Tag Archives: copper nanoparticles

Algae outbreaks (dead zones) in wetlands and waterways

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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.

Are copper nanoparticles good candidates for synthesizing medicine?

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This research appears to be a collaboration between Russian and Indian scientists. From a December 5, 2017 news item on Nanowerk (Note: A link has been removed),

Chemists of Ural Federal University with colleagues from India proved the effectiveness of copper nanoparticles as a catalyst on the example of analysis of 48 organic synthesis reactions (Coordination Chemistry Reviews, “Copper nanoparticles as inexpensive and efficient catalyst: A valuable contribution in organic synthesis”).

One of the advantages of the catalyst is its insolubility in traditional organic solvents. This makes copper nanoparticles a valuable alternative to heavy metal catalysts, for example palladium, which is currently used for the synthesis of many pharmaceuticals and is toxic for cells.

“Copper nanoparticles are an ideal variant of a heterophasic catalyst, since they exist in a wide variety of geometric shapes and sizes, which directly affects the surface of effective mass transfer, so reactions in the presence of this catalyst are characterized by shorter reaction times, selectivity and better yields,” says co-author Grigory Zyryanov, Doctor of Chemistry, Associate Professor of the Department of Organic and Biomolecular Chemistry of UrFU.

A December 11, 2017 (there can be a gap between distributing a press release and posting it on the home website) Ural Federal University press release, which originated the news item, makes the case for copper nanoparticles as catalytic agents,

Copper nanoparticles are inexpensive since there are many simple ways to obtain them from cheap raw materials and these methods are constantly being modified. As a result, it is possible to receive a highly porous structure of catalyst based on copper nanoparticles with a pore size of several tens to several hundred nanometers. Due to the small particle size, the area of the catalytic surface is enormous. Moreover, due to the insolubility of copper nanoparticles, the reactions catalyzed by them go on the surface of the catalyst. After the reaction is completed, the copper nanoparticles that do not interact with the solvents are easily removed, which guarantees the absence of the catalyst admixture in the composition of the final product. These catalysts are already in demand for organic synthesis by the methods of “green chemistry”. Its main principles are simplicity, cheapness, safety of production, recyclability of the catalysts.

One of the promising areas of application of the copper nanoparticle catalyst is, first of all, the creation of medical products using cross-coupling reactions. In 2010, for work in the field of palladium catalyzed cross-coupling reactions, the Nobel Prize in Chemistry was awarded to scientists from Japan and the USA: Richard Heck, Ei-ichi Negishi and Akira Suzuki. Despite worldwide recognition, palladium catalyzed cross-coupling reactions are undesirable for the synthesis of most medications due to the toxicity of palladium for living cells and the lack of methods for reliable removal of palladium traces from the final product. In addition to toxicity, the high cost of catalysts based on palladium, as well as another catalyst for pharmaceuticals, platinum, makes the use of copper nanoparticles economically and environmentally justified.

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

Copper nanoparticles as inexpensive and efficient catalyst: A valuable contribution in organic synthesis by Nisha Kant Ojha, Grigory V. Zyryanov, Adinath Majee, Valery N. Charushin, Oleg N. Chupakhin, Sougata Santra. Coordination Chemistry Reviews Volume 353, 15 December 2017, Pages 1-57 https://doi.org/10.1016/j.ccr.2017.10.004

This paper is behind a paywall.

Nano-spike catalysts offer one step conversion of carbon dioxide to ethanol

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An Oct. 12, 2016 news item on ScienceDaily makes an exciting announcement, if carbon-dixoide-conversion-to-fuel is one of your pet topics,

In a new twist to waste-to-fuel technology, scientists at the Department of Energy’s Oak Ridge National Laboratory [ORNL] have developed an electrochemical process that uses tiny spikes of carbon and copper to turn carbon dioxide, a greenhouse gas, into ethanol. Their finding, which involves nanofabrication and catalysis science, was serendipitous.

An Oct. 12, 2016 ORNL news release, which originated the news item, explains in greater detail,

“We discovered somewhat by accident that this material worked,” said ORNL’s Adam Rondinone, lead author of the team’s study published in ChemistrySelect. “We were trying to study the first step of a proposed reaction when we realized that the catalyst was doing the entire reaction on its own.”

The team used a catalyst made of carbon, copper and nitrogen and applied voltage to trigger a complicated chemical reaction that essentially reverses the combustion process. With the help of the nanotechnology-based catalyst which contains multiple reaction sites, the solution of carbon dioxide dissolved in water turned into ethanol with a yield of 63 percent. Typically, this type of electrochemical reaction results in a mix of several different products in small amounts.

“We’re taking carbon dioxide, a waste product of combustion, and we’re pushing that combustion reaction backwards with very high selectivity to a useful fuel,” Rondinone said. “Ethanol was a surprise — it’s extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst.”

The catalyst’s novelty lies in its nanoscale structure, consisting of copper nanoparticles embedded in carbon spikes. This nano-texturing approach avoids the use of expensive or rare metals such as platinum that limit the economic viability of many catalysts.

“By using common materials, but arranging them with nanotechnology, we figured out how to limit the side reactions and end up with the one thing that we want,” Rondinone said.

The researchers’ initial analysis suggests that the spiky textured surface of the catalysts provides ample reactive sites to facilitate the carbon dioxide-to-ethanol conversion.

“They are like 50-nanometer lightning rods that concentrate electrochemical reactivity at the tip of the spike,” Rondinone said.

Given the technique’s reliance on low-cost materials and an ability to operate at room temperature in water, the researchers believe the approach could be scaled up for industrially relevant applications. For instance, the process could be used to store excess electricity generated from variable power sources such as wind and solar.

“A process like this would allow you to consume extra electricity when it’s available to make and store as ethanol,” Rondinone said. “This could help to balance a grid supplied by intermittent renewable sources.”

The researchers plan to refine their approach to improve the overall production rate and further study the catalyst’s properties and behavior.

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

High-Selectivity Electrochemical Conversion of CO2 to Ethanol using a Copper Nanoparticle/N-Doped Graphene Electrode by Yang Song, Rui Peng, Dale Hensley, Peter Bonnesen, Liangbo Liang, Zili Wu, Harry Meyer III, Miaofang Chi, Cheng Ma, Bobby Sumpter and Adam Rondinone. Chemistry Select DOI: 10.1002/slct.201601169 First published: 28 September 2016

This paper is open access.

Removing titanium dioxide nanoparticles from water may not be that easy

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A March 10, 2015 news item on Nanowerk highlights some research into the removal of nanoscale titanium dioxide particles from water supplies (Note: A link has been removed),

The increased use of engineered nanoparticles (ENMs) in commercial and industrial applications is raising concern over the environmental and health effects of nanoparticles released into the water supply. A timely study that analyzes the ability of typical water pretreatment methods to remove titanium dioxide, the most commonly used ENM, is published in Environmental Engineering Science (“Titanium Dioxide Nanoparticle Removal in Primary Prefiltration Stages of Water Treatment: Role of Coating, Natural Organic Matter, Source Water, and Solution Chemistry”). The article is available free on the Environmental Engineering Science website until April 10, 2015.

A March 10, 2015 Mary Ann Liebert, Inc., publishers news release (also on EurekAlert), which originated the news item, provides more details about the work (Note: A link has been removed),

Nichola Kinsinger, Ryan Honda, Valerie Keene, and Sharon Walker, University of California, Riverside, suggest that current methods of water prefiltration treatment cannot adequately remove titanium dioxide ENMs. They describe the results of scaled-down tests to evaluate the effectiveness of three traditional methods—coagulation, flocculation, and sedimentation—in the article “Titanium Dioxide Nanoparticle Removal in Primary Prefiltration Stages of Water Treatment: Role of Coating, Natural Organic Matter, Source Water, and Solution Chemistry.”

“As nanoscience and engineering allow us to develop new exciting products, we must be ever mindful of associated consequences of these advances,” says Domenico Grasso, PhD, PE, DEE, Editor-in-Chief of Environmental Engineering Science and Provost, University of Delaware. “Professor Walker and her team have presented an excellent report raising concerns that some engineered nanomaterials may find their ways into our water supplies.”

“While further optimization of such treatment processes may allow for improved removal efficiencies, this study illustrates the challenges that we must be prepared to face with the emergence of new engineered nanomaterials,” says Sharon Walker, PhD, Professor of Chemical and Environmental Engineering, University of California, Riverside.

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

Titanium Dioxide Nanoparticle Removal in Primary Prefiltration Stages of Water Treatment: Role of Coating, Natural Organic Matter, Source Water, and Solution Chemistry by Nichola Kinsinger, Ryan Honda, Valerie Keene, and Sharon L. Walker. Environmental Engineering Science. doi:10.1089/ees.2014.0288.

This paper is freely available until April 10, 2015.

Interestingly Sharon Walker and Nichola Kinsinger recently co-authored a paper (mentioned in my March 9, 2015 post) about copper nanoparticles and water treatment which concluded this about copper nanoparticles in water supplies,

The researchers found that the copper nanoparticles, when studied outside the septic tank, impacted zebrafish embryo hatching rates at concentrations as low as 0.5 parts per million. However, when the copper nanoparticles were released into the replica septic tank, which included liquids that simulated human digested food and household wastewater, they were not bioavailable and didn’t impact hatching rates.

Taking these these two paper into account (and the many others I’ve read), there is no simple or universal answer to the question of whether or not ENPs or ENMs are going to pose environmental problems.

Copper nanoparticles, toxicity research, colons, zebrafish, and septic tanks

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Alicia Taylor, a graduate student at UC Riverside, surrounded by buckets of effluent from the septic tank system she used for her research. Courtesy: University of California at Riverside

Alicia Taylor, a graduate student at UC Riverside, surrounded by buckets of effluent from the septic tank system she used for her research. Courtesy: University of California at Riverside

Those buckets of efflluent are strangely compelling. I think it’s the abundance of orange. More seriously, a March 2, 2015 news item on Nanowerk poses a question about copper nanoparticles,

What do a human colon, septic tank, copper nanoparticles and zebrafish have in common?

They were the key components used by researchers at the University of California, Riverside and UCLA [University of California at Los Angeles] to study the impact copper nanoparticles, which are found in everything from paint to cosmetics, have on organisms inadvertently exposed to them.

The researchers found that the copper nanoparticles, when studied outside the septic tank, impacted zebrafish embryo hatching rates at concentrations as low as 0.5 parts per million. However, when the copper nanoparticles were released into the replica septic tank, which included liquids that simulated human digested food and household wastewater, they were not bioavailable and didn’t impact hatching rates.

A March 2, 2015 University of California at Riverside (UCR) news release (also on EurekAlert), which originated the news item, provides more detail about the research,

“The results are encouraging because they show with a properly functioning septic tank we can eliminate the toxicity of these nanoparticles,” said Alicia Taylor, a graduate student working in the lab of Sharon Walker, a professor of chemical and environmental engineering at the University of California, Riverside’s Bourns College of Engineering.

…

The research comes at a time when products with nanoparticles are increasingly entering the marketplace. While the safety of workers and consumers exposed to nanoparticles has been studied, much less is known about the environmental implications of nanoparticles. The Environmental Protection Agency is currently accessing the possible effects of nanomaterials, including those made of copper, have on human health and ecosystem health.

The UC Riverside and UCLA [University of California at Los Angeles] researchers dosed the septic tank with micro copper and nano copper, which are elemental forms of copper but encompass different sizes and uses in products, and CuPRO, a nano copper-based material used as an antifungal agent to spray agricultural crops and lawns.

While these copper-based materials have beneficial purposes, inadvertent exposure to organisms such as fish or fish embryos has not received sufficient attention because it is difficult to model complicated exposure environments.

The UC Riverside researchers solved that problem by creating a unique experimental system that consists of the replica human colon and a replica two-compartment septic tank, which was originally an acyclic septic tank. The model colon is made of a custom-built 20-inch-long glass tube with a 2-inch diameter with a rubber stopper at both ends and a tube-shaped membrane typically used for dialysis treatments within the glass tube.

To simulate human feeding, 100 milliliters of a 20-ingredient mixture that replicated digested food was pumped into the dialysis tube at 9 a.m., 3 p.m. and 9 p.m. for five-day-long experiments over nine months.

The septic tank was filled with waste from the colon along with synthetic greywater, which is meant to simulate wastewater from sources such as sinks and bathtubs, and the copper nanoparticles. The researchers built a septic tank because 20 to 30 percent of American households rely on them for sewage treatment. Moreover, research has shown up to 40 percent of septic tanks don’t function properly. This is a concern if the copper materials are disrupting the function of the septic system, which would lead to untreated waste entering the soil and groundwater.

Once the primary chamber of the septic system was full, liquid began to enter the second chamber. Once a week, the effluent was drained from the secondary chamber and it was placed into sealed five-gallon containers. The effluent was then used in combination with zebrafish embryos in a high content screening process using multiwall plates to access hatching rates.

The remaining effluent has been saved and sits in 30 five-gallon buckets in a closet at UC Riverside because some collaborators have requested samples of the liquid for their experiments.

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

Understanding the Transformation, Speciation, and Hazard Potential of Copper Particles in a Model Septic Tank System Using Zebrafish to Monitor the Effluent* by Sijie Lin, Alicia A. Taylor, Zhaoxia Ji, Chong Hyun Chang, Nichola M. Kinsinger, William Ueng, Sharon L. Walker, and André E. Nel. ACS Nano, 2015, 9 (2), pp 2038–2048 DOI: 10.1021/nn507216f
Publication Date (Web): January 27, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

* Link added March 10, 2015.

Protecting food with copper nanoparticles

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It’s usually silver nanoparticles protecting us from bacteria (sports clothing, bandages, food, socks,, etc.)  but this time, according to a July 24, 2013 news item on ScienceDaily, it’s copper,

Microbes lurk almost everywhere, from fresh food and air filters to toilet seats and folding money. Most of the time, they are harmless to humans. But sometimes they aren’t. Every year, thousands of people sicken from E. coli infections and hundreds die in the US alone. Now Michigan Technological University scientist Jaroslaw Drelich has found a new way to get them before they get us.

His innovation relies on copper, an element valued for centuries for its antibiotic properties. Drelich, a professor of materials science and engineering, has discovered how to embed nanoparticles of the red metal into vermiculite, an inexpensive, inert compound sometimes used in potting soil. In preliminary tests on local lake water, it killed 100 percent of E. coli bacteria in the sample. Drelich also found that it was effective in killing Staphylococcus aureus, the common staph bacteria.

The news item was originated by a March 18, 2013 Michigan Technical University news release by Marcia Goodrich (Note: It’s not unusual for an institution to resend a news release which didn’t get much notice the first time). Goodrich’s news release provides more details about Drelich’s commercialization plans for his work,

Bacteria aren’t the only microorganisms that copper can kill. It is also toxic to viruses and fungi. If it were incorporated into food packaging materials, it could help prevent a variety of foodborne diseases, Drelich says.

The copper-vermiculite material mixes well with many other materials, like cardboard and plastic, so it could be used in packing beads, boxes, even cellulose-based egg cartons.

And because the cost is so low—25 cents per pound at most—it would be an inexpensive, effective way to improve the safety of the food supply, especially fruits and vegetables. Drelich is working with the Michigan Tech SmartZone to commercialize the product through his business, Micro Techno Solutions, the recipient of the 2012 Great Lakes Entrepreneur’s Quest Food Safety Innovation Award. He expects to further test the material and eventually license it to companies that pack fresh food.

The material could have many other applications as well. It could be used to treat drinking water, industrial effluent, even sewage.  “I’ve had inquiries from companies interested in purifying water,” Drelich says.

And it could be embedded in products used in public places where disease transmission is a concern: toilet seats, showerheads, even paper toweling.

“When you make a discovery like this, it’s hard to envision all the potential applications,” he says. It could even be mixed into that wad of dollar bills in your wallet. “Money is the most contaminated product on the market.”

The research Drelich performed was discussed in a 2011 paper,

Vermiculite decorated with copper nanoparticles: Novel antibacterial hybrid material by Jaroslaw Drelich, Bowen Li, Patrick Bowen, Jiann-Yang Hwang, Owen Mills, Daniel Hoffman.  Applied Surface Science, Volume 257, Issue 22, 1 September 2011, Pages 9435–9443. http://dx.doi.org/10.1016/j.apsusc.2011.06.027

This paper is behind a paywall.

Clay disks and flowerpots that purify water

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Ben Schiller writes in a Mar. 1, 2013 article for Fast Company about a not-for-profit organization, PureMadi, a joint venture between the University of Virginia (US) and the University of Venda (South Africa) and its water purification technology,

PuriMadi has already built a factory in the Limpopo province of South Africa and hopes to expand further. “Eventually that factory will be capable of producing about 500 to 1,000 filters per month, and our 10-year plan is to build 10 to 12 factories in South Africa and other countries,” Smith says. “We plan to eventually serve at least 500,000 people per year with new filters.”

The University of Virginia Feb. 5, 2013 news release by Fariss Samarrai describes both a disc and a flowerpot version of the water purification technology (Note: Some links have been removed),

PureMadi, a nonprofit University of Virginia organization, will introduce a new invention – a simple ceramic water purification tablet – during its one-year celebration event Friday [Feb. 8, 2013] from 7 to 11 p.m. at Alumni Hall.

Called MadiDrop, the tablet – developed and extensively tested at U.Va. – is a small ceramic disk impregnated with silver or copper nanoparticles. It can repeatedly disinfect water for up to six months simply by resting in a vessel where water is poured. It is being developed for use in communities in South Africa that have little or no access to clean water.

“Madi” is the Tshivenda South African word for water. PureMadi brings together U.Va. professors and students to improve water quality, human health, local enterprise and quality of life in the developing world. The organization includes students and faculty members from engineering, architecture, medicine, nursing, business, commerce, economics, anthropology and foreign affairs.

During the past year, PureMadi has established a water filter factory in Limpopo province, South Africa, employing local workers. The factory produced several hundred flowerpot-like water filters, according to James Smith, a U.Va. civil and environmental engineer who co-leads the project with Dr. Rebecca Dillingham, director of U.Va.’s Center for Global Health.

Here’s the flowerpot filter,

A worker molds a filter from local clay, sawdust and water. (Photo: Rachel Schmidt)


A worker molds a filter from local clay, sawdust and water. (Photo: Rachel Schmidt)

Here are the discs or, as they are known, the MadiDrops,

The new MadiDrops can be produced in the same factories as the filters. (Photo: Rachel Schmidt)


The new MadiDrops can be produced in the same factories as the filters. (Photo: Rachel Schmidt)

The factory is more than just a producer of water purification technologies, from the University of Virgina news release,

“Eventually that factory will be capable of producing about 500 to 1,000 filters per month, and our 10-year plan is to build 10 to 12 factories in South Africa and other countries,” Smith said. “Each filter can serve a family of five or six for two to five years, so we plan to eventually serve at least 500,000 people per year with new filters.”

The idea is to create sustainable businesses that serve their communities and employ local workers. A small percentage of the profits go back to PureMadi and will be used to help establish more factories.

The PureMadi website’s About page offers more information about the partners, the technology, and the economic impact,

PureMadi has been created by an interdisciplinary collaboration of students and faculty at the University of Virginia.  In partnership with the University of Venda in Thohoyandou, South Africa, and developing-world communities in Limpopo Province, South Africa, PureMadi is working to provide sustainable solutions to global water problems.

Our first project is the development of a sustainable, ceramic water filter factory in South Africa.  Ceramic filters are a point-of-use (e.g. household-level) water treatment technology.  Ceramic filters can be produced with local materials (clay, sawdust, and water) and local labor. The materials are mixed in appropriate proportions, pressed into the shape of a filter pot, and fired in a kiln at 900 ˚C.  Upon firing, the clay forms a ceramic and the sawdust combusts, leaving a porous ceramic matrix for filtration.  In addition, the filters are treated with a dilute solution of silver nanoparticles.  The nanoparticles lodge in the pore space of the ceramic matrix and act as a highly effective disinfectant for waterborne pathogens like Vibrio cholerae and pathogenic strains of Escherichia coli.   Untreated water can then be passed through the filter and collected in a lower reservoir with a spigot to obtain purified water.

In the field and in the laboratory, we have demonstrated that this technology is highly effective at purifying water and the filters are socially acceptable to developing-world communities.  In some of our most recent work, we have shown that the filters significantly improve the health outcomes of human populations using the filters relative to groups who only drink untreated water.

A filter factory can become a sustainable business venture that provides economic stimulus to the local community.  Our goal is to create a blueprint for a successful factory, including its architecture, efficiency of water and energy use, technological performance of the filter itself, and an effective and sustainable business model.

While the flowerpot filter has been well received the MadiDrop fills another need, from the University of Virginia news release,

MadiDrop is an alternative to the flowerpot filter, but ideally would be used in conjunction with it. The plan is to mass-produce the product at the same factories where the PureMadi filters are produced.

“MadiDrop is cheaper, easier to use, and is easier to transport than the PureMadi filter, but because it is placed into the water, rather than having the water filter through it, the MadiDrop is not effective for removing sediment in water that causes discoloration or flavor impairment,” Smith said. “But its ease of use, cost-effectiveness and simple manufacturing process should allow us to make it readily available to a substantial population of users, more so than the more expensive PureMadi filter.”

Testing shows that the filters are safe to use and release only trace amounts of silver or copper particles, well within the safe water standards of the developed world. The filters also would be useful in rural areas of developed countries such as the United States where people rely on untreated well water.

Smith noted that U.Va. Architecture School professor Anselmo Canfora and his students have worked closely with PureMadi to design sustainable filter factories for developing countries that would optimize use of local labor and materials.

The National Science Foundation, the National Institutes of Health, U.Va.’s Jefferson Public Citizen Program and the Vice Provost for Global Affairs provide support to PureMadi. Partners include the University of Venda in South Africa; Potters for Peace, a nonprofit organization committed to providing safe drinking water in the developing world; and local communities in Limpopo province in South Africa.

Taken in conjunction with my Feb. 28, 2013 posting titled, Silver nanoparticles, water, the environment, and toxicity, where I juxtaposed two articles about toxicity and silver nanoparticles (they’re ok/they’re not ok) to illustrate the complexity surrounding the question of risk, this article which features silver (and copper) nanoparticles in use for water purification adds another dimension to the question. What are the risks?, to add, are they worth taking?

Nanoparticle size doesn’t matter

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Does size matter when regulating nanomaterials? As I’ve noted (more than once), I waffle on this issue. Earlier this week, I featured my thoughts on Health Canada’s definition of nanomaterial (Oct. 24, 2011)  and posted an interview with Dr. Andrew Maynard (Oct. 24, 2011) where he expressed reservations about basing nanomaterial regulations on definitions which rely on  nanoparticle size.

Hours after posting my thoughts and the interview with Andrew, I came across this Oct. 24, 2011 news item on Nanowerk titled, Nanoparticles and their size may not be big issues. From the news item,

If you’ve ever eaten from silverware or worn copper jewelry, you’ve been in a perfect storm in which nanoparticles were dropped into the environment, say scientists at the University of Oregon.

Since the emergence of nanotechnology, researchers, regulators and the public have been concerned that the potential toxicity of nano-sized products might threaten human health by way of environmental exposure.

Now, with the help of high-powered transmission electron microscopes, chemists captured never-before-seen views of miniscule metal nanoparticles naturally being created by silver articles such as wire, jewelry and eating utensils in contact with other surfaces. It turns out, researchers say, nanoparticles have been in contact with humans for a long, long time. [emphasis mine]

…

“Our findings show that nanoparticle ‘size’ may not be static, especially when particles are on surfaces. For this reason, we believe that environmental health and safety concerns should not be defined — or regulated — based upon size,” said James E. Hutchison, who holds the Lokey-Harrington Chair in Chemistry. [emphasis mine] “In addition, the generation of nanoparticles from objects that humans have contacted for millennia suggests that humans have been exposed to these nanoparticles throughout time. Rather than raise concern, I think this suggests that we would have already linked exposure to these materials to health hazards if there were any.”

This discussion is becoming quite interesting.