Uranyl carbonate

Uranyl carbonate, UO₂(CO₃), is a carbonate of uranium that forms the backbone of several uranyl mineral species such as andersonite, mckelveyite-(Y) and wyartite and most importantly rutherfordine. It is also found in both the mineral and organic fractions of coal and its fly ash and is the main component of uranium in mine tailing seepage water.

Uranium like other actinides readily forms a dioxide uranyl core (UO₂). In the environment, this uranyl core readily complexes with carbonate to form charged complexes. Although uranium forms insoluble solids or adsorbs to mineral surfaces at alkaline pH it is these soluble carbonate complexes that increase its solubility, availability, and mobility with low affinities to soil. Uranium(VI) generally forms a pH-dependent suite of uranyl carbonate and various hydrated complexes in ground water solutions.

A common method for concentrating uranium from a solution uses solutions of uranyl carbonates, which are passed through a resin bed where the complex ions are transferred to the resin by ion exchange with a negative ion like chloride. After build-up of the uranium complex on the resin, the uranium is eluted with a salt solution and the uranium is precipitated in another process.