MoF6在NaF颗粒上的吸附平衡及吸附动力学

Adsorption equilibrium and kinetics of molybdenum hexafluoride on sodium fluoride adsorbent

为阐明六氟化钼(Molybdenum hexafluoride,Mo F6)在氟化钠(Sodium fluoride,Na F)颗粒上的吸附机制,在静态吸附实验装置上研究了Mo F6在Na F颗粒上的吸附平衡及吸附动力学行为,结果表明在50-100oC内,Na F颗粒对Mo F6的吸附速率和平衡吸附量随着温度而升高,在100oC平衡吸附量达到115 mg Mo F6·g-1 Na F。当温度超过100oC时,Na F对Mo F6的吸附作用减弱,吸附量减小。Langmuir模型能较好描述Na F颗粒对Mo F6的吸附过程,并推测Mo F6在Na F颗粒上的吸附为单分子层吸附。吸附动力学模型分析表明,Na F颗粒对Mo F6的吸附符合准二级动力学方程,同时吸附过程受到颗粒内扩散控制,但其并不是唯一速率控制步骤。

Background：The fluoride volatility processhas been developed to recover uranium from spent nuclear fuel. And the fluoride adsorption and desorption technique is usually applied to the purification of UF6 in the fluoride volatility process.Purpose： This study aims to investigate the adsorption mechanism of MoF6 on NaF adsorbent. Methods： The adsorption equilibrium and kinetics of MoF6 on NaF adsorbent at different temperatures and initial MoF6 pressure were experimentally studied by using statistic adsorption equipment. Langmuir adsorption model and adsorption kinetics model were applied to analyse experimental data.Results：The adsorption rate and equilibrium adsorption capacity of MoF6 on NaF adsorbent increased with the temperature increasing from 50 oC to 100 oC, and the adsorption capacity was 115 mg MoF6·g-1 NaF at 100 oC.The experimental data were fitted by pseudo-second-order kinetics as well as Langmuir adsorption model.Conclusion：The adsorption of MoF6on NaF adsorbent was monolayer adsorption according to Langmuir adsorption model, and was controlled by diffusion of MoF6 inside NaF adsorbent which was not the unique rate-determining step, though.