Pathways and Challenges for Biomimetic Desalination Membranes with Sub-Nanometer Channels – The Future of Desalination?


The authors acknowledge the support received from the National Science Foundation through the Engineering Research Center for Nanotechnology-Enabled Water Treatment (EEC1449500) and via Grant CBET 1437630. The authors also acknowledge funding from the National Science Foundation Graduate Research Fellowship Program under grant no. DGE-1752134, awarded to C.J.P. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

ABSTRACT

Transmembrane protein channels, including ion channels and aquaporins that are responsible for fast and selective transport of water, have inspired membrane scientists to exploit and mimic their performance in membrane technologies. These biomimetic membranes comprise discrete nanochannels aligned within amphiphilic matrices on a robust support. While biological components have been used directly, extensive work has also been conducted to produce stable synthetic mimics of protein channels and lipid bilayers.

However, the experimental performance of biomimetic membranes remains far below that of biological membranes. In this review, we critically assess the status and potential of biomimetic desalination membranes. We first review channel chemistries and their transport behavior, identifying key characteristics to optimize water permeability and salt rejection.

We compare various channel types within an industrial context, considering transport performance, processability, and stability. Through a re-examination of previous vesicular stopped-flow studies, we demonstrate that incorrect permeability equations result in an overestimation of the water permeability of nanochannels. We find in particular that the most optimized aquaporin-bearing bilayer had a pure water permeability of 2.1 L m–2 h–1 bar–1, which is comparable to that of current state-of-the-art polymeric desalination membranes.

Through a quantitative assessment of biomimetic membrane formats, we analytically show that formats incorporating intact vesicles offer minimal benefit, whereas planar biomimetic selective layers could allow for dramatically improved salt rejections. We then show that the persistence of nanoscale defects explains observed subpar performance. We conclude with a discussion on optimal strategies for minimizing these defects, which could enable breakthrough performance.

Biomimetic Desalination Membranes

As stressors like population growth, industrialization, and climate change threaten to deplete and contaminate our freshwater resources, larger bodies of saline water could provide a vast supply of water for drinking, agricultural, and industrial use.(1) However, desalination of these waters requires more energy and financial resources than traditional freshwater purification methods.(2) Currently, the state-of-the-art technology for desalination is reverse osmosis (RO) using thin-film-composite (TFC) polyamide membranes.(3,4) Fully aromatic TFC-RO membranes are readily produced at industrial scale through interfacial polymerization, whereby a rapid reaction occurs at the interface of immiscible organic and aqueous phases to form a highly cross-linked polyamide selective layer on a porous support(5) (Figure 1). With the advent of the TFC-RO membrane and energy recovery devices, seawater desalination energy requirements for the RO stage have drastically reduced from ∼15 kWh m–3 using the original cellulose acetate membranes of the 1970s down to only ∼2 kWh m–3, only ∼25% above the practical minimum energy.(2)

Figure 1. Transition in desalination research from focusing on dense polymers that reject salt by a solution-diffusion mechanism to considering sub-nanometer channels capable of molecularly sieving ions. In the solution-diffusion panel (left), common reactants for TFC-RO membranes are represented, which rapidly react at an organic–aqueous interface during interfacial polymerization to form a cross-linked, fully aromatic polyamide selective layer with characteristic ridge-valley morphology. Salt rejection determined by a solution-diffusion mechanism results from the higher partitioning and/or diffusion rates of water over ions. In the ion sieving panel (right), common molecular sieves that have been considered for desalination are shown, with ideal water pathways illustrated. In pores similar in size to water, single-file water transport is induced. Nanotubes and nanochannels can be synthetic (e.g., carbon nanotubes) or biological (e.g., aquaporins). To produce nanoporous sheets, sub-nanometer pores where only a few atoms are vacant have been etched in single-layer graphene using chemical oxidation, electron beam irradiation, doping, and ion bombardment.(12) For 2D laminates, the water pathway is through interlayer spaces between sheets. Studies so far have primarily considered graphene oxide nanosheets for 2D laminates.(13,14) The molecular sieving mechanism for ion rejection is by size exclusion, where highly uniform pores exclude larger solutes and ideally transport only molecules similar in size to water.

Reduced Operational Costs, Improved Reliability and Efficiency and Enhanced Product Water Quality

Despite the substantial reduction in energy consumption and overall cost, seawater RO still has room for improvement. While current water permeabilities enable near-optimal performance, increased water-solute selectivity would allow for reduced operational costs, improved reliability and efficiency, and enhanced product water quality.(4) For example, TFC-RO membranes inadequately retain chloride and some small neutral solutes, such as boron in seawater desalination and trace organic contaminants in wastewater reuse, necessitating extra purification steps which increase the cost of desalination.(4)Transport through the polyamide layer is well described by the solution-diffusion model, in which permeants (i.e., water and solutes) partition into the dense polyamide layer and diffuse through it (Figure 1).(6) 

The resultant permselectivity of the membrane is attributed to differences in abilities and rates of species to dissolve into and diffuse through the polyamide membrane material.(7) Although intrinsic water permeability can far exceed salt permeability during solution diffusion, as it does for polyamide, historical data suggest that it will be difficult to significantly advance performance with polymeric systems. Commercial desalination and water purification membranes typically exhibit a permeability–selectivity trade-off, similar to the Robeson plot for polymeric gas separations.(8−11) 

Furthermore, despite many decades of extensive research, no polymeric material has yet surpassed the desalination performance (i.e., water permeability, water-salt selectivity, and cost-effectiveness) of fully aromatic polyamide.

To overcome the limitations of the solution-diffusion-based polyamide membranes, research focus has shifted toward the development of desalination membranes that remove solutes via molecular sieving. In this mechanism of ion rejection, highly uniform, rigid pores that are smaller than the diameter of hydrated salt ions transport water and nearly completely reject ions by size exclusion (Figure 1). Recent formats of molecular sieves considered for desalination include nanotubes and nanochannels, two-dimensional (2D) laminates, and nanoporous sheets (Figure 1).(14) 

However, these top-down efforts have failed so far to achieve adequate salt rejection due to the persistence of defects coupled with the daunting challenges of tuning interlayer spacing or pore size.(12,13,15) 

Biomimetic membranes, or composites comprising an amphiphilic matrix with discrete, aligned nanochannels on a robust support, may provide a platform for industrial-scale molecular sieves that overcome the limitations of solution-diffusion-based polyamide membranes.

After over 3.5 billion years of evolution,(16,17) the cell membranes of modern organisms can perform an array of highly complicated functions, which rely on a system of complex transmembrane proteins aligned within the amphiphilic lipid bilayer. In this system, water and only select ions pass through channel pores and pumps, depending on the energy and nutrient needs of the cell.(18,19) In pioneering work, Preston et al. determined that an integral membrane protein formed a biological channel that selectively transports water in and out of many types of cells. This protein was the CHannel-forming Integral Protein of 28 kDa (CHIP28),(20,21) later called the aquaporin. For these discoveries, Peter Agre and Roderick MacKinnon shared the 2003 Nobel Prize in Chemistry. Through additional biophysical studies, ion channels also showed impressive selectivity, inspiring the design of synthetic ion channels.(22−25) 

Eventually, researchers realized the potential implications of these channels for industrial-scale water purification, especially aquaporin in the use of desalination, and attempted to produce biomimetic membranes, or materials that mimic the structure and performance of biological membranes.(26−35) 

While much of the work has focused on water-solute separations, the biomimetic membrane format also presents opportunities to develop membranes with tunable selectivity based on a chosen channel type.However, translating biological mechanisms into industrial-scale technology necessitates scale-up by orders of magnitude—from the microscopic size of a cell membrane to tens of square meters.(36) For industrial relevance, the synthesis of a biomimetic membrane would need to be cost-effective and simple. Simultaneously, such a membrane would need to be mechanically stable under RO pressures exceeding 70 bar and chemically stable during repeated membrane cleaning and usage.(37) Notably, even at the lab scale, sufficiently high-salt rejection has not yet been achieved for biomimetic desalination membranes after over a decade of research.(37,38) 

Therefore, channels, selective layer formats, synthesis strategies, and support layer types must be carefully considered to attain the capabilities of this technology. While certain aspects of biomimetic desalination membranes have been reviewed recently,(37−42) a critical analysis of their performance and their potential application in water-treatment processes remains necessary.In this critical review, we examine efforts toward biomimetic desalination membranes for water purification in order to identify the best strategies to realize their full potential for both desalination and solute–solute selectivity. We first examine molecular transport, contrasting solution-diffusion with molecular sieving and assessing transport through the mixed matrix of biomimetic selective layers. We next identify the key characteristics of the aquaporin that explain its ultraselectivity and fast water transport, comparing this biological channel to several synthetic channels and placing each in industrial context. Using corrected analysis of reported permeability measurements, we then show that the water permeabilities of many channels have been overestimated. Subsequently, we predict best-case-scenario outcomes for common biomimetic formats, including membranes with intact vesicles and membranes with planar biomimetic layers. For the more promising planar format, the biggest challenge is the presence of nanoscale defects. Through mathematical models, we estimate the defect density for several reported biomimetic membranes. We then discuss synthesis pathways that could limit both the presence of defects and the effect of defects on transport performance.

We conclude with a discussion on the practicality of biomimetic desalination membranes and how to best exploit the strengths of discrete nanochannels as molecular sieves in other applications beyond desalination.

Figure 2. Channel types for biomimetic membranes, including biological as well as bioinspired and bioderived. (a) Single channel water permeability versus pore interior diameter. The pore interior diameter here is defined as the inner diameter of the most constricted region. For PAH[4], the pore diameter shown refers to the average width of dynamic voids that formed in channel clusters.

Channel permeabilities from stopped-flow data and simulations were adjusted to 25 °C and corrected for any previous errors in permeability calculation (see SI, Section S1 for details). (b) (left) Overhead view of AqpZ tetramer and (right) side view of single AqpZ channel with characteristic hourglass shape. (c) GramA dimer as it exists in biological and vesicular environments. In organic solvents, the monomers can intertwine to form a parallel or antiparallel helix. AqpZ and GramA diagrams were drawn using PyMOL(69) with protein sequences from the Research Collaboratory for Structural Bioinformatics Protein Data Bank (RCSB-PDB, https://www.rcsb.org/), PDB-ID codes 1RC2(70) and 1NRM.(71) (d) Dependence of water diffusivity through pores on the number of interior hydrogen-bond points.

Data extracted from ref (56). (e) Cyclic peptide nanotubes. (left) Hydrogen-bonding pattern of pore-forming, stacked cyclic peptides. A polyglycine structure is shown for simplicity; side residues would typically be present. (right) Modified cyclic peptide with interior peptide-mimicking functional groups. The analogous unmodified cyclic peptide is radially symmetrical with a fourth primary amine side chain (cyclo[(d-Ala-Lys)4]).(72) (f) Single-walled carbon nanotube porins (wide and narrow) with armchair pattern. Number of carbons approximate those of wCNTP and nCNTP. (g) (left) PAP[5] and (right) PAH[4] nanochannels with peptide appendages that form interarm hydrogen bonds. (h) (left) Aquafoldamer subunits with “sticky” ends. Differences in end groups that comprise Aqf1 and Aqf2 subunits are illustrated. (right) Weak hydrogen-bonding pattern of pore-forming, stacked aquafoldamers. Six subunits are needed to cross a DOPC membrane. (i) Pure water permeability versus total channel areal coverage in a DOPC bilayer. Single channel permeabilities from (a) were divided by channel cross-sectional area and converted into channel water permeability (A) coefficients using eq 3. Overall biomimetic layer A coefficients were calculated for various densities of channels within a DOPC bilayer using eq 7. DOPC bilayer hydraulic permeability was taken as 0.15 L m–2 h–1 bar–1.(73) The shaded region indicates the water permeability of current commercial TFC-RO membranes, an adequate range for desalination performance. Permeabilities are listed in Table S1.

** Read the Complete Paper and Conclusions from AZ Nano by Following the Link Below

https://pubs.acs.org/doi/10.1021/acsnano.0c05753#

Authors

  • Cassandra J. Porter: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 
  • Jay R. Werber: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 
  • Mingjiang Zhong: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 
  • Corey J. Wilson: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
  • Menachem Elimelech: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 

COULD TECHNION RESEARCHERS SOLVE THE WORLD’S WATER CRISIS?


 

The World Health Organization (WHO) estimates that by 2025, about half of the world’s population will live in areas where there is a shortage of clean drinking water. Is it possible that the solution to the global water crisis is, literally, right under our noses? Technion researchers have developed a model for a system that separates the moisture naturally present in the air around us and converts it into drinking water. The patented system, and how it can help prevent the water crisis that awaits the world, was recently presented by Associate Professor David Broday of Technion’s Faculty of Civil and Environmental Engineering at a seminar on water, energy, treatment, and recycling.

2.-Water-option-1“Water is available and free to everyone”

Associate Professor Broday, who developed the system together with his colleague Associate Professor Eran Friedler, explains that the idea is to take advantage of a resource that is constantly and abundantly present around us.

“The atmosphere is everywhere, and there is humidity everywhere,” says Broday. “No atmosphere is completely dry; there is humidity even in the air of the arid Sahara Desert. In fact, the amount of moisture in the atmosphere is equal to the amount of fresh liquid water in the world (i.e. not accounting for glaciers). This is a huge amount of water freely available to everyone with no restrictions.”

Harvesting moisture from the air is not new, and there are several companies around the world that have already developed technologies around this concept. This existing technology, says Broday, is similar to a domestic air conditioner that cools air that comes from the outdoors, uses the cold air, and discards the water condensed during the cooling process. In the case of moisture harvesting technology, it is the air that is discarded and the water that is used. “The existing technology actually takes air and cools it to extract the moisture from it,” explains Broday. “It is brought to a state where the moisture condenses on a cold surface and drips from it, then it is collected and used for drinking.”

But, says Prof. Broday, there is a problem with this technology. “Air is composed not only of moisture but also of other gases like oxygen and nitrogen, and this technology invests in cooling them along with the humidity,” he explains. “Air volume contains only 4 to 5 percent humidity, at best, which is a very small part. A lot of energy is invested in cooling something of which more than 90 percent doesn’t get used at all. This is an ineffective use of energy. This process is expensive to begin with, and in effect most of the energy goes towards cooling material that we are not at all interested in.”

With their system, the researchers propose to optimize this process by separating moisture from the air before cooling it. Doing so will make it possible to invest energy in cooling only the moisture itself and converting it into available water.

 

Global Maps for ‘Water from Air Resources

wvd-world-2006to2015-06-jun_orig

 

The Technion system is also a radical departure from attempts by others who are trying to develop membranes that will separate the moisture out of the air (like the desalination process in which membranes separate salt from seawater).

“The alternative we are proposing is based on the use of an absorbent substance called a desiccant, which is a highly concentrated saline solution that naturally absorbs the moisture from the air when it comes into contact with it,” Broday explains. “The idea is to use this material to absorb a large amount of moisture from the air, and to cool the moisture only after this has been accomplished.”

“Our system is composed of several stages,” he explains. “In the first stage, it will circulate air to transfer moisture from the air to the dessicant, which is in a liquid state. This cycle is repeated over and over again, as the dessicant collects more and more moisture from the air. In the second stage, we transfer a small portion of the dessicant to another part of the system, where we produce conditions that cause the desiccant to release the moisture. This moisture is then condensed and turned into water. For this to happen, we need to cool it down – this is the third stage, which is actually similar to what happens in existing systems; but unlike them, at this stage we cool 100 percent humidity rather than air, only a fraction of which is relevant to our needs.”

Drinkable water in the middle of the desert

According to the researchers, their proposed system isn’t just more energy-efficient. It also provides cleaner water. After cooling, the water collected in the system should be suitable for immediate drinking, as opposed to existing technologies in which air is cooled in its entirety. “If the air spinning in a system – in addition to moisture – contains disease-causing bacteria, when it is cooled and the water condenses, the bacteria in the air may also find their way into the water,” Broday explains. “This means this water may require purification to make it fit for consumption.­­­­

“In our system, the air does not meet the cooling coils at all – only the moisture that is separated from it. As a result, even if the air contains substances we do not want to reach the water, they are absorbed into the dessicant but not released in the next stage,” he says. “Even if bacteria, dust, and the like have accumulated, because it is a very concentrated salt solution, it simply dries up. So the resulting moisture would be clean, and the water, pure. Of course they would be tested, but the need for water treatment processes would probably be much smaller, which is expected to lower the price of using it.”

Using the system would not be without cost, and the researchers emphasize that their method of producing water is more expensive than desalination.

“Where water can be desalinated – that is, in proximity to a source of water such as a sea or brackish lakes – desalination is the preferred option,” explains Broday. “Economically speaking, it makes sense to desalinate and produce a system for transporting water to places that are up to about 62 miles away. Any further than this, and the cost of transportation becomes more expensive than the cost of desalination. There are also towns located close to rivers where water is suitable for use. But when we take all of these out of the equation, there are quite a few places in the world where desalination and direct use are not economically viable.”

The Technion researchers’ system has not yet been built, but they have already performed simulations with a model to see how the system would function in different climatic and humidity conditions. “We wanted to see whether the system can be used in areas where the air is arid,” says Broday, “for example in the Sahara Desert, and in Yemen, which is currently experiencing a severe hunger crisis and lack of drinking water.” He says the system is both relatively small and allows for distributed production of water that does not depend on one source from which the water must be piped to all the other localities.

“We strongly believe in the idea and the preliminary results,” says Broday. “But we still have to put the theory into practice. That’s the next stage.”

The Technion-Israel Institute of Technology is a major source of the innovation and brainpower that drives the Israeli economy, and a key to Israel’s renown as the world’s “Start-Up Nation.” Its three Nobel Prize winners exemplify academic excellence. Technion people, ideas and inventions make immeasurable contributions to the world including life-saving medicine, sustainable energy, computer science, water conservation and nanotechnology.

American Technion Society (ATS) donors provide critical support for the Technion—nearly $2.5 billion since its inception in 1940. Based in New York City, the ATS and its network of supporters across the U.S. provide funds for scholarships, fellowships, faculty recruitment and chairs, research, buildings, laboratories, classrooms and dormitories, and more.

Rapid Nano-filter for clean water: Australian researchers design a rapid nano-filter that cleans dirty water 100X faster than current technology


quickandnots
The new technology can filter drinking water 100 times faster than current tech. Credit: Free stock photo 

Australian researchers have designed a rapid nano-filter that can clean dirty water over 100 times faster than current technology.

Simple to make and simple to scale up, the technology harnesses naturally occurring nano-structures that grow on .

The RMIT University and University of New South Wales (UNSW) researchers behind the innovation have shown it can filter both heavy metals and oils from water at extraordinary speed.

RMIT researcher Dr. Ali Zavabeti said water contamination remains a significant challenge globally—1 in 9 people have no clean water close to home.

“Heavy  contamination causes serious health problems and children are particularly vulnerable,” Zavabeti said.

“Our new nano-filter is sustainable, environmentally-friendly, scalable and low cost.

“We’ve shown it works to remove lead and oil from water but we also know it has potential to target other common contaminants.

“Previous research has already shown the materials we used are effective in absorbing contaminants like mercury, sulfates and phosphates.

“With further development and commercial support, this new nano-filter could be a cheap and ultra-fast solution to the problem of .”

Quick and not-so-dirty: A rapid nano-filter for clean water
A liquid metal droplet with flakes of aluminium oxide compounds grown on its surface. Each 0.03mm flake is made up of about 20,000 nano-sheets stacked together. Credit: RMIT University

The liquid metal chemistry process developed by the researchers has potential applications across a range of industries including electronics, membranes, optics and catalysis.

“The technique is potentially of significant industrial value, since it can be readily upscaled, the liquid metal can be reused, and the process requires only short reaction times and low temperatures,” Zavabeti said.

Project leader Professor Kourosh Kalantar-zadeh, Honorary Professor at RMIT, Australian Research Council Laureate Fellow and Professor of Chemical Engineering at UNSW, said the liquid metal chemistry used in the process enabled differently shaped nano-structures to be grown, either as the atomically thin sheets used for the nano-filter or as nano-fibrous structures.

“Growing these materials conventionally is power intensive, requires high temperatures, extensive processing times and uses toxic metals. Liquid metal chemistry avoids all these issues so it’s an outstanding alternative.”

How it works

The groundbreaking technology is sustainable, environmentally-friendly, scalable and low-cost.

The researchers created an alloy by combining gallium-based liquid metals with aluminium.

When this alloy is exposed to water, nano-thin sheets of  compounds grow naturally on the surface.

These atomically thin layers—100,000 times thinner than a human hair—restack in a wrinkled fashion, making them highly porous.

Quick and not-so-dirty: A rapid nano-filter for clean water
Microscope image of nano-sheets, magnified over 11,900 times. Credit: RMIT University

This enables water to pass through rapidly while the aluminium oxide compounds absorbs the contaminants.

Experiments showed the nano-filter made of stacked atomically thin sheets was efficient at removing lead from water that had been contaminated at over 13 times safe drinking levels, and was highly effective in separating oil from water.

The process generates no waste and requires just aluminium and , with the liquid metals reused for each new batch of nano-structures.

The method developed by the researchers can be used to grow nano-structured materials as ultra-thin sheets and also as nano-fibres.

These different shapes have different characteristics—the ultra-thin sheets used in the nano-filter experiments have high mechanical stiffness, while the nano-fibres are highly translucent.

The ability to grow materials with different characteristics offers opportunities to tailor the shapes to enhance their different properties for applications in electronics, membranes, optics and catalysis.

The research is funded by the Australian Research Council Centre for Future Low-Energy Electronics Technologies (FLEET).

The findings are published in the journal Advanced Functional Materials.

 Explore further: Liquid metal discovery ushers in new wave of chemistry and electronics

More information: Advanced Functional Materials (2018). DOI: 10.1002/adfm.201804057

 

Australian scientists develop nanotechnology to purify water


Scientists in Australia have developed a ground-breaking new way to strip impurities from waste water, with the research set to have massive applications for a number of industries.

Scientists in Australia have developed a ground-breaking new way to strip impurities from waste water, with the research set to have massive applications for a number of industries.

By using a new type of crystalline alloy, researchers at Edith Cowan University (ECU) are able to extract the contaminants and pollutants that often end up in water during industrial processing.

“Mining and textile production produces huge amounts of waste water that is contaminated with heavy metals and dyes,” lead researcher Associate Professor Laichang Zhang from ECU’s School of Engineering technology said in a statement on Friday.

Although it is already possible to treat waste water with iron powder, according to Zhang, the cost is very high.

“Firstly, using iron powder leaves you with a large amount of iron sludge that must be stored and secondly it is expensive to produce and can only be used once,” he explained.

We can produce enough crystalline alloy to treat one tonne of waste water for just 15 Australian Dollars (10.8 US dollars), additionally, we can reuse the crystalline alloy up to five times while still maintaining its effectiveness.” Based on his previous work with “metal glass,” Zhang updated the nanotechnology to make it more effective.

“Whereas metallic glasses have a disordered atomic structure, the crystalline alloy we have developed has a more ordered atomic structure,” he said.

“We produced the crystalline alloy by heating metallic glass in a specific way.””This modifies the structure, allowing the electrons in the crystalline alloy to move more freely, thereby improving its ability to bind with dye molecules or heavy metals leaving behind usable water.”Zhang said he will continue to expand his research with industry partners to further improve the technology.

Rice University engineers develop system to remove contaminants from water


Rice0806_SULFATE-3-WEB-2hajrg6_800x533

Engineer Qilin Li at Rice University’s lab is building a treatment system that can be tuned to selectively pull toxins from wastewater from factories, sewage systems and oil and gas wells, as well as drinking water. The researchers said their technology will cut costs and save energy compared to conventional systems.

“Traditional methods to remove everything, such as reverse osmosis, are expensive and energy intensive,” said Li, the lead scientist and co-author of a study about the new technology in the American Chemical Society journal Environmental Science & Technology. “If we figure out a way to just fish out these minor components, we can save a lot of energy.”

The heart of Rice’s system is a set of novel composite electrodes that enable capacitive deionization. The charged, porous electrodes selectively pull target ions from fluids passing through the maze-like system. When the pores get filled with toxins, the electrodes can be cleaned, restored to their original capacity and reused.

“This is part of a broad scope of research to figure out ways to selectively remove ionic contaminants,” said Li, a professor of civil and environmental engineering and of materials science and nanoengineering. “There are a lot of ions in water. Not everything is toxic. For example, sodium chloride (salt) is perfectly benign. We don’t have to remove it unless the concentration gets too high.”

In tests, an engineered coating of resin, polymer and activated carbon removed and trapped harmful sulfate ions, and other coatings can be used in the same platform to target other contaminants. Illustration by Kuichang Zuo

The proof-of-principal system developed by Li’s team removed sulfate ions. The system’s electrodes were coated with activated carbon, which was in turn coated by a thin film of tiny resin particles held together by quaternized polyvinyl alcohol. When sulfate-contaminated water flowed through a channel between the charged electrodes, sulfate ions were attracted by the electrodes, passed through the resin coating and stuck to the carbon. Tests in the Rice lab showed the positively charged coating on the cathode preferentially captured sulfate ions over salt at a ratio of more than 20 to 1. The electrodes retained their properties over 50 cycles. “But in fact, in the lab, we’ve run the system for several hundred cycles and I don’t see any breaking or peeling of the material,” said Kuichang Zuo, lead author of the paper and a postdoctoral researcher in Li’s lab. “It’s very robust.”

In Rice’s new water-treatment platform, electrode coatings can be swapped out to allow the device to selectively remove a range of contaminants from wastewater, drinking water and industrial fluids. Illustration by Kuichang Zuo

“The true merit of this work is not that we were able to selectively remove sulfate, because there are many other contaminants that are perhaps more important,” she said. “The merit is that we developed a technology platform that we can use to target other contaminants as well by varying the composition of the electrode coating.”

The research was supported by the Rice-based National Science Foundation-backed Center for Nanotechnology-Enabled Water Treatment, the Welch Foundation and the Shanghai Municipal International Cooperation Foundation.

Nidec Motor Corp. appoints CEO

Nidec Motor Corporation (NMC) named Henk van Duijnhoven as its CEO and global business leader of ACIM (Appliances, Commercial and Industrial Motors). Van Duijnhoven was most recently a partner and managing director of The Boston Consulting Group where he was responsible for business turnaround, mergers and acquisitions, and strategy planning for clients in the industrial and medtech markets. He holds a Bachelor of Science degree from the College of Automotive Engineering and a Master of Business Administration from the Massachusetts Institute of Technology.

Woodard & Curran names new business unit leader

Woodard & Curran named Peter Nangeroni as its new industrial and commercial strategic business unit leader. He brings experience managing large, multidisciplinary projects for industrial clients with emphasis on generating positive environmental outcomes, return on investment and improved risk management. He has been with Woodard & Curran for 13 years in various roles, most recently as director of technical practices. He takes over for the long-time leader of the business unit, Mike Curato, who is retiring after 11 years in the role and 20 with the firm.

Nangeroni is a Professional Engineer with a degree in civil engineering from Tufts University and more than 35 years of experience working with clients on engineering and construction management projects. In his new role, he will oversee staffing, business development and project execution at a strategic level for the industrial and commercial strategic business unit, which focuses on water treatment, manufacturing and process utilities for clients in a wide range of industrial sectors.

Canadian Nanotechnology Firm Finds Water in the Driest of Air


A Canadian startup could have a new breakthrough in pulling moisture from the driest of places. For years, researchers around the world have been looking for new technology and methods of making drinkable water out of the atmosphere.

The company Awn Nanotech, based out of Montreal, have been leveraging the latest in nanotechnology to make that water harvesting a reality. Awn Nanotech, most recently, released new information about their progress at the American Physical Society’s March meeting — the world’s largest gathering of physicists.

Founder Richard Boudreault made the presentation, who is both a physicist and an entrepreneur with a sizeable number of other tech-based startup companies under his belt. He said the company got its inspiration after hearing about the water crises in southern California and South Africa. While most others were looking to solve the problem by desalination techniques and new technologies, he wanted to look to the sky instead.

He also wondered if he could create a more cost-efficient alternative to the other expensive options on the market. By tapping into nanotechnology, he could pull the particles toward each other and use the natural tension found in the surface as a force of energy to power the nanotechnology itself.

“It’s extremely simple technology, so it’s extremely durable,” Boudreault said at the press conference.

Boudreault partnered with college students throughout Canada to develop a specific textile. The fine mesh of carbon nanotubes would be both hydrophilic (attracts water to the surface) on one side and hydrophobic (repels water away from the surface) on the other.

Water particles hit the mesh and get pushed through the film from one side to the other. This ultimately forms droplets.

“Because of the surface tension, (the water) finds its way through,” Boudreault explained. The water then gets consolidated into storage tanks as clean water where it can await consumption. While there’s no need for power with the system, the Awn Nanotech team realized they could significantly speed up the water harvesting process by adding a simple fan. The team quickly added a small fan of a size that cools a computer. To make sure the fan also kept energy usage low, the fan itself runs on a small solar panel.

There have been some other attempts around the world to scale up water harvesting technology. In April 2017, a team from MIT partnered with University of California at Berkeley to harvest fog. They turned their attention to already very moist air and created a much cheaper alternative to other fog-harvesting methods using metal-organic frameworks.

However, unlike the small frameworks developed by the MIT researchers, Boudreault said that they’ve quickly scaled up their technology. In fact, the Awn Nanotech team has already created a larger alternative to their smaller scale that can capture 1,000 liters in one day. They’re currently selling their regular-scale water capture systems for $1,000 each, but the company intends on partnering with agricultural companies and farms for the more extensive systems.

Eco-Friendly Desalination using MOF’s could Supply the Lithium needed to Manufacture Batteries required to Mainstream EV’s


A new water purification (desalination) technology could be the key to more electric cars. How?

“Eco-Friendly Mining” of world’s the oceans for the vast amounts of lithium required for EV batteries, could “mainstream” our acceptance (affordability and accessibility) of Electric Vehicles and provide clean water – forecast to be in precious short supply in many parts of the World in the not so distant future.

energy_storage_2013-042216-_11-13-1Humanity is going to need a lot of lithium batteries if electric cars are going to take over, and that presents a problem when there’s only so much lithium available from conventional mines.

A potential solution is being researched that turns the world’s oceans into eco-friendly “Lithium supply mines.”

Scientists have outlined a desalination technique that would use metal-organic frameworks (sponge-like structures with very high surface areas) with sub-nanometer pores to catch lithium ions while purifying ocean water.

The approach mimics the tendency of cell membranes to selectively dehydrate and carry ions, leaving the lithium behind while producing water you can drink.

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While the concept of extracting lithium from our oceans certainly isn’t new, this new technology method would be much more efficient and environmentally friendly.

Instead of tearing up the landscape to find mineral deposits, battery makers would simply have to deploy enough filters.

It could even be used to make the most of water when pollution does take place — recovering lithium from the waste water at shale gas fields.

This method will require more research and development before it’s ready for real-world use.

However, the implications are already clear. If this desalination approach reaches sufficient scale, the world would have much more lithium available for electric vehicles, phones and other battery-based devices. It would also reduce the environmental impact of those devices. storedot-ev-battery-21-889x592 (1)

While some say current lithium mining practices negates some of the eco-friendliness of an EV, this “purification for Lithium” approach could let you drive relatively guilt-free

Reposted from Jonathan Fingas – Engadget

Toward a smart graphene membrane to desalinate water: Penn State University


Graphene H2O towardasmartA scalable graphene-based membrane for producing clean water Credit: Aaron Morelos-Gomez. Credit: Pennsylvania State University

An international team of researchers, including scientists from Shinshu University (Japan) and the director of Penn State’s ATOMIC Center, has developed a graphene-based coating for desalination membranes that is more robust and scalable than current nanofiltration membrane technologies. The result could be a sturdy and practical membrane for clean water solutions as well as protein separation, wastewater treatment and pharmaceutical and food industry applications.

“Our dream is to create a smart  that combines high flow rates, high efficiency, long lifetime, self-healing and eliminates bio and inorganic fouling in order to provide clean water solutions for the many parts of the world where clean water is scarce,” says Mauricio Terrones, professor of physics, chemistry and materials science and engineering, Penn State. “This work is taking us in that direction.”

The hybrid membrane the team developed uses a simple spray-on technology to coat a mixture of graphene oxide and few-layered graphene in solution onto a backbone support membrane of polysulfone modified with polyvinyl alcohol. The support membrane increased the robustness of the hybrid membrane, which was able to stand up to intense cross-flow, high pressure and chlorine exposure. Even in early stages of development, the membrane rejects 85 percent of salt, adequate for agricultural purposes though not for drinking, and 96 percent of dye molecules. Highly polluting dyes from textile manufacturing is commonly discharged into rivers in some areas of the world.

Chlorine is generally used to mitigate biofouling in membranes, but chlorine rapidly degrades the performance of current polymer membranes. The addition of few-layer graphene makes the new membrane highly resistant to chlorine.

Graphene is known to have high mechanical strength, and porous graphene is predicted to have 100 percent salt rejection, making it a potentially ideal material for desalination membranes. However, there are many challenges with scaling up graphene to industrial quantities including controlling defects and the need for complex transfer techniques required to handle the two-dimensional material. The current work attempts to overcome the scalability issues and provide an inexpensive, high quality membrane at manufacturing scale.

The work was performed in the Global Aqua Innovation Center and the Institute of Carbon Science and Technology at Shinshu University, Nagano, Japan, where Terrones is also a Distinguished Invited Professor. The team includes researchers Aaron Morelos-Gomez, Josue Ortiz-Medina and Rodolfo Cruz-Silva, former Ph.D. students of Terrones. Morelos-Gomez is lead author on a paper published online on August 28 in Nature Nanotechnology describing their work titled “Effective NaCL and dye rejection of hybrid graphene oxide/graphene layered membranes.” The Japanese researchers, Hiroyuki Muramatsu, Takumi Araki, Tomoyuki Fukuyo, Syogo Tejima, Kenji Takeuchi, and Takuya Hayashi, were also led by Professor Morinobu Endo.

First author Aaron Morelos-Gomez says, “Our membrane overcomes the water solubility of graphene oxide by using polyvinyl alcohol as an adhesive making it resistant against strong water flow and high pressures. By mixing  with  we could also improve significantly its chemical resistance.”

Professor Morinobu Endo concludes that “this is the first step towards more effective and smart membranes that could self-adapt depending on their environment.”

 Explore further: Graphene sieve turns seawater into drinking water

More information: Aaron Morelos-Gomez et al. Effective NaCl and dye rejection of hybrid graphene oxide/graphene layered membranes, Nature Nanotechnology (2017). DOI: 10.1038/nnano.2017.160

Read more at: https://phys.org/news/2017-09-smart-graphene-membrane-desalinate.html#jCp

Read more at: https://phys.org/news/2017-09-smart-graphene-membrane-desalinate.html#jCp

U of Pennsylvania: Large Scale Production of Graphene + Graphene Updates and Videos


Graphene Mem 050815 3-anewapproach
Draw a line with a pencil and it’s likely that somewhere along that black smudge is a material that earned two scientists the 2010 Nobel Prize in Physics. The graphite of that pencil tip is simply multiple layers of carbon atoms; where those layers are only one atom thick, it is known as graphene.

The properties of a material change at the nanoscopic scale, making graphene the strongest and most conductive substance known. Instead of marking mini-golf scores on paper, this form of carbon is suited for making faster and smaller electronic circuitry, flexible touchscreens, chemical sensors, diagnostic devices, and applications yet to be imagined.

Graphene is not yet as ubiquitous as plastic or silicon, however, and producing the material in bulk remains a challenge. Because graphene’s properties rely on it being only one atom thick, until recently, it was only possible to make it in small patches or flakes.

Physicists at Penn have discovered a way around these limitations, and have spun out their research into a company called Graphene Frontiers. Graphene Frontiers

 


More About Graphene

Turning saltwater into clean drinking water is an expensive, energy-intensive process, but could the wonder material graphene make it more accessible?

New Discovery Could Unlock Graphene’s Full Potential – 


Read More:

3D GrapheneFollow this direct link to Seeker.com for more information and Videos about the ‘Wonder Material’ of Graphene.

Seeker.com



Graphene sieve turns seawater into drinking water

“Graphene-oxide membranes have attracted considerable attention as promising candidates for new filtration technologies. Now the much sought-after development of making membranes capable of sieving common salts has been achieved. New research demonstrates the real-world potential of providing clean drinking water for millions of people who struggle to access adequate clean water sources.
The new findings from a group of scientists at The University of Manchester were published today in the journal Nature Nanotechnology. Previously graphene-oxide membranes have shown exciting potential for gas separation and water filtration.”

MIT Researchers develop new (low energy) way to Clear Pollutants from Water: w/ Video


MIT-PurifyingWater-1_0Researchers have developed a new method for removing even extremely low levels of unwanted compounds from water. The new method relies on an electrochemical process to selectively remove organic contaminants such as pesticides, chemical waste products, and pharmaceuticals. Photo: Melanie Gonick/MIT

Electrochemical method can remove even tiny amounts of contamination.

When it comes to removing very dilute concentrations of pollutants from water, existing separation methods tend to be energy- and chemical-intensive. Now, a new method developed at MIT could provide a selective alternative for removing even extremely low levels of unwanted compounds.

The new approach is described in the journal Energy and Environmental Science, in a paper by MIT postdoc Xiao Su, Ralph Landau Professor of Chemical Engineering T. Alan Hatton, and five others at MIT and at the Technical University of Darmstadt in Germany.

The system uses a novel method, relying on an electrochemical process to selectively remove organic contaminants such as pesticides, chemical waste products, and pharmaceuticals, even when these are present in small yet dangerous concentrations. The approach also addresses key limitations of conventional electrochemical separation methods, such as acidity fluctuations and losses in performance that can happen as a result of competing surface reactions. Watch the Video:

Current systems for dealing with such dilute contaminants include membrane filtration, which is expensive and has limited effectiveness at low concentrations, and electrodialysis and capacitive deionization, which often require high voltages that tend to produce side reactions, Su says. These processes also are hampered by excess background salts.

In the new system, the water flows between chemically treated, or “functionalized,” surfaces that serve as positive and negative electrodes. These electrode surfaces are coated with what are known as Faradaic materials, which can undergo reactions to become positively or negatively charged. These active groups can be tuned to bind strongly with a specific type of pollutant molecule, as the team demonstrated using ibuprofen and various pesticides. The researchers found that this process can effectively remove such molecules even at parts-per-million concentrations.

Previous studies have usually focused on conductive electrodes, or functionalized plates on just one electrode, but these often reach high voltages that produce contaminating compounds. By using appropriately functionalized electrodes on both the positive and negative sides, in an asymmetric configuration, the researchers almost completely eliminated these side reactions. Also, these asymmetric systems allow for simultaneous selective removal of both positive and negative toxic ions at the same time, as the team demonstrated with the herbicides paraquat and quinchlorac.

The same selective process should also be applied to the recovery of high-value compounds in a chemical or pharmaceutical production plant, where they might otherwise be wasted, Su says. “The system could be used for environmental remediation, for toxic organic chemical removal, or in a chemical plant to recover value-added products, as they would all rely on the same principle to pull out the minority ion from a complex multi-ion system.”

The system is inherently highly selective, but in practice it would likely be designed with multiple stages to deal with a variety of compounds in sequence, depending on the exact application, Su says. “Such systems might ultimately be useful,” he sugggests, “for water purification systems for remote areas in the developing world, where pollution from pesticides, dyes, and other chemicals are often an issue in the water supply. The highly efficient, electrically operated system could run on power from solar panels in rural areas for example.”

Unlike membrane-based systems that require high pressures, and other electrochemical systems that operate at high voltages, the new system works at relatively benign low voltages and pressures, Hatton says. And, he points out, in contrast to conventional ion exchange systems where release of the captured compounds and regeneration of the adsorbents would require the addition of chemicals, “in our case you can just flip a switch” to achieve the same result by switching the polarity of the electrodes.

The research team has already racked up a series of honors for the ongoing development of water treatment technology, including grants from the J-WAFS Solutions and Massachusetts Clean Energy Catalyst competitions, and the researchers were the top winners last year’s MIT Water Innovation Prize. The researchers have applied for a patent on the new process. “We definitely want to implement this in the real world,” Hatton says. In the meantime, they are working on scaling up their prototype devices in the lab and improving the chemical robustness.

This technique “is highly significant, as it extends the capabilities of electrochemical systems from basically nonselective toward highly selective removal of key pollutants,” says Matthew Suss, an assistant professor of mechanical engineering at Technion Institute of Technology in Israel, who was not involved in this work. “As with many emerging water purification techniques, it must still must be tested under real-world conditions and for long periods to check durability. However, the prototype system achieved over 500 cycles, which is a highly promising result.”

These researchers “have systematically explored a variety of device configurations and a variety of contaminants,” says Kyle Smith, a professor of mechanical science and engineering at the University of Illinois, who also was not involved in this work. “In the process they have identified general design principles by which to achieve selective removal of contaminants. In this regard, I find Hatton and co-workers’ study to be very thorough and thoughtful. It provides a framework or paradigm for other researchers to emulate.” But, he adds, “A significant challenge that remains is the scale-up of these technologies.”

The team also included Kai-Jher Tan, Johannes Elbert, and Robert R. Taylor Professor of Chemistry Timothy Jamison at MIT; and Christian Ruttiger and Markus Gallei at the Technical University of Darmstadt. The work was supported by a seed grant from the Abdul Latif Jameel World Water and Food Security Lab (J-WAFS) at MIT.