Method for producing lead-212 from an acidic aqueous solution A1 comprising thorium-228 and daughters thereof, which comprises the following successive steps: - a purification of the lead-212 present in the aqueous solution A1, which purification comprises the following steps: a) providing a first chromatography column comprising a first stationary phase which selectively retains lead with respect to thorium and radium when thorium-228 and the daughters thereof are in an acidic aqueous solution having a pH between a first pH value, pH 1, and a second pH value, pH 2, greater than pH 1; b) loading the first chromatography column with the aqueous solution A1, the aqueous solution A1 having a pH between pH 1 and pH 2; c) at least one washing of the first stationary phase with an acidic aqueous solution A2 having a pH between pH 1 and pH 2; d) eluting the lead-212 from the first stationary phase with an aqueous solution A3 having a pH greater than pH 2, whereby an aqueous solution A4 comprising lead-212 is obtained; then - a purification of the lead-212 present in the aqueous solution A4, which purification comprises the following steps: e) loading a second chromatography column with the aqueous solution A4, the second chromatography column comprising a second stationary phase which selectively retains lead with respect to thorium and radium when thorium-228 and the daughters thereof are in an acidic aqueous solution having a pH between a first pH value, pH 3, and a second pH value, pH 4, greater than pH 3; f) at least one washing of the second stationary phase with an acidic aqueous solution A5 having a pH between pH 3 and pH 4; and g) eluting the lead-212 from the second stationary phase with an aqueous solution A6 having a pH greater than pH 4. - a purification of the lead-212 present in the aqueous solution A1, which purification comprises the following steps: a) providing a first chromatography column comprising a first stationary phase which selectively retains lead with respect to thorium and radium when thorium-228 and the daughters thereof are in an acidic aqueous solution having a pH between a first pH value, pH 1, and a second pH value, pH 2, greater than pH 1; b) loading the first chromatography column with the aqueous solution A1, the aqueous solution A1 having a pH between pH 1 and pH 2; c) at least one washing of the first stationary phase with an acidic aqueous solution A2 having a pH between pH 1 and pH 2; d) eluting the lead-212 from the first stationary phase with an aqueous solution A3 having a pH greater than pH 2, whereby an aqueous solution A4 comprising lead-212 is obtained; then a) providing a first chromatography column comprising a first stationary phase which selectively retains lead with respect to thorium and radium when thorium-228 and the daughters thereof are in an acidic aqueous solution having a pH between a first pH value, pH 1, and a second pH value, pH 2, greater than pH 1; b) loading the first chromatography column with the aqueous solution A1, the aqueous solution A1 having a pH between pH 1 and pH 2; c) at least one washing of the first stationary phase with an acidic aqueous solution A2 having a pH between pH 1 and pH 2; d) eluting the lead-212 from the first stationary phase with an aqueous solution A3 having a pH greater than pH 2, whereby an aqueous solution A4 comprising lead-212 is obtained; then - a purification of the lead-212 present in the aqueous solution A4, which purification comprises the following steps: e) loading a second chromatography column with the aqueous solution A4, the second chromatography column comprising a second stationary phase which selectively retains lead with respect to thorium and radium when thorium-228 and the daughters thereof are in an acidic aqueous solution having a pH between a first pH value, pH 3, and a second pH value, pH 4, greater than pH 3; f) at least one washing of the second stationary phase with an acidic aqueous solution A5 having a pH between pH 3 and pH 4; and g) eluting the lead-212 from the second stationary phase with an aqueous solution A6 having a pH greater than pH 4. e) loading a second chromatography column with the aqueous solution A4, the second chromatography column comprising a second stationary phase which selectively retains lead with respect to thorium and radium when thorium-228 and the daughters thereof are in an acidic aqueous solution having a pH between a first pH value, pH 3, and a second pH value, pH 4, greater than pH 3; f) at least one washing of the second stationary phase with an acidic aqueous solution A5 having a pH between pH 3 and pH 4; and g) eluting the lead-212 from the second stationary phase with an aqueous solution A6 having a pH greater than pH 4.