The origin of the radioactive liquid waste object of this work was the incident that occurred in the steel factory of Acerinox in Cadiz (Spain) in 1998. In this incident, a Cs-137 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 Cs-137 extraction from ashes by a proper solvent, lixiviate must be treated to remove the radioisotope. One of the suitable processes for Cs-137 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 Cs-137 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. (C) 2013 Elsevier B.V. All rights reserved.