Radium contaminated water is mixed with magnesium oxide coated carbon nanotubes in a large tank. Radium bonds with the magnesium oxide on the nanotubes. These heavy nanotubes precipitate out of solution and settle to the bottom of the tank. The purified water is poured off. The nanotubes build up inside the tank. When the build up reaches a certain level, the tank is drained and cleaned. The nanotubes are cleaned and recycled. The radium sludge is disposed of properly.