Radium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily combines with nitrogen (rather than oxygen) on exposure to air, forming a black surface layer of radium nitride (Ra3N2). All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1600 years and decays into radon gas (specifically the isotope radon-222). When radium decays, ionizing radiation is a product, which can excite fluorescent chemicals and cause radioluminescence.
Radium is the daughter product of uranium decay and is heaviest alkaline earth metal. It was discovered in the form of radium chloride by Marie and Pierre Curie in 1898. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911.
It has the property of luminescence and was once used to make watch dials glow in the dark as well as for various quack products.
Radium forms a divalent cation in water and can be removed by water softening resins, along with other hardness ions. Except for the first exhaustion cycle, radium leakage occurs shortly after hardness leakage occurs, therefore the resin is used as an ordinary softener with brine regeneration at regular intervals.
The highly crosslinked macroporous cation resin have extended first cycle operation past hardness break and can be used in single use applications when hardness and TDS are not too high. RSM-50 has barium sulfate deposited in the pores of the resin. Radium is first exchanged and then transfer to the precipitant, allowing much higher loading and longer throughput.