Category Archives: water

Carbon nanotubes for water desalination

In discussions about water desalination and carbon nanomaterials,  it’s graphene that’s usually mentioned these days. By contrast, scientists from the US Department of Energy’s Lawrence Livermore National Laboratory (LLNL) have turned to carbon nanotubes,

There are two news items about the work at LLNL on ScienceDaily, this first one originated by the American Association for the Advancement of Science (AAAS) offers a succinct summary of the work (from an August 24, 2017 news item on ScienceDaily,

At just the right size, carbon nanotubes can filter water with better efficiency than biological proteins, a new study reveals. The results could pave the way to new water filtration systems, at a time when demands for fresh water pose a global threat to sustainable development.

A class of biological proteins, called aquaporins, is able to effectively filter water, yet scientists have not been able to manufacture scalable systems that mimic this ability. Aquaporins usually exhibit channels for filtering water molecules at a narrow width of 0.3 nanometers, which forces the water molecules into a single-file chain.

Here, Ramya H. Tunuguntla and colleagues experimented with nanotubes of different widths to see which ones are best for filtering water. Intriguingly, they found that carbon nanotubes with a width of 0.8 nanometers outperformed aquaporins in filtering efficiency by a factor of six.

These narrow carbon nanotube porins (nCNTPs) were still slim enough to force the water molecules into a single-file chain. The researchers attribute the differences between aquaporins and nCNTPS to differences in hydrogen bonding — whereas pore-lining residues in aquaporins can donate or accept H bonds to incoming water molecules, the walls of CNTPs cannot form H bonds, permitting unimpeded water flow.

The nCNTPs in this study maintained permeability exceeding that of typical saltwater, only diminishing at very high salt concentrations. Lastly, the team found that by changing the charges at the mouth of the nanotube, they can alter the ion selectivity. This advancement is highlighted in a Perspective [in Science magazine] by Zuzanna Siwy and Francesco Fornasiero.

The second Aug. 24, 2017 news item on ScienceDaily offers a more technical  perspective,

Lawrence Livermore scientists, in collaboration with researchers at Northeastern University, have developed carbon nanotube pores that can exclude salt from seawater. The team also found that water permeability in carbon nanotubes (CNTs) with diameters smaller than a nanometer (0.8 nm) exceeds that of wider carbon nanotubes by an order of magnitude.

The nanotubes, hollow structures made of carbon atoms in a unique arrangement, are more than 50,000 times thinner than a human hair. The super smooth inner surface of the nanotube is responsible for their remarkably high water permeability, while the tiny pore size blocks larger salt ions.

There’s a rather lovely illustration for this work,

An artist’s depiction of the promise of carbon nanotube porins for desalination. The image depicts a stylized carbon nanotube pipe that delivers clean desalinated water from the ocean to a kitchen tap. Image by Ryan Chen/LLNL

An Aug. 24, 2017 LLNL news release (also on EurekAlert), which originated the second news item, proceeds

Increasing demands for fresh water pose a global threat to sustainable development, resulting in water scarcity for 4 billion people. Current water purification technologies can benefit from the development of membranes with specialized pores that mimic highly efficient and water selective biological proteins.

“We found that carbon nanotubes with diameters smaller than a nanometer bear a key structural feature that enables enhanced transport. The narrow hydrophobic channel forces water to translocate in a single-file arrangement, a phenomenon similar to that found in the most efficient biological water transporters,” said Ramya Tunuguntla, an LLNL postdoctoral researcher and co-author of the manuscript appearing in the Aug. 24 [2017]edition of Science.

Computer simulations and experimental studies of water transport through CNTs with diameters larger than 1 nm showed enhanced water flow, but did not match the transport efficiency of biological proteins and did not separate salt efficiently, especially at higher salinities. The key breakthrough achieved by the LLNL team was to use smaller-diameter nanotubes that delivered the required boost in performance.

“These studies revealed the details of the water transport mechanism and showed that rational manipulation of these parameters can enhance pore efficiency,” said Meni Wanunu, a physics professor at Northeastern University and co-author on the study.

“Carbon nanotubes are a unique platform for studying molecular transport and nanofluidics,” said Alex Noy, LLNL principal investigator on the CNT project and a senior author on the paper. “Their sub-nanometer size, atomically smooth surfaces and similarity to cellular water transport channels make them exceptionally suited for this purpose, and it is very exciting to make a synthetic water channel that performs better than nature’s own.”

This discovery by the LLNL scientists and their colleagues has clear implications for the next generation of water purification technologies and will spur a renewed interest in development of the next generation of high-flux membranes.

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

Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins by Ramya H. Tunuguntla, Robert Y. Henley, Yun-Chiao Yao, Tuan Anh Pham, Meni Wanunu, Aleksandr Noy. Science 25 Aug 2017: Vol. 357, Issue 6353, pp. 792-796 DOI: 10.1126/science.aan2438

This paper is behind a paywall.

And, Northeastern University issued an August 25, 2017 news release (also on EurekAlert) by Allie Nicodemo,

Earth is 70 percent water, but only a tiny portion—0.007 percent—is available to drink.

As potable water sources dwindle, global population increases every year. One potential solution to quenching the planet’s thirst is through desalinization—the process of removing salt from seawater. While tantalizing, this approach has always been too expensive and energy intensive for large-scale feasibility.

Now, researchers from Northeastern have made a discovery that could change that, making desalinization easier, faster and cheaper than ever before. In a paper published Thursday [August 24, 2017] in Science, the group describes how carbon nanotubes of a certain size act as the perfect filter for salt—the smallest and most abundant water contaminant.

Filtering water is tricky because water molecules want to stick together. The “H” in H2O is hydrogen, and hydrogen bonds are strong, requiring a lot of energy to separate. Water tends to bulk up and resist being filtered. But nanotubes do it rapidly, with ease.

A carbon nanotube is like an impossibly small rolled up sheet of paper, about a nanometer in diameter. For comparison, the diameter of a human hair is 50 to 70 micrometers—50,000 times wider. The tube’s miniscule size, exactly 0.8 nm, only allows one water molecule to pass through at a time. This single-file lineup disrupts the hydrogen bonds, so water can be pushed through the tubes at an accelerated pace, with no bulking.

“You can imagine if you’re a group of people trying to run through the hallway holding hands, it’s going to be a lot slower than running through the hallway single-file,” said co-author Meni Wanunu, associate professor of physics at Northeastern. Wanunu and post doctoral student Robert Henley collaborated with scientists at the Lawrence Livermore National Laboratory in California to conduct the research.

Scientists led by Aleksandr Noy at Lawrence Livermore discovered last year [2016] that carbon nanotubes were an ideal channel for proton transport. For this new study, Henley brought expertise and technology from Wanunu’s Nanoscale Biophysics Lab to Noy’s lab, and together they took the research one step further.

In addition to being precisely the right size for passing single water molecules, carbon nanotubes have a negative electric charge. This causes them to reject anything with the same charge, like the negative ions in salt, as well as other unwanted particles.

“While salt has a hard time passing through because of the charge, water is a neutral molecule and passes through easily,” Wanunu said. Scientists in Noy’s lab had theorized that carbon nanotubes could be designed for specific ion selectivity, but they didn’t have a reliable system of measurement. Luckily, “That’s the bread and butter of what we do in Meni’s lab,” Henley said. “It created a nice symbiotic relationship.”

“Robert brought the cutting-edge measurement and design capabilities of Wanunu’s group to my lab, and he was indispensable in developing a new platform that we used to measure the ion selectivity of the nanotubes,” Noy said.

The result is a novel system that could have major implications for the future of water security. The study showed that carbon nanotubes are better at desalinization than any other existing method— natural or man-made.

To keep their momentum going, the two labs have partnered with a leading water purification organization based in Israel. And the group was recently awarded a National Science Foundation/Binational Science Foundation grant to conduct further studies and develop water filtration platforms based on their new method. As they continue the research, the researchers hope to start programs where students can learn the latest on water filtration technology—with the goal of increasing that 0.007 percent.

As is usual in these cases there’s a fair degree of repetition but there’s always at least one nugget of new information, in this case, a link to Israel. As I noted many times, the Middle East is experiencing serious water issues. My most recent ‘water and the Middle East’ piece is an August 21, 2017 post about rainmaking at the Masdar Institute in United Arab Emirates. Approximately 50% of the way down the posting, I mention Israel and Palestine’s conflict over water.

Masdar Institute and rainmaking

Water security, of course, is a key issue and of particular concern in many parts of the world including the Middle East. (In the Pacific Northwest, an area described as a temperate rain forest, there tends to be less awareness but even we are sometimes forced to ration water.) According to a July 5, 2017 posting by Bhok Thompson (on the Green Prophet website) scientists at the Masdar Institute of Science and Technology (in Abu Dhabi, United Arab Emirates [UA]E) have applied for a patent on a new technique for rainmaking,

Umbrella sales in the UAE may soon see a surge in pricing. Researchers at the Masdar Institute have filed for a provisional patent with the United States Patent and Trademark Office for their discovery – and innovative cloud seeding material that moves them closer to their goal of producing rain on demand. It appears to be a more practical approach than building artificial mountains.

Dr. Linda Zou is leading the project. A professor of chemical and environmental engineering, she is one of the first scientists to explore nanotechnology to enhance a cloud seeding material’s ability to produce rain. By filing a patent, the team is paving a way to commercialize their discovery, and aligning with Masdar Institute’s aim to position the UAE as a world leader in science and tech, specifically in the realm of environmental sustainability.

A January 31, 2017 posting by Erica Solomon for the Masdar Institute reveals more about the project,

The Masdar Institute research team that was one of the inaugural recipients of the US$ 5 million grant from the UAE Research Program for Rain Enhancement Science last year has made significant progress in their work as evidenced by the filing a provisional patent with the United States Patent and Trademark Office (USPTO).

By filing a patent on their innovative cloud seeding material, the research team is bringing the material in the pathway for commercialization, thereby supporting Masdar Institute’s goal of bolstering the United Arab Emirates’ local intellectual property, which is a key measure of the country’s innovation drive. It also signifies a milestone towards achieving greater water security in the UAE, as rainfall enhancement via cloud seeding can potentially increase rainfall between 10% to 30%, helping to refresh groundwater reserves, boost agricultural production, and reduce the country’s heavy reliance on freshwater produced by energy-intensive seawater desalination.

Masdar Institute Professor of Chemical and Environmental Engineering, Dr. Linda Zou, is the principal investigator of this research project, and one of the first scientists in the world to explore the use of nanotechnology to enhance a cloud seeding material’s ability to produce rain.

“Using nanotechnology to accelerate water droplet formation on a typical cloud seeding material has never been researched before. It is a new approach that could revolutionize the development of cloud seeding materials and make them significantly more efficient and effective,” Dr. Zou remarked.

Conventional cloud seeding materials are small particles such as pure salt crystals, dry ice and silver iodide. These tiny particles, which are a few microns (one-thousandth of a millimeter) in size, act as the core around which water condenses in the clouds, stimulating water droplet growth. Once the air in the cloud reaches a certain level of saturation, it can no longer hold in that moisture, and rain falls. Cloud seeding essentially mimics what naturally occurs in clouds, but enhances the process by adding particles that can stimulate and accelerate the condensation process.

Dr. Zou and her collaborators, Dr. Mustapha Jouiad, Principal Research Scientist in Mechanical and Materials Engineering Department, postdoctoral researcher Dr. Nabil El Hadri and PhD student Haoran Liang, explored ways to improve the process of condensation on a pure salt crystal by layering it with a thin coating of titanium dioxide.

The extremely thin coating measures around 50 nanometers, which is more than one thousand times thinner than a human hair. Despite the coating’s miniscule size, the titanium dioxide’s effect on the salt’s condensation efficiency is significant. Titanium dioxide is a hydrophilic photocatalyst, which means that when in contact with water vapor in the cloud, it helps to initiate and sustain the water vapor adsorption and condensation on the nanoparticle’s surface. This important property of the cloud seeding material speeds up the formation of large water droplets for rainfall.

Dr. Zou’s team found that the titanium dioxide coating improved the salt’s ability to adsorb and condense water vapor over 100 times compared to a pure salt crystal. Such an increase in condensation efficiency could improve a cloud’s ability to produce more precipitation, making rain enhancement operations more efficient and effective. The research will now move to the next stage of simulated cloud and field testing in the future.

Dr. Zou’s research grant covers two more years of research. During this time, her team will continue to study different design concepts and structures for cloud seeding materials inspired by nanotechnology.

To give you a sense of the urgent need for these technologies, here’s the title from my Aug. 24, 2015 posting, The Gaza is running out of water by 2016 if the United Nations predictions are correct. I’ve not come across any updates on the situation in the Gaza Strip but both Israel and Palestine have recently signed a deal concerning water. Dalia Hatuqa’s August 2017 feature on the water deal for Al Jazeera is critical primarily of Israel (as might be expected) but there are one or two subtle criticisms of Palestine too,

Critics have also warned that the plan does not address Israeli restrictions on Palestinian access to water and the development of infrastructure needed to address the water crisis in the occupied West Bank.

Palestinians in the West Bank consume only 70 litres of water per capita per day, well below what the World Health Organization recommends as a minimum (100).

In the most vulnerable communities in Area C – those not connected to the water network – that number further drops to 20, according to EWASH, a coalition of Palestinian and international organisations working on water and sanitation in the Palestinian territories.

The recent bilateral agreement, which does not increase the Palestinians’ quota of water in the Jordan River, makes an untenable situation permanent and guarantees Israel a lion’s share of its water, thus reinforcing the status quo, Buttu [Diana Buttu, a former adviser to the Palestinian negotiating team] said.

“They have moved away from the idea that water is a shared resource and instead adopted the approach that Israel controls and allocates water to Palestinians,” she added. “Israel has been selling water to Palestinians for a long time, but this is enshrining it even further by saying that this is the way to alleviate the water problem.”

Israeli officials say that water problems in the territories could have been addressed had the Palestinians attended the meetings of the joint committee. Palestinians attribute their refusal to conditions set by their counterparts, namely that they must support Israeli settlement water projects for any Palestinian water improvements to be approved.

According to Israeli foreign ministry spokesman Emmanuel Nahshon, “There are many things to be done together to upgrade the water infrastructure in the PA. We are talking about old, leaking pipes, and a more rational use of water.” He also pointed to the illegal tapping into pipes, which he maintained Palestinians did because they did not want to pay for water. “This is something we’ve been wanting to do over the years, and the new water agreement is one of the ways to deal with that. The new agreement … is not only about water quotas; it’s also about more coherent and better use of water, in order to address the needs of the Palestinians.”

But water specialists say that the root cause of the problem is not illegal activity, but the unavailability of water resources to Palestinians and the mismanagement and diversion of the Jordan River.

Access to water is gong to be of increasing urgency should temperatures continue to rise as they have. In many parts of the world, potable water is not easy to find and if temperatures continue to rise areas that did have some water security will lose it and the potential for conflict rises hugely. Palestine and Israel may be a harbinger of what’s to come. As for the commodification of water, I have trouble accepting it; I think everyone has a right to water.

Using only sunlight to desalinate water

The researchers seem to believe that this new desalination technique could be a game changer. From a June 20, 2017 news item on Azonano,

An off-grid technology using only the energy from sunlight to transform salt water into fresh drinking water has been developed as an outcome of the effort from a federally funded research.

The desalination system uses a combination of light-harvesting nanophotonics and membrane distillation technology and is considered to be the first major innovation from the Center for Nanotechnology Enabled Water Treatment (NEWT), which is a multi-institutional engineering research center located at Rice University.

NEWT’s “nanophotonics-enabled solar membrane distillation” technology (NESMD) integrates tried-and-true water treatment methods with cutting-edge nanotechnology capable of transforming sunlight to heat. …

A June 19, 2017 Rice University news release, which originated the news item, expands on the theme,

More than 18,000 desalination plants operate in 150 countries, but NEWT’s desalination technology is unlike any other used today.

“Direct solar desalination could be a game changer for some of the estimated 1 billion people who lack access to clean drinking water,” said Rice scientist and water treatment expert Qilin Li, a corresponding author on the study. “This off-grid technology is capable of providing sufficient clean water for family use in a compact footprint, and it can be scaled up to provide water for larger communities.”

The oldest method for making freshwater from salt water is distillation. Salt water is boiled, and the steam is captured and run through a condensing coil. Distillation has been used for centuries, but it requires complex infrastructure and is energy inefficient due to the amount of heat required to boil water and produce steam. More than half the cost of operating a water distillation plant is for energy.

An emerging technology for desalination is membrane distillation, where hot salt water is flowed across one side of a porous membrane and cold freshwater is flowed across the other. Water vapor is naturally drawn through the membrane from the hot to the cold side, and because the seawater need not be boiled, the energy requirements are less than they would be for traditional distillation. However, the energy costs are still significant because heat is continuously lost from the hot side of the membrane to the cold.

“Unlike traditional membrane distillation, NESMD benefits from increasing efficiency with scale,” said Rice’s Naomi Halas, a corresponding author on the paper and the leader of NEWT’s nanophotonics research efforts. “It requires minimal pumping energy for optimal distillate conversion, and there are a number of ways we can further optimize the technology to make it more productive and efficient.”

NEWT’s new technology builds upon research in Halas’ lab to create engineered nanoparticles that harvest as much as 80 percent of sunlight to generate steam. By adding low-cost, commercially available nanoparticles to a porous membrane, NEWT has essentially turned the membrane itself into a one-sided heating element that alone heats the water to drive membrane distillation.

“The integration of photothermal heating capabilities within a water purification membrane for direct, solar-driven desalination opens new opportunities in water purification,” said Yale University ‘s Menachem “Meny” Elimelech, a co-author of the new study and NEWT’s lead researcher for membrane processes.

In the PNAS study, researchers offered proof-of-concept results based on tests with an NESMD chamber about the size of three postage stamps and just a few millimeters thick. The distillation membrane in the chamber contained a specially designed top layer of carbon black nanoparticles infused into a porous polymer. The light-capturing nanoparticles heated the entire surface of the membrane when exposed to sunlight. A thin half-millimeter-thick layer of salt water flowed atop the carbon-black layer, and a cool freshwater stream flowed below.

Li, the leader of NEWT’s advanced treatment test beds at Rice, said the water production rate increased greatly by concentrating the sunlight. “The intensity got up 17.5 kilowatts per meter squared when a lens was used to concentrate sunlight by 25 times, and the water production increased to about 6 liters per meter squared per hour.”

Li said NEWT’s research team has already made a much larger system that contains a panel that is about 70 centimeters by 25 centimeters. Ultimately, she said, NEWT hopes to produce a modular system where users could order as many panels as they needed based on their daily water demands.

“You could assemble these together, just as you would the panels in a solar farm,” she said. “Depending on the water production rate you need, you could calculate how much membrane area you would need. For example, if you need 20 liters per hour, and the panels produce 6 liters per hour per square meter, you would order a little over 3 square meters of panels.”

Established by the National Science Foundation in 2015, NEWT aims to develop compact, mobile, off-grid water-treatment systems that can provide clean water to millions of people who lack it and make U.S. energy production more sustainable and cost-effective. NEWT, which is expected to leverage more than $40 million in federal and industrial support over the next decade, is the first NSF Engineering Research Center (ERC) in Houston and only the third in Texas since NSF began the ERC program in 1985. NEWT focuses on applications for humanitarian emergency response, rural water systems and wastewater treatment and reuse at remote sites, including both onshore and offshore drilling platforms for oil and gas exploration.

There is a video but it is focused on the NEWT center rather than any specific water technologies,

For anyone interested in the technology, here’s a link to and a citation for the researchers’ paper,

Nanophotonics-enabled solar membrane distillation for off-grid water purification by Pratiksha D. Dongare, Alessandro Alabastri, Seth Pedersen, Katherine R. Zodrow, Nathaniel J. Hogan, Oara Neumann, Jinjian Wu, Tianxiao Wang, Akshay Deshmukh,f, Menachem Elimelech, Qilin Li, Peter Nordlander, and Naomi J. Halas. PNAS {Proceedings of the National Academy of Sciences] doi: 10.1073/pnas.1701835114 June 19, 2017

This paper appears to be open access.

Sustainable water desalination with self-cleaning membranes

This desalination technology comes from the United Arab Emirates (UAE). from an April 13, 2017 news item on Nanowerk,

An advanced water treatment membrane made of electrically conductive nanofibers developed at Masdar Institute was highlighted by Dr. Raed Hashaikeh, Professor of Mechanical and Materials Engineering at Masdar Institute, in his keynote speech during the 3rd International Conference on Desalination using Membrane Technology held last week in Spain.

An April 13, 2017 Masdar Institute press release by Erica Solomon, which originated the news item, expands on the theme,

Self-cleaning membranes offer a critically needed solution to the problem of fouling, which is the unwanted build-up of organic and inorganic deposits on a membrane’s surface that reduces the membrane’s ability to filter impurities. Water treatment and purification membranes that can easily clean themselves when fouled could make pressure-driven membrane filtration systems used to treat and desalinate water more energy-efficient.

“Keeping membranes clean, permeable and functional is a great challenge to membrane desalination technologies. When a membrane becomes fouled, its pores get blocked and its flux is severely reduced, which means that much less water can pass through the membrane at a constant pressure,” Dr. Hashaikeh explained.

Conventional methods for cleaning fouled membranes involve expensive and harsh chemical treatments, and often lead to water treatment plant shut-downs, which can cost millions of dollars in lost operational hours. In the UAE, annual spending on desalination is already estimated to cost AED12 billion, indicating a pressing need for solutions that avoid costly shut-downs and treatments.

In addition to posing a heavy financial burden, fouled membranes are also a sustainability issue, as once a membrane becomes fouled, the higher pressure needed to push water through clogged pores significantly increases the plant’s energy consumption. The harsh chemicals used to clean a fouled membrane are also bad for the environment and require neutralizing. Thus, finding a way to easily and quickly clean fouled membranes not only makes financial sense, but environmental sense.

In a country like the UAE, where natural gas-powered thermal desalination produces over 80% of the country’s domestic water, innovative technologies like self-cleaning membranes to support a shift toward lower-energy and lower-cost membrane-based desalination are essential for achieving economic and environmental balance while meeting the UAE’s water demands.

And now, Dr. Hashaikeh’s research group may have brought the UAE closer towards realizing a more sustainable and economic approach to membrane desalination through their research on the application of advanced nanofibers for enhanced, self-cleaning membranes.

The group has leveraged the electrically conductive nature of a special kind of nanofiber, called carbon nanotubes (CNT). CNTs are tiny cylindrical tubes made of tightly bonded carbon atoms, measuring just one atom thick. But the CNTs Dr. Hashaikeh’s team used, which were provided by global security, aerospace, and information technology company Lockheed Martin, are not ordinary CNTs.

“The carbon nanostructures supplied by Lockheed Martin are special; they are networked. This means that they are composed of many interconnecting channels that branch off in all directions. This interconnectivity is what enables the entire membrane to become completely cleaned when electricity is applied to it,” Dr. Hashaikeh said.

The networked CNTs, also known as carbon nanostructures (CNS), coupled with the team’s expert membrane fabrication know-how, resulted in the development of two different types of membranes that can clean themselves when a low-voltage electric current is run through them.

The first type is a microfiltration membrane, which has pores sizes ranging from 100 nanometers to 10 micrometers, where a nanometer is approximately one hundred thousand times smaller than the width of a human hair and a micrometer one thousand times larger than a nanometer. The second is a nanofiltration membrane with pore sizes ranging from one to ten nanometers. Both membranes demonstrated the ability to clean themselves in response to an electric shock, which resulted in the immediate restoration of the membranes’ flux.

Dr. Hashaikeh’s investigation of a self-cleaning membrane began four years ago, when he realized that electrolytic cleaning – which is the process of removing soil, scale or corrosion from a metal’s surface by subjecting it to an electric current – could also be used to clean membranes. To prove his theory, he coated a membrane with ordinary CNTs. When a voltage was applied to the membrane, the parts of the membranes that were coated with CNTs were successfully cleaned. Dr. Hashaikeh filed a patent for this in-situ electrolytic cleaning process with the United States Patent and Trademark Office (USPTO) in 2014.

However, there were limitations to this discovery, namely that only specific areas in the coated CNTs were cleaned, not the entire membrane. Thus, to develop an efficient, self-cleaning membrane with commercial potential, Dr. Hashaikeh required a material that would easily allow electric shockwaves to penetrate through the entire membrane’s surface area.

The unique, interconnected structure of Lockheed Martin’s carbon nanostructures proved to be just the right type of electrically conductive, nano-fibrous material required.

“We immediately recognized that Lockheed Martin’s CNTs might enable electricity to pass through the entire surface, but we had to modify the nanostructures to transform the material into a membrane. To do this, we controlled certain properties, such as wettability and pore size, and improved its mechanical strength by incorporating polymer materials,” he explained.

Dr. Haishaikeh’s team successfully developed a self-cleaning microfiltration membrane in 2014 and a paper describing the research was published in the Journal of Membrane Science. But they did not stop there; they wanted to take their research a step further and find a way to develop a self-cleaning nanofiltration membrane. While microfiltration membranes are useful for removing larger particles, including sand, silt, clays, algae and some forms of bacteria, nanofiltration membranes can go a step further, removing most organic molecules, nearly all viruses, most of the natural organic matter and a range of salts. Nanofiltration membranes also remove divalent ions, which make water hard, making nanofiltration a popular and eco-friendly option to soften hard water.

To create self-cleaning nanofiltration membranes out of Lockheed Martin’s networked CNTs, the team needed to overcome the problem of the CNTs’ large pore sizes, which prevented the material from functioning as a nanofiltration membrane.

To achieve this they looked to a second advanced nanofiber material previously developed by Dr. Hashaikeh’s research group, known as networked cellulose. Networked cellulose is a modified type of cellulose made from wood pulp. When dried, the networked cellulose gel shrinks in volume, but maintains its integrity and shape, becoming harder as it shrinks. The research team asserted that the networked cellulose gel could reduce the membrane’s pore sizes while maintaining its structural integrity.

The researchers then mixed the carbon nanostructures with the networked cellulose gel and as the mixture dried, the networked cellulose shrank. The shrinking of the network cellulose in turn pressurized the nanostructures in the membrane. The resulting membrane is strong with much smaller pore sizes. Dr. Hashaikeh reports that the pore size dropped from 60 nanometers to just three nanometers with the addition of the networked cellulose in a paper describing the study, which was published in the journal Desalination last month. Co-authors from Masdar Institute include PhD student Farah Ahmad and postdoctoral researcher Boor Lalia, along with Dr. Nidal Hilal of Swansea University.

Dr. Hashaikeh’s prolific scientific contribution to the field of membrane desalination has led to his recent appointment as an associate editor for the journal Desalination; a position that is essential to the quality of the international journal and its peer review process.

The innovative research conducted by Dr. Hashaikeh and the team will help position Abu Dhabi as a leader in membrane desalination research and technology development. This project has already yielded a patent filing, and is hoped to provide the emirate with novel intellectual property in the critical industry of desalination.

Here are the links and citations for the 2014 and 2017 papers,

A novel in situ membrane cleaning method using periodic electrolysis by Raed Hashaikeh, Boor Singh Lalia, Victor Kochkodan, Nidal Hilal. Journal of Membrane Science Volume 471, 1 December 2014, Pages 149–154 https://doi.org/10.1016/j.memsci.2014.08.017

Electrically conducting nanofiltration membranes based on networked cellulose and carbon nanostructures by Farah Ejaz Ahmed, Boor Singh Lalia, Nidal Hilal, Raed Hashaikeh. Desalination Volume 406, 16 March 2017, Pages 60–66 https://doi.org/10.1016/j.desal.2016.09.005

Both papers a behind a paywall.

‘Hunting’ pharmaceuticals and removing them from water

Pharmaceuticals are not the first pollutants people think of when discussing water pollution but, for those who don’t know, it’s a big issue and scientists at the University of Surrey (UK) have developed a technology they believe will help to relieve the contamination. From an April 10, 2017 University of Surrey press release (also on EurekAlert),

The research involves the detection and removal of pharmaceuticals in or from water, as contamination from pharmaceuticals can enter the aquatic environment as a result of their use for the treatment of humans and animals. This contamination can be excreted unchanged, as metabolites, as unused discharge or by drug manufacturers.

The research has found that a new type of ‘supermolecule’, calix[4], actively seeks certain pharmaceuticals and removes them from water.

Contamination of water is a serious concern for environmental scientists around the world, as substances include hormones from the contraceptive pill, and pesticides and herbicides from allotments. Contamination can also include toxic metals such as mercury, arsenic, or cadmium, which was previously used in paint, or substances that endanger vital species such as bees.

Professor Danil de Namor, University of Surrey Emeritus Professor and leader of the research, said: “Preliminary extraction data are encouraging as far as the use of this receptor for the selective removal of these drugs from water and the possibility of constructing a calix[4]-based sensing devices.

“From here, we can design receptors so that they can bind selectively with pollutants in the water so the pollutants can be effectively removed. This research will allow us to know exactly what is in the water, and from here it will be tested in industrial water supplies, so there will be cleaner water for everyone.

“The research also creates the possibility of using these materials for on-site monitoring of water, without having to transport samples to the laboratory.”

Dr Brendan Howlin, University of Surrey co-investigator, said: “This study allows us to visualise the specific receptor-drug interactions leading to the selective behaviour of the receptor. As well as the health benefits of this research, molecular simulation is a powerful technique that is applicable to a wide range of materials.

“We were very proud that the work was carried out with PhD students and a final year project student, and research activities are already taking place with the Department of Chemical and Processing Engineering (CPI) and the Advanced Technology Institute (ATI).

“We are also very pleased to see that as soon as the paper was published online by the European Journal of Pharmaceutical Sciences, we received invitations to give keynote lectures at two international conferences on pharmaceuticals in Europe later this year.”

That last paragraph is intriguing and it marks the first time I’ve seen that claim in a press release announcing the publication of a piece of research.

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

A calix[4]arene derivative and its selective interaction with drugs (clofibric acid, diclofenac and aspirin) by Angela F Danil de Namor, Maan Al Nuaim, Jose A Villanueva Salas, Sophie Bryant, Brendan Howlin. European Journal of Pharmaceutical Sciences Volume 100, 30 March 2017, Pages 1–8 https://doi.org/10.1016/j.ejps.2016.12.027

This paper is behind a paywall.

Edible water bottles by Ooho!

Courtesy: Skipping Rocks Lab

As far as I’m concerned, that looks more like a breast implant than a water bottle, which, from a psycho-social perspective, could lead to some interesting research papers. It is, in fact a new type of water bottle.  From an April 10, 2017 article by Adele Peters for Fast Company (Note: Links have been removed),

If you run in a race in London in the near future and pass a hydration station, you may be handed a small, bubble-like sphere of water instead of a bottle. The gelatinous packaging, called the Ooho, is compostable–or even edible, if you want to swallow it. And after two years of development, its designers are ready to bring it to market.

Three London-based design students first created a prototype of the edible bottle in 2014 as an alternative to plastic bottles. The idea gained internet hype (though also some scorn for a hilarious video that made the early prototypes look fairly impossible to use without soaking yourself).
The problem it was designed to solve–the number of disposable bottles in landfills–keeps growing. In the U.K. alone, around 16 million are trashed each day; another 19 million are recycled, but still have the environmental footprint of a product made from oil. In the U.S., recycling rates are even lower. …

The new packaging is based on the culinary technique of spherification, which is also used to make fake caviar and the tiny juice balls added to boba tea [bubble tea?]. Dip a ball of ice in calcium chloride and brown algae extract, and you can form a spherical membrane that keeps holding the ice as it melts and returns to room temperature.

An April 25, 2014 article by Kashmira Gander for Independent.co.uk describes the technology and some of the problems that had to be solved before bringing this product to market,

To make the bottle [Ooho!], students at the Imperial College London gave a frozen ball of water a gelatinous layer by dipping it into a calcium chloride solution.

They then soaked the ball in another solution made from brown algae extract to encapsulate the ice in a second membrane, and reinforce the structure.

However, Ooho still has teething problems, as the membrane is only as thick as a fruit skin, and therefore makes transporting the object more difficult than a regular bottle of water.

“This is a problem we’re trying to address with a double container,” Rodrigo García González, who created Ooho with fellow students Pierre Paslier and Guillaume Couche, explained to the Smithsonian. “The idea is that we can pack several individual edible Oohos into a bigger Ooho container [to make] a thicker and more resistant membrane.”

According to Peters’ Fast Company article, the issues have been resolved,

Because the membrane is made from food ingredients, you can eat it instead of throwing it away. The Jell-O-like packaging doesn’t have a natural taste, but it’s possible to add flavors to make it more appetizing.

The package doesn’t have to be eaten every time, since it’s also compostable. “When people try it for the first time, they want to eat it because it’s part of the experience,” says Pierre Paslier, cofounder of Skipping Rocks Lab, the startup developing the packaging. “Then it will be just like the peel of a fruit. You’re not expected to eat the peel of your orange or banana. We are trying to follow the example set by nature for packaging.”

The outer layer of the package is always meant to be peeled like fruit–one thin outer layer of the membrane peels away to keep the inner layer clean and can then be composted. (While compostable cups are an alternative solution, many can only be composted in industrial facilities; the Ooho can be tossed on a simple home compost pile, where it will decompose within weeks).

The company is targeting both outdoor events and cafes. “Where we see a lot of potential for Ooho is outdoor events–festivals, marathons, places where basically there are a lot of people consuming packaging over a very short amount of time,” says Paslier.

I encourage you to read Peters’ article in its entirety if you have the time. You can also find more information on the Skipping Rocks Lab website and on the company’s crowdfunding campaign on CrowdCube.

Cleaning wastewater with fruit peel

A March 23, 2017 news item on phys.org announces a water purification process based on fruit peel,’

A collaborative of researchers has developed a process to clean water containing heavy metals and organic pollutants using a new adsorbent material made from the peels of oranges and grapefruits.

A March 23, 2017 University of Granada press release explains more about the research (Note: Links have been removed),

Researchers from the University of Granada (UGR), and from the Center for Electrochemical Research and Technological Development (Centro de Investigación y Desarrollo Tecnológico en Electroquímica, CIDETEQ) and the Center of Engineering and Industrial Development (Centro de Ingeniería y Desarrollo Industrial, CIDESI), both in Mexico, have developed a process that allows to clean waters containing heavy metals and organic compounds considered pollutants, using a new adsorbent material made from the peels of fruits such as oranges and grapefruits.

Said peels are residues which pose a problem for the food industry, given that they take up a great volume and aren’t very useful nowadays. 38.2 million tons of said fruit peels are estimated to be produced worldwide each year in the food industry.

The research, in which the UGR participates, has served for designing a new process by which, thanks to an Instant Controlled Pressure Drop treatment, it is possible to modify the structure of said residues, giving them adsorbent properties such as a greater porosity and surface area.

Researcher Luis Alberto Romero Cano, from the Carbon Materials Research Team (Grupo de Investigación en Materiales de Carbón) at the Faculty of Science, UGR, explains that, by a subsequent chemical treatment, they “have managed to add functional groups to the material, thus making it selective in order to remove metals and organic pollutants present in water”.

A subsequent research carried out by the authors of this paper has showed that it is possible to pack those new materials in fixed bed columns, in a way similar to a filter by which wastewater runs on a constant flux process, like the usual wastewater treatments. This laboratory-scale study has allowed to obtain parameters to design a large-scale use of said materials.

“The results show a great potential for the use of said materials as adsorbents capable of competing with commercial activated carbon for the adsorption and recovery of metals present in wastewater, in a way that it could be possible to carry out sustainable processes in which products with a great commercial value could be obtained from food industry residues”, Romero Cano says.

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

Biosorbents prepared from orange peels using Instant Controlled Pressure Drop for Cu(II) and phenol removal by Luis A. Romero-Cano, Linda V. Gonzalez-Gutierrez, Leonardo A. Baldenegro-Perez. Industrial Crops and Products Volume 84, June 2016, Pages 344–349  http://dx.doi.org/10.1016/j.indcrop.2016.02.027

I’m not sure why they decided to promote this research so long after it was published but I’m glad they did. It’s always good to see work designed to make use of what is currently waste. By the way, this paper is behind a paywall.

Using a sponge to remove mercury from lake water

I’ve heard of Lake Como in Italy but Como Lake in Minnesota is a new one for me. The Minnesota lake is featured in a March 22, 2017 news item about water and sponges on phys.org,

Mercury is very toxic and can cause long-term health damage, but removing it from water is challenging. To address this growing problem, University of Minnesota College of Food, Agricultural and Natural Sciences (CFANS) Professor Abdennour Abbas and his lab team created a sponge that can absorb mercury from a polluted water source within seconds. Thanks to the application of nanotechnology, the team developed a sponge with outstanding mercury adsorption properties where mercury contaminations can be removed from tap, lake and industrial wastewater to below detectable limits in less than 5 seconds (or around 5 minutes for industrial wastewater). The sponge converts the contamination into a non-toxic complex so it can be disposed of in a landfill after use. The sponge also kills bacterial and fungal microbes.

Think of it this way: If Como Lake in St. Paul was contaminated with mercury at the EPA limit, the sponge needed to remove all of the mercury would be the size of a basketball.

A March 16, 2017 University of Minnesota news release, which originated the news item, explains why this discovery is important for water supplies in the state of Minnesota,

This is an important advancement for the state of Minnesota, as more than two thirds of the waters on Minnesota’s 2004 Impaired Waters List are impaired because of mercury contamination that ranges from 0.27 to 12.43 ng/L (the EPA limit is 2 ng/L). Mercury contamination of lake waters results in mercury accumulation in fish, leading the Minnesota Department of Health to establish fish consumption guidelines. A number of fish species store-bought or caught in Minnesota lakes are not advised for consumption more than once a week or even once a month. In Minnesota’s North Shore, 10 percent of tested newborns had mercury concentrations above the EPA reference dose for methylmercury (the form of mercury found in fish). This means that some pregnant women in the Lake Superior region, and in Minnesota, have mercury exposures that need to be reduced.  In addition, a reduced deposition of mercury is projected to have economic benefits reflected by an annual state willingness-to-pay of $212 million in Minnesota alone.

According to the US-EPA, cutting mercury emissions to the latest established effluent limit standards would result in 130,000 fewer asthma attacks, 4,700 fewer heart attacks, and 11,000 fewer premature deaths each year. That adds up to at least $37 billion to $90 billion in annual monetized benefits annually.

In addition to improving air and water quality, aquatic life and public health, the new technology would have an impact on inspiring new regulations. Technology shapes regulations, which in turn determine the value of the market. The 2015 EPA Mercury and Air Toxics Standards regulation was estimated to cost the industry around of $9.6 billion annually in 2020. The new U of M technology has a potential of bringing this cost down and make it easy for the industry to meet regulatory requirements.

Research by Abbas and his team was funded by the MnDRIVE Global Food Venture, MnDRIVE Environment, and USDA-NIFA. They currently have three patents on this technology. To learn more, visit www.abbaslab.com.

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

A Nanoselenium Sponge for Instantaneous Mercury Removal to Undetectable Levels by Snober Ahmed, John Brockgreitens, Ke Xu, and Abdennour Abbas. Advanced Functional Materials DOI: 10.1002/adfm.201606572 Version of Record online: 6 MAR 2017

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Desalination of sea water with a graphene sieve

The proposed use of graphene membranes for water purification and remediation isn’t new (I have a July 20, 2015 posting which covers some of this field of interest). However, there’s this April 3, 2017 news item on ScienceDaily announcing some new work on graphene and desalination at the University of Manchester,

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.

An April 3, 2017 University of Manchester press release (also on EurekAlert), which originated the news item, expands on the theme,

Graphene-oxide membranes developed at the National Graphene Institute have already demonstrated the potential of filtering out small nanoparticles, organic molecules, and even large salts. Until now, however, they couldn’t be used for sieving common salts used in desalination technologies, which require even smaller sieves.

Previous research at The University of Manchester found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger ions or molecules are blocked.

The Manchester-based group have now further developed these graphene membranes and found a strategy to avoid the swelling of the membrane when exposed to water. The pore size in the membrane can be precisely controlled which can sieve common salts out of salty water and make it safe to drink.

As the effects of climate change continue to reduce modern city’s water supplies, wealthy modern countries are also investing in desalination technologies. Following the severe floods in California major wealthy cities are also looking increasingly to alternative water solutions.

When the common salts are dissolved in water, they always form a ‘shell’ of water molecules around the salts molecules. This allows the tiny capillaries of the graphene-oxide membranes to block the salt from flowing along with the water. Water molecules are able to pass through the membrane barrier and flow anomalously fast which is ideal for application of these membranes for desalination.

Professor Rahul Nair, at The University of Manchester said: “Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology.

“This is the first clear-cut experiment in this regime. We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes.”

Mr. Jijo Abraham and Dr. Vasu Siddeswara Kalangi were the joint-lead authors on the research paper: “The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration capable of filtering out ions according to their sizes.” said Mr. Abraham.

By 2025 the UN expects that 14% of the world’s population will encounter water scarcity. This technology has the potential to revolutionise water filtration across the world, in particular in countries which cannot afford large scale desalination plants.

It is hoped that graphene-oxide membrane systems can be built on smaller scales making this technology accessible to countries which do not have the financial infrastructure to fund large plants without compromising the yield of fresh water produced.

Courtesy of the University of Manchester

I believe the previous image is an artist’s rendering of the graphene-oxide membrane trapping salt as water moves through it.

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

Tunable sieving of ions using graphene oxide membranes by Jijo Abraham, Kalangi S. Vasu, Christopher D. Williams, Kalon Gopinadhan, Yang Su, Christie T. Cherian, James Dix, Eric Prestat, Sarah J. Haigh, Irina V. Grigorieva, Paola Carbone, Andre K. Geim, & Rahul R. Nair. Nature Nanotechnology (2017) doi:10.1038/nnano.2017.21 Published online 03 April 2017

This paper is open access provided you sign up (or have already signed up) for a free registration with nature.com.

Understanding nanotechnology with Timbits; a peculiarly Canadian explanation

For the uninitiated, Timbits are also known as donut holes. Tim Hortons, founded by ex-National Hockey League player Tim Horton who has since deceased, has taken hold in the Canada’s language and culture such that one of our scientists trying to to explain nanotechnology thought it would be best understood in terms of Timbits. From a Jan. 14, 2017 article (How nanotechnology could change our lives) by Vanessa Lu for thestar.com,

The future is all in the tiny.

Known as nanoparticles, these are the tiniest particles, so small that we can’t see them or even imagine how small they are.

University of Waterloo’s Frank Gu paints a picture of their scale.

“Take a Timbit and start slicing it into smaller and smaller pieces, so small that every Canadian — about 35 million of us — can hold a piece of the treat,” he said. “And those tiny pieces are still a little bigger than a nanoparticle.”

For years, consumers have seen the benefits of nanotechnology in everything from shrinking cellphones to ultrathin televisions. Apple’s iPhones have become more powerful as they have become smaller — where a chip now holds billions of transistors.

“As you go smaller, it creates less footprint and more power,” said Gu, who holds the Canada research chair in advanced targeted delivery systems. “FaceTime, Skype — they are all powered by nanotechnology, with their retina display.”

Lu wrote a second January 14, 2017 article (Researchers developing nanoparticles to purify water) for thestar.com,

When scientists go with their gut or act on a hunch, it can pay off.

For Tim Leshuk, a PhD student in nanotechnology at the University of Waterloo, he knew it was a long shot.

Leshuk had been working with Frank Gu, who leads a nanotechnology research group, on using tiny nanoparticles that have been tweaked with certain properties to purify contaminated water.

Leshuk was working on the process, treating dirty water such as that found in Alberta’s oilsands, with the nanoparticles combined with ultraviolet light. He wondered what might happen if exposed to actual sunlight.

“I didn’t have high hopes,” he said. “For the heck of it, I took some beakers out and put them on the roof. And when I came back, it was far more effective that we had seen with regular UV light.

“It was high-fives all around,” Leshuk said. “It’s not like a Brita filter or a sponge that just soaks up pollutants. It completely breaks them down.”

Things are accelerating quickly, with a spinoff company now formally created called H2nanO, with more ongoing tests scheduled. The research has drawn attention from oilsands companies, and [a] large pre-pilot project to be funded by the Canadian Oil Sands Innovation Alliance is due to get under way soon.

The excitement comes because it’s an entirely green process, converting solar energy for cleanup, and the nanoparticle material is reuseable, over and over.

It’s good to see a couple of articles about nanotechnology. The work by Tim Leshuk was highlighted here in a Dec. 1, 2015 posting titled:  New photocatalytic approach to cleaning wastewater from oil sands. I see the company wasn’t mentioned in the posting so, it must be new; you can find H2nanO here.

Discussion of a divisive topic: the Oilsands

As for the oilsands, it’s been an interesting few days with the Prime Minister’s (Justin Trudeau) suggestion that dependence would be phased out causing a furor of sorts. From a Jan. 13, 2017 article by James Wood for the Calgary Herald,

Prime Minister Justin Trudeau’s musings about phasing out the oilsands Friday [Jan. 13, 2017] were met with a barrage of criticism from Alberta’s conservative politicians and a pledge from Premier Rachel Notley that the province’s energy industry was “not going anywhere, any time soon.”

Asked at a town hall event in Peterborough [Ontario] about the federal government’s recent approval of Kinder Morgan’s Trans Mountain pipeline expansion, Trudeau reiterated his longstanding remarks that he is attempting to balance economic and environmental concerns.

“We can’t shut down the oilsands tomorrow. We need to phase them out. We need to manage the transition off of our dependence on fossil fuels but it’s going to take time and in the meantime we have to manage that transition,” he added.

Northern Alberta’s oilsands are a prime target for environmentalists because of their significant output of greenhouse gas emissions linked to global climate change.

Trudeau, who will be in Calgary for a cabinet retreat on Jan. 23 and 24 [2017], also said again that it is the responsibility of the national government to get Canadian resources to market.

Meanwhile, Jane Fonda, Hollywood actress, weighed in on the issue of the Alberta oilsands with this (from a Jan. 11, 2017 article by Tristan Hopper for the National Post),

Fort McMurrayites might have assumed the celebrity visits would stop after the city was swept first by recession, and then by wildfire.

Or when the provincial government introduced a carbon tax and started phasing out coal.

And surely, with Donald Trump in the White House, even the oiliest corner of Canada would shift to the activist back burner.

But no; here comes Jane Fonda.

“We don’t need new pipelines,” she told a Wednesday [Jan. 11, 2017] press conference at the University of Alberta where she also dismissed Prime Minister Justin Trudeau as a “good-looking Liberal” who couldn’t be trusted.

Saying that her voice was joined with the “Indigenous people of Canada,” Fonda explained her trip to Alberta by saying “when you’re famous you can help amplify the voices of people that can’t necessarily get a lot of press people to come out.”

Fonda is in Alberta at the invitation of Greenpeace, which has brought her here in support of the Treaty Alliance Against Tar Sands Expansion — a group of Canadian First Nations and U.S. tribes opposed to new pipelines to the Athabasca oilsands.

Appearing alongside Fonda, at a table with a sign reading “Respect Indigenous Decisions,” was Grand Chief Stewart Phillip, who, as leader of the Union of B.C. Indian Chiefs, has led anti-pipeline protests and litigation in British Columbia.

“The future is going to be incredibly litigious,” he said in reference to the approved expansion of the Trans-Mountain pipeline.

The event also included Grand Chief Derek Nepinak of the Assembly of Manitoba Chiefs, which is leading a legal challenge to federal approval of the Line 3 pipeline.

Although much of Athabasca’s oil production now comes from “steam-assisted gravity drainage” projects that requires minimal surface disturbance, on Tuesday Fonda took the requisite helicopter tour of a Fort McMurray-area open pit mine.

As you can see, there are not going to be any easy answers.