Described are methods for preparing radionuclides, such as radionuclides having a high specific activity. The disclosed methods include irradiating target nuclide materials, in solution, with a neutron source. The radionuclides can be separated from the target nuclide material by providing a solid carbon nanostructured material, as a suspension of solids, proximal to the target nuclide material in solution and using the recoil to drive adsorption of the radionuclide onto the solid carbon nanostructured material to transfer the radionuclides from the liquid phase (in solution) to the solid phase (adsorbed to the suspended solid carbon nanostructured material). One or more surfactants can be incorporated into the solution to facilitate formation of a stable suspension of the solid carbon nanostructured material.