Ions at liquid interfaces play a central role in many processes, including materials development where they influence molecular and particle assembly, and chemical separations where they determine the efficiency and selectivity of critical element recovery. Many of these interfacial processes rely upon neighboring bulk phases as a reservoir of ions. Such processes can be influenced by controlling the properties of the reservoir, such as the concentration of free ions available to be transported to the interface. Control over this transport, from bulk to interface and back, can lead to the triggering of interfacial processes as demonstrated by electrochemical methods for the liquid-liquid interface between two immiscible electrolyte solutions. Here, we demonstrate that exposure to X-rays provides a method to move rare earth lanthanide ions between bulk liquid and its liquid-vapor interface. This method utilizes complexants and extractants like those used in solvent extraction processes to separate and purify lanthanides and actinides.