Leaching is the key technology in in-situ leaching of uranium.  In alkali in-situ leaching uranium, oxygen is the most common oxidizer, with bicarbonate used as complexing agent.  For those sandstone uranium deposits with strong reducing capacity and/or complicated geological environment, the oxidation by oxygen may be less efficiency resulting in lower uranium values in leaching solution or longer leaching duration. An efficient leaching method, therefore, is needed for these uranium deposits.

Corresponding to the above difficulty in alkali leach in those specific sandstone uranium deposits, the synergetic oxidation of oxygen and other oxidizer used in in-situ leach uranium was proposed.  In this paper, we selected a typical sandstone uranium deposit to compare the effect of oxygen with synergetic oxidation by oxygen and other oxidizer.  The deposit is located in the Tuhar basin, Xinjiang Uygur autonomous region, which behaves characteristics with high TDS and high chloride content in groundwater, and intractable uranium leaching.  The previous work in alkaline leach with oxygen gives rise to low recovery of only 30%-50%, and traditional acid leach with hydrogen peroxide encountered the difficulties of precipitation and clogging leading to lower uranium values.  In our studies, synergetic oxidizers such as hydrogen peroxide, potassium permanganate, sodium dichloroisocyanate urea were chosen, and batch leaching tests and field test were carried through.

The results of batch leach indicate that synergetic oxidization could be achieved by potassium permanganate and sodium dichloroisocyanate urea in oxygen leach process with pH 6.5-8.5.  Hydrogen peroxide, however, doesn’t show oxidation and any synergetic effect.  Recovery of uranium is proportionate to the oxygen pressure and appropriate concentration of synergetic oxidizers.   Leaching tests show that minor oxidizer has good synergetic oxidization with oxygen and leach effect on uranium minerals.  The quantity of synergetic oxidizer can be used as less as 50mg/L, and higher level of oxidizers may not take effect.  The further field tests were conducted to compare the synergetic effect with or without sodium dichloroisocyanate urea.  The preliminary results confirmed the faster leaching by complexing oxidizers in alkali leach.

In general, synergetic oxidation can be achieved in the studied deposits with strong reducing capacity and high TDS groundwater environment.  However, the oxidizing effect has certain selectivity on various ore samples.  The applicability, therefore, should be further studied by larger scale pilot tests. 


Synergetic Oxidation in Alkaline In-Situ Leaching Uranium: A Preliminary Case Study

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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