Researchers at the UK’s Birmingham University have recovered uranium from the radioactive waters of uranium mines using bacteria and inositol phosphate, a chemical parallel of a cheap waste material from plants. The same technology can also be used to clean up nuclear waste.
Professor Lynne Macaskie Sunday presented the group’s work to the Society for General Microbiology’s meeting at Heriot-Watt University, Edinburgh.
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.
This process was first described in 1995, but then a more expensive additive was used and that, combined with the then low price of uranium, made the process uneconomic.
The discovery that inositol phosphate is 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.
As an example, if pure inositol phosphate, bought from a commercial supplier is used, the cost of this process is $19.30 per gram of uranium recovered. If a cheaper source of inositol phosphate is used such as calcium phytate, the cost reduces to $0.14 for each gram of recovered uranium. At 2007 prices, uranium cost $0.34/gram; it is currently $0.14/gram. These prices make the process economic overall because there is also an environmental protection benefit. Use of low-grade inositol phosphate from agricultural wastes would bring the cost down still further and the economic benefit will also increase as the price of uranium is forecast to rise again.
Microbial bioremediation of nuclear and industrial wastes
Some micro-organisms can accumulate heavy metals and this may be of use in the remediation of contaminated streams and soils. We are looking at the underlying biochemical and chemical mechanisms of this, and using immobilised cells and biofilms for biodegradation of wastes and pollutants.