Category Archives: water

Algae outbreaks (dead zones) in wetlands and waterways

It’s been over seven years since I first started writing about Duke University’s  Center for the Environmental Implications of Nanotechnology and mesocosms (miniature ecosystems) and the impact that nanoparticles may have on plants and water (see August 11, 2011 posting). Since then, their focus has shifted from silver nanoparticles and their impact on plants, fish, bacteria, etc. to a more general examination of metallic nanoparticles and water. A June 25, 2018 news item on ScienceDaily announces some of their latest work,

The last 10 years have seen a surge in the use of tiny substances called nanomaterials in agrochemicals like pesticides and fungicides. The idea is to provide more disease protection and better yields for crops, while decreasing the amount of toxins sprayed on agricultural fields.

But when combined with nutrient runoff from fertilized cropland and manure-filled pastures, these “nanopesticides” could also mean more toxic algae outbreaks for nearby streams, lakes and wetlands, a new study finds.

A June 25, 2018 Duke University news release (also on EurekAlert) by Robin A. Smith, which originated the news item, provides more detail,

Too small to see with all but the most powerful microscopes, engineered nanomaterials are substances manufactured to be less than 100 nanometers in diameter, many times smaller than a hair’s breadth.

Their nano-scale gives them different chemical and physical properties from their bulk counterparts, including more surface area for reactions and interactions.

Those interactions could intensify harmful algal blooms in wetlands, according to experiments led by Marie Simonin, a postdoctoral associate with biology professor Emily Bernhardt at Duke University.

Carbon nanotubes and teeny tiny particles of silver, titanium dioxide and other metals are already added to hundreds of commercial products to make everything from faster, lighter electronics, self-cleaning fabrics, and smarter food packaging that can monitor food for spoilage. They are also used on farms for slow- or controlled-release plant fertilizers and pesticides and more targeted delivery, and because they are effective at lower doses than conventional products.

These and other applications have generated tremendous interest and investment in nanomaterials. However the potential risks to human health or the environment aren’t fully understood, Simonin said.

Most of the 260,000 to 309,000 metric tons of nanomaterials produced worldwide each year are eventually disposed in landfills, according to a previous study. But of the remainder, up to 80,400 metric tons per year are released into soils, and up to 29,200 metric tons end up in natural bodies of water.

“And these emerging contaminants don’t end up in water bodies alone,” Simonin said. “They probably co-occur with nutrient runoff. There are likely multiple stressors interacting.”

Algae outbreaks already plague polluted waters worldwide, said Steven Anderson, a research analyst in the Bernhardt Lab at Duke and one of the authors of the research.

Nitrogen and phosphorous pollution makes its way into wetlands and waterways in the form of agricultural runoff and untreated wastewater. The excessive nutrients cause algae to grow out of control, creating a thick mat of green scum or slime on the surface of the water that blocks sunlight from reaching other plants.

These nutrient-fueled “blooms” eventually reduce oxygen levels to the point where fish and other organisms can’t survive, creating dead zones in the water. Some algal blooms also release toxins that can make pets and people who swallow them sick.

To find out how the combined effects of nutrient runoff and nanoparticle contamination would affect this process, called eutrophication, the researchers set up 18 separate 250-liter tanks with sandy sloped bottoms to mimic small wetlands.

Each open-air tank was filled with water, soil and a variety of wetland plants and animals such as waterweed and mosquitofish.

Over the course of the nine-month experiment, some tanks got a weekly dose of algae-promoting nitrates and phosphates like those found in fertilizers, some tanks got nanoparticles — either copper or gold — and some tanks got both.

Along the way the researchers monitored water chemistry, plant and algae growth and metabolism, and nanoparticle accumulation in plant tissues.

“The results were surprising,” Simonin said. The nanoparticles had tiny effects individually, but when added together with nutrients, even low concentrations of gold and copper nanoparticles used in fungicides and other products turned the once-clear water a murky pea soup color, its surface covered with bright green smelly mats of floating algae.

Over the course of the experiment, big algal blooms were more than three times more frequent and more persistent in tanks where nanoparticles and nutrients were added together than where nutrients were added alone. The algae overgrowths also reduced dissolved oxygen in the water.

It’s not clear yet how nanoparticle exposure shifts the delicate balance between plants and algae as they compete for nutrients and other resources. But the results suggest that nanoparticles and other “metal-based synthetic chemicals may be playing an under-appreciated role in the global trends of increasing eutrophication,” the researchers said.

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

Engineered nanoparticles interact with nutrients to intensify eutrophication in a wetland ecosystem experiment by Marie Simonin, Benjamin P. Colman, Steven M. Anderson, Ryan S. King, Matthew T. Ruis, Astrid Avellan, Christina M. Bergemann, Brittany G. Perrotta, Nicholas K. Geitner, Mengchi Ho, Belen de la Barrera, Jason M. Unrine, Gregory V. Lowry, Curtis J. Richardson, Mark R. Wiesner, Emily S. Bernhardt. Ecological Applications, 2018; DOI: 10.1002/eap.1742 First published: 25 June 2018

This paper is behind a paywall.

Metcalf Institute Science Immersion Fellowship 2019 for journalists: applications open

I received this January 4, 2018 announcement from the Metcalf Institute at the University of Rhode Island (URI; US) in my email this morning. In other words, this is fresh off the email,

Get Science Tools to Break Stories
About Global Change & Water Resources

Apply for Metcalf Institute’s Career-Changing Science Immersion Fellowship
tuition, room and board, and travel support included

Global Change Impacts and Water
According to the United Nations, water is the “primary medium through which we will feel the effects of climate change” and water scarcity alone affects nearly half the global population.

Do you have the science tools to make the connection between shrinking water supplies, water quality, food production and climate change? Are you looking for story ideas to convey these global change impacts to your news audience? Would you like to build your confidence in discerning the credibility of scientific sources?

Call for Applications
The University of Rhode Island’s Metcalf Institute is accepting applications for its 21th Annual Science Immersion Workshop for Journalists, June 2-7, 2019. Ten journalists will be awarded Workshop fellowships, which include tuition, room and board, and travel support, thanks to the generosity of private donors and Metcalf Institute’s endowment. Two of the ten slots will be awarded to journalists based outside of the U.S.

Apply for the Workshop here.

About the Workshop
The Metcalf Institute Annual Science Immersion Workshop provides professional journalists with hands-on experience in field and laboratory science with expertise from leading scientists and policymakers who are working to project the impacts of global change, identify adaptation measures, and investigate the most effective ways to communicate these challenges. The workshop will address water resource and climate change topics of global significance while focusing on local and regional case studies in and around Narragansett Bay, among the world’s best studied estuaries. Held at the URI Graduate School of Oceanography, one of the nation’s premier oceanographic research institutions, the Metcalf Workshop provides an intense week of learning in the field, classroom and lecture hall.

Metcalf Fellows will:

  • Receive a comprehensive overview of climate science and global change
  • Gain a deeper understanding of how scientists conduct research and handle scientific uncertainty
  • Develop the skills and confidence to interpret and translate the language of scientific journals for news audiences
  • Build confidence in their abilities to discern the credibility of scientific sources
  • Board a research vessel to study the impacts of rising water temperatures and ocean acidification on coastal ecosystems
  • Explore the study of “emerging contaminants” such as PFAS that affect freshwater and marine ecosystems and public health
  • Visit wetlands, shorelines, and coastal communities to better understand adaptive management efforts and solutions in response to sea level rise and coastal storms
  • Discover new ways to write about global change to build audience understanding and engagement
  • Cultivate new sources by interacting with leading researchers and policy experts in an informal, off-deadline atmosphere
  • Network and develop lasting relationships with journalists from around the globe

Metcalf Alumni
Metcalf Institute has helped nearly 900 journalists cover the environment with greater accuracy and nuance since its first program in 1999. Metcalf alumni represent all media types and a wide variety of large and small news organizations ranging from local and regional newspapers and broadcast outlets to online and national/international outlets such as the Los Angeles Times, Reuters, National Geographic, China Global Television Network, Marketplace, Politico and PBS NewsHour. Metcalf Institute alumni hail from the U.S. and around the world, including Pakistan, Brazil, Nigeria, Israel, Egypt, Italy, South Africa, and China.

“This experience has changed my entire outlook on covering the environment and climate science. I may have only been in Rhode Island for a week, but the tools I gained during my Metcalf fellowship will stay with me for the entirety of my career.” Tony Briscoe, Chicago Tribune reporter and 2018 Annual Workshop alumnus.
                                                    
“Metcalf has greatly enhanced my ability to break down complex issues for my audience. Not only am I headed back home with a bunch of great story ideas, but the ability to set them against an international background and draw broader connections between issues in my region and the rest of the world.” Tegan Wendland, New Orleans Public Radio interim news director, lead coastal reporter, and 2017 Annual Workshop alumna.

Note for journalists applying from outside of the U.S.
While the Workshop addresses environmental topics of global significance, it focuses on U.S. case studies and a U.S. perspective on environmental policies. Metcalf Institute receives applications from journalists worldwide. However, due to funding limitations, only two of the ten fellowships will be awarded to journalists based outside of the U.S.

Eligibility
The Fellowship is designed for early- to mid-career, full-time journalists from all media who are looking to start or expand their coverage of the environment. Applicants must demonstrate a clear need for scientific training in topics relating to global change in coastal environments, specifically related to climate change and water resources. The fellowship includes room, board, tuition, and travel reimbursement paid after the program in the amount of up to US$500 for U.S.-based journalists and up to US$1,000 for journalists based outside of the U.S. Journalists applying from outside the U.S. must provide written assurance that they have full travel funds and can obtain the appropriate visa. Applications for the 2019 Annual Science Immersion Workshop for Journalists must be submitted by February 18, 2019.

Apply for the Workshop here.

About Metcalf Institute
Metcalf Institute is a global leader in environmental science training for journalists and communication training for scientists and other science communicators, as well as provider of science resources for journalists and free public programs and webinars on environmental topics. Metcalf Institute was established at the University of Rhode Island’s Graduate School of Oceanography in 1997 with funding from three media foundations: the Belo Corporation, the Providence Journal Charitable Foundation and the Philip L. Graham Fund, with additional support from the Telaka Foundation. In 2017, the Institute joined the URI College of the Environment and Life Sciences.

Metcalf Institute Funding
Metcalf programming is underwritten by federal and foundation grants, as well as donations from individuals and an endowment managed by the University of Rhode Island Foundation.

I headed off to the Metcalf Institute Fellowship application webpage and decided to include a few details here,

Email Stamp/Postmark Deadline: February 18, 2019

This application has two parts – an online form and a set of required inclusions. Read thoroughly before applying for the workshop below.

Application packages (online form and required enclosures together) will be used to evaluate applicants. Any hard copies of application materials will not be returned.

All application forms and required enclosures must be submitted in English. Application packages in languages other than English will not be reviewed.

Application packages that are not complete by midnight, U.S. Eastern Time, on February 18, 2019, will not be reviewed. …

Good luck!

Nanoplastics accumulating in marine organisms

I’m starting to have a collection of postings related to plastic nanoparticles and aquatic life (I have a listing below). The latest originates in Singapore (from a May 31, 2018 news item on ScienceDaily),

Plastic nanoparticles — these are tiny pieces of plastic less than 1 micrometre in size — could potentially contaminate food chains, and ultimately affect human health, according to a recent study by scientists from the National University of Singapore (NUS). They discovered that nanoplastics are easily ingested by marine organisms, and they accumulate in the organisms over time, with a risk of being transferred up the food chain, threatening food safety and posing health risks.

A May 31, 2018 NUS press release (also on EurekAlert), which originated the news item, expands on the theme,

Ocean plastic pollution is a huge and growing global problem. It is estimated that the oceans may already contain over 150 million tonnes of plastic, and each year, about eight million tonnes of plastic will end up in the ocean. Plastics do not degrade easily. In the marine environment, plastics are usually broken down into smaller pieces by the sun, waves, wind and microbial action. These micro- and nanoplastic particles in the water may be ingested by filter-feeding marine organisms such as barnacles, tube worms and sea-squirts.

Using the acorn barnacle Amphibalanus amphitrite as a model organism, the NUS research team demonstrated for the first time that nanoplastics consumed during the larval stage are retained and accumulated inside the barnacle larvae until they reach adulthood.

“We opted to study acorn barnacles as their short life cycle and transparent bodies made it easy to track and visualise the movement of nanoplastics in their bodies within a short span of time,” said Mr Samarth Bhargava, a PhD student from the Department of Chemistry at the NUS Faculty of Science, who is the first author of the research paper.

“Barnacles can be found in all of the world’s oceans. This accumulation of nanoplastics within the barnacles is of concern. Further work is needed to better understand how they may contribute to longer term effects on marine ecosystems,” said Dr Serena Teo, Senior Research Fellow from the Tropical Marine Science Institute at NUS, who co-supervised the research.

Studying the fate of nanoplastics in marine organisms

The NUS research team incubated the barnacle larvae in solutions of their regular feed coupled with plastics that are about 200 nanometres in size with green fluorescent tags. The larvae were exposed to two different treatments: ‘acute’ and ‘chronic’.

Under the ‘acute’ treatment, the barnacle larvae were kept for three hours in a solution that contained 25 times more nanoplastics than current estimates of what is present in the oceans. On the other hand, under the ‘chronic’ treatment, the barnacle larvae were exposed to a solution containing low concentrations of nanoplastics for up to four days.

The larvae were subsequently filtered from the solution, and examined under the microscope. The distribution and movement of the nanoplastics were monitored by examining the fluorescence from the particles present within the larvae over time.

“Our results showed that after exposing the barnacle larvae to nanoplastics in both treatments, the larvae had not only ingested the plastic particles, but the tiny particles were found to be distributed throughout the bodies of the larvae,” said Ms Serina Lee from the Tropical Marine Science Institute at NUS, who is the second author of the paper.

Even though the barnacles’ natural waste removal pathways of moulting and excretion resulted in some removal of the nanoplastics, the team detected the continued presence of nanoplastics inside the barnacles throughout their growth until they reached adulthood.

“Barnacles may be at the lower levels of the food chain, but what they consume will be transferred to the organisms that eat them. In addition, plastics are capable of absorbing pollutants and chemicals from the water. These toxins may be transferred to the organisms if the particles of plastics are consumed, and can cause further damage to marine ecosystems and human health,” said marine biologist Dr Neo Mei Lin from the Tropical Marine Science Institute at NUS, who is one of the authors of the paper.

The team’s research findings were first published online in the journal ACS Sustainable Chemistry & Engineering in March 2018. The study was funded under the Marine Science Research and Development Programme of the National Research Foundation Singapore.

Next steps

The NUS research team seeks to further their understanding of the translocation of nanoparticles within the marine organisms and potential pathways of transfer in the marine ecosystem.

“The life span and fate of plastic waste materials in marine environment is a big concern at the moment owing to the large amounts of plastic waste and its potential impact on marine ecosystem and food security around the world. The team would like to explore such topics in the near future and possibly to come up with pathways to address such problems,” explained Associate Professor Suresh Valiyaveettil from the Department of Chemistry at the NUS Faculty of Science, who co-supervised the research.

The team is currently examining how nanoplastics affect other invertebrate model organisms to understand the impact of plastics on marine ecosystems.

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

Fate of Nanoplastics in Marine Larvae: A Case Study Using Barnacles, Amphibalanus amphitrite by Samarth Bhargava, Serina Siew Chen Lee, Lynette Shu Min Ying, Mei Lin Neo, Serena Lay-Ming Teo, and Suresh Valiyaveettil. ACS Sustainable Chem. Eng., 2018, 6 (5), pp 6932–6940 DOI: 10.1021/acssuschemeng.8b00766 Publication Date (Web): March 21, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.

Other plastic nanoparticle postings:

While this doesn’t relate directly to aquatic life, the research focuses on how plastic degrades into plastic nanoparticles,

That’s it for now.

Spooling strips of graphene

An April 18, 2018 news item on phys.org highlights an exciting graphene development at the Massachusetts Institute of Technology (MIT),

MIT engineers have developed a continuous manufacturing process that produces long strips of high-quality graphene.

The team’s results are the first demonstration of an industrial, scalable method for manufacturing high-quality graphene that is tailored for use in membranes that filter a variety of molecules, including salts, larger ions, proteins, or nanoparticles. Such membranes should be useful for desalination, biological separation, and other applications.

A new manufacturing process produces strips of graphene, at large scale, for use in membrane technologies and other applications. Image: Christine Daniloff, MIT

An April 17, 2018 MIT news release (also on EurekAlert) by Jennifer Chu, which originated the news item,. provides more detail,

“For several years, researchers have thought of graphene as a potential route to ultrathin membranes,” says John Hart, associate professor of mechanical engineering and director of the Laboratory for Manufacturing and Productivity at MIT. “We believe this is the first study that has tailored the manufacturing of graphene toward membrane applications, which require the graphene to be seamless, cover the substrate fully, and be of high quality.”

Hart is the senior author on the paper, which appears online in the journal Applied Materials and Interfaces. The study includes first author Piran Kidambi, a former MIT postdoc who is now an assistant professor at Vanderbilt University; MIT graduate students Dhanushkodi Mariappan and Nicholas Dee; Sui Zhang of the National University of Singapore; Andrey Vyatskikh, a former student at the Skolkovo Institute of Science and Technology who is now at Caltech; and Rohit Karnik, an associate professor of mechanical engineering at MIT.

Growing graphene

For many researchers, graphene is ideal for use in filtration membranes. A single sheet of graphene resembles atomically thin chicken wire and is composed of carbon atoms joined in a pattern that makes the material extremely tough and impervious to even the smallest atom, helium.

Researchers, including Karnik’s group, have developed techniques to fabricate graphene membranes and precisely riddle them with tiny holes, or nanopores, the size of which can be tailored to filter out specific molecules. For the most part, scientists synthesize graphene through a process called chemical vapor deposition, in which they first heat a sample of copper foil and then deposit onto it a combination of carbon and other gases.

Graphene-based membranes have mostly been made in small batches in the laboratory, where researchers can carefully control the material’s growth conditions. However, Hart and his colleagues believe that if graphene membranes are ever to be used commercially they will have to be produced in large quantities, at high rates, and with reliable performance.

“We know that for industrialization, it would need to be a continuous process,” Hart says. “You would never be able to make enough by making just pieces. And membranes that are used commercially need to be fairly big – some so big that you would have to send a poster-wide sheet of foil into a furnace to make a membrane.”

A factory roll-out

The researchers set out to build an end-to-end, start-to-finish manufacturing process to make membrane-quality graphene.

The team’s setup combines a roll-to-roll approach – a common industrial approach for continuous processing of thin foils – with the common graphene-fabrication technique of chemical vapor deposition, to manufacture high-quality graphene in large quantities and at a high rate. The system consists of two spools, connected by a conveyor belt that runs through a small furnace. The first spool unfurls a long strip of copper foil, less than 1 centimeter wide. When it enters the furnace, the foil is fed through first one tube and then another, in a “split-zone” design.

While the foil rolls through the first tube, it heats up to a certain ideal temperature, at which point it is ready to roll through the second tube, where the scientists pump in a specified ratio of methane and hydrogen gas, which are deposited onto the heated foil to produce graphene.

“Graphene starts forming in little islands, and then those islands grow together to form a continuous sheet,” Hart says. “By the time it’s out of the oven, the graphene should be fully covering the foil in one layer, kind of like a continuous bed of pizza.”

As the graphene exits the furnace, it’s rolled onto the second spool. The researchers found that they were able to feed the foil continuously through the system, producing high-quality graphene at a rate of 5 centimers per minute. Their longest run lasted almost four hours, during which they produced about 10 meters of continuous graphene.

“If this were in a factory, it would be running 24-7,” Hart says. “You would have big spools of foil feeding through, like a printing press.”

Flexible design

Once the researchers produced graphene using their roll-to-roll method, they unwound the foil from the second spool and cut small samples out. They cast the samples with a polymer mesh, or support, using a method developed by scientists at Harvard University, and subsequently etched away the underlying copper.

“If you don’t support graphene adequately, it will just curl up on itself,” Kidambi says. “So you etch copper out from underneath and have graphene directly supported by a porous polymer – which is basically a membrane.”

The polymer covering contains holes that are larger than graphene’s pores, which Hart says act as microscopic “drumheads,” keeping the graphene sturdy and its tiny pores open.

The researchers performed diffusion tests with the graphene membranes, flowing a solution of water, salts, and other molecules across each membrane. They found that overall, the membranes were able to withstand the flow while filtering out molecules. Their performance was comparable to graphene membranes made using conventional, small-batch approaches.

The team also ran the process at different speeds, with different ratios of methane and hydrogen gas, and characterized the quality of the resulting graphene after each run. They drew up plots to show the relationship between graphene’s quality and the speed and gas ratios of the manufacturing process. Kidambi says that if other designers can build similar setups, they can use the team’s plots to identify the settings they would need to produce a certain quality of graphene.

“The system gives you a great degree of flexibility in terms of what you’d like to tune graphene for, all the way from electronic to membrane applications,” Kidambi says.

Looking forward, Hart says he would like to find ways to include polymer casting and other steps that currently are performed by hand, in the roll-to-roll system.

“In the end-to-end process, we would need to integrate more operations into the manufacturing line,” Hart says. “For now, we’ve demonstrated that this process can be scaled up, and we hope this increases confidence and interest in graphene-based membrane technologies, and provides a pathway to commercialization.”

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

A Scalable Route to Nanoporous Large-Area Atomically Thin Graphene Membranes by Roll-to-Roll Chemical Vapor Deposition and Polymer Support Casting by Piran R. Kidambi, Dhanushkodi D. Mariappan, Nicholas T. Dee, Andrey Vyatskikh, Sui Zhang, Rohit Karnik, and A. John Hart. ACS Appl. Mater. Interfaces, 2018, 10 (12), pp 10369–10378 DOI: 10.1021/acsami.8b00846 Publication Date (Web): March 19, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.

Finally, there is a video of the ‘graphene spooling out’ process,

Robust reverse osmosis membranes made of carbon nanotubes

Caption: SEM images of MWCNT-PA (Multi-Walled Carbon Nanotube-Polyamide) nanocomposite membranes, for plain PA, and PA with 5, 9.5, 12.5, 15.5, 17 and 20 wt.% of MWCNT, where the typical lobe-like structures appear at the surface. Note the tendency towards a flatter membrane surface as the content of MWCNT increases. Scale bar corresponds to 1.0?μm for all the micrographs. Credit: Copyright 2018, Springer Nature, Licensed under CC BY 4.0

It seems unlikely that the image’s resemblance to a Japanese kimono on display is accidental. Either way, nicely done!

An April 12, 2018 news item on phys.org describes a technique that would allow large-scale water desalination,

A research team of Shinshu University, Japan, has developed robust reverse osmosis membranes that can endure large-scale water desalination. The team published their results in early February [2018] in Scientific Reports.

“Since more than 97 percent of the water in the world is saline water, reverse osmosis desalination plants for producing fresh water are increasingly important for providing a safe and consistent supply,” said Morinobu Endo, Ph.D., corresponding author on the paper. Endo is a distinguished professor of Shinshu University and the Honorary Director of the Institute of Carbon Science and Technology. “Even though reverse osmosis membrane technology has been under development for several decades, new threats like global warming and increasing clean water demand in populated urban centers challenge the conventional water supply systems.”

Reverse osmosis membranes typically consist of thin film composite systems, with an active layer of polymer film that restricts undesired substances, such as salt, from passing through a permeable porous substrate. Such membranes can turn seawater into drinkable water, as well as aid in agricultural and landscape irrigation, but they can be costly to operate and spend a large amount of energy.

To meet the demand of potable water at low cost, Endo says more robust membranes capable of withstanding harsh conditions, while remaining chemically stable to tolerate cleaning treatments, are necessary. The key lays in carbon nanotechnology.

An April 11, 2018 Shinshu University press release, which originated the news item, provides more details about the work,

Endo is a pioneer of carbon nanotubes [sic] synthesis by catalytic chemical vapor deposition. In this research, Endo and his team developed a multi-walled carbon nanotube-polyamide nanocomposite membrane, which is resistant to chlorine–one of the main cause of degradation or failure cases in reverse osmosis membranes. The added carbon nanotubes create a protective effect that stabilized the linked molecules of the polyamide against chlorine.

“Carbon nanotechnology has been expected to bring benefits, and this is one promising example of the contribution of carbon nanotubes to a very critical application: water purification,” Endo said. “Carbon nanotubes and fibers are already superb reinforcements for other applications in materials science and engineering, and this is yet another field where their exceptional properties can be used for improving conventional technologies.”

The researchers are working to stabilize and expand the production and processing of multi-walled carbon nanotube-polyamide nanocomposite membranes.

“We are currently working on scaling up our method of synthesis, which, in principle, is based on the same method used to prepare current polyamide membranes,” Endo said. He also noted that his team is planning a collaboration to produce commercial membranes.

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

Robust water desalination membranes against degradation using high loads of carbon nanotubes by J. Ortiz-Medina, S. Inukai, T. Araki, A. Morelos-Gomez, R. Cruz-Silva, K. Takeuchi, T. Noguchi, T. Kawaguchi, M. Terrones, & M. Endo. Scientific Reports volume 8, Article number: 2748 (2018) doi:10.1038/s41598-018-21192-5 Published online: 09 February 2018

This paper is open access.

Clean up oil spills (on water and/or land) with oil-eating bacterium

Quebec’s Institut national de la recherche scientifique (INRS) announced an environmentally friendly way of cleaning up oil spills in an April 9, 2018 news item on ScienceDaily,

From pipelines to tankers, oil spills and their impact on the environment are a source of concern. These disasters occur on a regular basis, leading to messy decontamination challenges that require massive investments of time and resources. But however widespread and serious the damage may be, the solution could be microscopic — Alcanivorax borkumensis — a bacterium that feeds on hydrocarbons. Professor Satinder Kaur Brar and her team at INRS have conducted laboratory tests that show the effectiveness of enzymes produced by the bacterium in degrading petroleum products in soil and water. Their results offer hope for a simple, effective, and eco-friendly method of decontaminating water and soil at oil sites.

An April 8, 2018 INRS news release by Stephanie Thibaut, which originated the news item, expands on the theme,

In recent years, researchers have sequenced the genomes of thousands of bacteria from various sources. Research associate Dr.Tarek Rouissi poured over “technical data sheets” for many bacterial strains with the aim of finding the perfect candidate for a dirty job: cleaning up oil spills. He focused on the enzymes they produce and the conditions in which they evolve.

A. borkumensis, a non-pathogenic marine bacterium piqued his curiosity. The microorganism’s genome contains the codes of a number of interesting enzymes and it is classified as “hydrocarbonoclastic”—i.e., as a bacterium that uses hydrocarbons as a source of energy. A. borkumensis is present in all oceans and drifts with the current, multiplying rapidly in areas where the concentration of oil compounds is high, which partly explains the natural degradation observed after some spills. But its remedial potential had not been assessed.

“I had a hunch,” Rouissi said, “and the characterization of the enzymes produced by the bacterium seems to have proven me right!” A. borkumensis boasts an impressive set of tools: during its evolution, it has accumulated a range of very specific enzymes that degrade almost everything found in oil. Among these enzymes, the bacteria’shydroxylases stand out from the ones found in other species: they are far more effective, in addition to being more versatile and resistant to chemical conditions, as tested in coordination by a Ph.D. student, Ms. Tayssir Kadri.

To test the microscopic cleaner, the research team purified a few of the enzymes and used them to treat samples of contaminated soil. “The degradation of hydrocarbons using the crude enzyme extract is really encouraging and reached over 80% for various compounds,” said Brar. The process is effective in removing benzene, toluene, and xylene, and has been tested under a number of different conditions to show that it is a powerful way to clean up polluted land and marine environments.”

The next steps for Brar’s team are to find out more about how these bacteria metabolize hydrocarbons and explore their potential for decontaminating sites. One of the advantages of the approach developed at INRS is its application in difficult-to-access environments, which present a major challenge during oil spill cleanup efforts.

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

Ex-situ biodegradation of petroleum hydrocarbons using Alcanivorax borkumensis enzymes by Tayssir Kadri, Sara Magdouli, Tarek Rouissi, Satinder Kaur Brar. Biochemical Engineering Journal Volume 132, 15 April 2018, Pages 279-287 DOI: https://doi.org/10.1016/j.bej.2018.01.014

This paper is behind a paywall.

In light of this research, it seems remiss not to mention the recent setback for Canada’s Trans Mountain pipeline expansion. Canada’s Federal Court of Appeal quashed the approval as per this August 30, 2018 news item on canadanews.org. There were two reasons for the quashing (1) a failure to properly consult with indigenous people and (2) a failure to adequately assess environmental impacts on marine life. Interestingly, no one ever mentions environmental cleanups and remediation, which could be very important if my current suspicions regarding the outcome for the next federal election are correct.

Regardless of which party forms the Canadian government after the 2019 federal election, I believe that either Liberals or Conservatives would be equally dedicated to bringing this pipeline to the West Coast. The only possibility I can see of a change lies in a potential minority government is formed by a coalition including the NDP (New Democratic Party) and/or the Green Party; an outcome that seems improbable at this juncture.

Given what I believe to be the political will regarding the Trans Mountain pipeline, I would dearly love to see more support for better cleanup and remediation measures.

Killing bacteria on contact with dragonfly-inspired nanocoating

Scientists in Singapore were inspired by dragonflies and cicadas according to a March 28, 2018 news item on Nanowerk (Note: A link has been removed),

Studies have shown that the wings of dragonflies and cicadas prevent bacterial growth due to their natural structure. The surfaces of their wings are covered in nanopillars making them look like a bed of nails. When bacteria come into contact with these surfaces, their cell membranes get ripped apart immediately and they are killed. This inspired researchers from the Institute of Bioengineering and Nanotechnology (IBN) of A*STAR to invent an anti-bacterial nano coating for disinfecting frequently touched surfaces such as door handles, tables and lift buttons.

This technology will prove particularly useful in creating bacteria-free surfaces in places like hospitals and clinics, where sterilization is important to help control the spread of infections. Their new research was recently published in the journal Small (“ZnO Nanopillar Coated Surfaces with Substrate-Dependent Superbactericidal Property”)

Image 1: Zinc oxide nanopillars that looked like a bed of nails can kill a broad range of germs when used as a coating on frequently-touched surfaces. Courtesy: A*STAR

A March 28, 2018 Agency for Science Technology and Research (A*STAR) press release, which originated the news item, describes the work further,

80% of common infections are spread by hands, according to the B.C. [province of Canada] Centre for Disease Control1. Disinfecting commonly touched surfaces helps to reduce the spread of harmful germs by our hands, but would require manual and repeated disinfection because germs grow rapidly. Current disinfectants may also contain chemicals like triclosan which are not recognized as safe and effective 2, and may lead to bacterial resistance and environmental contamination if used extensively.

“There is an urgent need for a better way to disinfect surfaces without causing bacterial resistance or harm to the environment. This will help us to prevent the transmission of infectious diseases from contact with surfaces,” said IBN Executive Director Professor Jackie Y. Ying.

To tackle this problem, a team of researchers led by IBN Group Leader Dr Yugen Zhang created a novel nano coating that can spontaneously kill bacteria upon contact. Inspired by studies on dragonflies and cicadas, the IBN scientists grew nanopilllars of zinc oxide, a compound known for its anti-bacterial and non-toxic properties. The zinc oxide nanopillars can kill a broad range of germs like E. coli and S. aureus that are commonly transmitted from surface contact.

Tests on ceramic, glass, titanium and zinc surfaces showed that the coating effectively killed up to 99.9% of germs found on the surfaces. As the bacteria are killed mechanically rather than chemically, the use of the nano coating would not contribute to environmental pollution. Also, the bacteria will not be able to develop resistance as they are completely destroyed when their cell walls are pierced by the nanopillars upon contact.

Further studies revealed that the nano coating demonstrated the best bacteria killing power when it is applied on zinc surfaces, compared with other surfaces. This is because the zinc oxide nanopillars catalyzed the release of superoxides (or reactive oxygen species), which could even kill nearby free floating bacteria that were not in direct contact with the surface. This super bacteria killing power from the combination of nanopillars and zinc broadens the scope of applications of the coating beyond hard surfaces.

Subsequently, the researchers studied the effect of placing a piece of zinc that had been coated with zinc oxide nanopillars into water containing E. coli. All the bacteria were killed, suggesting that this material could potentially be used for water purification.

Dr Zhang said, “Our nano coating is designed to disinfect surfaces in a novel yet practical way. This study demonstrated that our coating can effectively kill germs on different types of surfaces, and also in water. We were also able to achieve super bacteria killing power when the coating was used on zinc surfaces because of its dual mechanism of action. We hope to use this technology to create bacteria-free surfaces in a safe, inexpensive and effective manner, especially in places where germs tend to accumulate.”

IBN has recently received a grant from the National Research Foundation, Prime Minister’s Office, Singapore, under its Competitive Research Programme to further develop this coating technology in collaboration with Tan Tock Seng Hospital for commercial application over the next 5 years.

1 B.C. Centre for Disease Control

2 U.S. Food & Drug Administration

(I wasn’t expecting to see a reference to my home province [BC Centre for Disease Control].) Back to the usual, here’s a link to and a citation for the paper,

ZnO Nanopillar Coated Surfaces with Substrate‐Dependent Superbactericidal Property by Guangshun Yi, Yuan Yuan, Xiukai Li, Yugen Zhang. Small https://doi.org/10.1002/smll.201703159 First published: 22 February 2018

This paper is behind a paywall.

One final comment, this research reminds me of research into simulating shark skin because that too has bacteria-killing nanostructures. My latest about the sharkskin research is a Sept, 18, 2014 posting.

3D printed all liquid electronics

Even after watching the video, I still don’t quite believe it. A March 28, 2018 news item on ScienceDaily announces the work,

Scientists from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab [or LBNL]) have developed a way to print 3-D structures composed entirely of liquids. Using a modified 3-D printer, they injected threads of water into silicone oil — sculpting tubes made of one liquid within another liquid.

They envision their all-liquid material could be used to construct liquid electronics that power flexible, stretchable devices. The scientists also foresee chemically tuning the tubes and flowing molecules through them, leading to new ways to separate molecules or precisely deliver nanoscale building blocks to under-construction compounds.

A March 28, 2018 Berkeley Lab March 26, 2018 news release (also on EurekAlert), which originated the news item, describe the work in more detail,

The researchers have printed threads of water between 10 microns and 1 millimeter in diameter, and in a variety of spiraling and branching shapes up to several meters in length. What’s more, the material can conform to its surroundings and repeatedly change shape.

“It’s a new class of material that can reconfigure itself, and it has the potential to be customized into liquid reaction vessels for many uses, from chemical synthesis to ion transport to catalysis,” said Tom Russell, a visiting faculty scientist in Berkeley Lab’s Materials Sciences Division. He developed the material with Joe Forth, a postdoctoral researcher in the Materials Sciences Division, as well as other scientists from Berkeley Lab and several other institutions. They report their research March 24 [2018] in the journal Advanced Materials.

The material owes its origins to two advances: learning how to create liquid tubes inside another liquid, and then automating the process.

For the first step, the scientists developed a way to sheathe tubes of water in a special nanoparticle-derived surfactant that locks the water in place. The surfactant, essentially soap, prevents the tubes from breaking up into droplets. Their surfactant is so good at its job, the scientists call it a nanoparticle supersoap.

The supersoap was achieved by dispersing gold nanoparticles into water and polymer ligands into oil. The gold nanoparticles and polymer ligands want to attach to each other, but they also want to remain in their respective water and oil mediums. The ligands were developed with help from Brett Helms at the Molecular Foundry, a DOE Office of Science User Facility located at Berkeley Lab.

In practice, soon after the water is injected into the oil, dozens of ligands in the oil attach to individual nanoparticles in the water, forming a nanoparticle supersoap. These supersoaps jam together and vitrify, like glass, which stabilizes the interface between oil and water and locks the liquid structures in position.

This stability means we can stretch water into a tube, and it remains a tube. Or we can shape water into an ellipsoid, and it remains an ellipsoid,” said Russell. “We’ve used these nanoparticle supersoaps to print tubes of water that last for several months.”

Next came automation. Forth modified an off-the-shelf 3-D printer by removing the components designed to print plastic and replacing them with a syringe pump and needle that extrudes liquid. He then programmed the printer to insert the needle into the oil substrate and inject water in a predetermined pattern.

“We can squeeze liquid from a needle, and place threads of water anywhere we want in three dimensions,” said Forth. “We can also ping the material with an external force, which momentarily breaks the supersoap’s stability and changes the shape of the water threads. The structures are endlessly reconfigurable.”

This image illustrates how the water is printed,

These schematics show the printing of water in oil using a nanoparticle supersoap. Gold nanoparticles in the water combine with polymer ligands in the oil to form an elastic film (nanoparticle supersoap) at the interface, locking the structure in place. (Credit: Berkeley Lab)

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

Reconfigurable Printed Liquids by Joe Forth, Xubo Liu, Jaffar Hasnain, Anju Toor, Karol Miszta, Shaowei Shi, Phillip L. Geissler, Todd Emrick, Brett A. Helms, Thomas P. Russell. Advanced Materials https://doi.org/10.1002/adma.201707603 First published: 24 March 2018

This paper is behind a paywall.

Better hair dyes with graphene and a cautionary note

Beauty products aren’t usually the first applications that come to mind when discussing graphene or any other research and development (R&D) as I learned when teaching a course a few years ago. But research and development  in that field are imperative as every company is scrambling for a short-lived competitive advantage for a truly new products or a perceived competitive advantage in a field where a lot of products are pretty much the same.

This March 15, 2018 news item on ScienceDaily describes graphene as a potential hair dye,

Graphene, a naturally black material, could provide a new strategy for dyeing hair in difficult-to-create dark shades. And because it’s a conductive material, hair dyed with graphene might also be less prone to staticky flyaways. Now, researchers have put it to the test. In an article published March 15 [2018] in the journal Chem, they used sheets of graphene to make a dye that adheres to the surface of hair, forming a coating that is resistant to at least 30 washes without the need for chemicals that open up and damage the hair cuticle.

Courtesy: Northwestern University

A March 15, 2018 Cell Press news release on EurekAlert, which originated the news item, fills in more the of the story,

Most permanent hair dyes used today are harmful to hair. “Your hair is covered in these cuticle scales like the scales of a fish, and people have to use ammonia or organic amines to lift the scales and allow dye molecules to get inside a lot quicker,” says senior author Jiaxing Huang, a materials scientist at Northwestern University. But lifting the cuticle makes the strands of the hair more brittle, and the damage is only exacerbated by the hydrogen peroxide that is used to trigger the reaction that synthesizes the dye once the pigment molecules are inside the hair.

These problems could theoretically be solved by a dye that coats rather than penetrates the hair. “However, the obvious problem of coating-based dyes is that they tend to wash out very easily,” says Huang. But when he and his team coated samples of human hair with a solution of graphene sheets, they were able to turn platinum blond hair black and keep it that way for at least 30 washes–the number necessary for a hair dye to be considered “permanent.”

This effectiveness has to do with the structure of graphene: it’s made of up thin, flexible sheets that can adapt to uneven surfaces. “Imagine a piece of paper. A business card is very rigid and doesn’t flex by itself. But if you take a much bigger sheet of newspaper–if you still can find one nowadays–it can bend easily. This makes graphene sheets a good coating material,” he says. And once the coating is formed, the graphene sheets are particularly good at keeping out water during washes, which keeps the water from eroding both the graphene and the polymer binder that the team also added to the dye solution to help with adhesion.

The graphene dye has additional advantages. Each coated hair is like a little wire in that it is able to conduct heat and electricity. This means that it’s easy for graphene-dyed hair to dissipate static electricity, eliminating the problem of flyaways on dry winter days. The graphene flakes are large enough that they won’t absorb through the skin like other dye molecules. And although graphene is typically black, its precursor, graphene oxide, is light brown. But the color of graphene oxide can be gradually darkened with heat or chemical reactions, meaning that this dye could be used for a variety of shades or even for an ombre effect.

What Huang thinks is particularly striking about this application of graphene is that it takes advantage of graphene’s most obvious property. “In many potential graphene applications, the black color of graphene is somewhat undesirable and something of a sore point,” he says. Here, though, it’s applied to a field where creating dark colors has historically been a problem.

The graphene used for hair dye also doesn’t need to be of the same high quality as it does for other applications. “For hair dye, the most important property is graphene being black. You can have graphene that is too lousy for higher-end electronic applications, but it’s perfectly okay for this. So I think this application can leverage the current graphene product as is, and that’s why I think that this could happen a lot sooner than many of the other proposed applications,” he says.

Making it happen is his next goal. He hopes to get funding to continue the research and make these dyes a reality for the people whose lives they would improve. “This is an idea that was inspired by curiosity. It was very fun to do, but it didn’t sound very big and noble when we started working on it,” he says. “But after we deep-dived into studying hair dyes, we realized that, wow, this is actually not at all a small problem. And it’s one that graphene could really help to solve.”

Northwestern University’s Amanda Morris also wrote a March 15, 2018 news release (it’s repetitive but there are some interesting new details; Note: Links have been removed),

It’s an issue that has plagued the beauty industry for more than a century: Dying hair too often can irreparably damage your silky strands.

Now a Northwestern University team has used materials science to solve this age-old problem. The team has leveraged super material graphene to develop a new hair dye that is less harmful [emphasis mine], non-damaging and lasts through many washes without fading. Graphene’s conductive nature also opens up new opportunities for hair, such as turning it into in situ electrodes or integrating it with wearable electronic devices.

Dying hair might seem simple and ordinary, but it’s actually a sophisticated chemical process. Called the cuticle, the outermost layer of a hair is made of cells that overlap in a scale-like pattern. Commercial dyes work by using harsh chemicals, such as ammonia and bleach, to first pry open the cuticle scales to allow colorant molecules inside and then trigger a reaction inside the hair to produce more color. Not only does this process cause hair to become more fragile, some of the small molecules are also quite toxic.

Huang and his team bypassed harmful chemicals altogether by leveraging the natural geometry of graphene sheets. While current hair dyes use a cocktail of small molecules that work by chemically altering the hair, graphene sheets are soft and flexible, so they wrap around each hair for an even coat. Huang’s ink formula also incorporates edible, non-toxic polymer binders to ensure that the graphene sticks — and lasts through at least 30 washes, which is the commercial requirement for permanent hair dye. An added bonus: graphene is anti-static, so it keeps winter-weather flyaways to a minimum.

“It’s similar to the difference between a wet paper towel and a tennis ball,” Huang explained, comparing the geometry of graphene to that of other black pigment particles, such as carbon black or iron oxide, which can only be used in temporary hair dyes. “The paper towel is going to wrap and stick much better. The ball-like particles are much more easily removed with shampoo.”

This geometry also contributes to why graphene is a safer alternative. Whereas small molecules can easily be inhaled or pass through the skin barrier, graphene is too big to enter the body. “Compared to those small molecules used in current hair dyes, graphene flakes are humongous,” said Huang, who is a member of Northwestern’s International Institute of Nanotechnology.

Ever since graphene — the two-dimensional network of carbon atoms — burst onto the science scene in 2004, the possibilities for the promising material have seemed nearly endless. With its ultra-strong and lightweight structure, graphene has potential for many applications in high-performance electronics, high-strength materials and energy devices. But development of those applications often require graphene materials to be as structurally perfect as possible in order to achieve extraordinary electrical, mechanical or thermal properties.

The most important graphene property for Huang’s hair dye, however, is simply its color: black. So Huang’s team used graphene oxide, an imperfect version of graphene that is a cheaper, more available oxidized derivative.

“Our hair dye solves a real-world problem without relying on very high-quality graphene, which is not easy to make,” Huang said. “Obviously more work needs to be done, but I feel optimistic about this application.”

Still, future versions of the dye could someday potentially leverage graphene’s notable properties, including its highly conductive nature.

“People could apply this dye to make hair conductive on the surface,” Huang said. “It could then be integrated with wearable electronics or become a conductive probe. We are only limited by our imagination.”

So far, Huang has developed graphene-based hair dyes in multiple shades of brown and black. Next, he plans to experiment with more colors.

Interestingly, the tiny note of caution”less harmful” doesn’t appear in the Cell Press news release. Never fear, Dr. Andrew Maynard (Director Risk Innovation Lab at Arizona State University) has written a March 20, 2018 essay on The Conversation suggesting a little further investigation (Note: Links have been removed),

Northwestern University’s press release proudly announced, “Graphene finds new application as nontoxic, anti-static hair dye.” The announcement spawned headlines like “Enough with the toxic hair dyes. We could use graphene instead,” and “’Miracle material’ graphene used to create the ultimate hair dye.”

From these headlines, you might be forgiven for getting the idea that the safety of graphene-based hair dyes is a done deal. Yet having studied the potential health and environmental impacts of engineered nanomaterials for more years than I care to remember, I find such overly optimistic pronouncements worrying – especially when they’re not backed up by clear evidence.

Tiny materials, potentially bigger problems

Engineered nanomaterials like graphene and graphene oxide (the particular form used in the dye experiments) aren’t necessarily harmful. But nanomaterials can behave in unusual ways that depend on particle size, shape, chemistry and application. Because of this, researchers have long been cautious about giving them a clean bill of health without first testing them extensively. And while a large body of research to date doesn’t indicate graphene is particularly dangerous, neither does it suggest it’s completely safe.

A quick search of scientific papers over the past few years shows that, since 2004, over 2,000 studies have been published that mention graphene toxicity; nearly 500 were published in 2017 alone.

This growing body of research suggests that if graphene gets into your body or the environment in sufficient quantities, it could cause harm. A 2016 review, for instance, indicated that graphene oxide particles could result in lung damage at high doses (equivalent to around 0.7 grams of inhaled material). Another review published in 2017 suggested that these materials could affect the biology of some plants and algae, as well as invertebrates and vertebrates toward the lower end of the ecological pyramid. The authors of the 2017 study concluded that research “unequivocally confirms that graphene in any of its numerous forms and derivatives must be approached as a potentially hazardous material.”

These studies need to be approached with care, as the precise risks of graphene exposure will depend on how the material is used, how exposure occurs and how much of it is encountered. Yet there’s sufficient evidence to suggest that this substance should be used with caution – especially where there’s a high chance of exposure or that it could be released into the environment.

Unfortunately, graphene-based hair dyes tick both of these boxes. Used in this way, the substance is potentially inhalable (especially with spray-on products) and ingestible through careless use. It’s also almost guaranteed that excess graphene-containing dye will wash down the drain and into the environment.

Undermining other efforts?

I was alerted to just how counterproductive such headlines can be by my colleague Tim Harper, founder of G2O Water Technologies – a company that uses graphene oxide-coated membranes to treat wastewater. Like many companies in this area, G2O has been working to use graphene responsibly by minimizing the amount of graphene that ends up released to the environment.

Yet as Tim pointed out to me, if people are led to believe “that bunging a few grams of graphene down the drain every time you dye your hair is OK, this invalidates all the work we are doing making sure the few nanograms of graphene on our membranes stay put.” Many companies that use nanomaterials are trying to do the right thing, but it’s hard to justify the time and expense of being responsible when someone else’s more cavalier actions undercut your efforts.

Overpromising results and overlooking risk

This is where researchers and their institutions need to move beyond an “economy of promises” that spurs on hyperbole and discourages caution, and think more critically about how their statements may ultimately undermine responsible and beneficial development of a technology. They may even want to consider using guidelines, such as the Principles for Responsible Innovation developed by the organization Society Inside, for instance, to guide what they do and say.

If you have time, I encourage you to read Andrew’s piece in its entirety.

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

Multifunctional Graphene Hair Dye by Chong Luo, Lingye Zhou, Kevin Chiou, and Jiaxing Huang. Chem DOI: https://doi.org/10.1016/j.chempr.2018.02.02 Publication stage: In Press Corrected Proof

This paper appears to be open access.

*Two paragraphs (repetitions) were deleted from the excerpt of Dr. Andrew Maynard’s essay on August 14, 2018

Panning for silver nanoparticles in your clothes washer

A March 20, 2018 news item on phys.org describes a new approach to treating wastewater (Note: Links have been removed),

Humans have known since ancient times that silver kills or stops the growth of many microorganisms. Hippocrates, the father of medicine, is said to have used silver preparations for treating ulcers and healing wounds. Until the introduction of antibiotics in the 1940s, colloidal silver (tiny particles suspended in a liquid) was a mainstay for treating burns, infected wounds and ulcers. Silver is still used today in wound dressings, in creams and as a coating on medical devices.

Since the 1990s, manufacturers have added silver nanoparticles to numerous consumer products to enhance their antibacterial and anti-odor properties. Examples include clothes, towels, undergarments, socks, toothpaste and soft toys. Nanoparticles are ultra-small particles, ranging from 1 to 100 nanometers in diameter – too small to see even with a microscope. According to a widely cited database, about one-fourth of nanomaterial-based consumer products currently marketed in the United States contain nanosilver.

Multiple studies have reported that nanosilver leaches out of textiles when they are laundered. Research also reveals that nanosilver may be toxic to humans and aquatic and marine organisms. Although it is widely used, little is understood about its fate or long-term toxic effects in the environment.

We are developing ways to convert this potential ecological crisis into an opportunity by recovering pure silver nanoparticles, which have many industrial applications, from laundry wastewater. In a recently published study, we describe a technique for silver recovery and discuss the key technical challenges. Our approach tackles this problem at the source – in this case, individual washing machines. We believe that this strategy has great promise for getting newly identified contaminants out of wastewater.

A March 20, 2018 essay by Sukalyan Sengupta, Professor of Wastewater Treatment, and Tabish Nawaz. Doctoral Student, both at University of Massachusetts at Dartmouth on The Conversation website, which originated the news item, expands on the theme (Note: Links have been removed),

Use of nanosilver in consumer products has steadily risen in the past decade. The market share of silver-based textiles rose from 9 percent in 2004 to 25 percent in 2011.

Several investigators have measured the silver content of textiles and found values ranging from 0.009 to 21,600 milligrams of silver per kilogram of textile. Studies show that the amount of silver leached in the wash solution depends on many factors, including interactions between detergent and other chemicals and how silver is attached to the textiles.

In humans, exposure to silver can harm liver cells, skin and lungs. Prolonged exposure or exposure to a large dose can cause a condition called Argyria, in which the victim’s skin turns permanently bluish-gray.

Once silver goes down the drain and ends up at wastewater treatment plants, it can potentially harm bacterial treatment processes, making them less efficient, and foul treatment equipment. More than 90 percent of silver nanoparticles released in wastewater end up in nutrient-rich biosolids left over at the end of sewage treatment, which often are used on land as agricultural fertilizers.

Silver is toxic in aquatic environments, a concern that’s becoming more serious with the increased use of silver nanoparticles and awareness that oceans, rivers, and lakes are dangerously stressed.

Sengupta and Nawaz go on to describe their proposed solution (Note: Links have been removed),

Our research shows that the most efficient way to remove silver from wastewater is by treating it in the washing machine. At this point silver concentrations are relatively high, and silver is initially released from treated clothing in a chemical form that is feasible to recover.

A bit of chemistry is helpful here. Our recovery method employs a widely used chemistry process called ion exchange. Ions are atoms or molecules that have an electrical charge. In ion exchange, a solid and a liquid are brought together and exchange ions with each other.

For example, household soaps do not lather well in “hard” water, which contains high levels of ions such as magnesium and calcium. Many home water filters use ion exchange to “soften” the water, replacing those materials with other ions that do not affect its properties in the same way.

For this process to work, the ions that switch places must both be either positively or negatively charged. Nanosilver is initially released from textiles as silver ion, which is a cation – an ion with a positive charge (hence the plus sign in its chemical symbol, Ag+).

Even at the source, removing silver from washwater is challenging. Silver concentrations in the wash solution are relatively low compared to other cations, such as calcium, that could interfere with the removal process. Detergent chemistry complicates the picture further because some detergent components can potentially interact with silver.

To recover silver without picking up other chemicals, the recovery process must use materials that have a chemical affinity for silver. In a previous study, we described a potential solution: Using ion-exchange materials embedded with sulfur-based chemicals, which bind preferentially with silver.

In our new study, we passed washwater through an ion-exchange resin column and analyzed how each major detergent ingredient interacted with silver in the water and affected the resin’s ability to remove silver from the water. By manipulating process conditions such as pH, temperature and concentration of nonsilver cations, we were able to identify conditions that maximized silver recovery.

We found that pH and the levels of calcium ions (Ca2+) were critical factors. Higher levels of hydrogen or calcium ions bind up detergent ingredients and prevent them from interacting with silver ions, so the ion-exchange resin can remove the silver from the solution. We also found that some detergent ingredients – particularly bleaching and water-softening agents – made the ion-exchange resin work less efficiently. Depending on these conditions, we recovered between 20 percent and 99 percent of the silver in the washwater.

The researchers go on to propose a new approach to treating wastewater (Note: A link has been removed),

Today wastewater is collected from multiple sources, such as homes and businesses, and piped over long distances to centralized wastewater treatment plants. But increasing evidence shows that these facilities are ill-equipped to keep newly identified contaminants out of the environment, since they use one common treatment scheme for many different waste streams.

We believe the future is in decentralized systems that can treat different types of wastewater with specific technologies designed specifically for the materials they contain. If wastewater from laundromats contains different contaminants than wastewater from restaurants, why treat them the same way?

Interesting, non? In any event, here’s a link to and a citation for what I believe is the researchers’ latest paper on this subject,

Silver Recovery from Laundry Washwater: The Role of Detergent Chemistry by Tabish Nawaz and Sukalyan Sengupta. ACS Sustainable Chem. Eng., 2018, 6 (1), pp 600–608 DOI: 10.1021/acssuschemeng.7b02933 Publication Date (Web): November 21, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall. For anyone who can’t get access, Karla Lant provides a bit more technical detail about the work in her February 2, 2018 article for fondriest.com.