Tiny Membrane Key to Safe Drinking Water

Date: February 14, 2018
Source: CSIRO Australia
Summary: Using their own specially designed form of graphene, 'Graphair' scientists have supercharged water purification, making it simpler, more effective and quicker.

Sydney's iconic harbour has played a starring role in the development of new CSIRO technology that could save lives around the world.

Using their own specially designed form of graphene, 'Graphair', CSIRO scientists have supercharged water purification, making it simpler, more effective and quicker.

The new filtering technique is so effective, water samples from Sydney Harbour were safe to drink after passing through the filter.

The breakthrough research was published today in Nature Communications.

"Almost a third of the world's population, some 2.1 billion people, don't have clean and safe drinking water," the paper's lead author, CSIRO scientist Dr Dong Han Seo said.

"As a result, millions -- mostly children -- die from diseases associated with inadequate water supply, sanitation and hygiene every year.

"In Graphair we've found a perfect filter for water purification. It can replace the complex, time consuming and multi-stage processes currently needed with a single step."

While graphene is the world's strongest material and can be just a single carbon atom thin, it is usually water repellent.

Using their Graphair process, CSIRO researchers were able to create a film with microscopic nano-channels that let water pass through, but stop pollutants.

As an added advantage Graphair is simpler, cheaper, faster and more environmentally friendly than graphene to make.

It consists of renewable soybean oil, more commonly found in vegetable oil.

Looking for a challenge, Dr Seo and his colleagues took water samples from Sydney Harbour and ran it through a commercially available water filter, coated with Graphair.

Researchers from QUT, the University of Sydney, UTS, and Victoria University then tested and analysed its water purification qualities.

The breakthrough potentially solves one of the great problems with current water filtering methods: fouling.

Over time chemical and oil based pollutants coat and impede water filters, meaning contaminants have to be removed before filtering can begin. Tests showed Graphair continued to work even when coated with pollutants.

Without Graphair, the membrane's filtration rate halved in 72 hours.

When the Graphair was added, the membrane filtered even more contaminants (99 per cent removal) faster.

"This technology can create clean drinking water, regardless of how dirty it is, in a single step," Dr Seo said.

"All that's needed is heat, our graphene, a membrane filter and a small water pump. We're hoping to commence field trials in a developing world community next year."

CSIRO is looking for industry partners to scale up the technology so it can be used to filter a home or even town's water supply.

It's also investigating other applications such as the treatment of seawater and industrial effluents.

Story Source: CSIRO Australia. "Tiny membrane key to safe drinking water." ScienceDaily. ScienceDaily, 14 February 2018. https://www.sciencedaily.com/releases/2018/02/180214181846.htm.

Bacteria, Graphene and Nanotech Produce Usable Electricity From Wastewater

Check out the kitchen timer counting down in the gif above. There’s nothing special about it except for how it is being powered. The instrument isn’t equipped with batteries. In fact, its electricity comes from the vial behind it, where bacteria are eating organic matter in wastewater and producing electricity as a result.

It’s the first time that researchers have produced enough electricity for practical use from what are called microbial fuel cells. Scientists in China reported their breakthrough late last week in the journal Science Advances. Their work could one day help provide the huge amounts of power needed to treat wastewater, a process that currently consumes up to 5 percent of all the electricity produced in the U.S.

For a while now, researchers have been investigating the bacterium Shewanella oneidensis, which naturally targets heavy metal ions and other pollutants in wastewater as a source of energy. The bacterium reduces these materials as a way to power its own metabolism, meanwhile converting them into less harmful derivatives. Engineers have figured out how to tap S. oneidensis’s to start harvesting the current for human use, but so far they haven’t been able to get enough out of the reaction because of technological limitations to do anything useful.

Shenlong Zhao and colleagues focused their work not on the bacterium, but on the material part of the battery that collects the electrons the microbe harvests. They worked out a better electrode made of a three-dimensional graphene aerogel decorated with platinum nanoparticles. The aerogel’s complex pores allows the microbe to colonize throughout it, maximizing the density of cells. The platinum nanoparticles, meanwhile, improve the material’s conductivity while also creating an environment more amenable to the organism’s survival.

The power output is enough for two of the vial-sized microbial fuel cells to power the kitchen timer. Meanwhile, tests with the fuel cells running on wastewater retrieved from a Beijing treatment plant indicated that real-world municipal wastewater could be used to produce electricity. Zhao’s team are now setting their sights on scaling up their preliminary work into larger applications.

Top gif: Digital photo of microbial fuel cells driving a timer. The two single biofuel cells have been assembled in series and successfully run a timer, strongly exemplifying that the graphene aerogel/platinum nanoparticle anode enables the superior performance and the actual application potential. Video and caption courtesy of Zhao et al./Science Advances.

Source: http://txchnologist.com/post/133351599065/bacteria-graphene-and-nanotech-produce-usable

Structure of 'Concrete Disease' Solved

Previously undocumented sheet-silicate crystal structure

Date: November 5, 2015
Source: Swiss Federal Laboratories for Materials Science and Technology (EMPA)
Summary: When bridges, dam walls and other structures made of concrete are streaked with dark cracks after a few decades, the culprit is AAR: the alkali-aggregate reaction. AAR damages concrete structures all over the world and makes complex renovations or reconstructions necessary. Researchers have now solved the structure of the material produced in the course of AAR at atomic Level.


Researchers from the Paul Scherrer Institute (PSI) teamed up with colleagues from the Swiss Materials Science Lab Empa to study a degenerative sign of ageing in concrete: the so-called alkali-aggregate reaction (AAR). In the course of AAR, a material forms that takes up more space than the original concrete and thus gradually cracks the concrete from within as the decades go by.

The researchers have now explored the exact structure of this material. They managed to demonstrate that its atoms are arranged extremely regularly, making it a crystal. They also showed that the structure of this crystal is a so-called sheet-silicate structure. This specific structure had never been observed before. The researchers made their discovery thanks to measurements at the Swiss Light Source SLS at PSI. The research results could help towards the development of more durable concrete in future.

A Global Problem

AAR is a chemical reaction that affects outdoor concrete structures all over the world. It happens when concrete is exposed to water or moisture. For instance, numerous bridges and up to twenty per cent of the dam walls in Switzerland are affected by AAR. With AAR, the basic ingredients in the concrete are actually the problem: cement -- the main component of concrete -- contains alkali metals such as sodium and potassium. Any moisture infiltrating the concrete -- stemming for example from rainwater -- reacts with these alkali metals, leading to an alkaline solution.

The second main ingredient in concrete is sand and gravel, which in turn are composed of minerals, such as quartz or feldspar. Chemically speaking, these minerals are so-called silicates. The alkaline water reacts with these silicates and forms a so-called alkali calcium silicate hydrate. This is itself able to absorb more moisture, which causes it to expand and gradually crack the concrete from within. This entire process is referred to as AAR.

AAR takes place extremely slowly, so that the cracks are initially only tiny and invisible to the naked eye. Over the course of three or four decades, however, the cracks widen significantly and eventually jeopardise the durability of the entire concrete structure.

A New Crystal

Even if the chemical processes involved in AAR have long been known, nobody had identified the physical structure of the alkali calcium silicate hydrate formed in the course of AAR. The researchers at PSI and Empa have now managed to fill this knowledge gap. They studied the substance of a Swiss bridge constructed in 1969, which has been affected heavily by AAR. Researchers from Empa cut out a material sample from the bridge and ground down a small piece of it until they were left with a wafer-thin sample that was merely 0.02 millimetres thick. The sample was then taken to the Swiss Light Source SLS and irradiated with an extremely narrow x-ray beam, fifty times thinner than a human hair. Performing so-called diffraction measurements and a complex data analysis, the PSI researchers were eventually able to determine the crystal structure of the material with pinpoint precision.

They found that the alkali calcium silicate hydrate has a previously undocumented sheet-silicate crystal structure. "Normally, discovering an uncatalogued crystal structure means you get to name it," explains Rainer Dähn, the first author of the study. "But it has to be a crystal found in nature, therefore we didn't get that honour," says the researcher with a smile. Andreas Leemann, Head of the Concrete Technology Group at Empa, had the idea for the current study. The researchers from PSI then brought their knowledge of the x-ray beam method to the table. "In principle, it's possible to add organic materials to the concrete that are able to reduce the build-up of tension," explains materials scientist Leemann. "Our new results provide a scientific basis for these considerations and could pave the way for the development of new materials.

Story Source: Swiss Federal Laboratories for Materials Science and Technology (EMPA). "Structure of 'concrete disease' solved: Previously undocumented sheet-silicate crystal structure." ScienceDaily. ScienceDaily, 5 November 2015. .

Wonder-Material Graphene Could be Dangerous to Humans and the Environment

Jacob D Lanphere, a Ph.D. student at UC Riverside, holds a sample of graphene oxide.

People have been waiting for some time to write a headline along the lines of "scientists discover thing that graphene is not amazing at" ... and here it is. Everybody's favorite nanomaterial may have a plethora of near-magical properties, but as it turns out, it could also be bad for the environment – and bad for you, too.

It's easy to get carried away when you start talking about graphene. Comprised of single atom thick layers of carbon, graphene is incredibly light, incredibly strong, extremely flexible and highly conductive both of heat and electricity. Its properties hold the promise of outright technological revolution in so many fields that it has been called a wonder material.

But it's only been 10 years since graphene was first isolated in the laboratory, and as researchers and industries scramble to bring graphene out of the lab and into a vast range of commercial applications, far less money is being spent examining its potential negative effects.

Two recent studies give us a less than rosy angle. In the first, a team of biologists, engineers and material scientists at Brown University examined graphene's potential toxicity in human cells. They found that the jagged edges of graphene nanoparticles, super sharp and super strong, easily pierced through cell membranes in human lung, skin and immune cells, suggesting the potential to do serious damage in humans and other animals.

"These materials can be inhaled unintentionally, or they may be intentionally injected or implanted as components of new biomedical technologies," said Robert Hurt, professor of engineering and one of the study's authors. "So we want to understand how they interact with cells once inside the body."

Another study by a team from University of California, Riverside's Bourns College of Engineering examined how graphene oxide nanoparticles might interact with the environment if they found their way into surface or ground water sources.

The team found that in groundwater sources, where there's little organic material and the water has a higher degree of hardness, graphene oxide nanoparticles tended to become less stable and would eventually settle out or be removed in sub-surface environments.

But in surface water such as lakes or rivers, where there's more organic material and less hardness, the particles stayed much more stable and showed a tendency to travel further, particularly under the surface.

So a spill of these kinds of nanoparticles would appear to have the potential to cause harm to organic matter, plants, fish, animals, and humans. The affected area could be quick to spread, and could take some time to become safe again.

"The situation today is similar to where we were with chemicals and pharmaceuticals 30 years ago," said the paper's co-author Jacob D. Lanphere. "We just don't know much about what happens when these engineered nanomaterials get into the ground or water. So we have to be proactive so we have the data available to promote sustainable applications of this technology in the future."

At this stage, the Material Safety Data Sheet governing the industrial use of graphene is incomplete. It's listed as a potential irritant of skin and eyes, and potentially hazardous to breathe in or ingest. No information is available on whether it has carcinogenic effects or potential developmental toxicity.

But researchers from the first study point out that this is a material in its infancy, and as a man-made material, there are opportunities at this early stage to examine and understand the potential harmful properties of graphene and try to engineer them out. We've got a few years yet before graphene really starts being a big presence in our lives, so the challenge is set to work out how to make it as safe as possible for ourselves and our planet.

Source: http://ucrtoday.ucr.edu/22044