Tag Archives: desalination

Crowd computing for improved nanotechnology-enabled water filtration

This research is the product of a China/Israel/Switzerland collaboration on water filtration with involvement from the UK and Australia. Here’s some general information about the importance of water and about the collaboration in a July 5, 2015 news item on Nanowerk (Note: A link has been removed),

Nearly 800 million people worldwide don’t have access to safe drinking water, and some 2.5 billion people live in precariously unsanitary conditions, according to the Centers for Disease Control and Prevention. Together, unsafe drinking water and the inadequate supply of water for hygiene purposes contribute to almost 90% of all deaths from diarrheal diseases — and effective water sanitation interventions are still challenging scientists and engineers.

A new study published in Nature Nanotechnology (“Water transport inside carbon nanotubes mediated by phonon-induced oscillating friction”) proposes a novel nanotechnology-based strategy to improve water filtration. The research project involves the minute vibrations of carbon nanotubes called “phonons,” which greatly enhance the diffusion of water through sanitation filters. The project was the joint effort of a Tsinghua University-Tel Aviv University research team and was led by Prof. Quanshui Zheng of the Tsinghua Center for Nano and Micro Mechanics and Prof. Michael Urbakh of the TAU School of Chemistry, both of the TAU-Tsinghua XIN Center, in collaboration with Prof. Francois Grey of the University of Geneva.

A July 5, 2015 American Friends of Tel Aviv University news release (also on EurekAlert), which originated the news item, provides more details about the work,

“We’ve discovered that very small vibrations help materials, whether wet or dry, slide more smoothly past each other,” said Prof. Urbakh. “Through phonon oscillations — vibrations of water-carrying nanotubes — water transport can be enhanced, and sanitation and desalination improved. Water filtration systems require a lot of energy due to friction at the nano-level. With these oscillations, however, we witnessed three times the efficiency of water transport, and, of course, a great deal of energy saved.”

The research team managed to demonstrate how, under the right conditions, such vibrations produce a 300% improvement in the rate of water diffusion by using computers to simulate the flow of water molecules flowing through nanotubes. The results have important implications for desalination processes and energy conservation, e.g. improving the energy efficiency for desalination using reverse osmosis membranes with pores at the nanoscale level, or energy conservation, e.g. membranes with boron nitride nanotubes.

Crowdsourcing the solution

The project, initiated by IBM’s World Community Grid, was an experiment in crowdsourced computing — carried out by over 150,000 volunteers who contributed their own computing power to the research.

“Our project won the privilege of using IBM’s world community grid, an open platform of users from all around the world, to run our program and obtain precise results,” said Prof. Urbakh. “This was the first project of this kind in Israel, and we could never have managed with just four students in the lab. We would have required the equivalent of nearly 40,000 years of processing power on a single computer. Instead we had the benefit of some 150,000 computing volunteers from all around the world, who downloaded and ran the project on their laptops and desktop computers.

“Crowdsourced computing is playing an increasingly major role in scientific breakthroughs,” Prof. Urbakh continued. “As our research shows, the range of questions that can benefit from public participation is growing all the time.”

The computer simulations were designed by Ming Ma, who graduated from Tsinghua University and is doing his postdoctoral research in Prof. Urbakh’s group at TAU. Ming catalyzed the international collaboration. “The students from Tsinghua are remarkable. The project represents the very positive cooperation between the two universities, which is taking place at XIN and because of XIN,” said Prof. Urbakh.

Other partners in this international project include researchers at the London Centre for Nanotechnology of University College London; the University of Geneva; the University of Sydney and Monash University in Australia; and the Xi’an Jiaotong University in China. The researchers are currently in discussions with companies interested in harnessing the oscillation knowhow for various commercial projects.

 

Here’s a link to and a citation for the paper,

Water transport inside carbon nanotubes mediated by phonon-induced oscillating friction by Ming Ma, François Grey, Luming Shen, Michael Urbakh, Shuai Wu,    Jefferson Zhe Liu, Yilun Liu, & Quanshui Zheng. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.134 Published online 06 July 2015

This paper is behind a paywall.

Final comment, I find it surprising that they used labour and computing power from 150,000 volunteers and didn’t offer open access to the paper. Perhaps the volunteers got their own copy? I certainly hope so.

Sealing graphene’s defects to make a better filtration device

Making a graphene filter that allows water to pass through while screening out salt and/or noxious materials has been more challenging than one might think. According to a May 7, 2015 news item on Nanowerk, graphene filters can be ‘leaky’,

For faster, longer-lasting water filters, some scientists are looking to graphene –thin, strong sheets of carbon — to serve as ultrathin membranes, filtering out contaminants to quickly purify high volumes of water.

Graphene’s unique properties make it a potentially ideal membrane for water filtration or desalination. But there’s been one main drawback to its wider use: Making membranes in one-atom-thick layers of graphene is a meticulous process that can tear the thin material — creating defects through which contaminants can leak.

Now engineers at MIT [Massachusetts Institute of Technology], Oak Ridge National Laboratory, and King Fahd University of Petroleum and Minerals (KFUPM) have devised a process to repair these leaks, filling cracks and plugging holes using a combination of chemical deposition and polymerization techniques. The team then used a process it developed previously to create tiny, uniform pores in the material, small enough to allow only water to pass through.

A May 8, 2015 MIT news release (also on EurkeAlert), which originated the news item, expands on the theme,

Combining these two techniques, the researchers were able to engineer a relatively large defect-free graphene membrane — about the size of a penny. The membrane’s size is significant: To be exploited as a filtration membrane, graphene would have to be manufactured at a scale of centimeters, or larger.

In experiments, the researchers pumped water through a graphene membrane treated with both defect-sealing and pore-producing processes, and found that water flowed through at rates comparable to current desalination membranes. The graphene was able to filter out most large-molecule contaminants, such as magnesium sulfate and dextran.

Rohit Karnik, an associate professor of mechanical engineering at MIT, says the group’s results, published in the journal Nano Letters, represent the first success in plugging graphene’s leaks.

“We’ve been able to seal defects, at least on the lab scale, to realize molecular filtration across a macroscopic area of graphene, which has not been possible before,” Karnik says. “If we have better process control, maybe in the future we don’t even need defect sealing. But I think it’s very unlikely that we’ll ever have perfect graphene — there will always be some need to control leakages. These two [techniques] are examples which enable filtration.”

Sean O’Hern, a former graduate research assistant at MIT, is the paper’s first author. Other contributors include MIT graduate student Doojoon Jang, former graduate student Suman Bose, and Professor Jing Kong.

A delicate transfer

“The current types of membranes that can produce freshwater from saltwater are fairly thick, on the order of 200 nanometers,” O’Hern says. “The benefit of a graphene membrane is, instead of being hundreds of nanometers thick, we’re on the order of three angstroms — 600 times thinner than existing membranes. This enables you to have a higher flow rate over the same area.”

O’Hern and Karnik have been investigating graphene’s potential as a filtration membrane for the past several years. In 2009, the group began fabricating membranes from graphene grown on copper — a metal that supports the growth of graphene across relatively large areas. However, copper is impermeable, requiring the group to transfer the graphene to a porous substrate following fabrication.

However, O’Hern noticed that this transfer process would create tears in graphene. What’s more, he observed intrinsic defects created during the growth process, resulting perhaps from impurities in the original material.

Plugging graphene’s leaks

To plug graphene’s leaks, the team came up with a technique to first tackle the smaller intrinsic defects, then the larger transfer-induced defects. For the intrinsic defects, the researchers used a process called “atomic layer deposition,” placing the graphene membrane in a vacuum chamber, then pulsing in a hafnium-containing chemical that does not normally interact with graphene. However, if the chemical comes in contact with a small opening in graphene, it will tend to stick to that opening, attracted by the area’s higher surface energy.

The team applied several rounds of atomic layer deposition, finding that the deposited hafnium oxide successfully filled in graphene’s nanometer-scale intrinsic defects. However, O’Hern realized that using the same process to fill in much larger holes and tears — on the order of hundreds of nanometers — would require too much time.

Instead, he and his colleagues came up with a second technique to fill in larger defects, using a process called “interfacial polymerization” that is often employed in membrane synthesis. After they filled in graphene’s intrinsic defects, the researchers submerged the membrane at the interface of two solutions: a water bath and an organic solvent that, like oil, does not mix with water.

In the two solutions, the researchers dissolved two different molecules that can react to form nylon. Once O’Hern placed the graphene membrane at the interface of the two solutions, he observed that nylon plugs formed only in tears and holes — regions where the two molecules could come in contact because of tears in the otherwise impermeable graphene — effectively sealing the remaining defects.

Using a technique they developed last year, the researchers then etched tiny, uniform holes in graphene — small enough to let water molecules through, but not larger contaminants. In experiments, the group tested the membrane with water containing several different molecules, including salt, and found that the membrane rejected up to 90 percent of larger molecules. However, it let salt through at a faster rate than water.

The preliminary tests suggest that graphene may be a viable alternative to existing filtration membranes, although Karnik says techniques to seal its defects and control its permeability will need further improvements.

“Water desalination and nanofiltration are big applications where, if things work out and this technology withstands the different demands of real-world tests, it would have a large impact,” Karnik says. “But one could also imagine applications for fine chemical- or biological-sample processing, where these membranes could be useful. And this is the first report of a centimeter-scale graphene membrane that does any kind of molecular filtration. That’s exciting.”

De-en Jiang, an assistant professor of chemistry at the University of California at Riverside, sees the defect-sealing technique as “a great advance toward making graphene filtration a reality.”

“The two-step technique is very smart: sealing the defects while preserving the desired pores for filtration,” says Jiang, who did not contribute to the research. “This would make the scale-up much easier. One can produce a large graphene membrane first, not worrying about the defects, which can be sealed later.”

I have featured graphene and water desalination work before  from these researchers at MIT in a Feb. 27, 2014 posting. Interestingly, there was no mention of problems with defects in the news release highlighting this previous work.

Here’s a link to and a citation for the latest paper,

Nanofiltration across Defect-Sealed Nanoporous Monolayer Graphene by Sean C. O’Hern, Doojoon Jang, Suman Bose, Juan-Carlos Idrobo, Yi Song §, Tahar Laoui, Jing Kong, and Rohit Karnik. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.5b00456 Publication Date (Web): April 27, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Water desalination by graphene and water purification by sapwood

I have two items about water. The first concerns a new technique from MIT (Massachusetts Institute of Technology) for desalination using graphene and sapwood, respectively*. From a Feb. 25, 2014 news release by David Chandler on EurekAlert,

Researchers have devised a way of making tiny holes of controllable size in sheets of graphene, a development that could lead to ultrathin filters for improved desalination or water purification.

The team of researchers at MIT, Oak Ridge National Laboratory, and in Saudi Arabia succeeded in creating subnanoscale pores in a sheet of the one-atom-thick material, which is one of the strongest materials known. …

The concept of using graphene, perforated by nanoscale pores, as a filter in desalination has been proposed and analyzed by other MIT researchers. The new work, led by graduate student Sean O’Hern and associate professor of mechanical engineering Rohit Karnik, is the first step toward actual production of such a graphene filter.

Making these minuscule holes in graphene — a hexagonal array of carbon atoms, like atomic-scale chicken wire — occurs in a two-stage process. First, the graphene is bombarded with gallium ions, which disrupt the carbon bonds. Then, the graphene is etched with an oxidizing solution that reacts strongly with the disrupted bonds — producing a hole at each spot where the gallium ions struck. By controlling how long the graphene sheet is left in the oxidizing solution, the MIT researchers can control the average size of the pores.

A big limitation in existing nanofiltration and reverse-osmosis desalination plants, which use filters to separate salt from seawater, is their low permeability: Water flows very slowly through them. The graphene filters, being much thinner, yet very strong, can sustain a much higher flow. “We’ve developed the first membrane that consists of a high density of subnanometer-scale pores in an atomically thin, single sheet of graphene,” O’Hern says.

For efficient desalination, a membrane must demonstrate “a high rejection rate of salt, yet a high flow rate of water,” he adds. One way of doing that is decreasing the membrane’s thickness, but this quickly renders conventional polymer-based membranes too weak to sustain the water pressure, or too ineffective at rejecting salt, he explains.

With graphene membranes, it becomes simply a matter of controlling the size of the pores, making them “larger than water molecules, but smaller than everything else,” O’Hern says — whether salt, impurities, or particular kinds of biochemical molecules.

The permeability of such graphene filters, according to computer simulations, could be 50 times greater than that of conventional membranes, as demonstrated earlier by a team of MIT researchers led by graduate student David Cohen-Tanugi of the Department of Materials Science and Engineering. But producing such filters with controlled pore sizes has remained a challenge. The new work, O’Hern says, demonstrates a method for actually producing such material with dense concentrations of nanometer-scale holes over large areas.

“We bombard the graphene with gallium ions at high energy,” O’Hern says. “That creates defects in the graphene structure, and these defects are more chemically reactive.” When the material is bathed in a reactive oxidant solution, the oxidant “preferentially attacks the defects,” and etches away many holes of roughly similar size. O’Hern and his co-authors were able to produce a membrane with 5 trillion pores per square centimeter, well suited to use for filtration. “To better understand how small and dense these graphene pores are, if our graphene membrane were to be magnified about a million times, the pores would be less than 1 millimeter in size, spaced about 4 millimeters apart, and span over 38 square miles, an area roughly half the size of Boston,” O’Hern says.

With this technique, the researchers were able to control the filtration properties of a single, centimeter-sized sheet of graphene: Without etching, no salt flowed through the defects formed by gallium ions. With just a little etching, the membranes started allowing positive salt ions to flow through. With further etching, the membranes allowed both positive and negative salt ions to flow through, but blocked the flow of larger organic molecules. With even more etching, the pores were large enough to allow everything to go through.

Scaling up the process to produce useful sheets of the permeable graphene, while maintaining control over the pore sizes, will require further research, O’Hern says.

Karnik says that such membranes, depending on their pore size, could find various applications. Desalination and nanofiltration may be the most demanding, since the membranes required for these plants would be very large. But for other purposes, such as selective filtration of molecules — for example, removal of unreacted reagents from DNA — even the very small filters produced so far might be useful.

“For biofiltration, size or cost are not as critical,” Karnik says. “For those applications, the current scale is suitable.”

Dexter Johnson in a Feb. 26,2014 posting provides some context for and insight into the work (from the Nanoclast blog on the IEEE [Institute of Electrical and Electronics Engineers]), Note: Links have been removed,

About 18 months ago, I wrote about an MIT project in which computer models demonstrated that graphene could act as a filter in the desalination of water through the reverse osmosis (RO) method. RO is slightly less energy intensive than the predominantly used multi-stage-flash process. The hope was that the nanopores of the graphene material would make the RO method even less energy intensive than current versions by making it easier to push the water through the filter membrane.

The models were promising, but other researchers in the field said at the time it was going to be a long road to translate a computer model to a real product.

It would seem that the MIT researchers agreed it was worth the effort and accepted the challenge to go from computer model to a real device as they announced this week that they had developed a method for creating selective pores in graphene that make it suitable for water desalination.

Here’s a link to and a citation for the paper,

Selective Ionic Transport through Tunable Subnanometer Pores in Single-Layer Graphene Membranes by Sean C. O’Hern, Michael S. H. Boutilier, Juan-Carlos Idrobo, Yi Song, Jing Kong, Tahar Laoui, Muataz Atieh, and Rohit Karnik. Nano Lett., Article ASAP DOI: 10.1021/nl404118f Publication Date (Web): February 3, 2014

Copyright © 2014 American Chemical Society

This article is behind a paywall.

The second item is also from MIT and concerns a low-tech means of purifying water. From a Feb. 27, 2014 news item on Azonano,

If you’ve run out of drinking water during a lakeside camping trip, there’s a simple solution: Break off a branch from the nearest pine tree, peel away the bark, and slowly pour lake water through the stick. The improvised filter should trap any bacteria, producing fresh, uncontaminated water.

In fact, an MIT team has discovered that this low-tech filtration system can produce up to four liters of drinking water a day — enough to quench the thirst of a typical person.

In a paper published this week in the journal PLoS ONE, the researchers demonstrate that a small piece of sapwood can filter out more than 99 percent of the bacteria E. coli from water. They say the size of the pores in sapwood — which contains xylem tissue evolved to transport sap up the length of a tree — also allows water through while blocking most types of bacteria.

Co-author Rohit Karnik, an associate professor of mechanical engineering at MIT, says sapwood is a promising, low-cost, and efficient material for water filtration, particularly for rural communities where more advanced filtration systems are not readily accessible.

“Today’s filtration membranes have nanoscale pores that are not something you can manufacture in a garage very easily,” Karnik says. “The idea here is that we don’t need to fabricate a membrane, because it’s easily available. You can just take a piece of wood and make a filter out of it.”

The Feb. 26, 2014 news release on EurekAlert, which originated the news item, describes current filtration techniques and the advantages associated with this new low-tech approach,

There are a number of water-purification technologies on the market today, although many come with drawbacks: Systems that rely on chlorine treatment work well at large scales, but are expensive. Boiling water to remove contaminants requires a great deal of fuel to heat the water. Membrane-based filters, while able to remove microbes, are expensive, require a pump, and can become easily clogged.

Sapwood may offer a low-cost, small-scale alternative. The wood is comprised of xylem, porous tissue that conducts sap from a tree’s roots to its crown through a system of vessels and pores. Each vessel wall is pockmarked with tiny pores called pit membranes, through which sap can essentially hopscotch, flowing from one vessel to another as it feeds structures along a tree’s length. The pores also limit cavitation, a process by which air bubbles can grow and spread in xylem, eventually killing a tree. The xylem’s tiny pores can trap bubbles, preventing them from spreading in the wood.

“Plants have had to figure out how to filter out bubbles but allow easy flow of sap,” Karnik observes. “It’s the same problem with water filtration where we want to filter out microbes but maintain a high flow rate. So it’s a nice coincidence that the problems are similar.”

The news release also describes the experimental procedure the scientists followed (from the news release),

To study sapwood’s water-filtering potential, the researchers collected branches of white pine and stripped off the outer bark. They cut small sections of sapwood measuring about an inch long and half an inch wide, and mounted each in plastic tubing, sealed with epoxy and secured with clamps.

Before experimenting with contaminated water, the group used water mixed with red ink particles ranging from 70 to 500 nanometers in size. After all the liquid passed through, the researchers sliced the sapwood in half lengthwise, and observed that much of the red dye was contained within the very top layers of the wood, while the filtrate, or filtered water, was clear. This experiment showed that sapwood is naturally able to filter out particles bigger than about 70 nanometers.

However, in another experiment, the team found that sapwood was unable to separate out 20-nanometer particles from water, suggesting that there is a limit to the size of particles coniferous sapwood can filter.

Finally, the team flowed inactivated, E. coli-contaminated water through the wood filter. When they examined the xylem under a fluorescent microscope, they saw that bacteria had accumulated around pit membranes in the first few millimeters of the wood. Counting the bacterial cells in the filtered water, the researchers found that the sapwood was able to filter out more than 99 percent of E. coli from water.

Karnik says sapwood likely can filter most types of bacteria, the smallest of which measure about 200 nanometers. However, the filter probably cannot trap most viruses, which are much smaller in size.

The researchers have future plans (from the news release),

Karnik says his group now plans to evaluate the filtering potential of other types of sapwood. In general, flowering trees have smaller pores than coniferous trees, suggesting that they may be able to filter out even smaller particles. However, vessels in flowering trees tend to be much longer, which may be less practical for designing a compact water filter.

Designers interested in using sapwood as a filtering material will also have to find ways to keep the wood damp, or to dry it while retaining the xylem function. In other experiments with dried sapwood, Karnik found that water either did not flow through well, or flowed through cracks, but did not filter out contaminants.

“There’s huge variation between plants,” Karnik says. “There could be much better plants out there that are suitable for this process. Ideally, a filter would be a thin slice of wood you could use for a few days, then throw it away and replace at almost no cost. It’s orders of magnitude cheaper than the high-end membranes on the market today.”

Here’s a link to and a citation for the paper,

Water Filtration Using Plant Xylem by Michael S. H. Boutilier, Jongho Lee, Valerie Chambers, Varsha Venkatesh, & Rohit Karnik. PLOS One Published: February 26, 2014 DOI: 10.1371/journal.pone.0089934

This paper is open access.

One final observation, two of the researchers (Michael S. H. Boutilier & Rohit Karnik) listed as authors on the graphene/water desalination paper are also listed on the low-tech sapwood paper solution.*

* The first sentence of the this post originally stated both items were graphene-related, it has been changed to say 1… using graphene and sapwood, respectively*’ on May 8, 2015.

The last sentence of this post was changed from

‘One final observation, two of the researchers listed as authors on the graphene/water desalination paper are also listed on the low-tech sapwood paper (Michael S. H. Boutilier & Rohit Karnik).’

to this

‘One final observation, two of the researchers (Michael S. H. Boutilier & Rohit Karnik) listed as authors on the graphene/water desalination paper are also listed on the low-tech sapwood paper solution.*’ for clarity on May 8, 2015.

China’s and NanoH2O’s desalination efforts

An Oct. 21, 2013 news item on Azonano describes a desalination business deal between China and NanoH2O, a company headquartered in California,

NanoH2O, Inc., manufacturer of the most efficient and cost-effective reverse osmosis (RO) membranes for seawater desalination, today announced plans to build a manufacturing facility in Liyang, China, a city in the Yangtze River Delta 250 kilometers west of Shanghai.

The 10,000 square meter facility will be the company’s second fully integrated manufacturing plant, following the first located in Los Angeles, California. The China facility comes at a total investment of $45 million and is expected to be operational by the end of 2014.

China, which represents one-fifth of the world’s population but just six percent of the global fresh water supply, plans to increase its seawater reverse osmosis desalination capacity three-fold by 2015. The overall membrane market in China is estimated to grow more than 20 percent per year over the next 10 years. The Chinese government’s current five-year plan also calls for 70 percent of equipment used in desalination plants to be produced domestically. Establishing a new NanoH2O facility in China will allow the company to take advantage of the growing domestic market for both desalination and wastewater treatment.

A few weeks ago in a Sept. 27, 2013 posting, I mentioned some negotiations and deal making between China and the Czech Republic, which concerned ‘green’ nanotechnology.

The signing of the Letter of Intent between NAFIGATE China (a subsidiary of the Czech company NAFIGATE Corporation JSC) and their Chinese partner Guodian Technology & Environment Group Corporation Limited (a subsidiary of one of the most prominent Chinese energy companies) is a significant milestone in Czech-Chinese cooperation in nanotechnology sector. Since January 2013 both companies have been preparing the foundation of the NANODEC (Nanofiber Development Center) project for the development of final applications for water and air cleaning.[emphasis added here]

The company does provide some details about its technology, reversoe osmosis membranes relying on thin-film nanocomposites (TFN) on the FAQs (Frequently Asked Questions) webpage on the NanoH2O website,

 About Thin-Film Nanocomposite (TFN) Technology

What does the term “thin-film nanocomposite” mean?

The term “thin-film nanocomposite” was first used by researchers at University of California, Los Angeles (UCLA) who found that by encapsulating benign nanomaterial into the thin-film polyamide layer of a traditional thin-film composite membrane, they were able to increase membrane permeability compared to conventional RO membranes. NanoH2O leverages nanotechnology to further change the structure of the thin-film of a conventional RO membrane and enhance membrane performance. Benign nanoparticles are introduced during the synthesis of a traditional polymer film and are fully encapsulated when the nanocomposite RO membrane is formed.

How do nanoparticles increase membrane performance?

NanoH2O’s encapsulation of benign nanoparticles changes the structure of the thin-film surface of a conventional RO membrane, allowing more water to pass through while rejecting unwanted materials such as salt. QuantumFlux membranes are 50-100% more permeable than conventional membranes while still meeting best-in-class salt rejection.

Do nanoparticles pose any potential risks to water quality?

No. NanoH2O’s QuantumFlux membrane elements are completely safe for the treatment of potable water. The Qfx SW 365 ES, Qfx SW 400 ES, Qfx SW 400 SR and Qfx SW 400 R are all NSF Standard 61 certified, which means that they have been independently evaluated by NSF International, the global organization that provides standards development, product certification, auditing, education and risk management for public health and safety. NSF Standard 61 certification attests to the safety and viability of the Qfx SW 365 ES, Qfx SW 400 ES, Qfx SW 400 SR and Qfx SW 400 R membrane elements when used in the production of drinking water.

Does NanoH2O use a nanoparticle coating applied to another manufacturer’s membrane?

No. NanoH2O introduces nanostructured materials into the monomers that form the polymer film manufactured solely at its El Segundo, California facility. The nanoparticles are encapsulated into NanoH2O’s patented and patent-pending thin-film polyamide formulation, which makes up the top layer of the thin-film nanocomposite membrane.

There’s no mention here of exactly what kind of nanoparticles are being used in the company’s Quantum Flux membranes (or as they’re known generically, reverse osmosis membranes) but the company does offer some technical papers here, where there is, hopefully, more detail.

About Thin-Film Nanocomposite (TFN) Technology

What does the term “thin-film nanocomposite” mean?

The term “thin-film nanocomposite” was first used by researchers at University of California, Los Angeles (UCLA) who found that by encapsulating benign nanomaterial into the thin-film polyamide layer of a traditional thin-film composite membrane, they were able to increase membrane permeability compared to conventional RO membranes. NanoH2O leverages nanotechnology to further change the structure of the thin-film of a conventional RO membrane and enhance membrane performance. Benign nanoparticles are introduced during the synthesis of a traditional polymer film and are fully encapsulated when the nanocomposite RO membrane is formed.

How do nanoparticles increase membrane performance?

NanoH2O’s encapsulation of benign nanoparticles changes the structure of the thin-film surface of a conventional RO membrane, allowing more water to pass through while rejecting unwanted materials such as salt. QuantumFlux membranes are 50-100% more permeable than conventional membranes while still meeting best-in-class salt rejection.

Do nanoparticles pose any potential risks to water quality?

No. NanoH2O’s QuantumFlux membrane elements are completely safe for the treatment of potable water. The Qfx SW 365 ES, Qfx SW 400 ES, Qfx SW 400 SR and Qfx SW 400 R are all NSF Standard 61 certified, which means that they have been independently evaluated by NSF International, the global organization that provides standards development, product certification, auditing, education and risk management for public health and safety. NSF Standard 61 certification attests to the safety and viability of the Qfx SW 365 ES, Qfx SW 400 ES, Qfx SW 400 SR and Qfx SW 400 R membrane elements when used in the production of drinking water.

Does NanoH2O use a nanoparticle coating applied to another manufacturer’s membrane?

No. NanoH2O introduces nanostructured materials into the monomers that form the polymer film manufactured solely at its El Segundo, California facility. The nanoparticles are encapsulated into NanoH2O’s patented and patent-pending thin-film polyamide formulation, which makes up the top layer of the thin-film nanocomposite membrane.