Department of Hydrogeological Modeling and Deep Burial of Liquid Waste, VNIPIpromtekhnologii JSC (Moscow, Russia)
I. N. Dedyulin, Research Trend Manager, Dedyulin.I.N@vnipipt.ru
P. Yu. Vasilevskiy, Head of Department, Candidate of Geologo-Mineralogical Sciences
V. M. Shumikhin, Specialist
In in-situ uranium leaching, it is vital to assess the potential formation or dissolution of mineral phases resulting from the interaction of leaching solutions with the geological environment under varying levels of the solution acidity. With a view to substantiating an acidification mode of ore strata with sulfuric-acid solutions at the Dobrovolnoe uranium deposit in the Kurgan Region, Russia, a thermodynamic simulation of the hydrogeochemical system comprising leaching solutions, groundwater and host rock minerals was implemented. An additional objective was identifying the main sources of calcium ions entering the solution as a result of pore clogging with gypsum. The optimal mode of acidification of an ore-bearing stratum, with minimized pore clogging with gypsum was selected. Modeling of interaction between the leaching solution, groundwater and host rocks used the series-connected chemical reactors. In this method, the medium is split to cells such that each cell contains certain quantity of the substance in solid and liquid phases. For simulating the interaction dynamics in the solution–stratum system, a cascade of reactors was used. It is found that the main sources of calcium in the pregnant solution are silicate minerals—tremolite, diopside and anorthite. According to calculation of saturation indexes, these phases are thermodynamically unstable in an acid environment and undergo complete dissolution. The total contribution of these minerals to gypsum-based clogging is threetime s as high as the contribution of calcite. Modeling of neutralization of leaching solutions revealed consistent zonality of sedimentation of manmade minerals.
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