利用海泡石合成MCM-48介孔分子筛其吸附性能研究

Adsorption behavior of the mesoporous molecular sieves MCM-48 prepared from sepiolite

海泡石除铁后用2 mol/L盐酸在80℃下处理3 h,使海泡石中的杂质和镁、铁等阳离子与热酸反应,通过过滤和洗涤去除,烘干后焙烧,得到脱镁海泡石。然后加十六烷基三甲基溴化铵(CTABBr)和去离子水,配比为n(CTAB):n(SiO_2):n(H_2O)=1:0.6:30的溶液,搅拌2 h后老化24 h,用NaOH调节pH值到12后,在110℃下密封水热合成反应72 h,用去离子水水洗、干燥后在空气中于550℃下焙烧,得到具有介孔特征的MCM-48介孔分子筛。用XRD、TEM、FT-IR、N_2吸附-脱附等方法,分析表征了MCM-48介孔分子筛的物相结构、孔径分布、比表面积等。结果表明,介孔MCM-48分子筛对亚甲基蓝的吸附量约为200 mg/g,吸附规律符合Frendlich等温吸附关系式。

This paper intends to introduce its author＇s research on the MCM-48 mesoporous molecular sieve and his successful hydrotbermal synthesis with the treated sepiolite as silica source. For the research purpose, we have first of all treated the post-Fe-extraction sepiolite with 2 moL/L chlnrhydric acid solution at the temperature of 80 ℃ for 3 h so as for the impurities, magnesium, iron and other cations in it to react with thermal acid through filtration and washing. As the result, the post-Mg-extraction sepiolite could be obtained by drying. After that, the cetyltrimethylammonium bromide （CTABBr） solution and deionized water couht be added to the resulted sepiolite so that the molar composition of the resulted synthesis gel could reach 0.6 SiO2：CTAB： 30 H2O. Such a synthesized solution would then be stirred vigorously for 2 h, on the condition that the pH value of the slurry should be adjusted till 12 by adding NaOH solution. Before transferring to a Teflon-lined stainless steel autoclave, the above synthesis solution should be let aged for 24 h in the room temperature and then hydrothermally treated for 72 h in an oven at a temperature of 110 ℃ . Treated hydrothermally, the products could be expected to get recovered thoroughly washed with deionized water, and then dried at 100 ℃ and calcined at 550 ℃ at a heating rate of 3℃/min so as to obtain MCM-48 mesoporous molecular sieves. Till then, the phase structure, pore size distribution and specific surface area of MCM-48 molecular sieves could be formed and characterized by XRD, TEN, FT-IR, N2 adsorption-desorption isotherms. TEM analysis helps to reveal the crystal shape of MCM-48 mesoporous molecular sieves, the better developed single crystal, the fairly crystal lattice with the dis- lance between the stripes being about 0.2 nm. methylene blue ad- sorption capacity of the MCM-48 of proves approximately 200 mg/g. The regularity of the adsorption turns to be in full accord with Frendlieh isotherm adsorption relation.