-based water purification using nano-silica-silver composite material as antifouling, antimicrobial and dye adsorptive material.
Micro- and nanoporous materials can widely be found in nature, be it zeolite minerals, cell membranes, or diatom skeletons. Researchers are developing artificial analogues of such materials, i.e. nanoporous materials, for industrial applications in areas such as catalysis, water purification, environmental clean-up, molecular separation and proton exchange membranes for fuel cells. Manufacturing nanosieves with straight nanopores is still challenging, especially when the pore size is less than 10 nm. Researchers in Korea have now developed a novel material and fabrication technique that allows easy fabrication of nanosieves with sub-10 nm nanopores with straight pore-structure. With it, controlling the pore size from sub-nm to 5 nm becomes very easy.
Among various technologies, reverse osmosis membranes have been widely used for water reclamation. However, external energy required and high operational pressure used make reverse osmosis membrane water reclamation processes energy intensive - not exactly an advantage given the rising cost of energy and the negative climate impact of fossil fuels. Today, forward osmosis is a well-recognized osmotic process for producing clean water with a bright future as it uses a natural phenomenon and does not require any operational pressure hence it saves large amount of energy compared with reverse osmosis process. Researchers now describe a novel forward osmosis membrane that presents remarkable properties superior over conventional membrane support layers.
One of the problems in modern separation science and technology is the challenge of separating gaseous mixtures that consist of very similar particles, for example, hydrogen isotope mixtures; mixtures of noble gases; etc. The problem arises because small particles such as hydrogen isotopes share similar size and shape (only their molecular mass is different). While this problem can be technically solved, currently available separation methods such as thermal diffusion, cryogenic distillation, and centrifugation, tend to be time and energy intensive. New theoretical work now shows that narrow carbon nanotubes (CNTs) seem to be an attractive alternative. By using CNTs as nanoporous molecular sieves, the separation of parahydrogen molecules from mixtures of classical particles at cryogenic temperatures seems to be possible.
One possible option for reducing CO2 emissions from power plants is to capture them before they hit the atmosphere and store the gas underground. This technique is called Carbon dioxide Capture and Storage. However, before CO2 can be stored, it must be separated from the other waste gases resulting from combustion or industrial processes. Most current methods used for this type of filtration are expensive and require the use of chemicals. Nanotechnology techniques to fabricate nanoscale thin membranes could lead to new membrane technology that could change that.
Current membranes are in many cases not competitive for large scale applications, because their permeance for carbon dioxide is not high enough. Researchers in Germany have now reported the development and manufacturing of nanometric thin film membranes with record performance.
Various nanotechnologies are being researched for applications in water treatment because the removal of bacteria and other organisms from water is an extremely important process, not only for drinking and sanitation but also industrially as biofouling is a commonplace and serious problem. In what could be developed as a a cheap point-of-use water filter for deactivating pathogens in water, or as a new component to be integrated into existing filtration systems to kill microorganisms which cause biofouling in downstream filters, researchers have now demonstrated a textile based device for the high speed electrical sterilization of water. They came up with a new strategy for taking advantage of silver nanowires' and carbon nanotubes' unique ability to form complex multiscale coatings on cotton to produce an electrically conducting and high surface area device for the active, high-throughput inactivation of bacteria in water.