In-situ recovery of mineral values

Abstract

Mineral values, particularly uranium, are recovered from subsurface earth formations containing the same, as well as cations which form precipitates with sulfuric acid leach solutions, by injecting into at least one injection well a preliminary acidic solution capable of forming soluble materials with at least one of the precipitate-forming cations, such as calcium and iron cations, passing the preliminary acidic solution through the subsurface formation for a time sufficient to form such soluble materials, withdrawing the preliminary acidic solution containing the solubilized materials from at least one producing well, thereafter, injecting a sulfuric acid leach solution into said injection well, contacting the subsurface formation with the leach solution for a time sufficient to extract significant amounts of mineral values from the formation and produce a pregnant leach solution containing the thus solubilized mineral values and withdrawing the pregnant leach solution from the production well. In a preferred aspect, the preliminary acidic solution capable of forming soluble materials from precipitate-forming cations is selected from the group consisting of solutions of acetic acid, hydrochloric acid, citric acid, mixtures thereof, one or more of the same in sequence and one or more of the same and mixtures thereof in combination with sulfuric acid.