Adsorption depends on the substrate and the specific species in question. Adsorption of radon on activated charcoal is an equilibrium process. Ion exchange is used to control water chemistry, typically to remove contaminants, soften potable water, or remove radium. Ion exchange does not cause mobilization of radionuclides, but once mobilized in water, any subsequent treatment by ion exchange has clear potential for reconcentration. Temperature-dependent variations in solubility result in increased concentrations of radionuclides, together with other elements in geothermal waters.
Thermal processes can mobilize radionuclides.
Any high-temperature process such as furnaces, kilns, roasters, calcination, and smelting can volatilize lead and polonium. Subsequent redeposition may occur in process equipment, in pollution control equipment, or in the environment. Minerals dissolved in naturally occurring geothermal waters typically plate out as the temperature drops. Deposits of scale containing substantial concentrations of radionuclides may result. As the water comes to the surface and the partial vapor pressure drops, radon dissolved in water partitions into the air.