Tuesday, September 22, 2009

E. Coli and Recovering Uranium

Credit:  Rocky Mountain Laboratories, NIAID, NIH 
  
Scanning electron micrograph of Escherichia coli, grown in culture and adhered to a coverslip 
We thought to call this post “Diseased Waste,” but decided it wasn’t only inaccurate but sounded like a death metal band. When we hear E. coli, we think disease, though of course, the critters live in our intestines from about three days after our births onwards and only a few strains of it prove dangerous via food contamination. You can read about E. coli here.

But still, unfairly, the first thought was disease. So we were intrigued by this Science Daily article about the use of E. coli to retrieve uranium from otherwise exhausted mines and even as a vehical to clean up sites. The bacterium isn’t the key here, though – it’s efficacy for this purpose has been known for awhile – it’s the additive.

Here’s how the process works:

Bacteria, in this case, E. coli, break down a source of inositol phosphate (also called phytic acid), a phosphate storage material in seeds, to free the phosphate molecules. The phosphate then binds to the uranium forming a uranium phosphate precipitate on the bacterial cells that can be harvested to recover the uranium.

But previous methods were expensive. Enter inositol phosphate:

The discovery that inositol phosphate was potentially six times more effective as well as being a cheap waste material means that the process becomes economically viable, especially as the world price of uranium is likely to increase as countries move to expand their nuclear technologies in a bid to produce low-carbon energy.

And how cheap is cheap?

As an example, if pure inositol phosphate, bought from a commercial supplier is used, the cost of this process is £1.72 [$2.81] per gram of uranium recovered. If a cheaper source of inositol phosphate is used (eg calcium phytate) the cost reduces to £0.09 [$0.14] for each gram of recovered uranium.

Now, we cannot pretend to understand why it took so long to understand that calcium phytate could be used as an alternate source – its properties seem well understood – but maybe the Birmingham University group that undertook this project to were starting with an idea that had been long abandoned.

Well, if so, abandoned no more. Read the whole thing for a full explanation. Even allow for the usual disclaimer that college work often doesn’t scale well to production level, this has great potential.

Your friend, E. coli.

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