Studies On The Process Mineralogy And Green Hydrometallurgical Techniques For Strongly Weathered And Oxidized Sandstone Uranium Ore

Sawafuqi uranium deposit is a steeply inclined and drained sandstone uranium deposit with strongly weathered and oxidized uranium ore newly discovered in China.In order to explore the high-efficienct and green hydrometallurgy techniques for this kind of sandstone uranium ore,this dissertation systematically and deeply studied the occurrence characteristics of the deposit,the structure of the uranium ore,process mineralogical characteristics,combined leaching process and techniques,heap leaching kinetic characteristics,uranium recovery process and techniques and waste water and waste residue treatment processes,and obtained the following research results:（1）Sawafuqi uranium ore belongs to glutenite uranium ore.The main uranium minerals include pitchblende,uranite and ilmenite,which are mainly occured in the form of independent uranium minerals,symbiosis with pyrite minerals or symbiosis with feldspar minerals.The common clay alteration includes kaolinization,illitization and chloritization.The chemical phase of iron ore is mainly siderite and pyrite,almost free of TOC and inorganic carbon components.The microstructure of the ore particles is loose,micro fractures and pores are well developed,and uranium minerals are exposed to air through fractures and pores.Uranium exists as compounds of U⁴⁺and U⁶⁺,and the content of U⁶⁺accounts for 96.8%,which belongs to strongly weathered and oxidized uranium ore.（2）The combined process from stirring leaching and heap leaching was devised,in which the ore was first broken to-10 mm and made to pass through 0.5 mm sieve,then stirring leaching for-0.5 mm ore and heap leaching for+0.5 mm ore were carried out.The uranium in this kind of strongly weathered and oxidized uranium ore can be leached efficiently.（3）A kinetic model describing the relationship between the influencing factors of heap leaching and its leaching rate was firstly established by using multiple groups of column leaching test data.Then,the calculation model of the number of full grain size uranium ore heap leaching particles was established using the mass fraction of each grain size uranium ore and the porosity of the ore heap.Finally,a coupled convection dispersion reaction dynamic model of uranium heap leaching was established using the convection,dispersion and reaction of solutes in ore heap porous media,which can be used to predict and regulate the heap leaching behaviour.（4）Based on the experimental data of uranium adsorption by strong alkaline anion resin column,the kinetic equation of uranium adsorption by the resin column was established,which describes the relationship between the effluent concentration from resin column and the cumulative volume of resin bed under the conditions of different cycle times,adsorption stock solution concentration and stock solution flow rate.With the increase of adsorption and washing cycles,the resin would be poisoned,and the peak concentration of the uranium ion in the washing solution would be decreased.At this time,sulfuric acid could be used to transform it.The saturated capacity of the transformed resin was almost the same as that of the new resin,indicating that the resin has good physicochemical stability and reusability.（5）A certain amount of qualified leaching solution was taken,a certain amount of Na OH was added,the first precipitation at p H 7-8 was conducted,and the bottom slurry was obtained by removing the supernatant.Then,the previous precipitation slurry was used as the bottom slurry for each precipitation,the same amount of qualified leaching solution as the first precipitation were added and p H value was adjusted to 4-5,Na OH were added,and it was made to precipitate at p H7-8 to obtain the bottom slurry.Such circulation was proceeded until the precipitated product was obtained.This whole slurry circulation granulation precipitation process significantly improved the sedimentation performance and quality of precipitated products.（6）Lime and Ba Cl₂were used to treat the mixture of tail liquor from resin adsorption and mother liquor from precipitation,and the uranium and radium in the mixture could be lowered to meet the emission standard of regulations on radiation protection and environmental protection of uranium mining and metallurgy.When lime was used to treat the waste residue,the residual acid on the surface of the waste residue particles was easy to neutralize,while the residual acid inside the waste residue particles was difficult to neutralize fully in a short time,and the waste residue would turn acidic with time.