Evaluation of ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) as a cesium selective sorbent for the removal of ¹³⁷Cs from acidic nuclear waste solutions

Ammonium molybdophosphate (AMP) immobilized on polyacrylonitrile (PAN) is an engineered form of cesium selective sorbent material developed at the Czech Technical University in Prague. The selective cesium capacity of this inorganic ion exchange media was evaluated with simulated sodium bearing waste (SBW) and dissolved pilot plant calcine at the Idaho Nuclear Technology and Engineering Center (INTEC). Equilibrium isotherms were obtained at 23°C and 50°C with 48-h equilibrium contact times. The equilibrium isotherms were of the 'favorable' type and showed asymptotic maximum cesium loading of approximately 8.7% by weight of dry AMP. Dynamic column tests were performed with similar feeds using a 1.5-cm³ bed in an up-flow configuration. Complete breakthrough curves were generated at feed rates up to 100 bed volumes (BV) per hour and sorbent capacities were determined to be approximately 32 g Cs/kg AMP-PAN (dry) at 100% breakthrough. Stop flow data were also obtained from the column tests. These stop flow data, in conjunction with column rate data, imply that cesium mass transfer is predominately particle diffusion limited at feed rates below 40 BV /h.