METHOD AND ARRANGEMENT OF RECOVERING RARE EARTH ELEMENTS FROM ION ADSORPTION CLAYS

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A method and arrangement of recovering REEs wherein the ion adsorption clay is leached in a leach solution for producing a leach slurry, which leach residue contained in the leach slurry is washed with water and a pregnant leach solution and the leach residue are separated from each other. Water is separated from the pregnant leach solution and a concentrated pregnant leach solution containing the dissolved solids is obtained. Rare earth elements are precipitated as rare earth oxalate(s) and they are separated from the rare earth element depleted leach solution. The rare earth element depleted leach solution obtained from the rare earth element recovery step is contacted with calcium compound for precipitating unused excess oxalic acid as calcium oxalate which is separated from the remaining leach solution. The separated calcium oxalate is contacted with sulphuric acid for producing oxalic acid, which may be further crystallized and precipitated calcium sulphate.