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 Post subject: Biological Uranium?
PostPosted: Jun 02, 2017 10:33 am 
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A New Twist on Uranium's Origin Story

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They found that up to 89 percent of the uranium from their 650-foot-deep samples wasn't crystalline uraninite at all, but rather, a non-crystalline uranium that was bound to organic matter or inorganic carbonate. Most of the uranium they found in that unmined site is estimated to be 3 million years old, and formed via reduction by microorganisms ­- microbes that respire not on oxygen, but on uranium.


The "greens" might really choke on the idea of biological organisms that actually utilize uranium. I've been told for many years by chemists that uranium has remarkable chemistry potential. I wouldn't be surprised if organisms found a way to exploit that chemistry.


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 Post subject: Re: Biological Uranium?
PostPosted: Aug 01, 2017 5:52 pm 
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Helpful uranium-munching bacteria breathe it through electric wires

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It’s well known that some members of Geobacter can utilize uranium as an electron acceptor, similar to how humans use oxygen. As part of that electron transfer reaction, hexavalent uranium (which has a charge of +6) becomes tetravalent uranium (which has a charge of +4). Hexavalent uranium is easily dissolved in water, meaning it is mobile in the subsurface and moves with groundwater flow. Tetravalent uranium, however, quickly precipitates in mineral form, locking it up in the sediment or bedrock. This is what makes the bacteria so helpful at uranium contamination sites—they prevent contamination from spreading in groundwater.


The tetravalent/hexavalent nature of uranium....ah, isn't it wonderful!


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 Post subject: Re: Biological Uranium?
PostPosted: Dec 08, 2017 9:04 pm 
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Uranium: the element of surprise

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Uranium belongs to a block of chemical elements known as the lanthanides and actinides, often drawn separately at the bottom of the periodic table. These heavy metals have some uses as catalysts in industrial chemistry, but they all tend to behave quite similarly, making them less interesting to chemists looking to develop new catalysts. Typically, the most fertile elements of the periodic table for discovering catalysts are the transition metals. These metals, grouped around the centre of the periodic table, have electrons in configurations that make them very good at helping other molecules to break and form new bonds. Now, Liddle and his team have shown that uranium can undergo two chemical processes which are usually associated with the transition metals, meaning that uranium may be able to access powerful new chemistry previously beyond its reach. The team achieved this change in the reactivity of uranium by attaching nitrogen-containing molecules to the metal, which modify its chemical behaviour. The Manchester researchers have shown that uranium can undergo important processes called “oxidative addition” and “reductive elimination.” Oxidative addition occurs when a metal (M) inserts itself into the bond between two elements (such as carbon and oxygen, for example), turning a C–O bond into C–M–O molecule. Reductive elimination is simply the reverse of oxidative elimination, where the metal is kicked out and two elements that were attached to the metal form a bond to each other. This ability to break and form bonds, usually limited to the transition metals, can be harnessed by chemists to synthesise a wide variety of organic molecules, giving us access to better fuels, drugs, agrochemicals and plastics. The ability of uranium to access these chemical processes brings together the chemistry of the transition metals with that of the lanthanides and actinides, offering the possibility of a new type of hybrid catalyst which may have previously unseen properties.


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