Removal of radium from sand filters by inorganic acids

Sand filters are used in water treatment stations to remove particulate matter from underground water, where iron and manganese are collected forming thin oxide films. These oxides of iron and manganese adsorb radium from underground water. Radium concentration increases in time on the filters, and consequently the level of radioactivity increases in the station. The removal of adsorbed radium on sand using inorganic acids was studied. Good efficiency of radium removal was obtained by controlling different parameters like temperature, time, pH, addition of competitive cations and anions. It was found that hydrochloric acid is the best for radium removal from sand filters. Maximum removal obtained was about 60% at 5M BaCl2 and 2M HCl at 50 deg C for 180-minute contact time. Kinetic parameters of the removal process were studied and compared with literature data. (author)