Silver Nanoparticles in Clothing Wash Out, May Be Toxic
By Sukalyan Sengupta and Tabish Nawaz
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 U.S. contain nanosilver.
Korean toothpaste containing nanosilver Alex Parlini, Project on Emerging Nanotechnologies, CC BY-ND
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 Textile Silver Lode
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.
Toxic effects of silver nanoparticles on zebra fish embryos Asharani et al., 2008., CC BY
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.
This poses multiple risks. If plants take up silver from soil, they could concentrate it and introduce it into the food chain. It also can leach into groundwater or wash into rivers via rainstorms or erosion.
Treating Laundry Water at the Source
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.
Once laundry washwater is piped to wastewater treatment plants and mixed with sewage and water from other sources, silver concentrations decrease significantly and can be converted into different chemical forms.
Deer Island Wastewater Treatment Plant, Boston, Massachusetts Doc Searls, CC BY
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.
Schematic of the silver recovery process using ion-exchange resinTabish Nawaz
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.
Our findings can spur research into alternative detergent formulations that improve silver recovery. They also show that ion-exchange technology can recover trace silver from washwater that contains high levels of detergent.
The Future of Wastewater Treatment
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?
Our approach is both more efficient and a more effective way to address new environmental problems—potentially through a step as simple as installing a specialized water treatment cartridge in your washing machine.
Are Dryer Sheets and Liquid Softeners Safe for the Environment? https://t.co/NTK3QGK1RG @CleanAirMoms @ewg @goodhealth— EcoWatch (@EcoWatch)1519666753.0
Reposted with permission from our media associate The Conversation.
Environmental officials and members of the U.S. Coast Guard are racing to clean up a mysterious oil spill that has spread to 11 miles of Delaware coastline.
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By Dr. Kate Raynes-Goldie
Of all the plastic we've ever produced, only 9% has been recycled. So what happened to all that plastic you've put in the recycling bin over the years?
Triangle of Mistruths<p>The myth created around plastic recycling has been one of simplicity. We look for the familiar triangle arrows, then pop the waste in the recycling bin so it can be reused.</p><p>But the true purpose of those triangles has been misunderstood by the general public ever since their invention in the 1980s.</p><p>These triangles were actually created by the plastics industry and, according to a report provided to them in July 1993, <a href="https://www.npr.org/transcripts/912150085" target="_blank">were creating "unrealistic expectations"</a> about what could be recycled. But they decided to keep using the codes.</p><p>Which is why many people still believe that these triangular symbols (also known as a <a href="https://sustainablepackaging.org/101-resin-identification-codes/" target="_blank" rel="noopener noreferrer">resin identifier code</a> or RIC) means something is recyclable.</p><p>But according to the American Society for Testing and Materials International (ASTM) – which controls the RIC system – the numbered triangles "<a href="https://www.astm.org/Standards/D7611.htm" target="_blank" rel="noopener noreferrer">are not recycle codes</a>." In fact, they weren't created for the general public at all. They were made for the post-consumer plastic industry.</p><p>In other words, the symbols make it easier to sort the different types of plastics, some of which cannot be recycled – <a href="https://www.ecobin.com.au/understand-recycling-codes/" target="_blank" rel="noopener noreferrer">depending on the recycling facility</a>.</p><p>"Unfortunately, just placing your plastic into the recycling bin doesn't mean it will get recycled," says Lara Camilla Pinho. She is an architect and lecturer at the UWA School of Design who is researching novel uses of plastic waste.</p><p>"The recycling system is complicated and often dictated by market demand. Not all plastic is recyclable. We cannot recycle plastic bags or straws for example."</p>
Behind the Scenes<p>So, what makes recycling plastics so difficult?</p><p>"Essentially, there are two types of plastics – thermoplastics and thermosets. While thermoplastics can be re-melted and re-molded, thermosets contain cross-linked polymers that cannot be separated meaning they cannot be recycled," says Lara.</p><p>"Even thermoplastics have a limit to the amount of times we can recycle them, as each time they are recycled they downgrade in quality."</p><p>Even when plastics are recyclable, it is <a href="https://www.theguardian.com/environment/2019/oct/13/war-on-plastic-waste-faces-setback-as-cost-of-recycled-material-soars" target="_blank">often more costly</a> than simply making new plastics.</p>
Sugar, Seaweed and Mushrooms<p>If the conventional recycling system isn't working, what else can we do with all the plastic we've created?</p><p>Lara is looking for ways to add value to recycled plastics such as using it in the design and development of architectural products. She hopes to use these architectural products to help underserved communities that are disproportionately affected by plastic waste.</p><p>In addition to recycling, we also need to find ways to reduce our use of virgin petroleum-based plastics.</p><p>Bioplastic is one such product that has been getting a lot of hype over the last few years. And although they're better than petroleum-based plastics, bioplastics also come with their own <a href="https://phys.org/news/2017-12-truth-bioplastics.html" target="_blank">set of challenges</a>.</p><p>"There are already a lot of bio-based alternatives to plastic, such as bagasse – a byproduct of sugar cane processing," says Lara.</p><p><a href="https://blogs.scientificamerican.com/observations/the-mycelium-revolution-is-upon-us/" target="_blank" rel="noopener noreferrer">Mycelium</a>, a type of fungi we most often associate with mushrooms, are also providing an interesting plastic alternative.</p><p>"In the field of architecture, mycelium is starting to be used as an alternative to plastic insulation, but also as compostable packaging and bricks," says Lara.</p><p>"The bricks take around five days to make and are strong, durable, water resistant and compostable at the end of their use."</p><p><a href="https://www.arup.com/news-and-events/hyfi-reinvents-the-brick" target="_blank" rel="noopener noreferrer">Hy-Fi Tower</a>, created by <a href="http://www.thelivingnewyork.com/living_about.html" target="_blank" rel="noopener noreferrer">The Living</a>, is an example of a building made from these bricks.</p><p>And finally, there's seaweed.</p><p>"[Seaweed is] cheap and can reproduce itself quickly without fertilizers. In architecture, there is use for seaweed as an alternative to plastic insulation but also as cladding," says Lara.</p>
More Money, More Problems<p>While all these alternatives are great, the main cause of our plastic dilemma is not scientific or technological, but economic.</p><p>As long as it remains <a href="https://engineering.mit.edu/engage/ask-an-engineer/why-is-it-cheaper-to-make-new-plastic-bottles-than-to-recycle-old-ones/" target="_blank">cheaper to create new plastics</a> from fossil fuels rather than from bioplastics or from recycling, we're going to be stuck with plastic garbage islands floating in our oceans.</p><p>The true cost to our health and our environment has yet to be included in the equation. But once it is, maybe that is when the real shift will happen.</p>
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- The Recycling Dilemma: Good Plastic, Bad plastic? - EcoWatch ›
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Plain Naturals is making waves in the CBD space with a new product line for retail customers looking for high potency CBD products at industry-low prices.
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Towards the end of the final presidential debate of the 2020 election season, the moderator asked both candidates how they would address both the climate crisis and job growth, leading to a nearly 12-minute discussion where Donald Trump did not acknowledge that the climate is changing and Joe Biden called the climate crisis an existential threat.
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By Zheng Chen and Darren H. S. Tan
As concern mounts over the impacts of climate change, many experts are calling for greater use of electricity as a substitute for fossil fuels. Powered by advancements in battery technology, the number of plug-in hybrid and electric vehicles on U.S. roads is increasing. And utilities are generating a growing share of their power from renewable fuels, supported by large-scale battery storage systems.