METHOD FOR SELECTIVE SEPARATION OF THORIUM AND CERIUM FROM A SOLID CONCENTRATE COMPRISING SAME AND ONE OR MORE FURTHER RARE EARTH METALS AND ACIDIC RARE EARTH SOLUTION THEREOF

摘要

The present disclosure relates to a method for separating thorium and cerium from a solid concentrate comprising compounds of thorium, cerium and one or more further rare earth metals, obtainable by increasing to pH 1.8 the pH of an aqueous composition comprising from 6 to 21 weight% nitric acid, from 25 to 33 weight% phosphoric acid, from 3.5 to 5 weight% calcium, and amounts of thorium, cerium and one or more further rare earth metals, the weight% being relative to the total weight of the aqueous composition, and subsequently precipitating and separating the solid concentrate comprising the compounds of thorium and cerium. The method comprises the steps of a) contacting the solid concentrate with an acid such as to achieve a composition with a pH of less than 0.5, b) reacting the acid composition obtained in step a) with ozone or heating the acid composition obtained in step a) at a temperature ranging from 110 °C to 130 °C for a time period ranging from 1 to 3 hours, thereby oxidizing the cerium ions in the acid composition to an oxidation state of +IV, c) increasing, to at most 2, such as between 1 and 2, the pH value of the composition obtained in step b), resulting in the precipitation of thorium and cerium compounds, and d) separating the solid concentrate comprising the compounds of thorium and cerium from the composition obtained in step c) to obtain an aqueous acidic rare earth solution depleted in thorium and cerium. The present disclosure further relates to an aqueous acidic rare earth solution depleted in thorium and cerium, obtainable by a method according to the method of the disclosure.