表面活性剂介质中有机化锂皂石的水热合成及结构特征

Study on Structure Characteristics of Organic Hectorite Hydrothermally Synthesized in Reaction Medium with the Presence of Surfactants

以氟化锂、氯化镁、水玻璃及氨水为主要原料,通过在水热合成反应体系中添加不同比例的十六烷基三甲基溴化铵(CTAB)表面活性剂和正十二烷胺(DDA),合成了层状结构的有机化锂皂石型固体,并用傅里叶变换红外光谱仪(FT-IR)、粉末X射线衍射仪(XRD)、电子扫描显微镜(SEM)、热重-差热分析(TGA/DTA)、N2等温吸附-脱附等手段对合成产物进行了表征。结果表明,在水热体系中,添加表面活性剂后可以合成层状结构的有机化锂皂石型固体产物。在水热生成有机化锂皂石型固体产物的过程中加入CTAB阳离子表面活性剂,其有机阳离子部分会发生插层作用,进入层间形成CTA+有机化的锂皂石。但中性DDA在水热过程中则难以发生插层作用。在DDA与CTAB同时存在下,DDA会阻碍CTAB插层作用和插层程度。反映在固体产物的形貌上和织构上,有机阳离子进入层间,导致固体产物微观结构蓬松;不同有机活性剂也影响了固体的微观堆积形态,形成不同的孔结构及分布。

Using lithium fluoride,magnesium chloride,water glass and ammonium hydroxide as the main reactants,the layered organic hectorite-type solids were synthesized hydrothermally in the reaction medium in the presence of surfactant.Cationic cetyltrimethyl ammonium bromide（CTAB） and neutral dodecyl amine（DDA）—two kinds of surfactants at different ratios were used in the hydrothermal process.The structures of the synthesized samples were characterized respectivery by Fourier transform infrared spectroscopy（FT-IR）,power X-ray diffraction（XRD）,field emission scanning electron microscopy（FESEM）,thermal gravimetric analysis and differential thermal analysis（TGA/DTA） and N2 adsorption-desorption isotherms.The results show that,with the addition of surfactant of either CTAB,DDA or CTAB＋DDA in the hydrothermal reaction medium,the layered hectorite-type solid could be obtain at all times.When only CTAB was added to the reaction medium,the moiety of cationic CTA＋ could partly intercalate into the interlayer of the hectorite-type solids.On the contrary,adding neutral DDA has no intercalation effect.In the presence of two mixed surfactants of CTAB and DDA,the DDA could hinder the intercalation of CTAB and reduce the amount of CTAB intercalating in the interlayer.Moreover,CTAB has a great influence on the morphology and pore size distribution of the synthesized compound,and it causes the compound to have a swelling layered structure.