Heavy Metals in Water Meet Their Match

Reusable, Carbon Nanotube-Reinforced Filters Clean Toxins from Water, study shows

Date: July 27, 2017
Source: Rice University
Summary: A high school student's project removes more than 99 percent of heavy metal toxins from water. A new article demonstrates its potential for water remediation in developing nations around the world.

Plain quartz fiber, top, gains the ability to remove toxic metals from water when carbon nanotubes are added, bottom. The filters absorbed more than 99 percent of metals from test samples laden with cadmium, cobalt, copper, mercury, nickel and lead. Once saturated, the filters can be washed and reused.
Credit: Barron Research Group/Rice University

Carbon nanotubes immobilized in a tuft of quartz fiber have the power to remove toxic heavy metals from water, according to researchers at Rice University.

Prize-winning filters produced in the lab of Rice chemist Andrew Barron by then-high school student and lead author Perry Alagappan absorb more than 99 percent of metals from samples laden with cadmium, cobalt, copper, mercury, nickel and lead. Once saturated, the filters can be washed with a mild household chemical like vinegar and reused.

The researchers calculated one gram of the material could treat 83,000 liters of contaminated water to meet World Health Organization standards -- enough to supply the daily needs of 11,000 people.

The lab's analysis of the new filters appears this month in Nature's open-access Scientific Reports.

The robust filters consist of carbon nanotubes grown in place on quartz fibers that are then chemically epoxidized. Lab tests showed that scaled-up versions of the "supported-epoxidized carbon nanotube" (SENT) filters proved able to treat 5 liters of water in less than one minute and be renewed in 90 seconds. The material retained nearly 100 percent of its capacity to filter water for up to 70 liters per 100 grams of SENT, after which the metals contained could be extracted for reuse or turned into a solid for safe disposal.

While the quartz substrate gives the filter form and the carbon nanotube sheath makes it tough, the epoxidation via an oxidizing acid appears to be most responsible for adsorbing the metal, they determined.

Alagappan, now an undergraduate student at Stanford University, was inspired to start the project during a trip to India, where he learned about contamination of groundwater from the tons of electronic waste -- phones, computers and the like -- that improperly end up in landfills.

"Perry contacted me wanting to gain experience in laboratory research," Barron said. "Since we had an ongoing project started by Jessica Heimann, an undergraduate who was taking a semester at Jacobs University Bremen, this was a perfect match."

Barron said the raw materials for the filter are inexpensive and pointed out the conversion of acetic acid to vinegar is ubiquitous around the globe, which should simplify the process of recycling the filters for reuse even in remote locations. "Every culture on the planet knows how to make vinegar," he said.

"This would make the biggest social impact on village-scale units that could treat water in remote, developing regions," Barron said. "However, there is also the potential to scale up metal extraction, in particular from mine wastewater."

Alagappan's research won a series of awards while he was still a high school student in Clear Lake, a Houston suburb, as well as a visiting student in Barron's Rice lab. First was the top prize for environmental sciences at the Science and Engineering Fair of Houston in 2014. That qualified him to enter the Intel International Science and Engineering Fair in Los Angeles the next year, where he also took the top environmental award.

He booted that into the top prize at the 2015 Stockholm Junior Water Prize, where the crown princess of Sweden presented him with the honor.

"It's been a tremendous honor to be recognized on an international level for this research, and I am grateful for the opportunity to work on this project alongside such a talented group of individuals," Alagappan said. "I also especially appreciated being able to meet with other young researchers at the Intel International Science Fair and the Stockholm Junior Water Prize, who inspired me with their firm commitment to elevate society through science and technology."

Story Source: Rice University. "Heavy metals in water meet their match: Reusable, carbon nanotube-reinforced filters clean toxins from water, study shows." ScienceDaily. ScienceDaily, 27 July 2017. www.sciencedaily.com/releases/2017/07/170727083159.htm

Bacteria, Graphene and Nanotech Produce Usable Electricity From Wastewater

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

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

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

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

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

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

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

Crowd Computing to Improve Water Filtration

The research was conducted by 150,000 volunteers

Date: July 6, 2015
Source: American Friends of Tel Aviv University
Summary: Scientists propose a novel nanotechnology-based strategy to improve water filtration. The project was an experiment in crowdsourced computing -- carried out by over 150,000 volunteers who contributed their own computing power to the research.

Nearly 800 million people worldwide don't have access to safe drinking water, and some 2.5 billion people live in precariously unsanitary conditions, according to the Centers for Disease Control and Prevention. Together, unsafe drinking water and the inadequate supply of water for hygiene purposes contribute to almost 90% of all deaths from diarrheal diseases -- and effective water sanitation interventions are still challenging scientists and engineers.

A new study published in Nature Nanotechnology proposes a novel nanotechnology-based strategy to improve water filtration. The research project involves the minute vibrations of carbon nanotubes called "phonons," which greatly enhance the diffusion of water through sanitation filters. The project was the joint effort of a Tsinghua University-Tel Aviv University research team and was led by Prof. Quanshui Zheng of the Tsinghua Center for Nano and Micro Mechanics and Prof. Michael Urbakh of the TAU School of Chemistry, both of the TAU-Tsinghua XIN Center, in collaboration with Prof. Francois Grey of the University of Geneva.

Shake, Rattle, and Roll

"We've discovered that very small vibrations help materials, whether wet or dry, slide more smoothly past each other," said Prof. Urbakh. "Through phonon oscillations -- vibrations of water-carrying nanotubes -- water transport can be enhanced, and sanitation and desalination improved. Water filtration systems require a lot of energy due to friction at the nano-level. With these oscillations, however, we witnessed three times the efficiency of water transport, and, of course, a great deal of energy saved."

The research team managed to demonstrate how, under the right conditions, such vibrations produce a 300% improvement in the rate of water diffusion by using computers to simulate the flow of water molecules flowing through nanotubes. The results have important implications for desalination processes and energy conservation, e.g. improving the energy efficiency for desalination using reverse osmosis membranes with pores at the nanoscale level, or energy conservation, e.g. membranes with boron nitride nanotubes.

Crowdsourcing the Solution

The project, initiated by IBM's World Community Grid, was an experiment in crowdsourced computing -- carried out by over 150,000 volunteers who contributed their own computing power to the research.

"Our project won the privilege of using IBM's world community grid, an open platform of users from all around the world, to run our program and obtain precise results," said Prof. Urbakh. "This was the first project of this kind in Israel, and we could never have managed with just four students in the lab. We would have required the equivalent of nearly 40,000 years of processing power on a single computer. Instead we had the benefit of some 150,000 computing volunteers from all around the world, who downloaded and ran the project on their laptops and desktop computers.

"Crowdsourced computing is playing an increasingly major role in scientific breakthroughs," Prof. Urbakh continued. "As our research shows, the range of questions that can benefit from public participation is growing all the time."

The computer simulations were designed by Ming Ma, who graduated from Tsinghua University and is doing his postdoctoral research in Prof. Urbakh's group at TAU. Ming catalyzed the international collaboration. "The students from Tsinghua are remarkable. The project represents the very positive cooperation between the two universities, which is taking place at XIN and because of XIN," said Prof. Urbakh.

Other partners in this international project include researchers at the London Centre for Nanotechnology of University College London; the University of Geneva; the University of Sydney and Monash University in Australia; and the Xi'an Jiaotong University in China. The researchers are currently in discussions with companies interested in harnessing the oscillation know-how for various commercial projects.

Story Source: American Friends of Tel Aviv University. "Crowd computing to improve water filtration: The research was conducted by 150,000 volunteers." ScienceDaily. ScienceDaily, 6 July 2015. www.sciencedaily.com/releases/2015/07/150706123738.htm.