CHANGES OF URANIUM OCCURRENCE STATE IN NEUTRAL CO2+O2 IN-SITU LEACHING IN THE MENGQIGUER SANDSTONE-TYPE URANIUM DE-POSIT IN YILI BASIN
The implementation of the CO2+O2 neutral leaching process for uranium extraction in our country has,to some extent,mitigated the challenges associated with blockage and low leaching rates that were prevalent with acid and alkali leaching methods in high-carbonate uranium deposits.The Monqiguer Uranium Deposit in Xinjiang is one of the representative high-carbonate sandstone-type uranium deposits in China,employing this leaching method.The focus of this paper is on a laboratory uranium leaching exper-iment to raw ore from the Mengqiguer uranium deposit,utilizing TESCAN Integrated Mineralogy Analy-sis(TIMA)and Scanning Electron Microscope(SEM)to analyses thin slices of samples,to illustrate changes in process parameters like uranium occurrence states,uranium mineral size,dissociation degree,and associated minerals before and after leaching.This comprehensive analysis aims to provide mineralogi-cal parameters as a basis for improving the uranium mining process.The results indicate that uranium pri-marily exists in independent uranium minerals,uranium-bearing minerals,and adsorbed uranium in the raw ore of the Mengqiguer uranium deposit.The predominant uranium minerals are identified as coffinite with a small amount of pitchblende.After the uranium ore leaching experiment,a significant amount of coffinite and pitchblende are successfully leached,with coffinite larger than 30 μm being completely leached,and only a small amount of pitchblende(8-9 μm)remaining unleached.The most notable change in the dissociation degree of coffinite before and after leaching is the proportion of less than 10％,which increases from 49.68％to 84.20％.Pitchblende in the raw ore exhibits a higher dissociation degree,accounting for 53.06％in the range of 80％-90％dissociation degrees.Only a small amount of pitch-blende with a 60％-70％dissociation degree remains unleached after leaching.Generally,uranium miner-als with higher dissociation degrees are more easily leached than those with lower dissociation degrees,and pitchblende is more susceptible to leaching compared to coffinite.Throughout the leaching process,it is crucial to control the pH of the leaching system to prevent the secondary precipitation of uranium-bearing calcite.The findings of this study regarding the occurrence state of uranium and the change characteristics of process parameters for uranium minerals before and after leaching contribute to understanding various factors influencing in-situ ore leaching efficiency.This information holds important theoretical and practi-cal significance for advancing the improvement and innovation of in-situ leaching technology at the Mengqiguer uranium deposit and similar uranium deposits in China.
Sandstone-type uranium depositsCO2+O2 neutral leachingTIMAOccurrence state
万方数据
