Extn. of uranium in situ from its ores - by oxidn. and leaching with oxygen enriched water under carbon di:oxide pressure and alkaline earth (bi)carbonate soln.

摘要

Uranium is extracted in situ from the ore deposit (or after ore mining and crushing) by a combination of oxidn. and leaching with O-enriched water under CO2 press. and alkaline earth carbonate or bicarbonate soln. The alkaline earth metals are either Ca or Mg. The CO2 pressure is reduced to 4 bar after the U has been oxidised and dissolved. This pressure is maintained and the CO2 released by the redn. in pressure is recovered for further use. The pressure is finally reduced to atmospheric press. and the soln. degassed by a vacuum treatment. The liq. is then treated with CaOH at pH 10-12 so that Ca uranate and CaCO3 ppte. are formed which are recovered. Process required adaption to the local conditions and there are therefore a number of variations and adjustments required, e.g. to restore the pH of the underground water alkaline earth hydroxide solns. are pumped into the bore holes. The Ca uranate may be treated with H2O2 in order to produce U peroxide which is recovered. The H2O2 treatment may also be used as a second leaching in situ operations. The U may also be recovered by ion exchange. In laboratory experiments a U recovery of up to 92% was obtd. The ore is oxidised in situ to produce a soluble phase, i.e. the method is much less expensive than a mining operation. The former (NH4)2CO3 process for the extn. left NH3 in the underground water and presented a serious pollution hazard. There is no pollution risk involved in the present process, and no ion exchange reaction takes place between Ca2+ and NH3+ ions as in prior art where Ca level of the leaching soln. was increased. When the soln. ascended from underground redn. of hydrostatic pressure caused released of CO2, so that the pH of the soln. increased thus precipitating CaCO3 which clogged the pipes.