稻壳沸石的合成及其对氨氮的吸附/脱附动力学

以稻壳为原料采用水热合成法制备了沸石，运用XRD、SEM和BET技术表征了合成沸石的结构特性。通过静态实验，研究了合成沸石对氨氮的吸附和脱附机理。结果表明：延长水热合成的晶化时间有利于合成沸石晶核的形成，合成沸石比表面积为28.418 m2·g-1，平均孔径为31.1 nm，孔体积为0.22 m3·g-1，属NaP型微介孔吸附材料。伪二级吸附动力学模型更适合描述合成沸石对氨氮的吸附过程，由伪二级吸附动力学模型拟合得到的平衡吸附量与实测值相差在1.0%以内。颗粒内扩散速率是由膜扩散和内扩散共同控制，颗粒内扩散速率常数kp随初始浓度的增加而提高。MNaOH/ANMNaOH/AN的增大，温度对脱附的促进作用变得越来越小，当MNaOH/AN>1.21时，氨氮的脱附率可达92.1%。伪二级脱附动力学模型的拟合结果优于伪一级，碱当量高于临界值之后对提高合成沸石脱附氨氮的效果不大。

Kinetics adsorption and desorption of ammonia-nitrogen on synthetic zeolite from rice husk

Rice husk was used for preparing synthetic zeolite via hydrothermal synthesis,which was characterized by XRD,SEM,and BET.The mechanisms for the adsorption and desorption of ammonium nitrogen on the synthetic zeolite were investigated by static experiments.The results demonstrated that a longer crystallization time was beneficial for nuclei formation of the synthetic zeolite.The specific surface area,average pore size,and pore volume were 148.81 m2·g-1,31.1 nm,and 0.22 m3·g-1,respectively.NaP zeolite,which belongs to the field of microporous and mesoporous adsorption materials,was synthesized.The ammonium nitrogen adsorption kinetics of the synthetic zeolite accords with the pseudo-second-order kinetics equation.The difference between the adsorption capacity calculated by the model and the actual measurement was smaller than 1.0%.The intraparticle diffusion was mainly influenced and controlled by the film and internal diffusions;the rate constant (kp) increased with the increment of the initial concentration.When MNaOH/AN was lower than 0.95,the desorption rate was significantly higher at 308 K than that at 298 K.However,with increasing MNaOH/AN,the effect of temperature on the desorption became smaller.When MNaOH/AN exceeded 1.21,its removal rate reached 92.1%.The pseudo-second-order kinetic desorption model was superior to the pseudo-first-order kinetic model.When MNaOH/AN increased to a critical value,the desorption efficiency did not significantly improve.