Selective leach recovery of minerals from composite ores

Abstract

Calcium (Ca), manganese (Mn) and magnesium (Mg) carbonate plus lead (Pb) and zinc (Zn) sulphide minerals in a permeable host, crushed ore, concentrates or as mine discharge tailing are selectively solution mined (in-situ or ex-situ) with a selected acid e.g. acetic acid to extract Ca, Mn, and Mg followed by multivalent oxidizing salts e.g. ferric salts to extract Pb and Zn sequentially. For in-situ leaching, an inter relationship has been identified between pressure, temperature, target depth and leachate concentration such that carbonate leaching is performed in a manner to prevent carbon dioxide gas (CO) discharge thereby plugging host rock permeability avenues to preclude further leaching. This requires controlling the rate of acetic acid leaching to be in step with availability of solution to dissolve the resulting discharged CO. Sulphide leaching is subsequently conducted on the carbonate-depleted host. The two resulting leachates are chemically treated to selectively recover extracted minerals as value added industrially ready products. The in situ method is particularly advantageous in preparing the high purity manganese products necessary for lithium ion batteries because it prevents occurrence of very fine metallic particles in the products that may happen during conventional mining. Alternatively, the in situ carbonate recovery steps can be independently employed; all in an environmentally friendly manner.