Treatment of 137Cs contaminated water by selective adsorption

•A treatment protocol for 137Cs removal by selective adsorption is defined.•Ammonium molybdophosphate is a suitable adsorbent for 137Cs removal.•Values around 98% of radioisotope removal can be achieved with proper operation conditions.•The treatment is suitable for initial activities lower than 5000 Bq/L.

The origin of the radioactive liquid waste object of this work was the incident that occurred in the steel factory of Acerinox in Cádiz (Spain) in 1998. In this incident, a 137Cs source was accidentally melted generating a significant amount of radioactively contaminated ashes. This research aims to study ash decontamination and declassification as radioactive wastes. After 137Cs extraction from ashes by a proper solvent, lixiviate must be treated to remove the radioisotope. One of the suitable processes for 137Cs removal from radioactive liquids is adsorption or ionic exchange, using inorganic materials as adsorbents. Among these materials, ammonium molybdophosphate (AMP) is at present the one with higher perspectives of industrial application. This paper aimed to study the application of AMP for 137Cs removal from the contaminated liquid extracted from radioactive ashes. The influence of different operating parameters such as pH, AMP concentration and operational time in the adsorption performance is studied. According to the results, the treatment protocol is established.