U of Illinois & Ben-Gurion U Create ‘Ultra’ Filtration Membranes that remove viruses from drinking water


 

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Current membrane filtration methods require intensive energy to adequately remove pathogenic viruses without using chemicals like chlorine, which can contaminate the water with disinfection byproducts. Researchers at UIUC and BGU collaborated on the new approach for virus pathogen removal, which was published in the current issue of Water Research.

“This is an urgent matter of public safety,” the researchers say. “Insufficient removal of human Adenovirus in municipal wastewater, for example, has been detected as a contaminant in U.S. drinking water sources, including the Great Lakes and worldwide.”

Researchers from Ben-Gurion University of the Negev (BGU) and the University of Illinois at Urbana-Champaign (UIUC) have developed novel ultrafiltration membranes that significantly improve the virus-removal process from treated municipal wastewater used for drinking in water-scarce cities (Water Research, “Improvement of virus removal using ultrafiltration membranes modified with grafted zwitterionic polymer hydrogels”).

The norovirus, which can cause nausea, vomiting and diarrhea, is the most common cause of viral gastroenteritis in humans, and is estimated to be the second leading cause of gastroenteritis-associated mortality. Human adenoviruses can cause a wide range of illnesses that include the common cold, sore throat (pharyngitis), bronchitis, pneumonia, diarrhea, pink eye (conjunctivitis), fever, bladder inflammation or infection (cystitis), inflammation of the stomach and intestines (gastroenteritis), and neurological disease.

 

In the study, Prof. Moshe Herzberg of the Department of Desalination and Water Treatment in the Zuckerberg Institute for Water Research at BGU and his group grafted a special hydrogel coating onto a commercial ultrafiltration membrane. The “zwitterionic polymer hydrogel” repels the viruses from approaching and passing through the membrane. It contains both positive and negative charges and improves efficiency by weakening virus accumulation on the modified filter surface. The result was a significantly higher rate of removal of waterborne viruses, including human norovirus and adenovirus.Nanofiltration II Membrane-Layers-01

 

“Utilizing a simple graft-polymerization of commercialized membranes to make virus removal more comprehensive is a promising development for controlling filtration of pathogens in potable water reuse,” says Prof. Nguyen, Department of Chemical Engineering, UIUC.
Source: American Associates, Ben-Gurion University of the Negev

 

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Atoms in a nanocrystal cooperate, much like in biomolecules


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Nanocrystals of cadmium selenide, known for their brilliant luminescence, display intriguing chemical behavior resulting from positive cooperation between atoms, a behavior akin to that found in biomolecules. Credit: Prashant Jain        

(Phys.org) —Researchers have long thought that biological molecules and synthetic nanocrystals were similar only in size. Now, University of Illinois at Urbana-Champaign chemists have found that they can add reactivity to the list of shared traits. Atoms in a nanocrystal can cooperate with each other to facilitate binding or switching, a phenomenon widely found in biological molecules.

The finding could catalyze manufacturing of for smart sensors, solar cells, tiny transistors for optical computers, and medical imaging. Led by chemistry professor Prashant Jain, the team published its findings in the journal Nature Communications.

“In geological, industrial and domestic environments, the nanoscale grains of any material undergo chemical transitions when they are put under reactive conditions,” Jain said. “Iron rusting over time and diamond forming from carbon are examples of two commonly occurring transitions. Understanding how these transitions occur on the scale of the tiniest grains of the material is a major motivation of our work.”

Scientists can exploit such transitions to make nanocrystals that conform to a particular structure. They can make a nanocrystal of one material and transform it into another material, essentially using the original nanocrystal framework as a template for creating a nanocrystal of the new material with the same size and shape. This lets researchers create nanocrystals of new materials in shapes and structures they may not be able to otherwise.

In the new study, the researchers transformed tiny crystals of the material cadmium selenide to crystals of copper selenide. Copper selenide nanocrystals have a number of interesting properties that can be used for solar energy harvesting, optical computing and laser surgery. Transformation from cadmium selenide creates nanocrystals with a purity difficult to attain from other methods.

The researchers, including graduate student Sarah White, used advanced microscopy and spectroscopy techniques to determine the dynamics of the atoms within the crystals during the transformation and found that the transformation occurs not as a slow diffusion process, but as a rapid switching thanks to co-operativity.

The researchers saw that once the cadmium-selenide nanocrystal has taken up a few initial copper “seed” impurities, atoms in the rest of the lattice can cooperate to rapidly swap out the rest of the cadmium for copper. Jain compares the crystals to hemoglobin, the molecule in red blood cells that carries oxygen. Once one oxygen molecule has bound to hemoglobin, other binding sites within hemoglobin slightly change conformation to more easily pick up more oxygen. He posits that similarly, copper impurities might cause a structural change in the nanocrystal, making it easier for more copper ions to infiltrate the nanocrystal in a rapid cascade.

The researchers reproduced the experiment with silver, in addition to copper, and saw similar, though slightly less speedy, cooperative behavior.

Now, Jain’s team is using its advanced imaging to watch transitions happen in single nanocrystals, in real time.

“We have a sophisticated optical microscope in our lab, which has now allowed us to catch a single nanocrystal in the act of making a transition,” Jain said. “This is allowing us to learn hidden details about how the transition actually proceeds. We are also learning how one nanocrystal behaves differently from another.”

Next, the researchers plan to explore biomolecule-like cooperative phenomena in other solid-state materials and processes. For example, co-operativity in catalytic processes could have major implications for or manufacturing of expensive specialty chemicals.

“In the long term, we are interested in exploiting the co-operative behavior to design artificial smart materials that respond in a switch-like manner like hemoglobin in our body does,” Jain said.

Explore further:     Researchers extend galvanic replacement reactions to metal oxide nanocrystals

More information: “Co-operativity in a nanocrystalline solid-state transition.” Sarah L. White, Jeremy G. Smith, Mayank Behl, Prashant K. Jain. Nature Communications 4, Article number: 2933 DOI: 10.1038/ncomms3933

Read more at: http://phys.org/news/2013-12-atoms-nanocrystal-cooperate-biomolecules.html#jCp

Read more at: http://phys.org/news/2013-12-atoms-nanocrystal-cooperate-biomolecules.html#jCp

Important mechanism behind nanoparticle reactivity discovered


Mix id32807Improving the understanding of – particularly those of iron and silver – is of key importance to scientists because of their many potential applications. For example, iron and are considered important in fields ranging from clean fuel technologies, high density data storage and catalysis, to water treatment, soil remediation, targeted drug delivery and cancer therapy.

The research team, which also included scientists from the University of Leicester, the National Institute for Materials Science, Japan and the University of Illinois at Urbana-Champaign, USA, used the unprecedented resolution attainable with aberration-corrected scanning transmission to study the oxidisation of cuboid iron nanoparticles and performed strain analysis at the atomic level.

Lead investigator Dr Roland Kröger, from the University of York’s Department of Physics, said: “Using an approach developed at York and Leicester for producing and analysing very well-defined nanoparticles, we were able to study the reaction of metallic nanoparticles with the environment at the and to obtain information on strain associated with the oxide shell on an iron core.

Read more at: http://phys.org/news/2013-11-important-mechanism-nanoparticle-reactivity.html#jCp

 

The scientists used a method known as Z-contrast imaging to examine the oxide layer that forms around a nanoparticle after exposure to the atmosphere, and found that within two years the particles were completely oxidised.

Corresponding author Dr Andrew Pratt, from York’s Department of Physics and Japan’s National Institute for Materials Science, said: “Oxidation can drastically alter a nanomaterial’s properties – for better or worse – and so understanding this process at the nanoscale is of critical importance. This work will therefore help those seeking to use metallic nanoparticles in environmental and technological applications as it provides a deeper insight into the changes that may occur over their desired functional lifetime.”

The experimental work was carried out at the York JEOL Nanocentre and the Department of Physics at the University of York, the Department of Physics and Astronomy at the University of Leicester and the Frederick-Seitz Institute for Materials Research at the University of Illinois at Urbana-Champaign.

The scientists obtained images over a period of two years. After this time, the nanoparticles, which were originally cube-shaped, had become almost spherical and were completely oxidised.

Professor Chris Binns, from the University of Leicester, said: “For many years at Leicester we have been developing synthesis techniques to produce very well-defined nanoparticles and it is great to combine this technology with the excellent facilities and expertise at York to do such penetrating science. This work is just the beginning and we intend to capitalise on our complementary abilities to initiate a wider collaborative programme.”

Read more at: http://phys.org/news/2013-11-important-mechanism-nanoparticle-reactivity.html#jCp