摘要
NaP zeolite particles were prepared through a template-free hydrothermal condition at 100oC. Parameters like Na2O/Si O2 and Si O2/Al2O3 molar ratios, gel aging time and aging temperature were investigated for regulating the crystallization of the final product. The samples at different synthesis stages were characterized with N2 adsorption at-196oC, field emission scanning electron microscopy(FE-SEM), temperature programmed desorption of ammonia adsorption, X-ray diffraction, thermogravimetric and differential scanning calorimetry analysis and Fourier transform infrared spectroscopy. The experimental results evidenced that a high ordering crystallinity of Na P zeolite was obtained at Na2O/Si O2 and Si O2/Al2O3 molar ratios of 1.10 and 1.40, respectively, and a temperature of 100°C for 4 days of aging. FE-SEM image exhibited polycrystalline aggregates of Na P zeolite with crystallite sizes ranging up to 5.04 μm with cactus/cabbage like structures. The quantitative analysis of the total number of acid sites was found to increase as Na2 O increases. The Na P zeolite sample with a Na2O/Si O2 molar ratio of 1.13 exhibited a large fraction of the acid sites on its external surface, contrary to that synthesized with a relevant ratio of 1.10. The optimized Na P zeolite could be successfully bestowed with excellent sorption properties of Ca(II) in aqueous solution. The kinetic parameters for Ca(II) adsorption were thoroughly investigated.
本文通过无模板水热法在100°C条件下制备了Na P沸石分子筛,并研究了Na2O/Si O2和Si O2/Al2O3摩尔比、凝胶老化时间和老化温度等参数,以调节最终产品的结晶度.不同合成阶段的样品,用-196°C氮吸附、场发射扫描电子显微镜(FE-SEM)、氨程序升温脱附、X-射线衍射、热重和差示扫描量热分析以及傅里叶变换红外光谱法进行了表征.实验结果表明,在Na2O/Si O2和Si O2/Al2O3摩尔比分别为1.10和1.40,100°C温度下老化4天,可以获得高度有序结晶化的Na P分子筛.FE-SEM图像显示Na P分子筛的多晶聚集体晶粒尺寸可达5.04μm,具有仙人掌/卷心菜样结构.定量分析发现酸位点总数随Na2O的增加而增加,Na2O/Si O2摩尔比为1.13的Na P沸石样品与1.10摩尔比合成的样品相比,在外表面上具有大量的酸位点.优化后的Na P分子筛在水溶液中具有优异的钙离子吸附性能,本文对钙离子吸附动力学参数进行了详细研究.
