Preliminary Study On Uranium Leaching Technology And Leaching Mechanism Of A Typical Sandstone Uranium Deposit In Western Tsaidam Basin

The sandstone uranium ore in western Tsaidam Basin is another typical uranium ore newly explored in China.Its genesis is closely related to petroleum and is characterised by high muddy organic matter content,high carbonate content,low permeability and low grade.Although a great deal of exploration has been carried out,there is still a gap in how to effectively extract uranium resources,and there is an urgent need to carry out process technology research on the extraction of uranium resources to provide a basis for the next step of industrialisation of this uranium mine.In this paper,Static batch and tube leaching tests have been carried out using process mineralogical research methods to obtain the process of uranium leaching and to initially explore the leaching mechanism.The main results achieved in this thesis are as follows:（1）Static batch leaching tests were conducted to investigate the effect of alkaline reagent type,alkaline concentration,oxidant type,oxidant concentration and sulphuric acid concentration on the leaching rate of uranium.The study showed that under single-run leaching conditions,the leaching rate of uranium from the Yuejin uranium mine was20.12%at 2 g/L H₂O₂+800 mg/L HCO₃^-（NH₄HCO₃）,and mineral analysis indicated that the clay mineral content could reach up to 40%,which severely affected its leaching;the leaching rate of uranium from the Seven Springs uranium mine was highest（28.87%）using a concentration of 30 g/L sulphuric acid The leaching rate was the highest at Qigequan（28.87%）and the second highest（27.79%）at 2 g/L KMn O₄+1000 mg/L HCO₃-（NH₄HCO₃）2 g/L.（2）On the basis of static tests,tube leaching tests were conducted to study the leaching effect under different leaching process conditions.The test showed that Yuejin uranium mine was leached by alkali method with potassium ferricyanide and H₂O₂as oxidant,and the leaching cycle was 83 days,with liquid count uranium leaching rate of25.74%and 28.28%,and slag count leaching rate of 19.33%and 22.77%respectively,which was poor;Qigequan were leached by KMn O₄alkali method and acid method respectively,and the leaching cycle was 83 days,with liquid count leaching rate of 55.13%,68.89%,and 48.52%,67.01%by residue respectively.The ore permeability coefficients of the two uranium ores were inversely proportional to the leach solution concentration during the leaching process.Geochemical simulation studies indicate that insoluble calcium carbonate precipitates and yellow potassium-iron-alum precipitates were generated during the leaching process by alkaline and acid methods respectively,which reduced the permeability of the ore and affected the leaching effect,and controlling the precipitation generation during the leaching process is another key process.（3）Process mineralogy was used to study the phase change of uranium ore before and after leaching.XRD analysis shows that Yuejin ore is mainly composed of quartz,feldspar and carbonate minerals,and alkali leaching can destroy quartz and feldspar in the ore;The main components of Qigequan ore are quartz and feldspar,and the feldspar in the ore is severely damaged by acid leaching.SEM analysis results show that the damage degree of hydrogen peroxide alkali leaching is stronger than that of potassium ferricyanide.The results show that the surface of Qigequan ore leached by sulfuric acid method is more loose with more voids and pores,which is beneficial to uranium leaching.（4）The mechanism of uranium leaching in the process of tube leaching was studied by shrinking core model,and the leaching characteristics of uranium in the process of tube leaching were revealed.The results show that the alkali leaching of Yuejin ore with potassium ferricyanide and hydrogen peroxide as oxidants is mainly controlled by chemical reaction and diffusion,respectively.The reaction rate of hydrogen peroxide is0.00118,which is higher than that of potassium ferricyanide with 0.000140.Both alkali leaching and acid leaching of Qigequan ore are mainly controlled by diffusion.The reaction rate of acid leaching is 0.00396,which is higher than that of potassium permanganate alkaline leaching by 0.00243.