浸铀过程中基于PHREEQC模拟的矿物演化与沉淀临界值探究

Exploration of the Borderline Value of Mineral Evolution and Precipitation Based on PHREEQC Simulation in Uranium Leaching Process

基于酸法浸铀试验中浸出液化学成分,利用PHREEQC模拟软件,探究了内蒙古哈达图铀矿石在不同酸度条件下的矿物溶解沉淀特征和临界值,系统分析了浸液化学成分和原、渣样主微量元素变化特征;浸出过程中铀、铁存在形式的变化;长石和黏土矿物含量以及渗透系数变化,计算了石膏、三水铝石、赤铁矿、针铁矿、Fe(OH)_(3)和Al_(2)O_(3)等矿物浸铀过程中饱和指数的变化。结果表明,酸度是矿物溶解的主要因素,阳离子浸出优势排序为ΣFe>Ca^(2+)>Mg^(2+)>Al^(3+)>Na^(+)>K^(+),浸出过程中铀、铁主要存在形式为UO_(2)SO_(4)、UO_(2)^(2+)、UO_(2)(SO_(4))_(2)^(2-)和Fe^(2+)、FeSO_(4)。当溶浸液酸度为10 g/L时,Ca^(2+)浓度低于503.2 mg/L,pH值低于2.94,便不会产生石膏和铁铝矿物沉淀。浸铀试验中渣样长石含量较原样降低了1.10%~5.70%,黏土矿物增高了0.62%~4.15%,说明柱浸中发生了黏土化蚀变。石膏、铁铝矿物沉淀和长石的黏土化蚀变是渗透系数大幅下降的重要原因。

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 Al_(2)O_(3) were calculated.The results show that acidity is the main factor of mineral dissolution,and the dominant order of cation leaching is ΣFe>Ca^(2+)>Mg^(2+)>Al^(3+)>Na^(+)>K^(+),and the main forms of uranium and iron in the leaching process are UO_(2)SO_(4),UO_(2)^(2+) and UO_(2)(SO_(4))_(2)^(2-),Fe^(2+)and FeSO_(4).When the acidity of the leaching solution was 10 g/L,Ca^(2+)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.