High Efficient Mineralization of Cesium in Waste Liquid by Hydrothermal Method

Abstract

During the nuclear fuel cycle, a large amount of radioactive cesium is produced, and at the same time, it is difficult to safely dispose of because of its extremely soluble in water and low boiling point. The safe disposal of radioactive cesium is a problem that needs to be solved urgently. The currently used methods to treat cesium-containing wastewater such as cement fixation, glass solidification and ion exchange, have certain drawbacks, and urgently need to be further optimized. Pollucite is an analcite molecular sieve. Many studies have shown that it is one of the potential final choices for radioactive cesium. Pollucite has an appropriate pore size, without destroying the structure of pollucite, radioactive cesium cannot diffuse out of pore of pollucite, pollucite also has a good stability and high cesium loading rate. In previous studies, pollucite needs to be synthesized under high temperature conditions above 1000°C. This method will cause the volatilization of cesium and increase the difficulty of exhaust gas treatment. How to quickly synthesize pollucite at a lower temperature has become an important research direction for the safe disposal of caesium. Different from the traditional calcination method to synthesize pollucite, this paper uses hydrothermal method to simulate the generation environment of zeolite in nature, and realizes the synthesis of pollucite at a lower temperature. Using cesium contained in simulated wastewater as synthetic raw materials, combined with commonly used silicon sources and aluminum sources as synthetic raw material, through exploring different reaction conditions such as reaction temperature, reaction time, and alkali addition, the hydrothermal synthesis of pollucite was finally successfully realized. Then the influence of different reaction conditions on synthesis and cesium removal efficiency was investigated, and its growth mechanism was also analyzed. Finally, it was realized that pollucite was successfully synthesized under 150°C hydrothermal conditions using common chemical reagents as raw materials, which further promoted pollucite application in the safe disposal of radioactive cesium.