Method for the separation of rare earth compounds from a mixture of solids

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The invention relates to a method for the separation of rare earth compounds from a phosphogypsum (2) comprising different mineral substances with a calcium sulfonate content of greater than 50%, comprising the steps of : -converting the residual to a mixture of solids comprising calcium oxide by thermal treatment, -mixing the thermally treated solids mixture with a first leaching agent, -wherein a selective solution of the calcium oxide takes place in the first leaching agent with respect to rare earth compounds, -separation of the rare-earth compounds containing solids from the first leaching agent, -mixing the separated solid with a second leaching agent, wherein the pH of the second lying means (12) is lower than the pH of the first and -selective dissolution of the rare-earth compounds in the second leaching agent lying means (12).