Analysis and modeling of fixed bed sorption of cesium by AMP-PAN

Cesium sorption on ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) from simulated acidic waste was investigated in a fixed-bed column. Batch equilibrium isotherm data were tested with Freundlich and Langmuir models and both were found to fit the sorption isotherm data well, but the Langmuir model was better. Cesium exchange on AMP-PAN followed pseudo second-order kinetics. The effects of influent Cs concentration (500-1000 mg/L), feed flow rate (5-15 mL/min) and bed height (14.5-21.5 cm) on the breakthrough characteristics of the ion-exchange system were determined. The uptake capacity increased with increase in initial ion concentration and bed height but decreased with increase in flow rate. Breakthrough occurred earlier for higher concentrations, higher flow rates and lower bed heights. The dynamics of the mass transfer zone were described for different column operating conditions. The height of mass transfer zone decreased with increase in initial concentration and increased with increase in flow rate. No significant effect was observed in the height of mass transfer zone with increase in height of bed. Mathematical models of Thomas, Yoon-Nelson and Bohart-Adams model were applied to the experimental data to analyze the column performance. The results fitted well to the Thomas and Yoon-Nelson models with correlation coefficient, R2 ≥ 0.98.