IMPACT OF LAYERED SILICATE MINERALS ON URANIUM LEACHING EFFICIENCY DURING SANDSTONE-TYPE URANIUM LEACHING PROCESS
In-situ leaching of uranium stands as a crucial method for the development and utilization of sandstone-type uranium ore,a significant uranium resource.Within the uranium in-situ leaching process,layered silicate minerals like muscovite and kaolinite in the ore body play a role in diminishing uranium leaching efficiency.This paper utilizes analyses of elemental geochemistry and process mineralogy to delve into the occurrence state and process mineralogical parameters of uranium before and after leaching experi-ments with sandstone-type uranium ore.The objective is to uncover the specific mechanisms through which layered silicate minerals reduce the leaching efficiency of uranium.It can be observed that before and after the leaching experiments,the contents of SiO2 remained approximately between 75％and 80％,and those of Al2O3 were around 10％.These two major elements exhibited the highest concentrations with minimal changes pre-and post-leaching.The uranium content decreased from 569 × 10-6 to a range of 200 to 300×10-6 after leaching.Furthermore,the primary associated minerals of uranium shifted from pyrite to feldspar,mica,and clay minerals post-leaching,with a slight increase in the specific surface area of lay-ered silicate minerals such as muscovite and chlorite.Scanning electron microscopy reveals that uranium in ores before in-situ leaching primarily exists in three forms:independent uranium minerals,adsorbed urani-um,and isomorphic uranium.During in-situ leaching,some independent uranium minerals and adsorbed uranium are leached away by the leaching solution,while some unleachable uranium minerals persist in feldspar pores or adhere to the surface of layered silicate minerals.The main reason for the presence of un-leachable uranium minerals is attributed to the lamellar structure of phyllosilicate,hindering contact be-tween uranium minerals and the leaching solution.Furthermore,new clay phyllosilicate minerals,genera-ted by the dissolution of the original clay minerals and feldspar,expand after absorbing water.This expan-sion blocks the pores,impedes the migration and flow of the leaching solution,consequently reducing leac-hing efficiency.
sandstone type uranium depositprocess mineralogyphyllosilicate mineralsinfluence mech-anism
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