NaCl改性沸石对氨氮吸附性能的研究

Effect of NaCl modification on ammonia-nitrogen adsorption property of zeolite

采用NaCl溶液对天然沸石进行改性,考察了NaCl浓度、温度及沸石用量对改性效果的影响。通过表面特征分析、吸附机制分析、吸附等温试验和吸附动力学试验,进一步比较了天然沸石和改性沸石对氨氮的吸附性能。结果表明,在NaCl溶液为6%(质量分数)、温度为303 K、天然沸石用量为15 g(以100 mL的NaCl溶液计)的优化条件下,改性沸石对氨氮的吸附效果最佳。扫描电子显微镜(SEM)和比表面积(BET)分析可知,沸石经改性后表面变粗糙,平均吸附孔径变小,比表面积变大。2种沸石对氨氮的吸附过程均可用Langmuir、Freundlich吸附等温方程较好地拟合,在温度为303 K时,改性沸石比天然沸石单分子层饱和吸附量增幅为34%以上。颗粒内扩散是沸石吸附氨氮的限制性因素,其吸附动力学较符合准二级反应动力学方程,拟合结果表明改性沸石具有更好的动力学性能,其吸附速率常数略大于天然沸石。

Natural zeolite was modified by NaCl solution and the effects of NaCl concentration,temperature and zeolite dosage on modification were studied.In addition,ammonia-nitrogen adsorption properties of natural and NaCl modified zeolite were compared through surface characteristics analysis,static adsorption and dynamical experiments.When 15 g of zeolite was modified in 100 mL of NaCl solution（mass ratio was 6%） at 303 K,the obtained zeolite presented the best ammonia-nitrogen adsorption property.SEM and BET analysis showed that the modified zeolite had rougher surface,smaller average adsorption pore size and larger specific surface area compared with natural zeolite.The adsorption of ammonia-nitrogen on two kinds of zeolite could be well fitted by both Langmuir and Freundlich isotherms equation,and NaCl modification could increase the theoretical maximum adsorption capacities（qm） by 34% or more.The intra-particle diffusion was the limiting factor for ammonia-nitrogen adsorption.The dynamic adsorption data were well described by pseudo second order reaction rate model,and the results indicated that adsorption of ammonia-nitrogen on modified zeolite was better than that on natural zeolite in view point of capacities and velocities.