A method for separating carbon dioxide from a gas flow, in particular from a flue gas flow, where a gas flow is brought in contact with a scrubbing medium in an absorber of a separating device and carbon dioxide contained in the gas flow is separated, the loaded scrubbing medium is fed to a desorber of the separating device in order to release the carbon dioxide, a vapor flow is drawn from the desorber and is fed to a cooling device in order to form condensate, and the condensate formed in the cooling device is at least partially fed to a purifying device, in which degradation products contained in the condensate are removed by reverse osmosis and/or by an ion exchanger. A separating device is adapted for separating carbon dioxide from a gas flow.