Magnetic Nanoparticles ease Removal of ‘microcontaminants’ from Wastewater


efficientremMany wastewater treatment plants do not completely remove chemical substances from wastewater. Credit: Symbol image: Shutterstock

Microcontaminants place a considerable burden on our water courses, but removing them from wastewater requires considerable technical resources. Now, ETH researchers have developed an approach that allows the efficient removal of these problematic substances.

In our , we all use a multitude of chemical substances, including cosmetics, medications, contraceptive pills, plant fertilisers and detergents—all of which help to make our lives easier. However, the use of such products has an adverse effect on the environment, because many of them cannot be fully removed from wastewater at today’s treatment plants. As , they ultimately end up in the environment, where they place a burden on fauna and flora in our water courses.

As part of a revision of the Waters Protection Act, parliament therefore decided in 2014 to fit an additional purification stage to selected water treatment plants by 2040 with a view to removing microcontaminants. Although the funding for this has in principle been secured, the project presents a challenge for plant operators because it is only possible to remove the critical substances using complex procedures, which are typically based on ozone, activated carbon or light.

Nanoparticles aid degradation

Now, researchers at ETH Zurich’s Institute of Robotics and Intelligent Systems have developed an elegant approach that could allow these substances to be removed more easily. Using multiferroic , they have succeeded in inducing the decomposition of chemical residues in contaminated water. Here, the nanoparticles are not directly involved in the chemical reaction but rather act as a catalyst, speeding up the conversion of the substances into harmless compounds.

“Nanoparticles such as these are already used as a catalyst in  in numerous areas of industry,” explains Salvador Pané, who has played a key role in advancing this research in his capacity as Senior Scientist. “Now, we’ve managed to show that they can also be useful for wastewater purification.”

Efficient removal of problem substances
Based on the example of various organic pigments, such as those used in the textile industry, the researchers are able to demonstrate the effectiveness of their approach. Picture left before treatment, right after treatment. Credit: ETH Zurich / Fajer Mushtaq

An 80 percent reduction

For their experiments, the researchers used aqueous solutions containing trace quantities of five common medications. The experiments confirmed that the nanoparticles can reduce the concentration of these substances in water by at least 80 percent. Fajer Mushtaq, a doctoral student in the group, underlines the importance of these results: “These  also included two compounds that can’t be removed using the conventional ozone-based method.”

“Remarkably, we’re able to precisely tune the catalytic output of the nanoparticles using magnetic fields,” explains Xiangzhong Chen, a postdoc who also participated in the project. The particles have a cobalt ferrite core surrounded by a bismuth ferrite shell. If an external alternating magnetic field is applied, some regions of the particle surface adopt positive electric charges, while others become negatively charged. These charges lead to the formation of reactive oxygen species in water, which break down the organic pollutants into harmless compounds. The magnetic nanoparticles can then be easily removed from water using , says Chen.

Positive responses from industry

The researchers believe that the new approach is a promising one, citing its easier technical implementation than that of ozone-based , for example. “The wastewater industry is very interested in our findings,” says Pané.

However, it will be some time before the method can be applied in practice, as it has been investigated only in the laboratory so far. At any rate, Mushtaq says that approval has already been given for a BRIDGE project jointly funded by the Swiss National Science Foundation and Innosuisse with a view to support the method’s transfer into practical applications. In addition, plans are already in place to establish a spin-off company, in which the researchers intend to develop their idea to market maturity.


Explore further

Chemists suggest a new method to synthesise titanium nanoparticles for water purification


More information: Fajer Mushtaq et al. Magnetoelectrically Driven Catalytic Degradation of Organics, Advanced Materials (2019). DOI: 10.1002/adma.201901378

Journal information: Advanced Materials
Provided by ETH Zurich
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University of Georgia – Microfluidic device may help researchers better understand (and isolate) Metastatic Cancer – “Finding the Needle in the Haystack”


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Instead of searching for a needle in a haystack, what if you were able to sweep the entire haystack to one side, leaving only the needle behind? That’s the strategy researchers in the University of Georgia College of Engineering followed in developing a new microfluidic device that separates elusive circulating tumor cells (CTCs) from a sample of whole blood.

CTCs break away from cancerous tumors and flow through the bloodstream, potentially leading to new metastatic tumors. The isolation of CTCs from the blood provides a minimally invasive alternative for basic understanding, diagnosis and prognosis of metastatic cancer. But most studies are limited by technical challenges in capturing intact and viable CTCs with minimal contamination.
“A typical sample of 7 to 10 milliliters of blood may contain only a few CTCs,” said Leidong Mao, a professor in UGA’s School of Electrical and Computer Engineering and the project’s principal investigator. “They’re hiding in whole blood with millions of white blood cells. It’s a challenge to get our hands on enough CTCs so scientists can study them and understand them.”
Leidong Mao (right) and graduate student Yang Liu in lab
Leidong Mao (right) and graduate student Yang Liu stand in Mao’s lab at UGA.
Circulating tumor cells are also difficult to isolate because within a sample of a few hundred CTCs, the individual cells may present many characteristics. Some resemble skin cells while others resemble muscle cells. They can also vary greatly in size.
“People often compare finding CTCs to finding a needle in a haystack,” said Mao. “But sometimes the needle isn’t even a needle.”
To more quickly and efficiently isolate these rare cells for analysis, Mao and his team have created a new microfluidic chip that captures nearly every CTC in a sample of blood ­- more than 99% – a considerably higher percentage than most existing technologies.
The team calls its novel approach to CTC detection “integrated ferrohydrodynamic cell separation,” or iFCS. They outline their findings in a study published in Lab on a Chip (“Tumor antigen-independent and cell size variation-inclusive enrichment of viable circulating tumor cells”).
The new device could be “transformative” in the treatment of breast cancer, according to Melissa Davis, an assistant professor of cell and developmental biology at Weill Cornell Medicine and a collaborator on the project.
“Physicians can only treat what they can detect,” Davis said. “We often can’t detect certain subtypes of CTCs, but with the iFCS device we will capture all the subtypes of CTCs and even determine which subtypes are the most informative concerning relapse and disease progression.”
Davis believes the device may ultimately allow physicians to gauge a patient’s response to specific treatments much earlier than is currently possible.
While most efforts to capture circulating tumor cells focus on identifying and isolating the few CTCs lurking in a blood sample, the iFCS takes a completely different approach by eliminating everything in the sample that’s not a circulating tumor cell.
The device, about the size of a USB drive, works by funneling blood through channels smaller in diameter than a human hair. To prepare blood for analysis, the team adds micron-sized magnetic beads to the samples. The white blood cells in the sample attach themselves to these beads. As blood flows through the device, magnets on the top and bottom of the chip draw the white blood cells and their magnetic beads down a specific channel while the circulating tumor cells continue into another channel.
The device combines three steps in one microfluidic chip, another advance over existing technologies that require separate devices for various steps in the process.
“The first step is a filter that removes large debris in the blood,” said Yang Liu, a doctoral student in UGA’s department of chemistry and the paper’s co-lead author. “The second part depletes extra magnetic beads and the majority of the white blood cells. The third part is designed to focus remaining white blood cells to the middle of channel and to push CTCs to the side walls.”
Wujun Zhao is the paper’s other lead author. Zhao, a postdoctoral scholar at Lawrence Berkeley National Laboratory, worked on the project while completing his doctorate in chemistry at UGA.
“The success of our integrated device is that it has the capability to enrich almost all CTCs regardless of their size profile or antigen expression,” said Zhao. “Our findings have the potential to provide the cancer research community with key information that may be missed by current protein-based or size-based enrichment technologies.”
The researchers say their next steps include automating the iFCS and making it more user-friendly for clinical settings. They also need to put the device through its paces in patient trials. Mao and his colleagues hope additional collaborators will join them and lend their expertise to the project.
Source: University of Georgia

Argonne National Laboratory – New coating could have big implications for lithium batteries


Argonne scientists have developed a new coating (shown in blue) for battery cathodes that can improve the electronic and ionic conductivity of a battery while improving its safety and cycling performance. Credit: Argonne National Laboratory

Building a better lithium-ion battery involves addressing a myriad of factors simultaneously, from keeping the battery’s cathode electrically and ionically conductive to making sure that the battery stays safe after many cycles.

In a new discovery, scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have developed a new   by using an oxidative chemical vapor deposition technique that can help solve these and several other potential issues with  all in one stroke.

“The coating we’ve discovered really hits five or six birds with one stone.” Khalil Amine, Argonne distinguished fellow and  scientist.

In the research, Amine and his fellow researchers took particles of Argonne’s pioneering nickel-manganese-cobalt (NMC) cathode material and encapsulated them with a sulfur-containing polymer called PEDOT. This polymer provides the cathode a layer of protection from the battery’s electrolyte as the battery charges and discharges.

Unlike conventional coatings, which only protect the exterior surface of the micron-sized cathode particles and leave the interior vulnerable to cracking, the PEDOT coating had the ability to penetrate to the cathode particle’s interior, adding an additional layer of shielding.

In addition, although PEDOT prevents the chemical interaction between the battery and the electrolyte, it does allow for the necessary transport of lithium ions and electrons that the battery requires in order to function.

“This coating is essentially friendly to all of the processes and chemistry that makes the battery work and unfriendly to all of the potential reactions that would cause the battery to degrade or malfunction,” said Argonne chemist Guiliang Xu, the first author of the research.

The coating also largely prevents another reaction that causes the battery’s cathode to deactivate. In this reaction, the  converts to another form called spinel. “The combination of almost no spinel formation with its other properties makes this coating a very exciting material,” Amine said.

The PEDOT material also demonstrated the ability to prevent oxygen release, a major factor for the degradation of NMC cathode materials at . “This PEDOT coating was also found to be able to suppress oxygen release during charging, which leads to better  and also improves safety,” Amine said.

Amine indicated that battery scientists could likely scale up the coating for use in nickel-rich NMC-containing batteries. “This polymer has been around for a while, but we were still surprised to see that it has all of the encouraging effects that it does,” he said.

With the coating applied, the researchers believe that the NMC-containing batteries could either run at higher voltages—thus increasing their —or have longer lifetimes, or both.

To perform the research, the scientists relied on two DOE Office of Science User Facilities located at Argonne: the Advanced Photon Source (APS) and the Center for Nanoscale Materials (CNM). In situ high-energy X-ray diffraction measurements were taken at beamline 11-ID-C of the APS, and focused ion beam lithography and  were performed at the CNM.

A paper based on the study, “Building ultra-conformal protective layers on both secondary and primary particles of layered lithium transition metal oxide cathodes,” appeared in the May 13 online edition of Nature Energy.

More information: Gui-Liang Xu et al, Building ultraconformal protective layers on both secondary and primary particles of layered lithium transition metal oxide cathodes, Nature Energy(2019).  DOI: 10.1038/s41560-019-0387-1

Journal information: Nature Energy

Provided by Argonne National Laboratory

KAUST – Putting the ‘Sense’ in Materials – Say Goodbye to Batteries as You Know Them


KAUST 5c6a94542b7e32661e7f8b63An interdisciplinary initiative is helping KAUST be at the forefront of a digital revolution, where sensors can find a use just about anywhere.

 

The ability to track minuscule but important changes across a range of systems—from the body to the borough and beyond—seems limitless with the emerging array of novel devices that are tiny, self-powering and wirelessly connected. KAUST’s Sensor Initiative comprises a broad range of experts, from marine scientists to electrical engineers, who are innovating solutions to some of the most challenging obstacles in sensor technology. Together, they are powering up to transform the exciting intersection between small interconnected devices and the world around us.

Capacity to monitor our surroundings also reveals new potential in environmental and community protection. For example, a sensor that can detect a flood or a fire can save lives; a sensor that can track animals could help to better manage an ecosystem; and a sensor that can read plant condition could promote sustainable farming.

To take advantage of the market opportunities for sensors in both medical and environmental fields, KAUST holds an annual meeting of biologists, engineers and chemists to discuss technology development. Since 2015, these meetings have produced ambitious collaborations that aim to improve the science that underpins next-gen sensors as well as to take them to the market.

Get ready to plug and play

Khaled Salama, professor of electrical engineering and director of the Sensor Initiative, explains that what sets KAUST apart are the University’s human resources and outstanding lab facilities that underpin its innovative sensor technologies. With the onslaught of data coming from the hundreds of billions of sensors in our cities, cars, homes and offices, we need machine learning to help us understand the data, the supercomputing power to manage it and the expertise to make sure the machines do it all effectively.

“KAUST has strength in materials research, which is where our expertise can be used for developing sensors with transducer components that can be quickly swapped out and replaced with ones customized for different biological or environmental applications,” says Salama.

“Some can stick to your skin and monitor your vital signs through changes in your sweat while others can be placed in petroleum installations to monitor hazardous gases,” says Salama. “We’re not bound to one specific application, and each new development gives us a chance to answer some fundamental scientific questions along the way.”

Say goodbye to batteries, as you know them

KAUST is deploying tiny sensors across the University’s campus to model future smart cities that can continuously monitor air quality or help self-driving cars navigate. Implementing this vision means making devices that are as self-sufficient as possible.

“If you have sensors containing regular batteries, they might last a thousand cycles,” says Husam Alshareef, professor of materials science. “We have to get them to last millions of times longer.”

Alshareef and several international collaborators are building a technology known as microsupercapacitors—next-generation batteries—to resolve challenges around energy storage. Through a special vacuum deposition process, the team has transformed ruthenium oxide into a thin-film electrode that can hold massive amounts of charge and quickly release it on demand.

Get plant smart with winged sensors

Professor Muhammad Hussain is a strong believer in the importance of availability in the sensor market. He insists that his sensors not only provide solutions to everyday problems but also that they be affordable to all. That said, he does not forgo creativity for affordability. Hussain’s plant sensors are flexible, inexpensive and range in size from 1-20 mm in diameter. When placed on a plant leaf, they can detect temperature, humidity and growth, data that can be used to help farmers farm smart—minimizing nutrient and water waste. But what makes them especially remarkable is their beautiful butterfly shape. When asked why he chose the butterfly shape Hussain told us, “Butterflies are aesthetically beautiful and natural in a plant environment. Their large wings allow us to integrate many different sensors, which is especially useful for the artificial intelligence chip we are currently integrating into the system. Ultimately, we aim to create a fully interactive system such that the butterfly can deliver nutrients or gather more data.”

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Sherjeel Khan, ph.D. student with Mohammed Hussain, fabricates the plant-monitoring sensors shaped like butterflies. © 2018 KAUST

Learn to talk effectively

One of the advanced sensors being developed at KAUST is the smart bandage from the group of Atif Shamim in the electrical engineering program. This gadget uses carbon-based transducers to directly contact chronic wounds and to predict signs of infection based on blood pH levels.

Shamim notes that wireless communication is crucial if sensors and other components of the Internet of things are to be integrated with everyday items. His team has pioneered the use of low-energy Bluetooth radio networks to help connect smart devices with each other and also with network servers.

“Even though the Internet of things is about inanimate objects, they have to make decisions for you,” says Shamim. “They need to sense and they need to communicate.”

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Shamim’s smart bandage may help to predict signs of infection in a wound by reading blood pH levels. © 2018 KAUST 

Be prepared to dive deep

Shamim is partnering with other KAUST researchers, including Jürgen Kosel, who specializes in using the property of magnetism in his sensor work to track animal behavior in the Red Sea. The team created stickers—each containing a self-powered, Bluetooth-connected position sensor—that are small enough to be attached to crabs, turtles and giant clams in the Red Sea.

Kosel and his group aimed to tackle the primary challenge associated with remote tracking of marine life—the tendency for water to scatter the radiofrequency waves used by most sensors for geolocation. Working with the KAUST Nanofabrication Core Lab to fabricate thin-film structures, the team created flexible sensors that reveal their global position using magnetic signals that easily access subsurface environments.

“Magnetic fields can penetrate many materials without affecting them, and that includes humans and other animals,” says Kosel. “We’ve shown that you can even derive how much energy a marine animal consumes using magnetic sensors that monitor water flow.”

Sense the future of sensors

For the Emeritus Senior Vice President for Research, Jean Frechet, the possibilities are great: “With our expertise and resources, we have built bridges across disciplines by bringing together researchers from KAUST and other institutions. They inspire each other to solve challenges as diverse as the survival of marine life, communications for the 21st century, and the exploitation of big data. The KAUST Sensor Initiative will stimulate the next generation and contribute to diversifying the country’s economy as we design and engineer sensors that collect the data we need to address global challenges.”

 

Colorful solution to a chemical industry bottleneck – KAUST Researchers Develop an “hourglass shape” Graphene-Oxide Membrane to rapidly separate chemical mixtures – Application Pharmaceuticals (other chemical mixtures)


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A graphene-oxide membrane design inspired by nature swiftly separates solvent molecules.

The nanoscale water channels that nature has evolved to rapidly shuttle water molecules into and out of cells could inspire new materials to clean up chemical and pharmaceutical production. KAUST researchers have tailored the structure of graphene-oxide layers to mimic the hourglass shape of these biological channels, creating ultrathin membranes to rapidly separate chemical mixtures.

“In making pharmaceuticals and other chemicals, separating mixtures of organic molecules is an essential and tedious task,” says Shaofei Wang, postdoctoral researcher in Suzana Nuñes lab at KAUST. One option to make these chemical separations faster and more efficient is through selectively permeable membranes, which feature tailored nanoscale channels that separate molecules by size.

But these membranes typically suffer from a compromise known as the permeance-rejection tradeoff. This means narrow channels may effectively separate the different-sized molecules, but they also have an unacceptably low flow of solvent through the membrane, and vice versa—they flow fast enough, but perform poorly at separation.

Nuñes, Wang and the team have taken inspiration from nature to overcome this limitation. Aquaporins have an hourglass-shaped channel: wide at each end and narrow at the hydrophobic middle section. This structure combines high solvent permeance with high selectivity. Improving on nature, the team has created channels that widen and narrow in a synthetic membrane.

The membrane is made from flakes of a two-dimensional carbon nanomaterial called graphene oxide. The flakes are combined into sheets several layers thick with graphene oxide. Organic solvent molecules are small enough to pass through the narrow channels between the flakes to cross the membrane, but organic molecules dissolved in the solvent are too large to take the same path. The molecules can therefore be separated from the solvent.

To boost solvent flow without compromising selectivity, the team introduced spacers between the graphene-oxide layers to widen sections of the channel, mimicking the aquaporin structure. The spacers were formed by adding a silicon-based molecule into the channels that, when treated with sodium hydroxide, reacted in situ to form silicon-dioxide nanoparticles. “The hydrophilic nanoparticles locally widen the interlayer channels to enhance the solvent permeance,” Wang explains.

When the team tested the membrane’s performance with solutions of organic dyes, they found that it rejected at least 90 percent of dye molecules above a threshold size of 1.5 nanometers. Incorporating the nanoparticles enhanced solvent permeance 10-fold, without impairing selectivity. The team also found there was enhanced membrane strength and longevity when chemical cross-links formed between the graphene-oxide sheets and the nanoparticles.

“The next step will be to formulate the nanoparticle graphene-oxide material into hollow-fiber membranes suitable for industrial applications,” Nuñes says.

References

Wang, S., Mahalingam, D., Sutisna, B. & Nunes, S.P. 2D-dual-spacing channel membranes for high performance organic solvent nanofiltration. Journal of Materials Chemistry Aadvance online publication, 10 January 2019.| article

 

Batteries can’t solve the world’s biggest energy-storage problem – One startup in Denmark has a solution – Solving CO2 Emissions and … Energy Storage


Copenhagen, Denmark

Sometimes, there can be too much of a good thing.

Every so often, from California to Germany, there’s news of “negative electricity prices,” a peculiar side effect of global efforts to generate clean energy.

Solar farms and wind turbines produce varying amounts of power based on the vagaries of the weather. So we build electrical grids to handle only the power levels we expect in a given location.

But in some cases, there’s more sun or wind than expected, and these renewable energy sources pump in more power than the grid can handle. The producers of that power then have to pay customers to use up the excess electricity; otherwise, the grid would be overloaded and fail.

As we build more and more renewable-power capacity in efforts to meet the emissions-reduction goals of the Paris climate agreement, these situations will become more common. Startups led by entrepreneurs who see this future on the horizon are now looking for ways to make money off the inevitable excess clean electricity.

On a mildly chilly day in April, with the smell of poo in the air, I met one of these startups at a sewage-water treatment plant in Copenhagen, Denmark. 

Electrochaea takes carbon dioxide produced during the process of cleaning wastewater, and converts it into natural gas. That alone would be impressive enough; if we want to stop global warming in its tracks, we need to do everything we can to keep CO2 from entering the atmosphere. But Electrochaea has also figured out a way to power the whole enterprise with the excess green energy produced during particularly sunny and windy days that otherwise would have gone to waste, because there would have been no way to store it.

In other words, when scaled up, Electrochaea’s process could be an answer to one of the biggest problems of the 21st century: energy storage, while also making a dent in cutting emissions.

The Electrochaea pilot plant in Copenhagen, with the Biofos water-treatment plant in the background.
This article is part of The Race to Zero Emissions series investigating carbon-capture technology. You can also read our feature laying out the case for using the technology to fight climate change.

The battery problem

The biggest problem with wind and solar energy is that they’re intermittent. There might be violent winds one day, and calm skies the next; broiling sunshine on Monday and 100% cloud cover on Tuesday. Some argue this problem is easily overcome by storing any excess energy in batteries until it’s needed at a later time. Further, battery advocates say, even though the bookcase-sized batteries required to store solar energy for a small home are expensive today, prices are falling and will continue to fall for some time.

Except it’s not that easy. The batteries on the market for these applications are, essentially, large versions of the lithium-ion batteries found in mobile phones. They can only store energy for a certain amount of time—weeks, at most. As soon as the charging source is removed, they start to lose the charge.

That’s not a problem if the batteries are for ironing out the peaks and troughs of daily use. The trouble is that humanity’s energy demand is skewed based on local seasons, which requires sometimes drawing on every available source, and sometimes not using much energy at all.

Mumbai’s peak energy demand is during the hottest days of summer, when people run air conditioners to survive. London’s peak energy demand comes during the coldest days of winters, when people burn natural gas to heat their homes and offices.

Peak energy demand, whether for heating or cooling, can be as much as 20 times the energy consumed on an average day. Today, we shovel more coal or pump more natural gas into fossil-fuel power plants on those high-demand days. Some places, like Bridgeport in Connecticut, have old fossil-fuel plants, often coal, that they keep shut down most of the year and fire up only during peak demand. Obviously, that won’t work in a future powered by renewable energy.

There are two solutions on the table for inter-seasonal energy storage, and they both involve massive investment in infrastructure: First, you could build so many solar panel fields or so many wind turbines that you could produce much more than 20 times the power of an average day. The upshot: you’d have much more excess energy on a low-demand day, but would at least be able to fill demand on peak-demand days. The second option is to get so many batteries that they can store up enough excess energy that, even as they lose their charge, there’s still enough power to get the grid through peak-demand days.

Even if both renewable generation and storage were affordable enough for these plans—and they’re not, yet—there’s still another economic wall that might be impossible to traverse: Most of the time, your new gigantic power plant and fleet of batteries would be useless, because peak demand happens only a few times each year. No government can waste the money needed to build something with so little utility.

Store it another way

Beyond batteries, there are other mechanical ways to store energy. One is to pump water into elevated lakes. Another is to compress air with excess energy. Yet another is to store energy in the form of a high-speed rotating disk. But, like batteries, none of these options can store energy between seasons.

There is one option for the inter-seasonal problem called underground thermal-energy storage. It works on a simple principle: no matter the temperature above ground, at a depth of about 15 meters, temperature in most places on Earth is about the same: 10°C (or 50°F). The planet’s soil provides natural insulation, and, in theory, we could use that insulation to store energy.

There have been successful pilot projects around the world showing you can set up solar panels that, after filling the grid, use any excess electricity to heat gravel, heat-carrying chemicals, or water stored in tanks deep underground. With enough insulation, the heat could be stored for months, until it’s needed in homes nearby, and delivered to them via pipes and heat pumps. (This heat energy can also be converted to run air conditioners, where cooling is needed instead of heating.)

There are just two problems when it comes to scaling up: First, it’s expensive to build. Even if the cost of construction and management were to come down, if cities and towns haven’t already planned for underground reservoirs (and most haven’t), then it can be prohibitively exorbitant to find and secure the space. Second, the solution only works at a local scale, because transporting heat comes with natural losses. So the farther you need to move it from the storage site, the more loss you have to deal with.

Electrochaea provides another option, where renewable energy could be stored indefinitely and transported without losses.

The green goo

If you don’t mind the smell, wastewater treatment plants are fascinating. The Copenhagen plant takes in all the water sent down toilets, bathrooms, and kitchen sinks, and puts out H2O that’s nearly clean enough to drink—just one more step would be required, the plant operator told me. But since the city has no shortage of water, the treatment plant dumps its clean, but non-potable water into the North Sea.

Before that, the water goes through dozens of steps, including one where organic matter is allowed to settled to the bottom of large, open tanks. This sludge, rich in carbon-containing molecules, is transferred to a sealed bioreactor where microbes filtered from local soil are added. If this were done in the open tanks, the microbes would break the matter down slowly to produce carbon dioxide. But, in the bioreactor, in the absence of oxygen, a different set of microbes springs into action. They produce methane—the primary component of natural gas—instead.

The facility takes the methane (and any remaining sludge that can’t be broken down) and then burns it in a biomass power plant. “We produce more energy than we consume to clean up the water coming into our plant,” says Dines Thornberg, a manager at Biofos, the part-government-owned company that operates the treatment plant.

” … Batteries can’t solve the world’s biggest energy-storage problem. One startup has a solution.”

That may be true. But the process still does pollute, since some chemical degradation happens independent of microbes and creates carbon dioxide. To help Denmark hit its Paris agreement goals, Biofos wants to cut its own carbon footprint. That’s why the company gave Electrochaea valuable space at its plant to build the pilot-scale chemical plant that completes the job that Biofos’s microbes couldn’t do: convert the carbon dioxide released in the bioreactor into methane. To achieve this amazing transformation, Electrochaea gets help from microbial life called archaea.

Archaea are the oldest of the three branches of life, which include bacteria and eukaryotes (consisting of all other more advanced organisms including humans). Their ancient survival skills include one that us humans now can put to good use: an ability to naturally take in CO2 and turn it into methane.

Most scientists believe life on Earth was formed in hydrothermal vents, created by underwater volcanoes. The temperatures there can reach 400°C (750°F), far higher than that of boiling water. But the water in the vents doesn’t boil and the gases the vents release—including carbon dioxide and hydrogen—don’t explode thanks to the tremendous pressure applied by miles of seawater above. Some archaea that live in the vents have learned to use carbon dioxide as food, combining the carbon (C) from carbon dioxide (CO2) with hydrogen (H2) to form and release methane (CH4). Humans do the reverse, consuming carbon-rich food and combining it with oxygen—both readily available on land—to make and expel carbon dioxide.

Electrochaea’s pilot plant on Biofos’s premises takes up an area the size of a tennis court. As usual for a chemical factory, there’s a tangle of stainless steel pipes with sensors and control valves. The pipes all lead to a big cylindrical bioreactor, about 10 meters (30 ft) tall, kept at 60°C (140°F) and eight times the atmospheric pressure. Through a small glass window at the bottom of the bioreactor, I can see a bubbling mixture the color of an avocado milkshake. That’s Electrochaea’s proprietary species of archaea, cultured and bred to efficiently combine carbon dioxide and hydrogen to produce methane.

           Electrochaea’s lab-scale bioreactor with archaea producing methane.

The gases injected into the bioreactor come from two sources. The wastewater-treatment plant sends a mixture of carbon dioxide and methane. Meanwhile, two shipping container-sized electrolyzers use renewable electricity to split water into hydrogen and oxygen. The oxygen is sent off into the atmosphere, and the hydrogen to the Electrochaea bioreactor.

The microbes are so effective that in the time the mixture of gases travels from the bottom of the bioreactor to its top, 99 out of every 100 molecules of carbon dioxide and hydrogen are converted into methane, water, and heat. The heat is useful: it helps keep the temperature inside the reactor steady. Meanwhile, as the archaea consume the CO2 and H2, they multiply. Because they are naturally occurring species, extra archaea can be simply dumped into sewers, flushed out by the water also created in the process.

The valuable product from the reaction is methane. In fact, the stuff created through this process is even more valuable than typical methane. It’s “renewable methane” or “biomethane,” because the gas was produced from non-fossil-fuel sources and without any fossil-fuel power. This methane can be used to run boilers in homes, power plants, and even cars or buses. It’s a cleaner fuel than coal and oil, producing the fewest emissions for each unit of energy released. Methane can also be very easily stored. In fact, across Europe, there are large underground stores, connected by pipes that can safely transport the gas.

When the system runs at full capacity, the archaea produce about 50 cubic meters of natural gas per hour. For every unit of energy of electricity fed into the system, it produces about 0.75 units of energy stored in the form of methane, according to Doris Hafenbradl, Electrochaea’s chief scientist. That’s not as good as lithium-ion batteries, which can reach near 100% efficiency. But unlike the energy stored in batteries, once methane is produced it can be stored indefinitely, because it doesn’t spontaneously degrade into other chemicals. If this process could be scaled up, it could solve renewable energy’s inter-seasonal storage problem.

Electrochaea’s plant does not need to be close to solar farms or wind turbines, because excess electricity can be extracted from anywhere on the grid. The limitations on location come based on access to CO2. Water treatment plants are fair game and so are ethanol producers (such as beer and liquor factories). Exhaust gases from power plants could be used, but they will need to be cleaned to remove sulfur and particulate emissions, which could harm archaea.

Solving problems at scale

The Copenhagen plant is one of three where Electrochaea has successfully installed its technology. The US National Renewable Energy Laboratory has one installation on its campus in Boulder, Colorado, and the last is part of a European Commission-funded project in Solothurn, Switzerland. Ultimately, Electrochaea’s core business model is to license the technology. The company is currently courting a Hungarian power company that wants to build a plant 10 times the size of the one in Copenhagen. It would be the startup’s biggest yet. And the carmaker Audi has shown interest in Electrochaea’s technology as a way to use biomethane in its natural-gas-powered cars.

Electrochaea is one of a growing number of players in the “power-to-gas” industry. ITM Power and Hydrogenics, for example, make electrolyzers that convert excess renewable energy into storable hydrogen. But hydrogen is not as widely used as natural gas. That’s why companies such as Electrochaea, MicrobEnergy, and ETOGas are betting that it’s worth the extra step of turning that hydrogen into methane. MicrobEnergy, as the name suggests, uses microbes for the conversion, just like Electrochaea. ETOGas, a Hitachi-supported startup, uses metal catalysts.

Doing it this way also gives these companies a potential second business model: Because these processes all involve injecting carbon dioxide into the system, it could turn out to be the case that they are hired to install their power-to-gas systems simply to reduce a facility’s CO2 emissions, whether it has an excess of renewable energy or not.

Electrochaea hasn’t secured a carbon-capture customer yet. And to be sure, its technology is carbon-capture and recycling—not storage or removal. The methane produced in the process will eventually be burned again, and that will put carbon dioxide into the atmosphere. In other words, it simply delays the production of greenhouse gases, instead of eliminating them.

That said, there is some value in delaying emissions. Every CO2 molecule not dumped in the atmosphere right now is a CO2 molecule that doesn’t absorb and retain sun’s heat. If nothing else, Electrochaea and companies like it may do their part in saving the planet simply by helping change the conversation around carbon dioxide, from treating it as a byproduct to considering it as a feedstock.

Plastic Gets a Do-Over: Breakthrough Discovery Recycles Plastic From the Inside Out


A 2015 investigation that estimates there are between 4.8 trillion and 12.7 trillion pieces of plastic entering the ocean every year.

Scientists from Berkeley Lab have made a next-generation plastic that can be recycled again and again into new materials of any color, shape, or form.

Plastic pollution in the world’s oceans may have a $2.5 trillion impact, negatively affecting “almost all marine ecosystem services,” including areas such as fisheries, recreation and heritage. But a breakthrough from scientists at Berkeley Lab could be the solution the planet needs for this eye-opening problem – recyclable plastics.

The study, published in Nature Chemistry, details how the researchers were able to discover a new way to assemble the plastics and reuse them “into new materials of any color, shape, or form.”

Most plastics were never made to be recycled,” said lead author Peter Christensen, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry, in the statement. “But we have discovered a new way to assemble plastics that takes recycling into consideration from a molecular perspective.”

Known as poly(diketoenamine), or PDK, the new type of plastic material could help stem the tide of plastics piling up at recycling plants, as the bonds PDK forms are able to be reversed via a simple acid bath, the researchers believe.

Poly(diketoenamine)s ‘click’ together from a wide variety of triketones and aromatic or aliphatic amines, yielding only water as a by-product,” the study’s abstract reads.

“Recovered monomers can be re-manufactured into the same polymer formulation, without loss of performance, as well as other polymer formulations with differentiated properties. The ease with which poly(diketoenamine)s can be manufactured, used, recycled and re-used—without losing value—points to new directions in designing sustainable polymers with minimal environmental impact.”

Unlike conventional plastics, the monomers of PDK plastic could be recovered and freed from any compounded additives simply by dunking the material in a highly acidic solution. (Credit: Peter Christensen et al./Berkeley Lab)

A byproduct of petroleum, plastic is inherently made up of molecules known as polymers that are composed of carbon-containing compounds known as monomers. Once chemicals are added to the plastic for use and consumption, the monomers bind with the chemicals and make it difficult to be processed at recycling plants, the researchers said.

Circular plastics and plastics upcycling are grand challenges,” said Brett Helms, a staff scientist in Berkeley Lab’s Molecular Foundry, in the statement. “We’ve already seen the impact of plastic waste leaking into our aquatic ecosystems, and this trend is likely to be exacerbated by the increasing amounts of plastics being manufactured and the downstream pressure it places on our municipal recycling infrastructure.”

Though PDK only exists in the lab currently (meaning products won’t be available for purchase for some time), the researchers are nonetheless excited by what they’ve discovered and the potential positive impact it could have.

“With PDKs, the immutable bonds of conventional plastics are replaced with reversible bonds that allow the plastic to be recycled more effectively,” Helms added. “We’re interested in the chemistry that redirects plastic lifecycles from linear to circular. We see an opportunity to make a difference for where there are no recycling options.”

Plastic recycling figures are trending down, making breakthroughs in recyclable plastic all the more important. According to the latest publicly available data, only 9.1 percent of the plastic created in the U.S. in 2015 was recycled, down from 9.5 percent in 2014, according to the EPA.

Last month, a separate study estimated that the pollution caused by plastics in the world’s oceans amounted to a $2.5 trillion problem that every country in the world has to deal with. The estimate did not take into account the impact on sectors of the global economy such as tourism, transport, fisheries and human health, the researchers wrote.

An ecosystem impact analysis demonstrates that there is global evidence of impact with medium to high frequency on all subjects, with a medium to high degree of irreversibility,” the study’s abstract reads, with the researchers adding that they looked at nearly 1,200 data points to come up with their conclusions.

Despite several efforts of countries around the world to reduce or stop the use of plastic altogether, the amount of plastic in the world’s oceans is increasing, and spreading across the planet.

A separate study, published in Nature on April 16, is the first study “to confirm a significant increase in open ocean plastics in recent decades,” going back nearly 60 years. Researchers found a plastic bag that had been snared on Ireland’s coast since 1965 and is possibly the first piece of plastic pollution ever found, according to the BBC.

Article Re-Posted from Chris Ciaccia of Fox Science News

What’s Coming: DARPA is Eyeing a High-Tech Contact Lens Straight Out of ‘Mission: Impossible’


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The Defense Advanced Research Projects Agency (DARPA) is reportedly interested in a new wirelessly-connected contact lens recently unveiled in France, the latest in the agency’s ongoing search for small-scale technology to augment U.S. service members’ visual capabilities in the field.

Researchers at leading French engineering IMT Atlantique in mid-April announced “the first autonomous contact lens incorporating a flexible micro-battery,” a lightweight lens capable of not only providing augmented vision assistance to users but relaying visual information wirelessly — not unlike, say, the lens Jeremy Renner uses in Mission: Impossible – Ghost Protocol to scan a batch of nuclear codes: (Watch)

More importantly, the new lens can perform its functions without a bulky external power supply, capable of “continuously supply[ing] a light source such as a light-emitting diode (LED) for several hours,” according to the IMT Atlantique announcement.

“Storing energy on small scales is a real challenge,” said Thierry Djenizian, head of the Flexible Electronics Department at the Centre Microélectronique de Provence Georges Charpak and co-head of the p

The lens was primarily designed for medical and automotive applications, but according to French business magazine L’Usine Nouvelle (‘The New Factory’), the lens has garnered interest from both DARPA and Microsoft, which was recently contracted by the the U.S. Army to furnish soldiers with with its HoloLens augmented reality headset.

DARPA’s been on the hunt for a high-tech eyepiece more than a decade, and the agency has funded several similar projects in recent years.

In January 2012, DARPA announced that U.S.-based tech firm Innovega was developing “iOptiks” contact lenses designed to enhance normal vision by projecting digital images onto a standard pair of eyeglasses like a miniaturized heads-up display, “allow[ing] a wearer to view virtual and augmented reality images without the need for bulky apparatus,” as the agency put it.

Three years later, researchers at Switzerland’s École Polytechnique Fédérale de Lausanne (EPFL) unveiled a DARPA-funded contact lens that “magnifies objects at the wink of an eye,” The Guardian reported, although researchers concluded that the technology was better suited for age-related visual deterioration rather than battlefield applications.

“[DARPA researchers] were really interested in supervision, but the reality is more tame than that,” researcher Eric Tremblay told the American Association for the Advancement of Science at the time.

These past projects, like most other blue sky research projects pursued by the DARPA, have likely informed the Pentagon’s research and development of augmented reality tech that U.S. military planners have increasingly pursued in recent years. And the technology is only poised to improve: as Wired recently reported, big tech companies like Google, Sony, and Samsung are all pushing the envelope when it comes to consumer-marketxed augmented vision tech.

But when “smart” contact lenses will actually hit Pentagon armories, like most futuristic DARPA efforts, remains to be seen. In the meantime, it looks like U.S. service members in search of enhanced vision will have to stick to their “birth control glasses.”

This article by Jared Keller originally appeared at Task & Purpose. Follow Task & Purpose onTwitter. This article first appeared in 2019.

Seven Rules for Nanotech Innovation – What 20 Years in the’Nano-Innovation’ World has Taught One Entrepreneur


 

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Tim Harper PWNanoApr19Harper_Harper-635x508Serial entrepreneur Tim Harper shares lessons from 20 years of good, bad and (occasionally) ugly experiences of starting and running nanotech businesses

Back in 2000, the field of nanotechnology was just starting to shift from something that involved tiny robots and molecular gearwheels to real, tangible science with potential applications. In October that year, I organized the first Trends in Nanotechnology (TNT) conference in Toledo, Spain, and as with all conferences, the real work happened in the hotel bar.

The atmosphere inside the Hotel Maria Cristina was febrile. The US National Science Foundation was predicting a trillion-dollar nanotechnology market by 2015. Huge national and European nanotechnology projects were taking shape, and there we were, the cream of the nanoscience community, poised and ready to change the world. New sensors, new ways of delivering drugs, molecular memories – even carbon nanotube-based space elevators to the stars – all seemed within reach. Surely, within a decade, we’d have changed all manufacturing from “top down” to “bottom up”, solving the interlinked problems of clean energy, climate change and human happiness at a stroke.

Ten years later, when I found myself having a similar discussion about graphene, I realized that the nanoscience and materials community could do with a few basic rules to avoid getting overexcited and wasting both time and money.

Rule 1: forget about the science

When you’re deeply involved in a particular field or technology, it is hard to imagine that there could be alternative views about its usefulness. However, before you can commercialize anything, you have to find someone who wants it. Your investors or funders (if any) need to know who will buy products based on your technology, what they will buy and why they will buy it. And the biggest problem you face when you step outside the laboratory door into the real world is…indifference.

Let’s face it. Most things, from medical imaging systems to communications devices, work pretty well these days. I gave up the annual iPhone upgrades years ago because the improvements in technology weren’t compelling enough to justify the hassle. New technologies have to be 10 times faster, 10 times cheaper and come with a highly scalable business model before they get much attention.

To avoid having doors repeatedly slammed in your face, start with the market, not the science. Find an unmet need, then quantify it by talking to people who have that need

A similar situation exists in the composites industry. While there are advantages to be gained from adding carbon nanotubes or graphene to a product, carbon fibre also works in many applications, is well understood and has a robust supply chain. Why would, say, Airbus base major business decisions on an immature technology from a company that might cease to exist long before its material makes it through the lengthy aerospace qualification process?

To avoid having doors repeatedly slammed in your face, start with the market, not the science. Find an unmet need, then quantify it by talking to people who have that need. If the answer to their problem is your technology, then go ahead. If it isn’t, then you’ll spend a lot of time battling indifference.

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Carbon dreams: “Space elevators” were an early proposed application of carbon nanotubes.

Rule 2: don’t assume anything

When I worked with the Massachusetts Institute of Technology (MIT) on the M+Vision IDEA3programme, we offered a structured scheme to help our students find unmet needs. Often, the students would start with a woolly concept such as “better detection of cancer”, to which we’d ask questions like “What sort of cancer? At what stage? Using imaging or biopsies or genetics or something else?” Once we had a focus, we would then start talking to clinicians and radiographers to find out what issues they had. In many cases, the response was that current technology was okay, with room for incremental improvements but no urgent demand for change.

The lesson here is that if you don’t properly research your end users or customers, you may end up producing a solution to a problem that doesn’t exist. But you probably won’t even get that far. Any business plan needs to show investors how they will get their money back. It doesn’t matter whether you are selling widgets or a service or licensing the technology: before you can make any predictions, you need to understand the market.

Here’s an example. When I was putting together my company G2O Water Technologies, which makes graphene-based water filtration membranes, I spent a lot of time talking to people in the water industry. I needed to understand how membranes are used, what their limitations are, and how often they are replaced. I spoke with water research institutes and membrane experts, and I attended multiple talks and conferences until I was sure that our product fulfilled an unmet need in the water industry. Only when I fully understood the market did it become possible to make sense of the myriad (and often contradictory) market research reports that purported to give me definitive numbers about an industry.

This information-gathering stage is also when you will often find out about some hitherto unknown regulatory issue surrounding the use of new materials in certain environments – with the result that all your revenue forecasts move a couple of years to the right on your spreadsheet. Once you’ve completed this exercise, though, you should have a good idea of how to answer questions about who will buy your widget, how much will they pay, and when.

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Rule 3: build a team

I spent six years at the European Space Agency, mostly working on electron microscopy, surface analysis and atomic force microscopy for failure analysis, and I’ll never forget the feeling I had when I left to set up my first business, Cientifica. After spending months designing a set of wings that would, I hoped, enable me to soar like an eagle, I was about to test them by jumping off a clifftop. I didn’t hit the ground with a big splat, but I came pretty close, and on the way down I had to learn all sorts of things: cash flow, margins, sales channels and (not least) the Kafkaesque bureaucracy that was, at the time, involved in filing social security and tax returns in Spain.

But perhaps the most valuable lesson I learned is the importance of working out what you are good at, where you need help, and then building a team to fill the gaps. For my second start-up, NanoSight, I brought in a chair who knew his way around the financial world and a managing director who could keep on top of the day-to-day issues – leaving me free to develop our technology to match our vision.

It is also important to build a good external team. I often recruit a scientific advisory board – half a dozen well-connected, respected and highly knowledgeable experts – and meet with them several times a year to check whether we are still on the right track. When you are 100% focused on building and promoting a business it is all too easy to start believing your own marketing story. Having to justify your strategy to independent people helps keep your feet on the ground. It also keeps you abreast of technology or competitive developments that you may have missed.

A note of caution, though: executive teams, like rock bands, do break up. Senior-level disagreements within a team are very common, and once money (or lack of money) is involved, best friends and colleagues can become bitter enemies. There’s always someone on the team who thinks they could do a better job of running the show.

Rule 4: don’t suffer fools

If you’ve followed rules one to three you will be confident that you have something that someone wants, as well as the team to take it to market. That’s when the hard work begins. There will always be people who will tell you it can’t be done. Sometimes the reason is a simple fear of change or corporate inertia; maybe you came up with a better idea than the people paid to come up with ideas. Other times it’s a lack of understanding of the technology. Occasionally, it might just be pure, bloody-minded stupidity.

The worst mistake I have made by far was to continue trying to salvage a failing business when everything pointed to closing it down. It was my business, my life, and what everyone knew me for

When I started testing the first nanoparticle imaging systems for NanoSight, several learned professors told me that what we were doing was impossible. Even after I ran a demo for them and explained the distinction between imaging and detecting the light scattered from a particle, some people were adamant that it was impossible to use optical methods to detect anything smaller than the wavelength of the laser we used.

The world is full of people who are so certain of their own beliefs that they will never change their minds, however wrong they may be. Don’t take it personally. Move on.

Rule 5: choose the right funder

How much is a start-up worth? I take the Adam Smith view that it is worth whatever someone is willing to pay for it, but no-one parts with money willingly – especially for a risky early-stage business. There are, however, some warning signs. Once, a potential investor offered me €100,000 for 90% of the business and received a lecture on idiotic time-wasting in return. Many other “investors” don’t actually have any money. Instead, they are looking for interesting deals that they can hawk around to people who do in the hope of taking a cut of the transaction. (California and China seem to be particularly good locations for people trying to squeeze themselves between you and a funder.)

In most cases, no deal is better than a bad deal. If your investors don’t believe in your team and your company’s vision, then it is going to be a long hard slog. Instead of building value into the business, you will end up having board meetings that focus on whether the CEO really needed an extra shot of espresso in their latte before the 6 a.m. Ryanair flight. However, there are times when you just can’t wait. In that case, make sure you go in with your eyes open, get your own legal advice and try to avoid joining the unfortunate group of founders whose stake gets diluted to almost zero by subsequent investors.

The best funding sources bring more than just money to the table. Expertise, contacts and access to markets can all add value. Good investors may help you flesh out your board of directors or introduce you to other companies in their portfolios. That may present opportunities. Investors like the idea of their portfolio companies working together to add even more value (and create a potential exit through acquisitions).

Rule 6: mind your ego

The life of an entrepreneur is a tough one. For every Mark Zuckerberg who hits the bullseye at the first attempt there are millions who fail, and that’s perfectly okay. I’ve had great businesses and terrible businesses. Sometimes it has been my fault that they failed, sometimes it was because of circumstances no-one could predict, but I’ve learned from them all. Most importantly, I’ve learned not to worry too much about what anyone else thinks. For every person who takes the plunge and tries to create a business, there will be hundreds waiting to tell you how you ought to have done it. Ignore the armchair entrepreneurs.

 

A year down the road, it may become apparent that the opportunity you are pursuing is not the right one, or that there is a more easily accessible prize. Sometimes a rethink is necessary. One medical diagnostics technology I helped develop ended up being used for water-quality testing. Of course, I had to go back to our investors and tell them that our game-changing diagnostics technology was actually being used in sewage treatment, but in a world where nine out of 10 start-ups fail completely, any return is better than nothing.

It’s embarrassing, at first, to have to admit that you didn’t get it right, but the biggest mistake is to be afraid to fail. The worst mistake I have made by far was to continue trying to salvage a failing business when everything pointed to closing it down. It was my business, my life and what everyone knew me for. Leaving it was tough. But in the end, a clean bail-out is always preferable to a messy failure; it’s quicker and you don’t get sued. When the time comes, bite the bullet and jump.

Have fun download

Rule 7: have fun

The past 25 years of entrepreneurship have produced some incredible highs and some terrible lows, but if I had the chance to do it all again, I’d jump at it. Success isn’t all about money and there’s nothing quite like the feeling of seeing an opportunity you identified, nurtured and grew become a success. And while there have been times when I worked 18-hour days and still struggled to pay the bills, the pain was more than balanced by having no office, no commute, no boss and complete responsibility for my own destiny.

Tim Harper is a physicist, materials scientist and entrepreneur who creates and builds international businesses based on emerging technologies, e-mail tim.harper@cientifica.com

Graphene Nanocomposite Foam Material Harvests Water from Air


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Researchers in China have demonstrated a graphene nanocomposite foam-based water harvesting system to harvest water from air. The team reports their findings in ACS Applied Materials & Interfaces (“Superelastic Graphene Nanocomposite for High Cycle-Stability Water Capture-Release under Sunlight”).
Only 30% of all freshwater on the planet is not locked up in ice caps or glaciers (not for much longer, though). Of that, some 20% is in areas too remote for humans to access and of the remaining 80% about three-quarters comes at the wrong time and place – in monsoons and floods – and is not always captured for use by people. The remainder is less than 0.08 of 1% of the total water on the planet (read more: “Nanotechnology and water treatment“)
An abundance of water equivalent to about 10% of the total freshwater in lakes exists in the earth atmosphere, which can be a non-negligible freshwater resource to fight against the water shortage.
That’s where the graphene nanocomposite foam comes in: The foam realizes water harvesting through a capture-release cycle:
1) the capture process is composed of moisture adsorption from air by lithium chloride (LiCl) and water preservation by poly(vinyl alcohol) (PVA) and
2) the release relies on the solar-to-thermal transformer, reduced graphene oxide (rGO), to facilitate evaporation. In addition, polyimide is employed as a substrate material for the purpose of 3D porous structure formation and mechanical property enhancement.

 

graphene nanocomposite foam for harvesting water from air
 

Photograph, schematic diagram, and SEM images of the graphene nanocomposite foam. (a) Photograph of the graphene nanocomposite foam. (b) Schematic diagram of the graphene nanocomposite foam. Foam was prepared through a three-step process: freeze-drying, thermal annealing, and hydrophilic treatment. rGO/PI nanosheet, as the basic unit, can achieve the water harvesting capture-release cycle without additional energy input. (c) SEM image presents a porous structure of the rGO/PI foam without hydrophilic treatment. (d) Magnified SEM image of the rGO/PI foam without hydrophilic treatment to show a relatively smooth surface of the nanosheet. (e) SEM image of the graphene nanocomposite foam after hydrophilic treatment. (f) Magnified SEM image of the hydrophilic rGO/PI foam with bumped nanostructures. (g) Schematic diagram of the water vapor capture-release cycle.

LiCl and PVA were responsible for the water capture and water storage, respectively. Adsorbed water was stored as crystallized water in LiCl hydrates and the free water molecules were restrained by hydroxyl groups on PVA through the hydrogen bond, which led to the transformation of the nanosheet from dry status to wet status. Opposite procedure, from wet status to dry status, was realized by the rGO converting the solar energy to thermal energy to facilitate water evaporation under irradiation. (Reprinted with permission by American Chemical Society) (click on image to enlarge)

 

The as-fabricated foam can adsorb water up to 2.87 g per gram in 24 hours at a relative humidity of 90% and a temperature of 30°C, and release almost all the uptake water when it is exposed under a flux of 1 sun (1000 W per square meter, equal to the light intensity of natural sunlight) for 3 hours.
At the same time, the functional foam shows superelasticity, lightweight, and remarkable reusability, thus revealing its possibility to practical use.
The researchers write that, even though the rGO/PI nanocomposite foam can harvest freshwater from air, it is essential to enhance water harvesting efficiency.
“Another big challenge impedes the water harvesting system utilization to explore a more cost-effective way to prepare the products,” they conclude. “Though the three-step synthesis method and the composition of the foam have been optimized, it is still necessary to reduce the cost and increase the fabrication efficiency. Meanwhile, environmentally friendly materials are recommended, which would take the water harvesting system one step further to commercial application and large-scale production.”
By Michael Berger – Nanowerk

Sources

Bo ChenXue Zhao, and Ya Yang*§ 
 CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-Nano Energy and Sensor, Beijing Institute of Nanoenergy and NanosystemsChinese Academy of Sciences, Beijing 100083, P. R. China
 School of Nanoscience and TechnologyUniversity of Chinese Academy of Sciences, Beijing 100049, P. R. China
§ Center on Nanoenergy Research, School of Physical Science and TechnologyGuangxi University, Nanning, Guangxi 530004, P. R. China