Simple method of binding pollutants in water with nanoadsorbers

New types of membrane adsorbers remove unwanted particles from water and also, at the same time, dissolved substances such as the hormonally active bis-phenol A or toxic lead. To do this, researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB imbed selective adsorber particles in filtration membranes. It was not until January 2015 that the European Food Safety Authority (EFSA) lowered the threshold value for bisphenol A in packaging. The hormonally active bulk chemical is among other things a basic material for polycarbonate from which, for example, CDs, plastic tableware or spectacles glasses are manufactured. Due to its chemical structure, bisphenol A is not completely degraded in the biological stages of treatment plants and is discharged into rivers and lakes by the purification facility. Activated carbon or adsorber materials are already used to remove chemicals, anti-biotics or heavy metals from waste or process water. However, a disadvantage of these highly porous materials is the long contact time that the pollutants require to diffuse into the pores. So that as many of the harmful substances as possible are captured even in a shorter time, the treatment plants use larger quantities of adsorbers in correspondingly large treatment basins. However, activated carbon can only be regenerated with a high energy input, resulting for the most part in the need to dispose of large quantities of material contaminated with pollutants. Also, membrane filtration with nanofiltration or reverse osmosis membranes, which can remove the contaminating substances, is not yet cost-effective for the removal of dissolved molecules from high-volume flows such as process or wastewater. Membranes filter the water through their pores when a pressure is built up on one side of the membrane, thus holding back larger molecules and solid particles. But the smaller the membrane pores are, the higher the pressure – and therefore the more energy – that is required to separate the substances from water. Membrane adsorbers – filtering and binding in one step Researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have opted for a new approach that combines the advantages of both methods. When manufacturing the membranes they add small, polymeric adsorber particles. The resulting membrane adsorbers can – in addition to their filtration function – adsorptively bind substances dissolved in water ("Nanostructured Composite Adsorber Membranes for the Reduction of Trace Substances in Water: The Example of Bisphenol A"). “We make use of the porous structure of the membrane located underneath the separation layer. The pores have a highly specific surface so that as many particles as possible can be imbedded, and they also provide optimum accessibility,” says Dr. Thomas Schiestel, Head of the “Inorganic Interfaces and Membranes” working group at the Fraunhofer IGB. Membrane adsorber Membrane adsorber “Unlike conventional adsorbers, our membrane adsorbers transport the pollutants convectively. This means that, with the water flowing rapidly through the membrane pores, a contact time lasting only a few seconds is sufficient to adsorb pollutants on the particle surface,” says the scientist. Up to 40 percent of the weight of the membrane adsorbers is accounted for by the particles, so their binding capacity is correspondingly high. At the same time the membrane adsorbers can be operated at low pressures. As the membranes can be packed very tightly, very large volumes of water can be treated even with small devices. Functional adsorber particles The researchers manufacture the adsorber particles in a one-step, cost-efficient process. In this patented process monomeric components are polymerized with the help of a crosslinking agent to generate 50 to 500 nanometer polymer globules. “Depending on which substances are to be removed from the water, we select the most suitable one from a variety of monomers with differing functional groups,” Schiestel explains. The spectrum here ranges from pyridine, which tends to be hydrophobic, by way of cationic ammonium compounds and includes anionic phosphonates. Selective removal of pollutants and metals The researchers were able to show in various tests that the membrane adsorbers remove pollutants very selectively by means of the particles, which are customized for the particular contaminant in question. For example, membrane adsorbers with pyridine groups bind the hydrophobic bisphenol A especially well, whereas those with amino groups adsorb the negatively charged salt of the antibiotic penicillin G. “The various adsorber particles can even be combined in one membrane. In this way we can remove several micropollutants simultaneously with just one membrane adsorber,” says Schiestel, pointing out a further advantage. Equipped with different functional groups, the membrane adsorbers can also remove toxic heavy metals such as lead or arsenic from the water. Phosphonate membrane adsorbers, for example, adsorb more than 5 grams of lead per square meter of membrane surface area – 40 percent more than a commercially available membrane adsorber. Cost-effective and regenerable So that the membrane adsorbers can be used several times, the adsorbed pollutants have to be detached once again from the particles in the membrane. “Membrane adsorbers for bisphenol A can be fully regenerated by a shift of the pH value,” Schiestel explains. The concentrated pollutants can then be disposed off cost-effectively or broken down using suitable oxidative processes. The regenerability of the membrane adsorbers also makes possible a further application: reutilization of the separated molecules. This additionally makes the technology attractive for recovering valuable precious metals or rare earth metals.
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The first observation of the effect of electron spin of molecular oxygen on the surface oxidation reaction

Mitsunori Kurahashi, a Chief Researcher of the Nano Characterization Unit (Unit Director: Daisuke Fujita), National Institute for Materials Science (President: Sukekatsu Ushioda) and Yasushi Yamauchi, a Group Leader in the same unit, presented the first spin-controlled O2 adsorption experiment indicating that the rate of surface oxidation is strongly affected by the electron spin of O2 ("Spin Correlation in O2 Chemisorption on Ni(111)"). Control of the oxygen spin direction by the defining magnetic field (a) Control of the O2 spin direction by the defining magnetic field. (b) Spin-dependent O2 adsorption on a Ni(111) film surface. The adsorption probability is changed when the O2 spin direction relative to the majority spin direction of the Ni film (SM) is alternated. No spin-dependent effect is observed for O2 adsorption on a non-magnetic W(110) surface. O2 adsorption on material surfaces is important as the initial step of catalytic reaction, corrosion and oxide film formation. O2 is magnetic due to its electron spin derived from two unpaired electrons. The potential effect of the O2 spin on the adsorption process has been pointed out theoretically, but the effect has been unclear because there has been no experimental evidence for it. Kurahashi and Yamauchi have realized the spin- and alignment-resolved O2 adsorption experiment by combining the quantum-state-selected O2 beam, which has been originally developed by them, with a magnetized Ni film. Their experiment has shown that O2 adsorption probability depends on the orientation of the O2 spin relative to the magnetization of the Ni film. The spin dependency is significant especially at low kinetic energy conditions, and amounts to more than 40% at thermal energy. These results indicate that thermal oxidation rate of ferromagnetic materials such as iron and nickel depends strongly on the spin orientation between O2 and the surface. It has been concluded that the magnetic exchange interaction between O2 and the surface is the main cause of the observed spin dependency. It is well known that solid and/or liquid oxygen exhibit magnetism, but this research presented the first experimental evidence that the magnetic property of O2 has a strong influence on its chemical reactivity. This research has established a new methodology for analyzing the spin effect in O2-surface interactions. Also, the observed clear spin effect may provide a firm basis to advance the theoretical technique for simulating oxygen adsorption. This research was conducted as part of the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research/Basic Research (B) “Development of a Single Spin-Rotational State-Selected O2 Beam and its Application to Surface Reaction Analysis,” sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT).
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Gold nanoparticles size up to cancer treatment

Treatments that attack cancer cells through the targeted silencing of cancer genes could be developed using small interfering RNA molecules (siRNA). However delivering the siRNA into the cells intact is a challenge as it is readily degraded by enzymes in the blood and small enough to be eliminated from the blood stream by kidney filtration. Now Kazunori Kataoka at the University of Tokyo and colleagues at Tokyo Institute of Technology have designed a protective treatment delivery vehicle with optimum stability and size for delivering siRNA to cells (, "Precise engineering of siRNA delivery vehicles to tumors using polyion complexes and gold nanoparticles"). text Top: Stability assay of the siRNA-loaded polymer complex (labelled uPIC, unimer polyion complex) without and with gold nanoparticles (AuNP) incubated with heparin at 0, 1, 2, and 3 µg/mL, and glutathione (GSH) at 0 and 10 mM. Bottom: Schematic illustration of the proposed mechanism for intracellular siRNA release from uPIC-AuNPs in the presence of GSH. (click on image to enlarge) The researchers formed a polymer complex with a single siRNA molecule. The siRNA-loaded complex was then bonded to a 20 nm gold nanoparticle, which thanks to advances in synthesis techniques can be produced with a reliably low size distribution. The resulting nanoarchitecture had the optimum overall size - small enough to infiltrate cells while large enough to accumulate. In an assay containing heparin – a biological anti-coagulant with a high negative charge density – the complex was found to release the siRNA due to electrostatic interactions. However when the gold nanoparticle was incorporated the complex remained stable. Instead, release of the siRNA from the complex with the gold nanoparticle could be triggered once inside the cell by the presence of glutathione, which is present in high concentrations in intracellular fluid. The glutathione bonded with the gold nanoparticles and the complex, detaching them from each other and leaving the siRNA prone to release. The researchers further tested their carrier in a subcutaneous tumour model. The authors concluded that the complex bonded to the gold nanoparticle “enabled the efficient tumor accumulation of siRNA and significant in vivo gene silencing effect in the tumor, demonstrating the potential for siRNA-based cancer therapies.”
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