The present invention provides the methods that 227Th is purified from the mixture comprising 227Th and 223Ra, which comprises i) the first solution of mixture of the preparation comprising 227Th the and 223Ra ions being dissolved in the aqueous solution of the first inorganic acid Ii) first solution is loaded on strong basic anion-exchange resin Iii) using the second inorganic acid in aqueous solution, 223Ra is eluted from the strong basic anion-exchange resin Iv) the strong basic anion-exchange resin optionally is rinsed using the first water-bearing media V) using the third inorganic acid in aqueous solution, 227Th is eluted from the strong basic anion-exchange resin, to generate the second solution comprising 227Th. Invention further provides the 227Th solution of purifying, corresponding pharmaceutical preparation and the methods for treating tumor disease.
