Exploration of the Borderline Value of Mineral Evolution and Precipitation Based on PHREEQC Simulation in Uranium Leaching Process
Based on the chemical composition of the leaching solution in the acid leaching uranium test,the characteristics and critical values of mineral dissolution and precipitation of Hadatu uranium ore in Inner Mongolia under different acidity were explored by using PHREEQC simulation software.The chemical composition of the leaching solution and the change characteristics of the main trace elements of the original and slag samples were systematically analyzed.The changes of the existing forms of uranium and iron during leaching were studied.The content of feldspar and clay mineral and the changes of permeability coefficients were studied,and the changes of saturation index in the process of uranium leaching such as gypsum,gibbsite,hematite,goethite,Fe(OH)3 and Al2O3 were calculated.The results show that acidity is the main factor of mineral dissolution,and the dominant order of cation leaching is ∑Fe＞Ca2+＞Mg2+＞Al3+＞Na+＞K+,and the main forms of uranium and iron in the leaching process are UO2SO4,UO22+and UO2(SO4)22-,Fe2+and FeSO4.When the acidity of the leaching solution was 10 g/L,Ca2+concentration was less than 503.2 mg/L,pH value was below 2.94,and no precipitation of gypsum and iron-aluminum minerals would be produced.In the uranium leaching test,compared with the original samples,the content of slag feldspar decreased by 1.10％—5.70％,and the clay mineral increased by 0.62％—4.15％,indicating that clay alteration occurred in column leaching.Gypsum,iron-aluminum mineral precipitation,and clay-altered feldspar are important reasons for the significant decrease in permeability.
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