Researchers led by Francesco Stellacci at MIT have created a new material that can selectively absorb oil from water and can thus be used to help clean up major oil spills at a significantly faster rate. This material is made up of a mesh of super hydrophobic manganese oxide nanowires that are around 50 micrometers thick. Normally, maganese oxide nanowires are attracted to water, but by adding a silicon coating the material becomes extremely water repellent. Tests have shown that it is able to suck up about 20 times its weight in oil and 10 times its weight in gasoline without even sucking up a drop of water. Thus, it has proven to be more selective than similar materials, such as glass fibers, which absorb small amounts of water as well as oil. The oil is drawn through capillary action and absorbed deep into the interstitial spaces between the nanowires. Stellaci deemed this process "selective superabsorbance". The material is also very durable and can withstand high temperatures while oil is evaporated off of it. These high temperatures will also evaporate the silicon coating, but another layer can be applied. However, further research needs to be done on these materials because it is suspected that maganese oxide can be toxic to the environment. The main advantage of the invention of this material according to a researcher from the University of Michigan in Ann Arbor, Joery Lahann, is that the new material "clearly provides a blueprint that can guide the design of future nanomaterials for environmental applications."
http://www.newscientist.com/article/dn14025-nanotech-tissue-loves-oil-spills-hates-water.html
http://pubs.acs.org/cen/news/86/i23/8623news3.html
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3 comments:
Did the article discuss how the nanowires are made or give a reference?
Yes, the C&EN article said that the oil absorbing membrane material was synthesized by heating manganese oxide nanowires with polydimethysiloxane and then cross-linking silicon with the manganese oxide.
Another article I found discussed the synthesis of these manganese oxide nanowires. This is the mechanism they came up with:
MnSO4+ (NH4)2S2O8+ 2H2O--> MnO2+ (NH4)2SO4+ 2H2SO4
They synthesized these nanowires using a liquid-phase oxidation method under hydrothermal conditions. (NH4)2S2O8 was used as an oxidizing reagent for MnSO4 to give MnO2. They also tried another method using KMnO4 as the oxidizing reagent.
Here is a more detailed excerpt from the article:
Method A: (NH4)2S2O8 was as the oxidizing reagent for MnSO4 this method. For a typical synthesis, MnSO4H2O (0.008 mol) and an equal amount of ammonium persulfate ((NH4)2S2O8) were put into distilled water at room temperature to form a homogeneous solution, which was then transferred into a 40 mL Teflon-lined stainless steel autoclave, sealed and maintained at 140 °C for 12 h. After the reaction was completed, the resulting solid product was filtered, washed with distilled water to remove ions possibly remnant in the final products, and finally dried in air. The amount of (NH4)2SO4, temperature, aging time, and pressure were altered on the basis of this synthesis.
Method B: On the basis of Method A, KMnO4 was used as the oxidizing reagents for MnSO4. The molar ratio of KMnO4 and MnSO4H2O was varied in the phase-controlled synthesis of alpha- and beta-MnO2 nanorods with the molar number of Mn atoms kept about 0.0044 mol. Temperature was kept about 160 °C for a typical synthesis, and varied in a range of 120-180 °C.
http://www3.interscience.wiley.com/cgi-bin/fulltext/102521431/HTMLSTART
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